U.S. patent application number 15/929415 was filed with the patent office on 2020-11-05 for method and apparatus for performing handover procedure in wireless communication system.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Donggun KIM, Soenghun KIM.
Application Number | 20200351725 15/929415 |
Document ID | / |
Family ID | 1000004811593 |
Filed Date | 2020-11-05 |
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United States Patent
Application |
20200351725 |
Kind Code |
A1 |
KIM; Donggun ; et
al. |
November 5, 2020 |
METHOD AND APPARATUS FOR PERFORMING HANDOVER PROCEDURE IN WIRELESS
COMMUNICATION SYSTEM
Abstract
A method performed by a terminal in a wireless communication
system includes: receiving, from a base station, a radio resource
control (RRC) reconfiguration message including configuration
information for conditional handover; identifying a cell for
conditional handover based on the configuration information for
conditional handover; and triggering a packet data convergence
protocol (PDCP) status report for a radio bearer, according to an
execution of a conditional handover for the identified cell for
conditional handover.
Inventors: |
KIM; Donggun; (Suwon-si,
KR) ; KIM; Soenghun; (Suwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
1000004811593 |
Appl. No.: |
15/929415 |
Filed: |
April 30, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 76/27 20180201;
H04W 76/19 20180201; H04W 36/0069 20180801; H04W 76/15 20180201;
H04W 80/02 20130101; H04W 36/0072 20130101 |
International
Class: |
H04W 36/00 20060101
H04W036/00; H04W 76/27 20060101 H04W076/27; H04W 76/15 20060101
H04W076/15; H04W 80/02 20060101 H04W080/02; H04W 76/19 20060101
H04W076/19 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2019 |
KR |
10-2019-0051827 |
Claims
1. A method performed by a terminal in a wireless communication
system, the method comprising: receiving, from a base station, a
radio resource control (RRC) reconfiguration message comprising
configuration information for conditional handover; identifying a
cell for conditional handover based on the configuration
information for conditional handover; and triggering a packet data
convergence protocol (PDCP) status report for a radio bearer
according to an execution of a conditional handover for the
identified cell for conditional handover.
2. The method of claim 1, further comprising reestablishing a PDCP
entity corresponding to the RRC reconfiguration message, wherein
the PDCP status report is triggered in response to the
reestablishment of the PDCP entity.
3. The method of claim 1, wherein the RRC reconfiguration message
comprises PDCP configuration information, and wherein the PDCP
status report is triggered in case that the PDCP configuration
information comprises information indicating that the PDCP status
report is required.
4. The method of claim 1, wherein the radio bearer is an
acknowledged mode (AM) data radio bearer (DRB).
5. The method of claim 1, wherein the configuration information for
conditional handover comprises information of at least one
candidate cell for conditional handover and information of
conditions for conditional handover.
6. The method of claim 5, wherein the identifying of the cell for
conditional handover comprises identifying the cell for conditional
handover from among the at least one candidate cell based on the
information of conditions for conditional handover.
7. The method of claim 1, further comprising transmitting the PDCP
status report to the identified cell for conditional handover.
8. A terminal in a wireless communication system, the terminal
comprising: a transceiver; and at least one controller configured
to: receive, from a base station, a radio resource control (RRC)
reconfiguration message comprising configuration information for
conditional handover, identify a cell for conditional handover
based on the configuration information for conditional handover,
and trigger a packet data convergence protocol (PDCP) status report
for a radio bearer according to an execution of a conditional
handover for the identified cell for conditional handover.
9. The terminal of claim 8, wherein the at least one controller is
further configured to reestablish a PDCP entity corresponding to
the RRC reconfiguration message, and wherein the PDCP status report
is triggered in response to the reestablishment of the PDCP
entity.
10. The terminal of claim 8, wherein the RRC reconfiguration
message comprises PDCP configuration information, and wherein the
PDCP status report is triggered in case that the PDCP configuration
information comprises information indicating that the PDCP status
report is required.
11. The terminal of claim 8, wherein the radio bearer is an
acknowledged mode (AM) data radio bearer (DRB).
12. The terminal of claim 8, wherein the configuration information
for conditional handover comprises information of at least one
candidate cell for conditional handover and information of
conditions for conditional handover.
13. The terminal of claim 12, wherein at least one controller is
further configured to identify the cell for conditional handover
from among the at least one candidate cell based on the information
of conditions for conditional handover.
14. The terminal of claim 8, wherein at least one controller is
further configured to transmit the PDCP status report to the
identified cell for conditional handover.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims priority under 35
U.S.C. .sctn. 119 to Korean Patent Application No. 10-2019-0051827,
filed on May 2, 2019, in the Korean Intellectual Property Office,
the disclosure of which is incorporated by reference herein in its
entirety.
BACKGROUND
1. Field
[0002] The disclosure relates to a method and apparatus for
performing a handover procedure in a wireless communication
system.
[0003] Also, the disclosure relates to a method and apparatus for
processing communication data in a wireless communication
system.
2. Description of Related Art
[0004] To meet the increasing demand for wireless data traffic
after the commercialization of 4.sup.th Generation (4G)
communication systems, efforts to develop enhanced 5.sup.th
Generation (5G) communication systems or pre-5G communication
systems are continuing. For this reason, a 5G communication system
or pre-5G communication system is called a Beyond 4G Network
communication system or a Post Long Term Evolution (LTE)
system.
[0005] To achieve a high data transmission rate, the implementation
of a 5G communication system in an ultra-high-frequency millimeter
wave (mmWave) band (for example, a 60 GHz band) is being
considered. To reduce path loss of radio waves and increase a
transfer distance of radio waves in an ultra-high-frequency band,
in a 5G communication system, technologies for beamforming, massive
Multiple Input Multiple Output (MIMO), Full Dimensional MIMO
(FD-MIMO), array antenna, analog beam-forming, and large-scale
antenna are being discussed.
[0006] Also, to improve the network of the system, various
technologies, such as advanced small cell, cloud radio access
network (cloud RAN), ultra-dense networks, Device to Device
communication (D2D), wireless backhaul, moving networks,
cooperative communication, Coordinated Multi-Points (CoMP), and
interference cancellation, have been developed for 5G communication
systems. In addition, other technologies, such as hybrid frequency
shift keying (FSK) and quadrature amplitude modulation (QAM)
Modulation (FQAM) and Sliding Window Superposition Coding (SWSC)
based on Advanced Coding Modulation (ACM) and Non Orthogonal
Multiple Access (NOMA) and Sparse Code Multiple Access (SCMA) based
on Filter Bank Multi Carrier (FBMC), have been developed for 5G
communication systems.
[0007] Meanwhile, the Internet is evolving from a human-centered
network in which humans generate and consume information to an
Internet of Things (IoT) network in which distributed components
such as objects transmit, receive, and process information.
Internet of Everything (IoE) technology resulting from combining
IoT technology with big data processing technology, etc. through a
connection to a cloud server or the like is on the rise. To
implement the IoT, various technical factors, such as sensing
technology, wired/wireless communication, network infrastructure,
service interface technology, and security technology, are
required. Recently, technologies including a sensor network,
Machine to Machine (M2M), and Machine Type Communication (MTC) for
connections between objects have been studied. In an IoT
environment, an intelligent Internet Technology (IT) service is
provided to collect and analyze data generated by connected objects
to create new value for human life. The IoT may be applied to
various fields, such as smart homes, smart buildings, smart cities,
smart cars/connected cars, smart grids, health care, smart
appliances, and advanced medical services, through convergence and
combination between existing Information Technology (IT) and
various industries.
[0008] Accordingly, various attempts to apply a 5G communication
system to an IoT network are being made. For example, technologies,
such as a sensor network, M2M, and MTC, are implemented by
technologies, such as beam forming, MIMO, and array antenna, which
are 5G communication technologies. Applying a cloud radio access
network (CRAN) as big data processing technology is also an example
of the convergence of 5G technology and IoT technology.
[0009] With the development of wireless communication systems as
described above, various services are being provided. Therefore, a
method for stably supporting services related to, particularly,
handover of a user equipment (UE) is required.
SUMMARY
[0010] The disclosure provides an apparatus and method capable of
effectively providing a service in a mobile communication
system.
[0011] Additional aspects will be set forth in part in the
description which follows and, in part, will be apparent from the
description, or may be learned by practice of the presented
embodiments of the disclosure.
[0012] According to an embodiment of the disclosure a method
performed by a terminal in a wireless communication system
includes: receiving, from a base station, a radio resource control
(RRC) reconfiguration message including configuration information
for conditional handover; identifying a cell for conditional
handover based on the configuration information for conditional
handover; and triggering a packet data convergence protocol (PDCP)
status report for a radio bearer, according to an execution of a
conditional handover for the identified cell for conditional
handover.
[0013] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document: the terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation; the term "or," is inclusive, meaning and/or; the
phrases "associated with" and "associated therewith," as well as
derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or
with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, or the like; and the term "controller" means
any device, system or part thereof that controls at least one
operation, such a device may be implemented in hardware, firmware
or software, or some combination of at least two of the same. It
should be noted that the functionality associated with any
particular controller may be centralized or distributed, whether
locally or remotely.
[0014] Moreover, various functions described below can be
implemented or supported by one or more computer programs, each of
which is formed from computer readable program code and embodied in
a computer readable medium. The terms "application" and "program"
refer to one or more computer programs, software components, sets
of instructions, procedures, functions, objects, classes,
instances, related data, or a portion thereof adapted for
implementation in a suitable computer readable program code. The
phrase "computer readable program code" includes any type of
computer code, including source code, object code, and executable
code. The phrase "computer readable medium" includes any type of
medium capable of being accessed by a computer, such as read only
memory (ROM), random access memory (RAM), a hard disk drive, a
compact disc (CD), a digital video disc (DVD), or any other type of
memory. A "non-transitory" computer readable medium excludes wired,
wireless, optical, or other communication links that transport
transitory electrical or other signals. A non-transitory computer
readable medium includes media where data can be permanently stored
and media where data can be stored and later overwritten, such as a
rewritable optical disc or an erasable memory device.
[0015] Definitions for certain words and phrases are provided
throughout this patent document, those of ordinary skill in the art
should understand that in many, if not most instances, such
definitions apply to prior, as well as future uses of such defined
words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other aspects, features, and advantages of
certain embodiments of the disclosure will be more apparent from
the following description taken in conjunction with the
accompanying drawings, in which:
[0017] FIG. 1A shows a structure of a long term evolution (LTE)
system to which an embodiment of the disclosure may be applied;
[0018] FIG. 1B shows a radio protocol architecture of an LTE system
to which an embodiment of the disclosure may be applied;
[0019] FIG. 1C shows a structure of a next-generation mobile
communication system to which an embodiment of the disclosure may
be applied;
[0020] FIG. 1D shows a radio protocol architecture of a
next-generation mobile communication system to which an embodiment
of the disclosure may be applied;
[0021] FIG. 1E is a view for describing a procedure in which a next
generation Node B (gNB) according to an embodiment of the
disclosure releases a connection of a user equipment (UE) for the
UE to change from a Radio Resource Control (RRC) connected mode to
an RRC idle mode and a procedure in which the UE sets up a
connection to the gNB to change from the RRC idle mode to the RRC
connected mode;
[0022] FIG. 1F shows a handover procedure in a next-generation
mobile communication system according to an embodiment of the
disclosure;
[0023] FIG. 1G shows a conditional handover procedure according to
an embodiment of the disclosure;
[0024] FIG. 1H shows operations of a conditional handover procedure
of a UE according to an embodiment of the disclosure;
[0025] FIG. 1I shows a structure of a UE or a wireless node
according to an embodiment of the disclosure;
[0026] FIG. 1J shows a block configuration of a
Transmission/Reception Point (TRP) or a wireless node in a wireless
communication system according to an embodiment of the
disclosure;
[0027] FIG. 2A shows a structure of an LTE system to which an
embodiment of the disclosure may be applied;
[0028] FIG. 2B shows a radio protocol architecture of an LTE system
to which an embodiment of the disclosure may be applied;
[0029] FIG. 2C shows a structure of a next-generation mobile
communication system to which an embodiment of the disclosure may
be applied;
[0030] FIG. 2D shows a radio protocol architecture of a
next-generation mobile communication system to which an embodiment
of the disclosure may be applied;
[0031] FIG. 2E is a view for describing a procedure in which a gNB
according to an embodiment of the disclosure releases a connection
of a UE for the UE to change from an RRC connected mode to an RRC
idle mode and a procedure in which the UE sets up a connection to
the gNB to change from the RRC idle mode to the RRC connected
mode;
[0032] FIG. 2F shows a handover procedure in a next-generation
mobile communication system according to an embodiment of the
disclosure;
[0033] FIG. 2G shows RLC header formats that may be applied in a
1-1 embodiment which are operations of a reception RLC layer in
which a RLC UM mode according to an embodiment of the disclosure is
set;
[0034] FIG. 2H shows RLC header formats that may be applied in a
1-2 embodiment which are operations of a reception RLC layer in
which an RLC AM mode according to an embodiment of the disclosure
is set;
[0035] FIG. 2IA shows RLC header formats that may be applied in a
2-1 embodiment, and are operations of a reception RLC layer in
which an RLC UM mode according to an embodiment of the disclosure
is set;
[0036] FIG. 2IB shows RLC header formats that may be applied in a
2-1 embodiment, and are operations of a reception RLC layer in
which an RLC UM mode according to an embodiment of the disclosure
is set;
[0037] FIG. 2J shows RLC header formats that may be applied in a
2-2 embodiment which are operations of a reception RLC layer in
which an RLC AM mode according to an embodiment of the disclosure
is set;
[0038] FIG. 2K shows operations of a reception RLC layer of a UE
according to an embodiment of the disclosure;
[0039] FIG. 2L shows a structure of a UE or a wireless node
according to an embodiment of the disclosure; and
[0040] FIG. 2M shows a block configuration of a TRP or a wireless
node in a wireless communication system according to an embodiment
of the disclosure.
DETAILED DESCRIPTION
[0041] FIGS. 1A through 2M, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented in any
suitably arranged system or device.
[0042] Hereinafter, an operation principle of an embodiment of the
disclosure will be described in detail with reference to the
accompanying drawings. However, when detailed descriptions about
known functions or configurations associated with the disclosure
are determined to unnecessarily obscure the gist of the disclosure,
the detailed descriptions will be omitted. Although the following
terms are defined in consideration of the functions of the
disclosure, they may vary according to a user or operator's
intentions, judicial precedents, etc. Hence, the terms must be
defined based on the contents of the entire specification.
[0043] Throughout the disclosure, the expression "at least one of
a, b or c" indicates only a, only b, only c, both a and b, both a
and c, both b and c, all of a, b, and c, or variations thereof.
[0044] Examples of a terminal may include a User Equipment (UE), a
Mobile Station (MS), a cellular phone, a smartphone, a computer, a
multimedia system capable of performing a communication function,
or the like.
[0045] In the disclosure, a controller may also be referred to as a
processor.
[0046] Throughout the specification, a layer (or a layer) may also
be referred to as an entity.
[0047] When detailed descriptions about known functions or
configurations associated with the disclosure are determined to
unnecessarily obscure the gist of the disclosure, the detailed
descriptions will be omitted. Hereinafter, an embodiment of the
disclosure will be described with reference to the accompanying
drawings.
[0048] In the following descriptions, the terms used to identify
connected nodes, the terms indicating network entities, the terms
indicating messages, the terms indicating interfaces between
network objects, the terms indicating various identification
information, etc. are examples for convenience of description.
Accordingly, an embodiment of the disclosure is not limited to
these terms, and other terms having the equivalent technical
meaning may be used.
[0049] For convenience of description, an embodiment of the
disclosure uses terms and names defined in a 3.sup.rd Generation
Partnership Project Long Term Evolution (3GPP LTE) standard and/or
a 3.sup.rd Generation Partnership Project New Radio (3GPP NR)
standard. However, an embodiment of the disclosure is not limited
to the terms and names, and may be applied in the same way to a
system based on another standard. In an embodiment of the
disclosure, evolved Node B (eNB) is mixed with next generation Node
B (gNB) for convenience of description. That is, a base station
mentioned as an eNB may represent a gNB. Also, the term UE may
represent other wireless communication devices, as well as mobile
phones, NB-IoT devices, and sensors.
[0050] A post LTE communication system, that is, a 5.sup.th
Generation (5G) communication system needs to freely reflect
various requirements from users and service providers. Therefore,
the 5G communication system needs to support services satisfying
various requirements simultaneously. Examples of services
considered for the 5G communication system are Enhanced Mobile
BroadBand (eMBB), massive Machine Type Communication (mMTC), and
Ultra Reliability Low Latency Communication (URLLC).
[0051] According to an embodiment of the disclosure, the eMBB is
aimed to provide a data rate that is higher than a data rate
supported by existing LTE, LTE-A or LTE-Pro. For example, in a 5G
communication system, the eMBB needs to provide a peak data rate of
20 Gbps in a downlink and a peak data rate of 10 Gbps in an uplink
with respect to a base station. Also, the 5G communication system
needs to provide a high user perceived data rate, while providing a
peak data rate. To satisfy the requirements, the 5G communication
system requires an improvement of various transmission/reception
technologies including enhanced Multi Input Multi Output (MIMO)
transmission technology. Also, existing LTE transmits signals by
using a transmission bandwidth of maximally 20 MHz in a 20 GHz
band, whereas the 5G communication system uses a wider frequency
bandwidth than 20 MHz in a frequency band of 3 to 6 GHz or more,
thereby satisfying a required data rate.
[0052] Simultaneously, mMTC is considered to support an application
service such as Internet of Thing (IoT) in the 5G communication
system. The mMTC may require supporting connections of massive UEs
(a large number of UEs) in a cell, UE coverage enhancement, an
improved battery lifetime, UE cost reduction, etc. to efficiently
provide the IoT. The IoT is connected to various sensors and
devices to provide a communication function. Therefore, the IoT
needs to support a large number of UEs (for example, 1,000,000
UEs/km.sup.2) in a cell. Also, because a UE supporting the mMTC has
a high probability of being located in a shadow zone such as the
basement of a building, which is not covered by a cell, due to its
service characteristics, the UE may require wide coverage compared
to those required by other services that a 5G communication system
provides. The UE supporting the mMTC needs to be a low-cost UE, and
requires a long battery lifetime of about 10 years to 15 years
because it has difficulties in frequently replacing the
batteries.
[0053] Finally, URLLC which is a mission-critical cellular-based
wireless communication service may be used in services of remote
control for robots or machinery, industrial automation, unmanned
aerial vehicle, remote health care, emergency alert, etc.
Accordingly, communication provided by the URLLC may need to
satisfy ultra-low latency and ultra reliability. For example, a
service supporting the URLLC needs to satisfy air interface latency
that is shorter than 0.5 milliseconds, and simultaneously, the
service may have a requirement of a packet error rate that is equal
to or lower than 10.sup.-5. Accordingly, for services supporting
the URLLC, the 5G system needs to provide a smaller Transmit Time
Interval (TTI) than other services, and simultaneously, the 5G
system requires a design of assigning a wide resource in a
frequency band to secure reliability of a communication link.
[0054] Three services (that is, eMBB, URLLC, and mMTC) which are
considered in the above-described 5G communication system may be
multiplexed in a system and transmitted. In this case, to satisfy
different requirements of the services, the services may use
different transmission/reception methods and different
transmission/reception parameters. However, the above-described
mMTC, URLLC, and eMBB are examples of different services types, and
service types to which the disclosure is applied are not limited to
the above-described examples.
[0055] Also, hereinafter, embodiments of the disclosure are
described based on examples of LTE, LTE-A, LTE Pro, or a 5G (or NR,
next-generation mobile communication) system, however, the
embodiments of the disclosure may be applied to other communication
systems having similar technical backgrounds or channel types.
Also, the embodiments of the disclosure may be applied to other
communication systems through slight modifications within a range
that does not greatly deviate from the scope of the disclosure,
under a determination of a person having a skilled technical
knowledge.
[0056] As described below, the disclosure proposes a conditional
handover method that is efficient in a next-generation mobile
communication system. According to an embodiment of the disclosure,
an issue that a source gNB starts late data forwarding to a target
gNB and an issue caused when a source gNB fails to recognize a
connection release time of a UE may be overcome.
[0057] The next-generation mobile communication system may support
various handover methods for reducing a data interruption time that
may be caused when a handover occurs. Particularly, according to a
conditional handover procedure, a source gNB sets a condition for a
UE together with a plurality of target gNB candidates, and the UE
checks signals from the target gNB candidates based on the
condition to select a target gNB candidate from among the plurality
of target gNB candidates as a target gNB, thereby starting a
handover procedure. Accordingly, because the source gNB is not
capable of expecting a target gNB to which the UE will perform a
handover, the source gNB starts late data forwarding to the target
gNB, and also the source gNB may not recognize a time at which the
UE releases a connection to the source gNB.
[0058] Hereinafter, a method and apparatus for performing a
handover procedure according to an embodiment of the disclosure
will be described with reference to FIGS. 1A to 1J.
[0059] FIG. 1A shows a structure of an LTE system to which an
embodiment of the disclosure may be applied.
[0060] Referring to FIG. 1A, a radio access network of the LTE
system may be configured with next-generation Evolved Nodes B
(ENBs) (hereinafter, also referred to as Nodes B or base stations)
1a-05, 1a-10, 1a-15, and 1a-20, a Mobility Management Entity (MME)
1a-25, and a Serving-Gateway (S-GW) 1a-30. A UE (hereinafter, also
referred to as a terminal) 1a-35 may be connected to an external
network through the ENBs 1a-05 to 1a-20 and the S-GW 1a-30.
[0061] In FIG. 1A, the ENBs 1a-05 to 1a-20 may correspond to
existing nodes B of a Universal Mobile Telecommunication System
(UMTS). The ENBs 1a-05 to 1a-20 may be connected to the UE 1a-35
through a wireless channel, and perform more complicated functions
than the existing nodes B. In the LTE system, because all user
traffics including a real-time service such as Voice over IP (VoIP)
are serviced through a shared channel, a device for performing
scheduling by collecting status information of UEs, such as buffer
statuses of UEs, available transmission power states of UEs,
channel states of UEs, etc., is needed. The ENBs 1a-05 to 1a-20 may
function as such a device. An ENB may generally control a plurality
of cells. For example, to implement a transmission speed of 100
Mbps, the LTE system uses, as radio access technology, Orthogonal
Frequency Division Multiplexing (OFDM), for example, in a bandwidth
of 20 MHz. Also, Adaptive Modulation & Coding (AMC) of
determining a modulation scheme and a channel coding rate according
to a channel state of a UE may be applied. The S-GW 1a-30, which is
a device for providing data bearers, may generate or remove data
bearers according to a control of the MME 1a-25. The MME 1a-25 may
be in charge of various control functions, as well as a mobility
management function for UEs, and may be connected to a plurality of
ENBs.
[0062] FIG. 1B shows a radio protocol architecture of an LTE system
to which an embodiment of the disclosure may be applied.
[0063] Referring to FIG. 1B, radio protocols of the LTE system may
include Packet Data Convergence Protocols (PDCPs) 1b-05 and 1b-40,
Radio Link Control (RLC) 1b-10 and 1b-35, and Medium Access Control
(MAC) 1b-15 and 1b-30 of an UE and an ENB. The PDCPs 1b-05 and
1b-40 may be in charge of operations of IP header
compression/restoration. Main functions of the PDCPs 1b-05 and
1b-40 may be summarized as follows. [0064] Header compression and
decompression: ROHC only [0065] Transfer of user data [0066]
In-sequence delivery of upper layer PDUs at PDCP re-establishment
procedure for RLC AM [0067] For split bearers in DC (only support
for RLC AM): PDCP PDU routing for transmission and PDCP PDU
reordering for reception [0068] Duplicate detection of lower layer
SDUs at PDCP re-establishment procedure for RLC AM [0069]
Retransmission of PDCP SDUs at handover and, for split bearers in
DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM [0070]
Ciphering and deciphering [0071] Timer-based SDU discard in
uplink
[0072] The RLC 1b-10 and 1b-35 may reconstruct a PDCP Packet Data
Unit (PDU) to an appropriate size to perform an ARQ operation, etc.
Main functions of the RLC 1b-10 and 1b-35 may be summarized as
follows. [0073] Transfer of upper layer PDUs [0074] Error
Correction through ARQ (only for AM data transfer) [0075]
Concatenation, segmentation and reassembly of RLC SDUs (only for UM
and AM data transfer) [0076] Re-segmentation of RLC data PDUs (only
for AM data transfer) [0077] Reordering of RLC data PDUs (only for
UM and AM data transfer) [0078] Duplicate detection (only for UM
and AM data transfer) [0079] Protocol error detection (only for AM
data transfer) [0080] RLC SDU discard (only for UM and AM data
transfer)
[0081] RLC re-establishment
[0082] The MAC 1b-15 and 1b-30 may be connected to several RLC
layers configured in the UE, and perform an operation of
multiplexing RLC PDUs into a MAC PDU and demultiplexing RLC PDUs
from a MAC PDU. Main functions of the MAC 1b-15 and 1b-30 may be
summarized as follows. [0083] Mapping between logical channels and
transport channels [0084] Multiplexing/demultiplexing of MAC SDUs
belonging to one or different logical channels into/from transport
blocks (TB) delivered to/from the physical layer on transport
channels [0085] Scheduling information reporting [0086] Error
correction through HARQ [0087] Priority handling between logical
channels of one UE [0088] Priority handling between UEs by means of
dynamic scheduling [0089] MBMS service identification [0090]
Transport format selection [0091] Padding
[0092] Physical layers (PHY) 1b-20 and 1b-25 may perform an
operation of performing channel coding and modulation on upper
layer data to generate an OFDM symbol and transmitting the OFDM
symbol through a wireless channel, or an operation of demodulating
an OFDM symbol received through the wireless channel, performing
channel decoding on the OFDM symbol, and transferring the
channel-decoded OFDM symbol to an upper layer.
[0093] FIG. 1C shows a structure of a next-generation mobile
communication system to which an embodiment of the disclosure may
be applied.
[0094] Referring to FIG. 1C, a radio access network of a
next-generation mobile communication system (hereinafter, referred
to as NR or 5G) may be configured with a next-generation New Radio
Node B (NR gNB) (also, referred to as a NR base station) 1c-10 and
a New Radio Core Network (NR CR) 1c-05. A New Radio User Equipment
(NR UE) (also, referred to as a UE) 1c-15 may be connected to an
external network through the NR gNB 1c-10 and the NR CN 1c-05.
[0095] In FIG. 1C, the NR gNB 1c-10 may correspond to an Evolved
Node B (eNB) of an existing LTE system. The NR gNB 1c-10 may be
connected to the NR UE 1c-15 through a wireless channel, and
provide a more excellent service than an existing node B. In a
next-generation mobile communication system, because all user
traffics are serviced through a shared channel, a device for
performing scheduling by collecting status information of UEs, such
as buffer statuses of UEs, available transmission power states of
UEs, channel states of UEs, etc., is needed. The NR gNB 1c-10 may
function as such a device. A NR gNB may generally control a
plurality of cells. To implement ultra high-speed data transmission
compared to existing LTE, OFDM as radio access technology may be
combined with beam-forming technology, while providing an existing
maximum bandwidth or more.
[0096] Also, AMC of determining a modulation scheme and a channel
coding rate according to a channel state of a UE may be applied.
The NR CN 1c-05 may perform functions, such as mobility support,
bearer setup, Quality of Service (QoS) setup, etc. The NR CN 1c-05
may be in charge of various control functions, as well as a
mobility management function for UEs, and may be connected to a
plurality of base stations. Also, the next-generation mobile
communication system may interwork with an existing LTE system, and
the NR CN 1c-05 may be connected to the MME 1c-25 through a network
interface. The MME 1c-25 may be connected to an eNB 1c-30 which is
an existing base station.
[0097] FIG. 1D shows a radio protocol architecture of a
next-generation mobile communication system to which an embodiment
of the disclosure may be applied.
[0098] Referring to FIG. 1D, radio protocols of the next-generation
mobile communication system may include NR SDAPs 1d-01 and 1d-45,
NR PDCPs 1d-05 and 1d-40, NR RLC 1d-10 and 1d-35, and NR MAC 1d-15
and 1d-30 of an UE and a NR gNB.
[0099] Main functions of the NR SDAPs 1d-01 and 1d-45 may include
some of the following functions. [0100] Transfer of user plane data
[0101] Mapping between a QoS flow and a DRB for both DL and UL
[0102] Marking QoS flow ID in both DL and UL packets [0103]
Reflective QoS flow to DRB mapping for the UL SDAP PDUs
[0104] In regard of a SDAP layer as described above, the UE may
receive, as an RRC message, a setting about whether to use a header
of the SDAP layer or whether to use a function of the SDAP layer
for each PDCP layer, for each bearer, or for each logical channel.
When a SDAP header is set, the SDAP header capable of indicating
the UE to update or reset mapping information about a QoS flow and
a data bearer of a uplink and a downlink with a 1-bit indicator NAS
reflective QoS for a NAS reflective QoS setting and a 1-bit
indicator AS reflective QoS for an AS reflective QoS setting of the
SDAP header may include QoS flow ID information representing QoS.
QoS information described above may be used as data processing
priority, scheduling information, etc. for supporting a stable
service.
[0105] Main functions of the NR PDCPs 1d-05 and 1d-40 may include
some of the following functions. [0106] Header compression and
decompression: ROHC only [0107] Transfer of user data [0108]
In-sequence delivery of upper layer PDUs [0109] Out-of-sequence
delivery of upper layer PDUs [0110] PDCP PDU reordering for
reception [0111] Duplicate detection of lower layer SDUs [0112]
Retransmission of PDCP SDUs [0113] Ciphering and deciphering [0114]
Timer-based SDU discard in uplink
[0115] The reordering function of a NR PDCP device among the
above-mentioned functions means a function of reordering PDCP PDUs
received from a lower layer in order based on PDCP Sequence Numbers
(SNs), and may include a function of transferring data to an upper
layer in the reordered order. Alternatively, the reordering
function of the NR PDCP device may include a function of directly
transferring data regardless of order, a function of reordering and
recording lost PDCP PDUs, a function of sending a status report for
lost PDCP PDUs to a transmitter, and a function of requesting
retransmission of lost PDCP PDUs.
[0116] Main functions of the NR RLC 1d-10 and 1d-35 may include
some of the following functions. [0117] Transfer of upper layer
PDUs [0118] In-sequence delivery of upper layer PDUs [0119]
Out-of-sequence delivery of upper layer PDUs [0120] Error
Correction through ARQ [0121] Concatenation, segmentation and
reassembly of RLC SDUs [0122] Re-segmentation of RLC data PDUs
[0123] Reordering of RLC data PDUs [0124] Duplicate detection
[0125] Protocol error detection [0126] RLC SDU discard [0127] RLC
re-establishment
[0128] The in-sequence delivery function of a NR RLC device among
the above-mentioned functions means a function of transferring RLC
SDUs received from a lower layer in order to an upper layer, and
may include a function of reassembling, when a RLC SDU is segmented
into several RLC SDUs and received, the RLC SDUs and transferring a
result of the reassembling, a function of reordering received RLC
PDUs based on RLC SNs or PDCP SNs, a function of reordering and
recording lost RLC PDUs, a function of sending a status report for
lost RLC PDUs to a transmitter, a function of requesting
retransmission of lost RLC PDUs, a function of transferring, when
there are lost RLC SDUs, RLC SDUs before the lost RLC SDUs in order
to the upper layer, a function of transferring, when a preset timer
has been expired although there are lost RLC SDUs, all RLC SDUs
received before the preset timer starts in order to the upper
layer, or a function of transferring, when the preset time has been
expired although there are lost RLC SDUs, all RLC SDUs received up
to now in order to the upper layer.
[0129] Also, RLC PDUs may be processed in order (in arrival order,
regardless of SNs or order of SNs) in which they are received, and
transferred to the PDCP device out of sequence delivery, and in the
case of segments, segments which have been stored in a buffer or
which are to be received later may be received and reconstructed as
a compete RLC PDU and then processed and transferred to the PDCP
device. A NR RLC layer as described above may include no
concatenation function, and the above-described function may be
performed in a NR MAC layer or replaced with a multiplexing
function of the NR MAC layer.
[0130] The out-of-sequence delivery function of the NR RLC device
as described above means a function of transferring RLC SDUs
received from a lower layer to the upper layer regardless of order,
and may include a function of reassembling, when a RLC SDU is
segmented into several RLC SDUs and received, the RLC SDUs and
transferring a result of the reassembling, and a function of
storing and ordering RLC SNs or PDCP SNs of the received RLC PDUs
and recording lost RLC PDUs.
[0131] The NR MAC 1d-15 and 1d-30 may be connected to several NR
RLC layers configured in the UE, and main functions of the NR MAC
1d-15 and 1d-30 may include some of the following functions. [0132]
Mapping between logical channels and transport channels [0133]
Multiplexing/demultiplexing of MAC SDUs [0134] Scheduling
information reporting [0135] Error correction through HARQ [0136]
Priority handling between logical channels of one UE [0137]
Priority handling between UEs by means of dynamic scheduling [0138]
MBMS service identification [0139] Transport format selection
[0140] Padding
[0141] NR PHY layers 1d-20 and 1d-25 may perform an operation of
performing channel coding and modulation on upper layer data to
generate an OFDM symbol and transferring the OFDM symbol through a
wireless channel, or performing demodulation and channel decoding
on an OFDM symbol received through the wireless channel and
transferring a result of the modulation and channel decoding to an
upper layer.
[0142] FIG. 1E is a view for describing a procedure in which a gNB
according to an embodiment of the disclosure releases a connection
of an UE for the UE to change from an RRC connected mode to an RRC
idle mode and a procedure in which the UE sets up a connection to
the gNB to change from the RRC idle mode to the RRC connected
mode.
[0143] Referring to FIG. 1E, when the UE transmitting and receiving
data receives or transmits no data for a certain reason or for a
preset time in an RRC connected mode, the gNB may transmit an
RRCConnectionRelease message to the UE to change the UE to the RRC
idle mode, in operation 1e-01. The UE (hereinafter, also referred
to as an idle mode UE) in which no connection is currently
established may perform, when data to be transmitted is generated,
an RRC connection establishment process together with the gNB. The
UE may establish reverse transmission synchronization with the gNB
through a random access process, and transmit an
RRCConnectionRequest message to the gNB, in operation 1e-05. The
RRCConnectionRequest message may include an identifier of the UE
and a cause establishmentCause for connection establishment.
[0144] The gNB may transmit an RRCConnectionSetup message to the UE
to enable the UE to establish an RRC connection, in operation
1e-10. The RRCConnectionSetup message may include RRC connection
configuration information, etc. Also, the RRCConnectionSetup
message may include at least one information of bearer
configuration information of the UE, configuration information of a
PHY layer, configuration information of a MAC layer, configuration
information of a RLC layer, configuration information of a PDCP
layer, or configuration information of a SDAP layer.
[0145] Also, the configuration information of the PDCP layer may
include an indicator indicating whether to trigger a PDCP status
report in an RLC UM (unacknowledged mode) mode or an RLC AM
(acknowledged mode) mode. The indicator may be an indicator
indicating the PDCP layer to generate, configure, and transmit a
PDCP status report when a PDCP re-establishment procedure is
performed. When the above-described indicator is included in an RRC
message, the UE may trigger, configure, and transmit a PDCP status
report for a bearer corresponding to the PDCP layer. According to
another method, when the above-described indicator is set, the UE
may trigger, configure, and transmit a PDCP status report at the
PDCP layer in the case that a conditional handover is indicated.
According to another method, when the above-described indicator is
set, the UE may trigger and configure a PDCP status report at the
PDCP layer and transmit the PDCP status report to a target gNB in
the case that a handover is indicated. According to another method,
when the above-described indicator is set, the UE may trigger and
configure a PDCP status report at the PDCP layer and transmit the
PDCP status report to a source gNB in the case that a handover is
indicated.
[0146] An RRC connection is also referred to as a Signaling Radio
Bearer (SRB), and may be used to transmit and receive an RRC
message which is a control message between a UE and a gNB. The UE
which has established an RRC connection may transmit an
RRCConnetionSetupComplete message to the gNB, in operation 1e-15.
The RRCConnetionSetupComplete message may include a SERVICE REQUEST
message as a control message through which the UE requests the MME
to set a bearer for a preset service.
[0147] The gNB may transmit the SERVICE REQUEST message included in
the RRCConnetionSetupComplete message to an Access and Mobility
Management Function (AMF), in operation 1e-20, and the AMF may
determine whether to provide the preset service requested by the
UE. When the AMF determines to provide the preset service requested
by the UE, the AMF may transmit an INITIAL CONTEXT SETUP REQUEST
message to the gNB, in operation 1e-25. The INITIAL CONTEXT SETUP
REQUEST message may include QoS information to be applied for a
Data Radio Bearer (DRB) setting, security-related information (for
example, a security key or a security algorithm) to be applied to
the DRB, etc.
[0148] The gNB may exchange a SecurityModeCommand message with a
SecurityModeComplete message to set security with the UE, in
operations 1e-30 and 1e-35. When a security setting is completed,
the gNB may transmit an RRCConnectionReconfiguration message to the
UE, in operation 1e-40.
[0149] Also, the RRCConnectionReconfiguration message may include
bearer configuration information, configuration information of the
PHY layer, configuration information of the MAC layer,
configuration information of the RLC layer, configuration
information of the PDCP layer, or configuration information of the
SDAP layer.
[0150] Also, the configuration information of the PDCP layer may
include an indicator indicating whether to trigger a PDCP status
report in the RLC UM mode or the RLC AM mode. The indicator may
indicate the PDCP layer to generate, configure, and transmit a PDCP
status report when a PDCP re-establishment procedure is performed.
When the indicator is included in an RRC message, the UE may
trigger, configure, and transmit a PDCP status report for a bearer
corresponding to the PDCP layer. According to another method, when
the indicator is set, the UE may trigger and configure a PDCP
status report at the PDCP layer and transmit the PDCP status
report, in the case that a conditional handover is indicated.
According to another method, when the indicator is set, the UE may
trigger and configure a PDCP status report at the PDCP layer and
transmit the PDCP status report to a target gNB, in the case that a
handover is indicated. According to another method, when the
indicator is set, the UE may trigger and configure a PDCP status
report at the PDCP layer and transmit the PDCP status report to a
source gNB, in the case that a conditional handover is
indicated.
[0151] The RRCConnectionReconfiguration message may include
configuration information of a DRB by which user data is to be
processed, and the UE may apply the configuration information of
the DRB to set up the DRB, and transmit an
RRCConnectionReconfigurationComplete message to the gNB, in
operation 1e-45.
[0152] The gNB may set up the DRB with the UE and then transmit an
initial context setup complete message to the AMF, in operation
1e-50. The AMF may receive the initial context setup complete
message, and perform a session management procedure with a User
Plane Function (UPF) to establish a PDU session, in operation
1e-60. When the above-described process is completed, the UE may
transmit/receive data to/from the gNB through the UPF, in
operations 1e-65 and 1e-70.
[0153] As described above, a general data transmission process may
be configured with three operations of RCC connection setup,
security setup, and DRB setup. Also, the gNB may transmit an
RRCConnectionReconfiguration message to newly set up, add, or
change a setting to the UE for a certain reason, in operation
1e-75.
[0154] According to an embodiment of the disclosure, the bearer may
have a meaning including a SRB and a DRB, wherein the SRB means a
Signaling Radio Bearer and the DRB means a Data Radio Bearer. The
SRB may be mainly used to transmit and receive RRC messages of the
RRC layer, and the DRB may be mainly used to transmit and receive
user layer data. Also, UM DRB means a DRB using the RLC layer
operating in an Unacknowledged Mode (UM), and AM DRB means a DRB
using the RLC layer operating in an Acknowledged Mode (AM).
[0155] FIG. 1F shows a handover procedure in a next-generation
mobile communication system according to an embodiment of the
disclosure.
[0156] Referring to FIG. 1F, a UE 1f-01 which is in the RRC
connected mode may send a cell measurement report to a source gNB
1f-02 periodically or when a preset event is satisfied, in
operation 1f-05. The source gNB 1f-02 may determine whether to
perform a handover of the UE 1f-01 to an adjacent cell based on the
cell measurement information. The handover may be a technique of
changing a source gNB providing a service to a UE being in a
connected mode to another gNB (or another cell in the same
gNB).
[0157] When the source gNB 1f-02 determines a handover, the source
gNB 1f-02 may send a handover (HO) request message to a new gNB,
that is, a target gNB 1f-03 that is to provide a service to the UE
1f-01, thereby requesting a handover, in operation 1f-10. When the
target gNB 1f-03 accepts the handover request, the target gNB 1f-03
may transmit a HO request Ack message to the source gNB 1f-02, in
operation 1f-15. When the source gNB 1f-02 receives the HO request
Ack message, the source gNB 1f-02 may transmit a HO command message
to the UE 1f-01, in operation 1f-20. The source gNB 1f-02 may
transfer the HO command message to the UE 1f-01 by using an RRC
Connection Reconfiguration message, in operation 1f-20. When the UE
1f-01 receives the HO command message, the UE 1f-01 may stop data
transmission/reception to/from the source gNB 1f-02, and start a
T304 timer, in operation 1f-25. The T304 timer may return the UE
1f-01 to its original setting and change the UE 1f-01 to an RRC
idle state, when the UE 1f-01 fails to perform a handover to the
target gNB 1f-03 within a preset time period. The source gNB 1f-02
may transfer a sequence number (SN) status about a
transmission/reception status of uplink or downlink data to the
target gNB 1f-03, and when there is downlink data, the source gNB
1f-02 may transfer the downlink data to the target gNB 1f-03, in
operations 1f-30 and 1f-35. The UE 1f-01 may attempt a random
access to a target cell indicated from the source gNB 1f-02, in
operation 1f-40. The random access may be aimed to notify the
target cell that the UE 1f-01 moves through a handover, while
synchronizing an uplink. For the random access, the UE 1f-01 may
transmit a preamble corresponding to a preamble ID received from
the source gNB 1f-02 or a randomly selected preamble ID to the
target cell. When a preset number of subframes elapse after the
preamble is transmitted, the UE 1f-01 may monitor whether a Random
Access Response (RAR) message is transmitted from the target cell.
A time period in which the UE 1f-01 monitors whether the RAR
message is transmitted is referred to as a RAR window. When a RAR
message is received within the time period of the monitoring in
operation 1f-45, the UE 1f-01 may transmit a HO complete message as
an RRC Reconfiguration Complete message to the target gNB 1f-03, in
operation 1f-55. When a random access response is successfully
received from the target gNB 1f-03, the UE 1f-01 may stop the T304
timer, in operation 1f-50.
[0158] To correct paths of bearers set to the source gNB 1f-02, the
target gNB 1f-03 may request a core network 1f-04 to correct paths
in operations 1f-60 and 1f-65, and notify the source gNB 1f-02 of
discarding UE context of the UE 1f-01, in operation 1f-70.
Accordingly, the UE 1f-01 may attempt to receive data with respect
to the target gNB 1f-03 from when the RAR window starts, and after
the RAR message is received, the UE 1f-01 may transmit the
RRCConnectionReconfigurationComplete message to the target gNB
1f-03 and start data transmission/reception to/from the target gNB
1f-30. Then, when the source gNB 1f-02 receives an end-marker
indicating final data from the core network 1f-04, the source gNB
1f-02 may determine that a path of downlink data for the UE 1f-01
has changed to the target gNB 1f-03, and perform forwarding of the
final data to the target gNB 1f-30. According to an embodiment of
the disclosure, the core network 1f-04 may include at least one of
a MME, a S-GW, or an ANTE, and further include at least one of a
UPF or a SMF.
[0159] In the above-described handover procedure, when the source
gNB 1f-02 transmits the HO command message (for example, an RRC
Reconfiguration message) to the UE 1f-01, at least one of
information about a target gNB to which the UE 1f-01 needs to
perform a handover, information about a random access transmission
resource for a cell, preamble information, bearer configuration
information, or cell information may be set in the HO command
message.
[0160] Also, the HO command message may include an indicator
defined to indicate what kind of handover the UE 1f-01 needs to
perform. For example, the source gNB 1f-02 may define indicators
for a plurality of handover methods, and set one of the defined
indicators such that the UE 1f-01 perform a handover method
corresponding to the set indicator. The plurality of handover
methods may include at least one method of a RACH-less handover
method, a make before break (MBB) handover method, an enhanced make
before break (eMBB) method, or a conditional handover method. Also,
the HO command message may include an indicator indicating whether
or not the UE 1f-01 generates a PDCP status report for each bearer
(UM DRB or AM DRB) or the PDCP layer and transmits the PDCP status
report to the source gNB 1f-02 or the target gNB 1f-03.
[0161] FIG. 1G shows a conditional handover procedure according to
an embodiment of the disclosure.
[0162] In FIG. 1G, a UE 1g-01 which is in the RRC connected mode
may send a cell measurement report to a source gNB 1g-02
periodically or when a preset event is satisfied, in operation
1g-05. The source gNB 1g-02 may determine whether to perform a
conditional handover of the UE 1g-01 to adjacent cells, based on
the cell measurement information.
[0163] The conditional handover may be a technique of changing a
source gNB providing a service to a UE being in a connected mode to
another gNB (or another cell in the same gNB). For conditional
handover a plurality of target gNB candidates and conditions for
determining a target gNB may be set for a UE to enable the UE to
select, as a target gNB, a target gNB candidate from among the
plurality of target gNB candidates according to the set conditions
and perform a handover. As the conditions for determining the
target gNB, various conditions, such as a greater frequency signal
intensity than a threshold value, a first synchronized signal
frequency, a determination according to a UE's implementation
without any condition, etc. may be set.
[0164] When the source gNB 1g-02 determines performing of a
conditional handover, the source gNB 1g-02 may send HO request
messages to a plurality of target gNB candidates including a
plurality of new gNBs that are to provide a service to the UE
1g-01, that is, a plurality of target gNBs Target gNB 1 1g-03 and
Target gNB 2 1g-04, thereby requesting a handover, in operation
1g-10. When the plurality of target gNBs 1g-03 and 1g-04 accept the
handover request, the plurality of target gNBs 1g-03 and 1g-04 may
transmit HO request Ack messages to the source gNB 1g-02, in
operation 1g-15. When the source gNB 1g-02 receives the HO request
Ack messages, the source gNB 1g-02 may transmit a HO command
message to the UE 1g-01, in operation 1g-20. The source gNB 1g-02
may transfer the HO command message to the UE 1g-01 by using an RRC
Connection Reconfiguration message, in operation 1g-20.
[0165] In the above-described handover procedure, when the source
gNB 1g-02 transmits the HO command message (for example, an RRC
Reconfiguration message) to the UE 1g-01, at least one of
information about the plurality of target gNBs 1g-03 and 1g-04 to
which the UE 1g-01 needs to perform a handover, information about a
random access transmission resource for a cell, preamble
information, bearer configuration information, or cell information
may be set in the HO command message.
[0166] Also, the HO command message may include an indicator
defined to indicate what kind of handover the UE 1g-01 needs to
perform. For example, the source gNB 1g-02 may define indicators
for a plurality of handover methods, and set one of the defined
indicators such that the UE 1g-01 performs a handover method
corresponding to the set indicator. The plurality of handover
methods may include at least one method of a RACH-less handover
method, a MBB handover method, an eMBB method, or a conditional
handover method. Also, the HO command message may include an
indicator indicating whether or not the UE 1g-01 generates a PDCP
status report for each bearer (UM DRB or AM DRB) or the PDCP layer
and transmits the PDCP status report to the source gNB 1g-02 or the
target gNB.
[0167] When the source gNB 1g-02 indicates a conditional handover,
the HO command message may include a condition for enabling the UE
1g-01 to select a target gNB from among the plurality of target
gNBs 1g-03 and 1g-04. As the condition for enabling the UE 1g-01 to
select the target gNB, various conditions, such as a greater
frequency signal intensity than a threshold value, a first
synchronized signal frequency, a determination according to
implementation of the UE 1g-01 without any condition, etc. may be
set.
[0168] When the UE 1g-01 receives the HO command message, the UE
1g-01 may start a T304 timer and perform a conditional handover
procedure. More specifically, the UE 1g-01 may start a cell
re-selection procedure or a cell search procedure for the plurality
of target gNBs 1g-03 and 1g-04 or a plurality of frequencies
according to the condition included in the HO command message or
the implementation of the UE 1g-01, in operation 1g-25.
[0169] Then, when the UE 1g-01 determines a target gNB (for
example, the target gNB 1g-03) or a cell that is suitable for the
condition or the implementation of the UE 1g-01, the UE 1g-01 may
attempt a random access to the determined target gNB 1g-03 or the
determined cell (also, referred to as a target cell, in operation
1g-40. The random access may be aimed to inform the target cell
that the UE 1g-01 moves through a handover, while synchronizing an
uplink. For the random access, the UE 1g-01 may transmit a preamble
corresponding to a preamble ID received from the source gNB 1g-02
or a randomly selected preamble ID to the target cell. When a
preset number of subframes elapse after the preamble is
transmitted, the UE 1g-01 may monitor whether a RAR message is
transmitted from the target cell. A time period in which the UE
1g-01 monitors whether the RAR message is transmitted is referred
to as a RAR window. When the RAR message is received within the
time period of the monitoring in operation 1g-45, the UE 1g-01 may
transmit a HO complete message as an
RRCConnectionReconfigurationComplete message to the target gNB
1g-03, in operation 1g-55. When a random access response is
successfully received from the target gNB 1g-03, the UE 1g-01 may
stop the T304 timer, in operation 1g-50.
[0170] To correct paths of bearers set to the source gNB 1g-02, the
target gNB 1g-03 may request route correction, and notify the
source gNB 1g-02 of discarding UE context of the UE 1g-01.
Accordingly, the UE 1g-01 may attempt to receive data with respect
to the target gNB 1g-03 from when the RAR window starts, and after
the RAR message is received, the UE 1g-01 may transmit the
RRCConnectionReconfigurationComplete message to the target gNB
1g-03 and start data transmission/reception to/from the target gNB
1g-30.
[0171] In the conditional handover method according to an
embodiment of the disclosure as described above with reference to
FIG. 1G, a time at which the UE 1g-01 releases a connection to the
source gNB 1g-02 may be determined by the UE 1g-01 based on a first
condition described below. The first condition is that when at
least one condition among a plurality of conditions described below
is satisfied, the UE 1g-01 may release a connection to the source
gNB 1g-02. [0172] When a UE performs a procedure of a random access
to a target gNB and receives a random access response from the
target gNB [0173] When a UE performs a procedure of a random access
to a target gNB, receives a random access response from the target
gNB, configures a handover complete message, and transmits the
handover complete message to the target gNB [0174] When a UE
completes a procedure of a random access to a target gNB and is
first assigned a PUCCH or PUSCH uplink transmission resource or
when a UE first transmits data in a PUCCH or PUSCH uplink
transmission resource [0175] When a gNB sets a separate timer
through an RRC message for a UE and the timer is expired [0176] The
timer may start at at least one time of a time at which the UE
receives a handover command message from a source gNB, a time at
which the UE starts a random access to the target gNB (a time at
which the UE transmits a preamble to the target gNB), a time at
which the UE receives a random access response from the target gNB,
a time at which the UE transmits a handover complete message to the
target gNB, or a time at which the UE first transmits data in a
PUCCH or PUSCH uplink transmission resource. [0177] When a UE
performs a procedure of a random access to a target gNB, receives a
random access response from the target gNB, configures a handover
complete message, and transmits the handover complete message to
the target gNB, and then a successful transfer of the handover
complete message is acknowledged by a MAC layer (HARQ ACK) or a RLC
layer (RLC ACK) [0178] When a UE performs a procedure of a random
access to a target gNB, receives a random access response from the
target gNB, configures a handover complete message, transmits the
handover complete message to the target gNB, and then is first
assigned or indicated a uplink transmission resource from the
target gNB.
[0179] The conditional handover method according to an embodiment
of the disclosure as described above with reference to FIG. 1G may
have two issues.
[0180] A first issue of the issues is that the source gNB 1g-02 is
not capable of accurately recognizing a time at which the UE 1g-01
releases a connection to the source gNB 1g-02, in the conditional
handover method. The reason is because, in a conditional handover,
the UE 1g-01 selects a gNB from among a plurality of target gNBs
according to a preset condition and itself releases a connection to
the source gNB 1g-02 according to the first condition described
above. Accordingly, the source gNB 1g-02 may transmit downlink data
to the UE 1g-01 even after the UE 1g-01 releases a connection to
the source gNB 1g-02. Therefore, massive downlink data loss may
occur.
[0181] A second issue of the issues is that, in a conditional
handover, the source gNB 1g-02 transmits a handover command message
including conditions and configuration information about a
plurality of target gNBs to the UE 1g-01 so that the source gNB
1g-02 is not capable of expecting a target gNB to which the UE
1g-01 will perform a handover.
[0182] In the handover procedure described above with reference to
FIG. 1F, because the source gNB 1f-02 transmits a handover command
message including information about the single target gNB 1f-03 to
the UE 1f-01, the source gNB 1f-02 may expect that the UE 1f-01
will perform a handover to the target gNB 1f-03. Accordingly,
referring to FIG. 1F, the source gNB 1g-02 may transmit a handover
command message to the UE 1g-01, and then immediately start
transmitting uplink or downlink data to the target gNB 1f-03
together with a transmission/reception status or a SN status of the
uplink or downlink data.
[0183] However, in the conditional handover shown in FIG. 1G,
although the UE 1g-01 completes a handover to the target gNB 1g-03
among the plurality of target gNBs 1g-03 and 1g-04, the source gNB
1g-02 may be not capable of recognizing the target gNB 1g-03 to
which the UE 1g-01 performs a handover until the target gNB 1g-03
indicates the source gNB 1g-02 of a successful handover of the UE
1g-01. Accordingly, the source gNB 1g-02 may start late performing
a procedure of transmitting uplink or downlink data to the target
gNB 1f-03 together with a transmission/reception status or a SN
status of the uplink or downlink data, resulting in a transmission
delay.
[0184] Hereinafter, a first embodiment of a conditional handover
operation for overcoming the first issue that may be occurred in a
conditional handover is proposed in detail.
[0185] In a handover procedure, when the UE 1g-01 receives a
handover command message and the handover command message indicates
a conditional handover procedure, the following operations may be
performed. [0186] The UE 1g-01 may complete a procedure for a
handover to a target gNB with respect to a UM bearer (or UM DRB) or
an AM bearer (or AM DRB) to prevent downlink data from being lost
in a conditional handover procedure, trigger, configure, and
generate a PDCP status report for the downlink data at a PDCP layer
of the UM bearer or the AM bearer, and transmit the PDCP status
report to the target gNB when transmitting uplink data (for
example, a handover complete message 1g-55 or uplink data) to the
target gNB.
[0187] When a handover command message is received, the PDCP layer
may trigger a PDCP re-establishment procedure, discard previously
generated data (for example, old PDCP PDU), newly apply header
compression, integrity protection, or a ciphering procedure, with a
new security key, to data (for example, PDCP SDU) not yet
transmitted among uplink data to generate data (for example, PDCP
PDU), and transmit the generated data to the target gNB after a
handover to the target gNB is completed.
[0188] When the handover command message includes a PDCP status
report indicator, the UE 1g-01 may trigger and configure a PDCP
status report for the corresponding bearer at the PDCP layer and
transmit the PDCP status report. According to another method, when
a PDCP status report indicator is set, the UE 1g-01 may trigger and
configure a PDCP status report at the PDCP layer and transmit the
PDCP status report, in the case that a conditional handover is
indicated. According to another method, when a PDCP status report
indicator is set, the UE 1g-01 may trigger and configure a PDCP
status report at the PDCP layer and transmit the PDCP status report
to the target gNB, in the case that a handover is indicated.
According to another method, when a PDCP status report indicator is
set, the UE 1g-01 may trigger and configure a PDCP status report at
the PDCP layer and transmit the PDCP status report to the source
gNB 1g-02, in the case that a handover is indicated. A time at
which the PDCP layer triggers a PDCP status report when a PDCP
status report indicator is set may be one of times included in the
first condition described above, when a connection to the source
gNB 1g-02 is released, or when a handover to the target gNB is
successfully performed. [0189] When the target gNB receives a PDCP
status report for downlink data with respect to the UM bearer or
the AM bearer from the UE 1g-01, the target gNB may retransmit data
for which a PDCP discard timer has not yet been expired with
respect to the UM bearer (or in consideration of a transmission
time) or data of which successive reception has not been confirmed,
to the UE 1g-01 through a downlink, based on the PDCP status
report, thereby reducing data loss.
[0190] Also, for example, the target gNB may discard data (for
example, PDCP PDU or PDCP SDU) of which successful transfer has
been confirmed from the PDCP status report with respect to the AM
bearer, and selectively retransmit data (for example, PDCP PDU or
PDCP SDU) of which successful transfer has not been confirmed,
thereby reducing data loss. [0191] Also, the UE 1g-01 may not
perform data retransmission until receiving a PDCP status report
for uplink data from the target gNB after completing a conditional
handover, to prevent unnecessary waste of transmission resources,
that is, to prevent waste of transmission resources that are caused
by accumulative retransmission in a PDCP re-establishment procedure
of the UE 1g-01. Although the UE 1g-01 does not perform data
retransmission until receiving a PDCP status report, the UE 1g-01
may newly apply header compression, integrity protection, or a
ciphering procedure to data not yet transmitted, with a new
security key, to generate data (for example, PDCP PDU) and transmit
the data to the target gNB. Also, after the UE 1g-01 receives a
PDCP status report for uplink data from the target gNB, the UE
1g-01 may newly apply header compression, integrity protection, or
a ciphering procedure to data (for example, PDCP SDU) of which
successful transfer has not been confirmed from the PDCP status
report, with a new security key, to generate data (for example,
PDCP PDU), and transmit the data to the target gNB after a handover
to the target gNB is completed. According to another method, the
target gNB may not assign uplink transmission resource to the UE
1g-01 until a PDCP status report for uplink data is configured and
transmitted.
[0192] Hereinafter, a second embodiment of a conditional handover
operation for overcoming the first issue that may be generated in a
conditional handover is proposed in detail.
[0193] The first issue of the conditional handover method proposed
in an embodiment of the disclosure is that the source gNB 1g-02 is
not capable of accurately recognizing a time at which the UE 1g-01
releases a connection to the source gNB 1g-02. The reason is
because, in a conditional handover, the UE 1g-01 selects a target
gNB from among the plurality of target gNBs 1g-03 and 1g-04
according to a preset condition and itself releases a connection to
the source gNB 1g-02 according to the first condition described
above. Accordingly, according to the second embodiment of the
disclosure, when the UE 1g-01 releases a connection to the source
gNB 1g-02 according to the first condition described above, the UE
1g-01 may indicate the source gNB 1g-02 of a connection release.
Detailed operations of the second embodiment may be as follows.
[0194] When the UE 1g-01 receives a handover command message in a
handover procedure and the handover command message indicates a
conditional handover procedure, the following operations may be
performed. [0195] When the UE 1g-01 releases a connection to the
source gNB 1g-02 according to the first condition, the UE 1g-01 may
transmit an indication indicating that a connection to the source
gNB 1g-02 has been released to the source gNB 1g-02. [0196] The
indication indicating that the connection to the source gNB 1g-02
has been released may be transmitted when the UE 1g-01 transmits a
new RRC message to the source gNB 1g-02 or defines a new indicator
in an existing RRC message and transmits the resultant RRC message
to the source gNB 1g-02 or when the UE 1g-01 defines a new MAC CE,
a new RLC control PDU, or a new PDCP control PDU and transmits the
new MAC CE, the new RLC control PDU, or the new PDCP control PDU to
the source gNB 1g-02.
[0197] In the case of the new MAC CE, when the UE 1g-01 releases a
connection to the source gNB 1g-02, the UE 1g-01 may configure the
new MAC CE and transmit the new MAC CE to the source gNB 1g-02 to
indicate a connection release from the source gNB 1g-02 and confirm
whether HARQ ACK/NACK of MAC PDU included in the MAC CE is
successfully transferred. When the UE 1g-01 defines a new RLC
control PDU or a new PDCP control PDU and indicates a connection
release from the source gNB 1g-02 by using the new RLC control PDU
or the new PDCP control PDU, the UE 1g-1 may transmit a RLC control
PDU or a PDCP control PDU newly defined for each bearer. The newly
defined RRC message, the newly defined indicator of the RRC
message, the newly defined MAC CE, the newly defined RLC control
PDU, or the newly defined PDCP control PDU may include an indicator
indicating a target gNB to which the UE 1g-01 performs, attempts,
or completes a handover among the plurality of target gNB
candidates in the conditional handover method. The indicator
indicating the target gNB may be at least one of an identifier of
the target gNB, a bitmap of the target gNB, or an indicator
indicating a certain target of the plurality of target gNB
candidates. [0198] According to another method, when the UE 1g-01
releases a connection to the source gNB 1g-02 according to the
first condition described above, the UE 1g-01 may transmit a PDCP
status report to the source gNB 1g-02 for each bearer (UM bearer or
AM bearer), wherein a 1-bit indicator indicating a connection
release may be defined and used in the PDCP status report. When the
source gNB 1g-02 receives a PDCP status report for each bearer from
the UE 1g-01 after indicating a conditional handover, the source
gNB 1g-02 may consider that the PDCP status report itself indicates
a connection release of the UE 1g-01 from the source gNB 1g-02 and
has been finally transmitted from the UE 1g-01. For example, when
the source gNB 1g-02 receives a PDCP status report for all DRBs
from the UE 1g-01, receives a PDCP status report for all AM DRBs
from the UE 1g-01, or receives a PDCP status report from at least
one bearer after indicating the UE 1g-01 to perform a conditional
handover, the source gNB 1g-02 may consider that the UE 1g-01 has
released a connection to the source gNB 1g-02. [0199] Therefore,
according to the second embodiment described above, when the source
gNB 1g-02 confirms that the UE 1g-01 has released a connection to
the source gNB 1g-02, the source gNB 1g-02 may be prevented from
transmitting unnecessary downlink data to the UE 1g-01 to avoid
data loss, may prepare downlink/uplink data which the UE 1g-01 is
to transfer with a target gNB to which the UE 1g-01 has completed a
handover or a SN status of the downlink/uplink data, and may start
transmitting the SN status or the downlink/uplink data. [0200] The
newly defined RRC message, the newly defined indicator of the RRC
message, the newly defined MAC CE, the newly defined RLC control
PDU, or the newly defined PDCP control PDU may include an indicator
indicating a target gNB to which the UE 1g-01 performs, attempts,
or completes a handover among the plurality of target gNB
candidates in the conditional handover method when a connection
release from the source gNB 1g-02 is indicated. The indicator
indicating the target gNB may be at least one of an identifier of
the target gNB, a bitmap of the target gNB, or an indicator
indicating a certain target of the plurality of target gNB
candidates. Accordingly, when the source gNB 1g-02 receives an
indicator indicating a target gNB from the UE 1g-01, the source gNB
1g-02 may immediately prepare downlink/uplink data that is to be
transferred to the target gNB or a SN status of the downlink/uplink
data, and start transmitting the SN status or the downlink/uplink
data to the target gNB, thereby reducing a transmission delay.
Therefore, according to the second embodiment, the second issue of
the conditional handover method may be overcome.
[0201] Hereinafter, a third embodiment of a conditional handover
operation for overcoming the second issue that may be generated in
a conditional handover is proposed in detail.
[0202] The second issue is that, in a conditional handover, the
source gNB 1g-02 transmits a handover command message including
conditions and configuration information about a plurality of
target gNBs to the UE 1g-01 so that the source gNB 1g-02 is not
capable of expecting a target gNB to which the UE 1g-01 will
perform a handover. However, in the conditional handover, although
the UE 1g-01 completes a handover to a target gNB among the
plurality of target gNB candidates, the source gNB 1g-02 may be not
capable of recognizing the target gNB to which the UE 1g-01
performs a handover until the target gNB indicates the source gNB
1g-02 of a successful handover of the UE 1g-01. Accordingly, the
source gNB 1g-02 may start late a procedure of transferring uplink
or downlink data to the target gNB together with a
transmission/reception status or a SN status of the uplink or
downlink data, resulting in a transmission delay.
[0203] The third embodiment of the conditional handover operation
for overcoming the second issue that may be generated in the
conditional handover according to an embodiment of the disclosure
is as follows. [0204] In FIG. 1G, when the UE 1g-01 indicates a
connection release from the source gNB 1g-02 as described above in
the second embodiment as soon as the source gNB 1g-02 transmits a
handover command message to the UE 1g-01 in operation 1g-20 or
after the source gNB 1g-02 transmits a handover command message to
the UE 1g-01, the source gNB 1g-02 may start transferring uplink or
downlink data and a SN (PDCP SN) status report for the uplink or
downlink data in duplicate to the plurality of target gNB
candidates. That is, in the third embodiment, the source gNB 1g-02
may transfer uplink or downlink data and a SN status in duplicate
to the plurality of target gNB s. [0205] In the third embodiment,
when a target gNB candidate of the plurality of target gNB
candidates confirms that the UE 1g-01 has performed a handover to
itself, the target gNB candidate may check lost data and retransmit
the lost data without any transmission delay by using the SN status
and uplink and downlink data transferred from the source gNB 1g-02
to reduce data loss, and perform data transmission/reception
to/from the UE 1g-01. [0206] Also, the remaining target gNB
candidates to which the UE 1g-01 has never performed a handover
among the plurality of target gNB candidates may discard the SN
status and uplink or downlink data transferred from the source gNB
1g-02. For example, after the plurality of target gNB candidates
transmit a message indicating allowance of a handover to the source
gNB 1g-02 or when the plurality of target gNB candidates receive a
SN status and uplink or downlink data from the source gNB 1g-02,
the target gNB candidates may start a timer. When the target gNB
candidates determine that the UE 1g-01 attempts no access for a
handover to the target gNB candidates until the timer is expired,
the target gNB candidates may determine that the UE 1g-01 has
performed a procedure of a handover to another target gNB
candidate, and discard the SN status and uplink or downlink data
transferred from the source gNB 1g-02. According to another method,
a target gNB to which the UE 1g-01 has completed a handover may
indicate the source gNB 1g-02 that the UE 1g-01 has completed a
handover, and the source gNB 1g-02 may indicate the remaining
target gNB candidates to which the UE 1g-01 has not performed a
handover to discard the SN status and uplink or downlink data
transferred from the source gNB 1g-02.
[0207] Hereinafter, a fourth embodiment of a conditional handover
operation for overcoming the second issue that may be generated in
the conditional handover according to an embodiment of the
disclosure is as follows. [0208] In FIG. 1G, the source gNB 1g-02
may indicate that the UE 1g-01 releases a connection to the source
gNB 1g-02 as in the second embodiment described above as soon as
the source gNB 1g-02 transmits a handover command message to the UE
1g-01 in operation 1g-20 or after the source gNB 1g-02 transmits a
handover command message to the UE 1g-01. And the UE 1g-01 may
indicate the source gNB 1g-02 of a target gNB to which the UE 1G-01
performs or completes a handover as in the second embodiment
described above. Then the source gNB 1g-02 may start transferring
uplink or downlink data and a SN (PDCP SN) status report about the
uplink or downlink data to the target gNB indicated in the second
embodiment or the target gNB to which the UE 1g-01 performs the
handover. [0209] In the fourth embodiment, the source gNB 1g-02 may
transmit the uplink or downlink data and the SN status to the
target gNB, based on the indication about the connection release of
the UE 1g-01 from the source gNB 1g-02, received from the UE 1g-01
and the indication about the target gNB to which the UE 1g-01
performs the handover, by using the second embodiment described
above. Accordingly, the target gNB may check lost data and
retransmit the lost data without any transmission delay by using
the SN status and uplink and downlink data to reduce data loss, and
perform data transmission/reception to/from the UE 1g-01.
[0210] The UE 1g-01 may perform at least one of the first
embodiment, the second embodiment, the third embodiment, or the
fourth embodiment of the efficient conditional handover methods
proposed in the disclosure, when performing a conditional handover.
For example, the UE 1g-01 may perform all of the first to fourth
embodiments or some of the above-described embodiments
together.
[0211] FIG. 1H shows operations of a conditional handover procedure
of a UE according to an embodiment of the disclosure.
[0212] Referring to FIG. 1H, a UE 1h-01 may receive a handover
command message from a source gNB, in operation 1h-05. The UE 1h-01
may check an indicator indicating a conditional handover from the
handover command message, and determine whether a conditional
handover is indicated, in operation 1h-10. When the handover
command message indicates a conditional handover method, the UE
1h-01 may perform a conditional handover method according to an
embodiment of the disclosure, in operation 1h-15. For example, the
UE 1h-01 may perform at least one of the first embodiment, the
second embodiment, the third embodiment, or the fourth embodiment.
The UE 1h-01 may perform all of the first to fourth embodiments or
some of the above-described embodiments together.
[0213] FIG. 1I shows a structure of a UE or a wireless node
according to an embodiment of the disclosure.
[0214] Referring to FIG. 1I, the UE may include a Radio Frequency
(RF) processor 1i-10, a baseband processor 1i-20, a storage device
1i-30, and a controller 1i-40. However, an internal structure of
the UE is not limited to the embodiment shown in FIG. 1I, and the
UE may include more or less components than those shown in FIG. 1I.
The RF processor 1i-10 may perform a function for transmitting and
receiving signals through a wireless channel, such as band
conversion, amplification, etc. of signals. That is, the RF
processor 1i-10 may up-convert a baseband signal provided from the
baseband processor 1i-20 into a RF band signal, transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through the antenna into a baseband signal. For example,
the RF processor 1i-10 may include a transmission filter, a
reception filter, an amplifier, a mixer, an oscillator, a
digital-to-analog converter (DAC), an analog-to-digital converter
(ADC), etc. In FIG. 1I, a single antenna is shown, however, the UE
may include a plurality of antennas. Also, the RF processor 1i-10
may include a plurality of RF chains. Furthermore, the RF processor
1i-10 may perform beamforming. For beamforming, the RF processor
1i-10 may adjust phases and magnitudes of signals that are
transmitted/received through the plurality of antennas or antenna
elements. Also, the RF processor 1i-10 may perform MIMO, and when
MIMO is performed, the RF processor 1i-10 may receive several
layers. The RF processor 1i-10 may perform sweeping of a received
beam by appropriately setting the plurality of antennas or antenna
elements according to a control of the controller 1i-40, or may
adjust a direction and width of a received beam such that the
received beam is coordinated with a beam that is to be
transmitted.
[0215] The baseband processor 1i-20 may perform a function of
conversion between baseband signals and bit streams according to a
physical layer specification of a system. For example, upon data
transmission, the baseband processor 1i-20 may encipher and
modulate a transmission bit stream to generate complex symbols.
Also, upon data reception, the baseband processor 1i-20 may
demodulate and decipher a baseband signal provided from the RF
processor 1i-10 to restore a reception bit stream. For example,
according to an OFDM method, upon data transmission, the baseband
processor 1i-20 may encipher and modulate a transmission bit stream
to generate complex symbols, map the complex symbols to
subcarriers, and then construct OFDM symbols through inverse fast
Fourier transform (IFFT) and cyclic prefix (CP) insertion. Also,
upon data reception, the baseband processor 1i-20 may segment a
baseband signal provided from the RF processor 1i-10 in units of
OFDM symbols, restore signals mapped to subcarriers through fast
Fourier transform (FFT), and then restore a reception bit stream
through demodulation and deciphering.
[0216] The baseband processor 1i-20 and the RF processor 1i-10 may
transmit and receive signals as described above. Accordingly, the
baseband processor 1i-20 and the RF processor 1i-10 are also
referred to as a transmitter, a receiver, a transceiver, or a
communicator. Furthermore, at least one of the baseband processor
1i-20 or the RF processor 1i-10 may include a plurality of
communication modules to support a plurality of different radio
access technologies. Also, at least one of the baseband processor
1i-20 or the RF processor 1i-10 may include different communication
modules to process signals of different frequency bands. For
example, the different radio access technologies may include a LET
network, a NR network, etc. Also, the different frequency bands may
include a super high frequency (SHF) (e.g., 2.1 GHz and 1 GHz) band
and a millimeter wave (e.g., 60 GHz) band. The UE may
transmit/receive a signal to/from a gNB by using the baseband
processor 1i-20 and the RF processor 1i-10, wherein the signal may
include control information and data.
[0217] The storage device 1i-30 may store data, such as basic
programs, application programs, and configuration information, for
operations of the UE. The storage device 1i-30 may provide the
stored data according to a request from the controller 1i-40. The
storage device 1i-30 may be configured with a storage medium, such
as read only memory (ROM), random access memory (RAM), a hard disc,
compact disc ROM (CD-ROM), digital versatile disc (DVD), and the
like, or a combination of such a storage media. Also, the storage
device 1i-30 may be configured with a plurality of memories.
[0218] The controller 1i-40 may control overall operations of the
UE. For example, the controller 1i-40 may transmit and receive
signals through the baseband processor 1i-20 and the RF processor
1i-10. Also, the controller 1i-40 may write data in the storage
device 1i-30 or read data from the storage device 1i-30. To write
or read data, the controller 1i-40 may include at least one
processor. For example, the controller 1i-40 may include a
communication processor CP for performing control for
communication, and an application processor AP for controlling an
upper layer of an application program, etc. Also, the controller
1i-40 may include multiple connection processor 1i-42 for
processing multiple connections. Also, the controller 1i-40 may
control the UE to perform a method for performing the handover
procedure described above. Also, at least one component of the UE
may be implemented as a single chip.
[0219] FIG. 1J shows a block configuration of a
Transmission/Reception Point (TRP) or a wireless node in a wireless
communication system according to an embodiment of the
disclosure.
[0220] Referring to FIG. 1J, a gNB (also, referred to as a TRP or a
wireless node) may include a RF processor 1j-10, a baseband
processor 1j-20, a backhaul communicator 1j-30, a storage device
1j-40, and a controller 1j-50. However, a configuration of the gNB
is not limited to the embodiment shown in FIG. 1J, and the gNB may
include more or less components than those shown in FIG. 1J.
[0221] The RF processor 1j-10 may perform a function for
transmitting and receiving signals through a wireless channel, such
as band conversion, amplification, etc. of signals. That is, the RF
processor 1j-10 may up-convert a baseband signal provided from the
baseband processor 1j-20 into a RF band signal, transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through the antenna into a baseband signal. For example,
the RF processor 1j-10 may include a transmission filter, a
reception filter, an amplifier, a mixer, an oscillator, a DAC, an
ADC, etc. In FIG. 1J, a single antenna is shown, however, the gNB
may include a plurality of antennas. Also, the RF processor 1j-10
may include a plurality of RF chains. Furthermore, the RF processor
1j-10 may perform beamforming. For beamforming, the RF processor
1j-10 may adjust phases and magnitudes of signals that are
transmitted/received through the plurality of antennas or antenna
elements. The RF processor 1j-10 may perform a downlink MIMO
operation by transmitting one or more layers.
[0222] The baseband processor 1j-20 may perform a function of
conversion between baseband signals and bit streams according to a
physical layer specification of first radio access technology. For
example, upon data transmission, the baseband processor 1j-20 may
encipher and modulate a transmission bit stream to generate complex
symbols. Also, upon data reception, the baseband processor 1j-20
may demodulate and decipher a baseband signal provided from the RF
processor 1j-10 to restore a reception bit stream. For example,
according to the OFDM method, upon data transmission, the baseband
processor 1j-20 may encipher and modulate a transmission bit stream
to generate complex symbols, map the complex symbols to
subcarriers, and then construct OFDM symbols through IFFT and CP
insertion. Also, upon data reception, the baseband processor 1j-20
may segment a baseband signal provided from the RF processor 1j-10
in units of OFDM symbols, restore signals mapped to subcarriers
through FFT, and then restore a reception bit stream through
demodulation and deciphering. The baseband processor 1j-20 and the
RF processor 1j-10 may transmit and receive signals as described
above. Accordingly, the baseband processor 1j-20 and the RF
processor 1j-10 are also referred to as a transmitter, a receiver,
a transceiver, a communicator, or a wireless communicator. The gNB
may transmit/receive a signal to/from the UE by using the baseband
processor 1j-20 and the RF processor 1j-10, wherein the signal may
include control information and data.
[0223] The communicator 1j-30 may provide an interface for
communicating with other nodes in a network.
[0224] The storage device 1j-40 may store data, such as basic
programs, application programs, and configuration information, for
operations of the gNB. Particularly, the storage device 1j-40 may
store information about a bearer assigned to a UE connected to the
gNB, a measurement result reported from the connected UE, etc.
Also, the storage device 1j-40 may store information that is used
as a determination criterion about whether to provide multiple
connections to the UE or whether to release multiple connections to
the UE. Also, the storage device 1j-40 may provide the stored data
according to a request from the controller 1j-50. The storage
device 1j-40 may be configured with a storage medium, such as ROM,
RAM, a hard disc, CD-ROM, DVD, and the like, or a combination of
such a storage media. Also, the storage device 1j-40 may be
configured with a plurality of memories.
[0225] The controller 1j-50 may control overall operations of the
gNB. For example, the controller 1j-50 may transmit and receive
signals through the baseband processor 1j-20 and the RF processor
1j-10 or through the backhaul communicator 1j-30. Also, the
controller 1j-50 may write data in the storage device 1j-40 or read
data from the storage device 1j-40. To write or read data, the
controller 1i-50 may include at least one processor. Also, the
controller 1j-50 may include multiple connection processor 1j-52
for processing multiple connections. For example, the controller
1i-50 may control the gNB such that the UE may perform a method for
performing an RRC connection resume procedure as described above.
Also, at least one component of the gNB may be implemented as a
single chip.
[0226] Hereinafter, according to the disclosure, an indicator may
be proposed to set an in-order delivery function for reception
operations of a reception RLC layer of a next-generation mobile
communication system with an RRC message, and when the in-order
delivery function is set in the RLC layer with the indicator,
detailed reception window operations of the RLC layer are proposed
for the RLC UM mode or the RLC AM mode. According to an embodiment
of the disclosure, data may be transferred in order to the PDCP
layer. Also, data loss that may be generated in the PDCP layer may
be prevented, and also, data processing that may be generated upon
a handover may be simplified.
[0227] When a UE and a gNB transmit and receive data in a
next-generation mobile communication system, a reception RLC layer
may always perform an out-of-order delivery function. The
out-of-order delivery function means a function of reassembling
data received by the reception RLC layer in arrival order, without
ordering the data in order of RLC SNs, and transferring a result of
the reassembling to an upper layer. The out-of-order delivery
function may be effective in view of transmission delay, but may
cause data loss and increase complexity of handover processing
because the PDCP layer drives a timer and moves a window when the
timer is expired.
[0228] Hereinafter, a method and apparatus for processing
communication data will be described with reference to FIGS. 2A to
2M.
[0229] FIG. 2A shows a structure of an LTE system to which an
embodiment of the disclosure may be applied.
[0230] Referring to FIG. 2A, a radio access network of an LTE
system may be configured with next-generation Evolved Node B (ENBs)
(hereinafter, also referred to as Nodes B or base stations), 2a-05,
2a-10, 2a-15, and 2a-20, a MME 2a-25, and a S-GW 2a-30. A UE 2a-35
may be connected to an external network through the ENBs 2a-05 to
2a-20 and the S-GW 2a-30.
[0231] In FIG. 2A, the ENBs 2a-05 to 2a-20 may correspond to
existing nodes B of a UMTS. The ENBs 2a-05 to 2a-20 may be
connected to the UE 2a-35 through a wireless channel, and perform
more complicated functions than the existing nodes B. In the LTE
system, because all user traffics including a real-time service
such as VoIP are serviced through a shared channel, a device for
performing scheduling by collecting status information of UEs, such
as buffer statuses of UEs, available transmission power states of
UEs, channel states of UEs, etc., is needed. The ENBs 2a-05 to
2a-20 may function as such a device. An ENB may generally control a
plurality of cells. For example, to implement a transmission speed
of 100 Mbps, the LTE system uses, as radio access technology, OFDM,
for example, in a bandwidth of 20 MHz. Also, AMC of determining a
modulation scheme and a channel coding rate according to a channel
state of a UE may be applied. The S-GW 2a-30, which is a device for
providing data bearers, may generate or remove data bearers
according to a control of the MME 2a-25. The MME 2a-25 may be in
charge of various control functions, as well as a mobility
management function for UEs, and may be connected to a plurality of
ENB s.
[0232] FIG. 2B shows a radio protocol architecture of an LTE system
to which an embodiment of the disclosure may be applied.
[0233] Referring to FIG. 2B, radio protocols of the LTE system may
include PDCPs 2b-05 and 2b-40, RLC 2b-10 and 2b-35, and MAC 2b-15
and 2b-30 of a UE and an ENB. The PDCPs 2b-05 and 2b-40 may be in
charge of operations of IP header compression/restoration. Main
functions of the PDCPs 2b-05 and 2b-40 may be summarized as
follows. [0234] Header compression and decompression: ROHC only
[0235] Transfer of user data [0236] In-sequence delivery of upper
layer PDUs at PDCP re-establishment procedure for RLC AM [0237] For
split bearers in DC (only support for RLC AM): PDCP PDU routing for
transmission and PDCP PDU reordering for reception [0238] Duplicate
detection of lower layer SDUs at PDCP re-establishment procedure
for RLC AM [0239] Retransmission of PDCP SDUs at handover and, for
split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure,
for RLC AM [0240] Ciphering and deciphering [0241] Timer-based SDU
discard in uplink
[0242] The RLC 2b-10 and 2b-35 may reconstruct a PDCP PDU to an
appropriate size to perform an ARQ operation, etc. Main functions
of the RLC 2b-10 and 2b-35 may be summarized as follows. [0243]
Transfer of upper layer PDUs [0244] Error Correction through ARQ
(only for AM data transfer) [0245] Concatenation, segmentation and
reassembly of RLC SDUs (only for UM and AM data transfer) [0246]
Re-segmentation of RLC data PDUs (only for AM data transfer) [0247]
Reordering of RLC data PDUs (only for UM and AM data transfer)
[0248] Duplicate detection (only for UM and AM data transfer)
[0249] Protocol error detection (only for AM data transfer) [0250]
RLC SDU discard (only for UM and AM data transfer) [0251] RLC
re-establishment
[0252] The MAC 2b-15 and 2b-30 may be connected to several RLC
layers configured in the UE, and perform an operation of
multiplexing RLC PDUs into a MAC PDU and demultiplexing RLC PDUs
from a MAC PDU. Main functions of the MAC 2b-15 and 2b-30 may be
summarized as follows. [0253] Mapping between logical channels and
transport channels [0254] Multiplexing/demultiplexing of MAC SDUs
belonging to one or different logical channels into/from transport
blocks (TB) delivered to/from the physical layer on transport
channels [0255] Scheduling information reporting [0256] Error
correction through HARQ [0257] Priority handling between logical
channels of one UE [0258] Priority handling between UEs by means of
dynamic scheduling [0259] MBMS service identification [0260]
Transport format selection [0261] Padding
[0262] Physical layers (PHY) 2b-20 and 2b-25 may perform an
operation of performing channel coding and modulation on upper
layer data to generate an OFDM symbol and transmitting the OFDM
symbol through a wireless channel, or demodulating an OFDM symbol
received through the wireless channel, performing channel decoding
on the OFDM symbol, and transferring the channel-decoded OFDM
symbol to an upper layer.
[0263] FIG. 2C shows a structure of a next-generation mobile
communication system to which an embodiment of the disclosure may
be applied.
[0264] Referring to FIG. 2C, a radio access network of a
next-generation mobile communication system (hereinafter, also
referred to as NR or 5G) may be configured with a next-generation
NR gNB (also, referred to as a NR base station) 2c-10 and a NR CR
2c-05. A NR UE (also, referred to as a UE) 2c-15 may be connected
to an external network through the NR gNB 2c-10 and the NR CN
2c-05.
[0265] In FIG. 2C, the NR gNB 2c-10 may correspond to an eNB of an
existing LTE system. The NR gNB 2c-10 may be connected to the NR UE
2c-15 through a wireless channel, and provide a more excellent
service than an existing node B. In a next-generation mobile
communication system, because all user traffics are serviced
through a shared channel, a device for performing scheduling by
collecting status information of UEs, such as buffer statuses of
UEs, available transmission power states of UEs, channel states of
UEs, etc., is needed. The NR gNB 2c-10 may function as such a
device. A NR gNB may generally control a plurality of cells. To
implement ultra high-speed data transmission compared to existing
LTE, OFDM as radio access technology may be combined with
beam-forming technology, while providing an existing maximum
bandwidth or more.
[0266] Also, AMC of determining a modulation scheme and a channel
coding rate according to a channel state of a UE may be applied.
The NR CN 2c-05 may perform functions, such as mobility support,
bearer setup, Quality of Service (QoS) setup, etc. The NR CN 2c-05
may be in charge of various control functions, as well as a
mobility management function for UEs, and may be connected to a
plurality of NR gNBs. Also, the next-generation mobile
communication system may interwork with an existing LTE system, and
the NR CN 2c-05 may be connected to the MME 2c-25 through a network
interface. The MME 1c-25 may be connected to an eNB 2c-30 which is
an existing base station.
[0267] FIG. 2D shows a radio protocol architecture of a
next-generation mobile communication system to which an embodiment
of the disclosure may be applied.
[0268] Referring to FIG. 2D, radio protocols of the next-generation
mobile communication system may include NR SDAPs 2d-01 and 2d-45,
NR PDCPs 2d-05 and 2d-40, NR RLC 2d-10 and 2d-35, and NR MAC 2d-15
and 2d-30 of an UE and a NR gNB.
[0269] Main functions of the NR SDAPs 2d-01 and 2d-45 may include
some of the following functions. [0270] Transfer of user plane data
[0271] Mapping between a QoS flow and a DRB for both DL and UL
[0272] Marking QoS flow ID in both DL and UL packets [0273]
Reflective QoS flow to DRB mapping for the UL SDAP PDUs
[0274] In regard of a SDAP layer as described above, the UE may
receive, as an RRC message, a setting about whether to use a header
of the SDAP layer or whether to use a function of the SDAP layer
for each PDCP layer, for each bearer, or for each logical channel.
When a SDAP header is set, the SDAP header capable of indicating
the UE to update or reset mapping information about a QoS flow and
a data bearer of a uplink and a downlink with a 1-bit indicator NAS
reflective QoS for a NAS reflective QoS setting and a 1-bit
indicator AS reflective QoS for an AS reflective QoS setting of the
SDAP header may include QoS flow ID information representing QoS.
QoS information may be used as data processing priority, scheduling
information, etc. for supporting a stable service.
[0275] Main functions of the NR PDCPs 2d-05 and 2d-40 may include
some of the following functions. [0276] Header compression and
decompression: ROHC only [0277] Transfer of user data [0278]
In-sequence delivery of upper layer PDUs [0279] Out-of-sequence
delivery of upper layer PDUs [0280] PDCP PDU reordering for
reception [0281] Duplicate detection of lower layer SDUs [0282]
Retransmission of PDCP SDUs [0283] Ciphering and deciphering [0284]
Timer-based SDU discard in uplink
[0285] The reordering function of a NR PDCP device among the
above-mentioned functions means a function of reordering PDCP PDUs
received from a lower layer in order based on PDCP SNs, and may
include a function of transferring data to an upper layer in the
reordered order. Alternatively, the reordering function of the NR
PDCP device may include a function of directly transferring data
regardless of order, a function of recording lost PDCP PDUs by
reordering, a function of sending a status report for lost PDCP
PDUs to a transmitter, and a function of requesting retransmission
of lost PDCP PDUs.
[0286] Main functions of the NR RLC 2d-10 and 2d-35 may include
some of the following functions. [0287] Transfer of upper layer
PDUs [0288] In-sequence delivery of upper layer PDUs [0289]
Out-of-sequence delivery of upper layer PDUs [0290] Error
Correction through ARQ [0291] Concatenation, segmentation and
reassembly of RLC SDUs [0292] Re-segmentation of RLC data PDUs
[0293] Reordering of RLC data PDUs [0294] Duplicate detection
[0295] Protocol error detection [0296] RLC SDU discard [0297] RLC
re-establishment
[0298] The in-sequence delivery function of a NR RLC device among
the above-mentioned functions means a function of transferring RLC
SDUs received from a lower layer in order to an upper layer, and
may include a function of reassembling, when a RLC SDU is segmented
into several RLC SDUs and received, the RLC SDUs and transferring a
result of the reassembling, a function of reordering received RLC
PDUs based on RLC SNs or PDCP SNs, a function of reordering and
recording lost RLC PDUs, a function of sending a status report for
lost RLC PDUs to a transmitter, a function of requesting
retransmission of lost RLC PDUs, a function of transferring, when
there are lost RLC SDUs, RLC SDUs before the lost RLC SDUs in order
to the upper layer, a function of transferring, when a preset timer
has been expired although there are lost RLC SDUs, all RLC SDUs
received before the preset timer starts in order to the upper
layer, or a function of transferring, when the preset time has been
expired although there are lost RLC SDUs, all RLC SDUs received up
to now in order to the upper layer.
[0299] Also, RLC PDUs may be processed in order (in arrival order,
regardless of SNs or order of SNs) in which they are received, and
transferred to the PDCP device out of sequence delivery, and in the
case of segments, segments which have been stored in a buffer or
which are to be received later may be received and reconstructed
into a compete RLC PDU and then processed and transferred to the
PDCP device. A NR RLC layer as described above may include no
concatenation function, and the above-described function may be
performed in a NR MAC layer or replaced with a multiplexing
function of the NR MAC layer.
[0300] The out-of-sequence delivery function of the NR RLC device
as described above means a function of transferring RLC SDUs
received from a lower layer to the upper layer regardless of order,
and may include a function of reassembling, when a RLC SDU is
segmented into several RLC SDUs and received, the RLC SDUs and
transferring a result of the reassembling, and a function of
storing and ordering RLC SNs or PDCP SNs of the received RLC PDUs
and recording lost RLC PDUs.
[0301] The NR MAC 2d-15 and 2d-30 may be connected to several NR
RLC layers configured in the UE, and main functions of the NR MAC
2d-15 and 2d-30 may include some of the following functions. [0302]
Mapping between logical channels and transport channels [0303]
Multiplexing/demultiplexing of MAC SDUs [0304] Scheduling
information reporting [0305] Error correction through HARQ [0306]
Priority handling between logical channels of one UE [0307]
Priority handling between UEs by means of dynamic scheduling [0308]
MBMS service identification [0309] Transport format selection
[0310] Padding
[0311] NR PHY layers 2d-20 and 2d-25 may perform an operation of
performing channel coding and modulation on upper layer data to
generate an OFDM symbol and transferring the OFDM symbol through a
wireless channel, or performing demodulation and channel decoding
on an OFDM symbol received through the wireless channel and
transferring a result of the modulation and channel decoding to an
upper layer.
[0312] FIG. 2E is a view for describing a procedure in which a gNB
according to an embodiment of the disclosure releases a connection
of a UE for the UE to change from the RRC connected mode to the RRC
idle mode and a procedure in which the UE sets up a connection to
the gNB to change from the RRC idle mode to the RRC connected
mode.
[0313] Referring to FIG. 2E, when the UE transmitting and receiving
data in the RRC connected mode receives or transmits no data for a
certain reason or for a preset time, the gNB may transmit an
RRCConnectionRelease message to the UE to change the UE to the RRC
idle mode, in operation 2e-01. The UE (hereinafter, also referred
to as an idle mode UE) in which no connection is currently
established may perform, when data to be transmitted is generated,
an RRC connection establishment process together with the gNB. The
UE may establish reverse transmission synchronization with the gNB
through a random access process, and transmit an
RRCConnectionRequest message to the gNB, in operation 2e-05. The
RRCConnectionRequest message may include an identifier of the UE
and a cause establishmentCause for connection establishment.
[0314] The gNB may transmit an RRCConnectionSetup message to the UE
to enable the UE to establish an RRC connection, in operation
2e-10. The RRCConnectionSetup message may include RRC connection
configuration information, etc. Also, the RRCConnectionSetup
message may include at least one information of bearer
configuration information of the UE, configuration information of a
PHY layer, configuration information of a MAC layer, configuration
information of a RLC layer, configuration information of a PDCP
layer, or configuration information of a SDAP layer.
[0315] The configuration information of the RLC layer may include
an indicator defined to indicate whether to set the RLC layer to
the RLC TM mode, the RLC UM mode, or the RLC AM mode and whether to
set or activate the in-order delivery function for the RLC layer.
The gNB may indicate the UE of a setting about an RLC mode and
whether or not the in-order delivery function is set for each
bearer or for each RLC layer, based on the configuration
information of the RLC layer. When an indicator for setting or
activating the in-order delivery function is included together with
configuration information about the RLC mode in the configuration
information of the RLC layer, the UE may set the RLC mode (for
example, RLC TM, RLC UM or RLC AM) for the reception RLC layer, and
perform an operation of the reception RLC layer to which the
in-order delivery function is applied. When no indicator for
setting or activating the in-order delivery function for the RLC
layer is included in the configuration information of the RLC
layer, the UE may perform an operation of the reception RLC layer
to which the out-of-order delivery function is basically
applied.
[0316] An RRC connection is also referred to as a Signaling Radio
Bearer (SRB), and may be used to transmit and receive an RRC
message which is a control message between a UE and a gNB. The UE
which has established the RRC connection may transmit an
RRCConnetionSetupComplete message to the gNB, in operation 2e-15.
The RRCConnetionSetupComplete message may include a SERVICE REQUEST
message as a control message through which the UE requests the MME
to set a bearer for a preset service.
[0317] The gNB may transmit the SERVICE REQUEST message included in
the RRCConnetionSetupComplete message to an Access and Mobility
Management Function (AMF), in operation 2e-20, and the AMF may
determine whether to provide the preset service requested by the
UE. When the AMF determines to provide the preset service requested
by the UE, the AMF may transmit an INITIAL CONTEXT SETUP REQUEST
message to the gNB, in operation 2e-25. The INITIAL CONTEXT SETUP
REQUEST message may include QoS information to be applied for a
Data Radio Bearer (DRB) setting, security-related information (for
example, a security key or a security algorithm) to be applied to
the DRB, etc.
[0318] The gNB may exchange a SecurityModeCommand message with a
SecurityModeComplete message to set security with the UE, in
operations 2e-30 and 2e-35. When a security setting is completed,
the gNB may transmit an RRCConnectionReconfiguration message to the
UE, in operation 2e-40.
[0319] Also, the RRCConnectionReconfiguration message may include
bearer configuration information of the UE, configuration
information of the PHY layer, configuration information of the MAC
layer, configuration information of the RLC layer, configuration
information of the PDCP layer, or configuration information of the
SDAP layer.
[0320] The configuration information of the RLC layer may include
an indicator defined to indicate whether to set the RLC layer to
the RLC TM mode, the RLC UM mode, or the RLC AM mode and whether to
set or activate the in-order delivery function for the RLC layer.
The gNB may indicate the UE of a setting about the RLC mode and
whether or not the in-order delivery function is set for each
bearer or for each RLC layer, based on the configuration
information of the RLC layer. When an indicator for setting or
activating the in-order delivery function is included together with
configuration information about the RLC mode in the configuration
information of the RLC layer, the UE may set the RLC mode (for
example, RLC TM, RLC UM or RLC AM) for the reception RLC layer, and
perform an operation of the reception RLC layer to which the
in-order delivery function is applied. When no indicator for
setting or activating the in-order delivery function for the RLC
layer is included in the configuration information of the RLC
layer, the UE may perform an operation of the reception RLC layer
to which the out-of-order delivery function is basically
applied.
[0321] The RRCConnectionReconfiguration message may include
configuration information of a DRB by which user data is to be
processed, and the UE may apply the configuration information of
the DRB to set up the DRB, and transmit an
RRCConnectionReconfigurationComplete message to the gNB, in
operation 2e-45.
[0322] After the gNB completes DRB setup with the UE, the gNB may
transmit an initial context setup complete message to the AMF, in
operation 2e-50. The AMF may receive the initial context setup
complete message, and perform a session management procedure with a
User Plane Function (UPF) to establish a PDU session, in operation
2e-60. When the above-described process is completed, the UE may
transmit/receive data to/from the gNB through the UPF, in
operations 2e-65 and 2e-70.
[0323] As described above, a general data transmission process may
be configured with three operations of RCC connection setup,
security setup, and DRB setup. Also, the gNB may transmit an
RRCConnectionReconfiguration message to newly set up, add, or
change a setting to the UE for a certain reason, in operation
2e-75.
[0324] According to an embodiment of the disclosure, the bearer may
have a meaning including a SRB and a DRB, wherein the SRB means a
Signaling Radio Bearer and the DRB means a Data Radio Bearer. The
SRB may be mainly used to transmit and receive RRC messages of the
RRC layer, and the DRB may be mainly used to transmit and receive
user layer data. Also, UM DRB means a DRB using the RLC layer
operating in an Unacknowledged Mode (UM), and AM DRB means a DRB
using the RLC layer operating in an Acknowledged Mode (AM).
[0325] FIG. 2F shows a handover procedure in a next-generation
mobile communication system according to an embodiment of the
disclosure.
[0326] Referring to FIG. 2F, a UE 2f-01 which is in the RRC
connected mode may send a cell measurement report to a source gNB
2f-02 periodically or when a preset event is satisfied, in
operation 2f-05. The source gNB 2f-02 may determine whether to
perform a handover of the UE 2f-01 to an adjacent cell based on the
cell measurement information. The handover may be a technique of
changing a source gNB providing a service to a UE being in a
connected mode to another gNB (or another cell in the same
gNB).
[0327] When the source gNB 2f-02 determines a handover, the source
gNB 2f-02 may send a Handover (HO) request message to a new gNB,
that is, a target gNB 2f-03 that is to provide a service to the UE
2f-01, thereby requesting a handover, in operation 2f-10. When the
target gNB 2f-03 accepts the handover request, the target gNB 2f-03
may transmit a HO request Ack message to the source gNB 2f-02, in
operation 2f-15. When the source gNB 2f-02 receives the HO request
Ack message, the source gNB 2f-02 may transmit a HO command message
to the UE 2f-01, in operation 2f-20. The source gNB 2f-02 may
transfer the HO command message to the UE 2f-01 by using an RRC
Connection Reconfiguration message, in operation 2f-20. When the UE
2f-01 receives the HO command message, the UE 2f-01 may stop data
transmission/reception to/from the source gNB 2f-02, and start a
T304 timer. The T304 timer may return the UE 2f-01 to its original
setting and change the UE 2f-01 to the RRC idle state, when the UE
2f-01 fails to perform a handover to the target gNB 2f-03 within a
preset time period. The source gNB 2f-02 may transfer a SN status
about a transmission/reception status of uplink/downlink data to
the target gNB 2f-03, and when there is downlink data, the source
gNB 2f-02 may transfer the downlink data to the target gNB 2f-03,
in operations 2f-30 and 2f-35. The UE 2f-01 may attempt a random
access to a target cell indicated from the source gNB 2f-02, in
operation 2f-40. The random access may be aimed to notify the
target cell that the UE 2f-01 moves through a handover, while
synchronizing an uplink. For the random access, the UE 2f-01 may
transmit a preamble corresponding to a preamble ID received from
the source gNB 2f-02 or a randomly selected preamble ID to the
target cell. When a preset number of subframes elapse after the
preamble is transmitted, the UE 2f-01 may monitor whether a Random
Access Response (RAR) message is transmitted from the target cell.
A time period in which the UE 2f-01 monitors whether the RAR
message is transmitted is referred to as a RAR window. When a RAR
message is received within the time period of the monitoring in
operation 2f-45, the UE 2f-01 may transmit a HO complete message as
an RRC Reconfiguration Complete message to the target gNB 2f-03, in
operation 2f-55. When a random access response is successfully
received from the target gNB 2f-03, the UE 2f-01 may stop the T304
timer, in operation 2f-50.
[0328] To correct paths of bearers set to the source gNB 2f-02, the
target gNB 2f-03 may request a core network 2f-04 to correct paths
in operations 2f-60 and 2f-65, and notify the source gNB 2f-02 of
discarding UE context of the UE 2f-01, in operation 2f-70.
Accordingly, the UE 2f-01 may attempt to receive data with respect
to the target gNB 2f-03 from when the RAR window starts, and after
the RAR message is received, the UE 2f-01 may transmit the
RRCConnectionReconfigurationComplete message to the target gNB
2f-03 and start data transmission/reception to/from the target gNB
2f-03. According to an embodiment of the disclosure, the core
network 2f-04 may include at least one of an MME, a S-GW, or an
AMF, and further include at least one of a UPF or a SMF.
[0329] In the above-described handover procedure, when the source
gNB 2f-02 transmits the HO command message (for example, an RRC
Reconfiguration message) to the UE 2f-01, at least one of
information about a target gNB to which the UE 2f-01 needs to
perform a handover, information about a random access transmission
resource for a cell, preamble information, bearer configuration
information, or cell information may be set in the HO command
message.
[0330] Also, the HO command message may include an indicator
defined to indicate what kind of handover the UE 2f-01 needs to
perform. For example, the source gNB 2f-01 may define indicators
for a plurality of handover methods, and set one of the defined
indicators such that the UE 2f-01 perform a handover method
corresponding to the set indicator. The plurality of handover
methods may include at least one method of a RACH-less handover
method, an MBB handover method, an eMBB method, or a conditional
handover method. Also, the HO command message may indicate whether
to set or activate the in-order delivery function for each RLC
layer of the UE 2f-01 through the indicator.
[0331] In an operation of a protocol layer of the next-generation
mobile communication system described above with reference to FIG.
2D, an issue that data loss is generated in the PDCP layer due to
the out-of-order delivery of the RLC layer may be generated.
[0332] For example, the reception PDCP layer may drive a PDCP
reordering timer. The PDCP reordering timer may be driven or start
when a PDCP SN gap is generated in the reception PDCP layer based
on PDCP SNs, and the reception PDCP layer may transfer data to an
upper layer in ascending order of the PDCP SNs or COUNT values when
data corresponding to the PDCP SN gap does not arrive until the
PDCP reordering timer is expired, and move after a PDCP SN
transferring a reception window. Accordingly, when data
corresponding to the PDCP SN gap arrives late after the PDCP
reordering timer is expired, the arrived data may not be data in
the reception window, and therefore, the reception PDCP layer may
discard the data, resulting in data loss. A reason why data arrives
late may be because several retransmissions of the RLC layer set to
the RLC AM mode. However, a reason why the PDCP reordering timer is
triggered may be because the reception RLC layer transfers data
quickly to the upper layer through the out-of-order delivery
function.
[0333] According to an embodiment of the disclosure, when AM DRB is
set for a UE with an RRC message, a gNB may set the in-order
delivery function with respect to a reception RLC layer for the UE.
When long retransmission of the RLC layer is required or when data
loss is fatal to a service, the gNB may set or activate the
in-order delivery function with respect to the reception RLC
layer.
[0334] Also, as shown in FIG. 2F, in the case that a handover
method for reducing a data interruption time generated in a
handover is indicated in a handover situation, for example, when a
UE performs a handover while continuously transmitting/receiving
data to/from a source gNB and simultaneously transmitting/receiving
data to/from a target gNB to prevent any data
transmission/reception interruption, each RLC layer may perform
out-of-order delivery of data received from different gNBs when a
reception PDCP layer of the UE needs to decipher downlink data with
different security keys for the different gNBs or needs to perform
a compression release procedure for releasing header compression in
order. In this case, the reception PDCP layer may have high
complexity in processing the out-of-order data. Accordingly, when a
preset handover method is indicated in a HO command message, the
gNB may cause the reception RLC layer of the UE to perform the
in-order delivery function, or may indicate the RLC layer to
perform the in-order delivery function together with an indicator
indicating the preset handover method through the indicator. The
indication for setting, activating or deactivating the in-order
delivery function may be dynamically set by a transmitter (gNB or
UE) by defining a new RLC control PDU instead of an RRC
message.
[0335] After performing the handover, the UE may itself fall back
to the out-of-order delivery function from the in-order delivery
function. For example, after the UE transmits a handover completion
message to the target gNB or when the UE drives a preset timer and
then the preset timer is expired, the UE may fall back to the
out-of-order delivery function from the in-order delivery function.
A value of the preset timer may be indicated by the gNB through a
handover command message. Alternatively, when the gNB indicates the
out-of-order delivery function through an RRC message or a new RLC
control PDU while the reception RLC layer of the UE continues to
apply an in-order delivery function even after a handover is
performed, the UE may change from the in-order delivery function to
the out-of-order delivery function.
[0336] Hereinafter, a first embodiment for operations of the
reception RLC layer proposed in the disclosure will be described in
detail and proposed in regard of the RLC UM mode and the RLC AM
mode.
[0337] In the first embodiment for operations of the reception RLC
layer proposed in an embodiment of the disclosure, the out-of-order
delivery function may be performed as a basic operation.
[0338] First, variables used for a window operation of the
reception RLC layer in the RLC UM mode may be defined as follows.
[0339] RX_Next_Reassembly: state variable indicating a lowest or
earliest RLC SN among data (RLC PDU or RLC SDU) considered to be
reassembled in the reception RLC layer [0340] RX_Timer_Trigger:
state variable indicating an RLC SN following an RLC SN triggering
an RLC reassembly timer [0341] RX_Next_Highest: state variable
indicating an RLC SN following a highest RLC SN among received
data
[0342] Detailed operations of a 1-1 embodiment when the reception
RLC layer according to an embodiment of the disclosure operates in
the RLC UM mode may be as follows.
[0343] The reception RLC layer may operate, when receiving a UMD
PDU from a lower layer, as follows. [0344] When no RLC SN is
included in a header of the received UMD PDU, [0345] Remove an RLC
header and transfer an RLC SDU to an upper layer. [0346] When an
RLC SN is included in the header of the received UMD PDU and the
RLC SN is equal to or greater than a RX_Next_Highest-UM_Window_Size
value and smaller than a RX_Next_Reassembly value, [0347] Discard
the received UMD PDU. [0348] When an RLC SN is included in the
header of the received UMD PDU and the RLC SN is smaller than the
RX_Next_Highest-UM_Window_Size value and equal to or greater than
the RX_Next_Reassembly value, [0349] Store the received UMD PDU in
a reception buffer.
[0350] The reception RLC layer may operate in regard of the UMD PDU
stored in the buffer in the above-described procedure, as follows.
That is, when a UMD PDU having an RLC SN of a x value is stored in
the buffer, the reception RLC layer may operate as follows. [0351]
When all segments having the RLC SN of the x value are received,
[0352] Reassemble all the segments having the RLC SN of the x value
to configure an RLC SDU, remove an RLC header, and then transfer
the RLC SDU to the upper layer. [0353] When the x value is equal to
the RX_Next_Reassembly value, [0354] Update a RX_Next_Reassembly
variable to a RLC SN of first data (or data having a lowest RLC SN
among data having great RLC SNs) having a RLC SN that is greater
than the current RX_Next_Reassembly value among data neither yet
reassembled nor transferred to the upper layer. [0355] When the x
value of the RLC SN is out of an RLC reassembly window, [0356]
Update a RX_Next_Highest variable to x+1. [0357] Discard all data
corresponding to RLC SNs being out of the RLC reassembly window.
[0358] When the RX_Next_Reassembly value is out of the RLC
reassembly window, [0359] Set the RX_Next_Reassembly variable to
the RLC SN of the first data (or data having the lowest RLC SN
among the data having the great RLC SNs) having a RLC SN that is
equal to or greater than the current RX_Next_Highest-UM_Window_Size
value among the data neither yet reassembled nor transferred to the
upper layer. [0360] When the RLC reassembly timer is being driven,
[0361] When a RX_Timer_Trigger value is equal to or smaller than
the RX_Next_Reassembly value, [0362] Or, when the RX_Timer_Trigger
value is out of the RLC reassembly window and the RX_Timer_Trigger
value is not equal to the RX_Next_Highest value, [0363] Or, when
the RX_Next_Highest value is equal to a RX_Next_Reassembly+1 value
and there is no segment lost before a final byte of all segments
currently received for a RLC SDU having the RX_Next_Reassembly
value as a RLC SN, [0364] Stop and initialize the RLC reassembly
timer. [0365] When the RLC reassembly timer is not driven
(including a case in which the RLC reassembly timer stops according
to a procedure), [0366] When the RX_Next_Highest value is greater
than the RX_Next_Reassembly+1 value, [0367] Or, when the
RX_Next_Highest value is equal to the RX_Next_Reassembly+1 value
and there is at least one segment lost before a final byte of all
segments currently received for a RLC SDU having the
RX_Next_Reassembly value as a RLC SN, [0368] Start the RLC
reassembly timer, and [0369] Set the RX_Timer_Trigger variable to
the RX_Next_Highest value.
[0370] When the RLC reassembly timer is expired in the
above-described procedure, the reception RLC layer may operate as
follows. [0371] Update the RX_Next_Reassembly variable to a RLC SN
of first data (or data having a lowest RLC SN) having a RLC SN that
is equal to or greater than the RX_Timer_Trigger value, the first
data not yet reassembled. [0372] Discard all segments having an RLC
SN that is smaller than the updated RX_Next_Reassembly value.
[0373] When the RX_Next_Highest value is greater than the
RX_Next_Reassumbly+1 value, [0374] Or, when the RX_Next_Highest
value is equal to the RX_Next_Reassumbly+1 value and there is at
least one segment lost before a final byte of all segments
currently received for a RLC SDU having the RX_Next_Reassembly
value as a RLC SN, [0375] Start the RLC reassembly timer, and
[0376] Set the RX_Timer_Trigger variable to the RX_Next_Highest
value.
[0377] FIG. 2G shows RLC header formats that may be applied in the
1-1 embodiment which are operations of the reception RLC layer in
which the RLC UM mode according to an embodiment of the disclosure
is set.
[0378] Referring to FIG. 2G, in the 1-1 embodiment which is an
operation of the reception RLC layer in which the RLC UM mode
according to an embodiment of the disclosure is set, when a
transmission RLC layer transmits data (RLC SDU or RLC PDU) as
complete data without segmenting the RLC SDU, the transmission RLC
layer may apply a RLC header 2g-05 including a segmentation info
(SI) field (indicating the complete data, a first segment, a final
segment, or a middle segment being neither the first segment nor
the final segment) without a RLC SN to the data and transmit the
data, in the case that a 6-bit RLC SN has been set in the RLC
layer. However, when the transmission RLC layer segments a RLC SDU
and transmits segments, the transmission RLC layer may apply a RLC
header 2g-10 including a RLC SN and a SI field to the first segment
and transmit the first segment, and apply a RLC header 2g-20
including a RLC SN, a SI field, and a segment offset (SO) field
(indicating a first byte segmented from the RLC SDU) to the middle
or final segment and transmit the middle or final segment.
[0379] Also, when the transmission RLC layer transmits a RLC SDU as
complete data without separating the RLC SDU, the transmission RLC
layer may apply the RLC header 2g-05 including a SI field to the
data without a RLC SN and transmit the data, in the case in which a
12-bit RLC SN has been set in the RLC layer. However, when the
transmission RLC layer segments a RLC SDU and transmits segments,
the transmission RLC layer may apply a RLC header 2g-15 including a
RLC SN and a SI field to the first segment data and transmit the
first segment, and apply a RLC header 2g-25 including a RLC SN, a
SI field, and a SO field (indicating a first byte segmented from
the RLC SDU) to the middle or final segment and transmit the middle
or final segment.
[0380] Detailed operations of a 1-2 embodiment when the reception
RLC layer according to an embodiment of the disclosure operates in
the RLC AM mode may be as follows. In the RLC AM mode, the RLC
layer may implement an ARQ function, receive an RLC status report
(indicating successful data transfer with an RLC SN) from a
receiving terminal, and retransmit data not successfully
transmitted, thereby preventing data loss.
[0381] First, in the RLC AM mode, variables that are used for a
window operation of the reception RLC layer may be defined as
follows. [0382] RX_Next: status variable indicating an RLC SN
following a highest or final RLC SN among completely received data
which is capable of being reassembled [0383]
RX_Next_Status_Trigger: status variable indicating an RLC SN
following an RLC SN triggering the RLC assembly timer [0384]
RX_Next_Highest: status variable indicating an RLC SN following a
highest RLC SN among received data [0385] RX_Next_Highest_Status:
status variable indicating a highest RLC SN (for example, an RLC SN
following a highest RLC SN successfully received) that may be
indicated as ACK_SN in an RLC status report when the RLC status
report is configured
[0386] When the reception RLC layer receives an AMD PDU including y
to z bytes of an RLC SDU having an RLC SN of a x value from a lower
layer, the reception RLC layer may operate as follows. [0387] When
the RLC SN of the x value of the received AMD PDU is out of an RLC
reception window, [0388] Or, when an AMD PDU including y to z bytes
of an RLC SDU having the RLC SN of the x value has been previously
received, [0389] Discard the received AMD PDU. [0390] Otherwise,
[0391] Store the received AMD PDU in the reception buffer. [0392]
When a portion or segment included in the AMD PDU has been
previously received, [0393] Consider that the portion or segment
included in the AMD PDU has been received in duplicate and discard
the portion or segment.
[0394] The reception RLC layer may operate in regard of the AMD PDU
stored in the reception buffer in the procedure, as follows. That
is, when the AMD PDU having the RLC SN of the x value is stored in
the reception buffer, the RLC layer may operate as follows. [0395]
When the RLC SN of the x value is equal to or greater than a
RX_Next_Highest value, [0396] Update the RX_Next_Highest value to
x+1 [0397] When all bytes of the RLC SDU corresponding to the RLC
SN of the x value are received, [0398] Reassemble data or segments
corresponding to the RLC SN of the x value to configure an RLC SDU,
remove an RLC header, and then transfer the reassembled RLC SDU to
an upper layer. [0399] When the x value is equal to a
RX_Highest_Status value, [0400] Update a RX_Highest_Status variable
to an RLC SN of first data (having a lowest RLC SN) which is
greater than the RX_Highest_Status value and of which all bytes are
not yet completely received. [0401] When the x value is equal to a
RX_Next value, [0402] update a RX_Next variable to an RLC SN of
first data (having a lowest RLC SN) which is greater than the
RX_Next value and of which all bytes are not yet completely
received. [0403] When the RLC reassembly timer is being driven,
[0404] When a RX_Next_Status_Trigger value is equal to the RX_Next
value, [0405] Or, when the RX_Next_Status_Trigger value is equal to
a RX_Next+1 value and there is no segment lost before a final byte
of all segments currently received for a RLC SDU having the RX_Next
value as a RLC SN, [0406] Or, when the RX_Next_Status_Trigger value
is out of an RLC reception window and the RX_Next_Status_Trigger
value is not equal to a RX_Next+AM_Window_Size value, [0407] Stop
and initialize the RLC reassembly timer. [0408] When the RLC
reassembly timer is not driven (including a case in which the RLC
reassembly timer stops according to a procedure), [0409] When the
RX_Next_Highest value is greater than the RX_Next+1 value, [0410]
When the RX_Next_Highest value is equal to the RX_Next+1 value and
there is at least one segment lost before a final byte of all
segments currently received for an RLC SDU having the RX_Next value
as an RLC SN, [0411] Start the RLC reassembly timer, and [0412] Set
the RX_Next_Status_Trigger variable to the RX_Next_Highest
value.
[0413] When the RLC reassembly timer is expired in the procedure,
the reception RLC layer may operate as follows. [0414] Update the
RX_Highest_Status variable to an RLC SN of first data (or data
having a lowest RLC SN) not yet completely received, the RLSN SN
being equal to or greater than the RX_Next_Status_Trigger value.
[0415] When the RX_Next_Highest value is greater than the RX_Next+1
value, [0416] When the RX_Next_Highest value is equal to the
RX_Next+1 value and there is at least one segment lost before a
final byte of all segments currently received for an RLC SDU having
the RX_Next value as an RLC SN, [0417] Start the RLC reassembly
timer [0418] Set the RX_Next_Status_Trigger variable to the
RX_Next_Highest value.
[0419] FIG. 2H shows RLC header formats that may be applied in a
1-2 embodiment which are operations of the reception RLC layer in
which the RLC AM mode according to an embodiment of the disclosure
is set.
[0420] Referring to FIG. 2H, in the 1-2 embodiment which are the
operations of the reception RLC layer in which the RLC AM mode
according to an embodiment of the disclosure is set, when the
transmission RLC layer transmits data (RLC SDU or RLC PDU) as
complete data without segmenting the RLC SDU or when the
transmission RLC layer transmits a first segment segmented from the
RLC SDU, the transmission RLC layer may apply a RLC header 2h-05
including a RLC SN and a SI field (indicating the complete data,
the first segment, a final segment, or a middle segment being
neither the first segment nor the final segment) to the data and
transmit the data, in the case that a 12-bit RLC SN has been set in
the RLC layer. However, when the transmission RLC layer segments a
RLC SDU and transmits segments, the transmission RLC layer may
apply a RLC header 2h-15 including a RLC SN, a SI field, and a SO
field (indicating a first byte segmented from the RLC SDU) to the
middle or final segment and transmit the middle or final
segment.
[0421] Also, in the 1-2 embodiment which are the operations of the
reception RLC layer in which the RLC AM mode according to an
embodiment of the disclosure is set, when the transmission RLC
layer transmits data (RLC SDU or RLC PDU) as complete data without
segmenting a RLC SDU or when the transmission RLC layer transmits a
first segment segmented from a RLC SDU, the transmission RLC layer
may apply, in the case that a 18-bit RLC SN has been set in the RLC
layer, a RLC header 2h-10 including a RLC SN and a SI field
(indicating the complete data, the first segment, a final segment,
or a middle segment being neither the first segment nor the final
segment) to the data and transmit the data. However, when the
transmission RLC layer segments the RLC SDU and transmits segments,
the transmission RLC layer may apply a RLC header 2h-20 including a
RLC SN, a SI field, and a SO field (indicating a first byte
segmented from the RLC SDU) to the middle or final segment and
transmit the middle or final segment.
[0422] Hereinafter, a second embodiment for operations of the
reception RLC layer proposed in the disclosure will be described in
detail in regard of the RLC UM mode and the RLC AM mode.
[0423] In the second embodiment for the operations of the reception
RLC layer according to an embodiment of the disclosure, the RLC
layer may order data based on RLC SNs and transfer the data to an
upper layer, when setting or activating of the in-order delivery
function is indicated with an RRC message or a RLC control PDU by a
gNB, although the RLC layer performs the out-of-order delivery
function as a basic operation. Also, according to the
above-described second embodiment, when the RLC layer applies the
out-of-order delivery function, the RLC layer may immediately
discard segments being out of the RLC reassembly window. However,
when the in-order delivery function is set or activated, the RLC
layer may attempt to reassemble, instead of immediately discarding
the segments being out of the RLC reassembly window, the segments
being out of the RLC reassembly window, transfer, when the segments
are reassembled into complete RLC SDUs, the RLC SDUs to an upper
layer in ascending order of RLC SNs, and discard segments that has
failed to be reassembled into the complete RLC SDUs. Also, when the
in-order delivery function is set or activated in the RLC layer,
the RLC layer may order, instead of immediately reassembling a RLC
SDU corresponding to a RLC SN when all bytes of the RLC SDU is
received and transferring the RLC SDU to the upper layer, RLC SDUs
in order of RLC SNs, then reassemble the RLC SDUs, and transfer the
RLC SDUs to the upper layer in ascending order of the RLC SNs. When
the out-of-order delivery function is applied to the RLC layer, the
RLC layer may immediately reassemble an RLC SDU corresponding to an
RLC SN when all bytes of the RLC SDU are received, and then
transfer the RLC SDU to the upper layer.
[0424] First, variables that are used in a window operation of the
reception RLC layer in the RLC UM mode may be defined as follows.
[0425] RX_Next_Reassembly: status variable indicating a lowest or
earliest RLC SN among data (RLC PDU or RLC SDU) considered to be
reassembled in the reception RLC layer. [0426] RX_Timer_Trigger:
status variable indicating an RLC SN following an RLC SN triggering
the RLC reassembly timer [0427] RX_Next_Highest: status variable
indicating an RLC SN following a highest RLC SN among received
data
[0428] Detailed operations of a 2-1 embodiment when the reception
RLC layer according to an embodiment of the disclosure operates in
the RLC UM mode may be as follows.
[0429] The reception RLC layer may operate, when receiving a UMD
PDU from a lower layer, as follows. [0430] When no RLC SN is
included in a header of the received UMD PDU, [0431] Remove an RLC
header and transfer an RLC SDU to an upper layer. [0432] When an
RLC SN is included in the header of the received UMD PDU and the
RLC SN is equal to or greater than a RX_Next_Highest-UM_Window_Size
value and smaller than a RX_Next_Reassembly value, [0433] Discard
the received UMD PDU. [0434] When an RLC SN is included in the
header of the received UMD PDU and the RLC SN is smaller than the
RX_Next_Highest-UM_Window_Size value or equal to or greater than
the RX_Next_Reassembly value, [0435] Store the received UMD PDU in
a reception buffer.
[0436] The reception RLC layer may operate in regard of the UMD PDU
stored in the buffer in the above-described procedure, as follows.
That is, when a UMD PDU having an RLC SN of an x value is stored in
the buffer, the reception RLC layer may operate as follows. [0437]
When all segments having the RLC SN of the x value are received,
[0438] When the in-order-delivery function is not set, [0439]
Reassemble all the segments having the RLC SN of the x value to
configure an RLC SDU, remove an RLC header, and then transfer the
resultant RLC SDU to an upper layer. [0440] When the x value is
equal to a RX_Next_Reassembly value, [0441] Update a
RX_Next_Reassembly variable to a RLC SN of first data (or data
having a lowest RLC SN among data having great RLC SNs) among data
neither yet reassembled nor transferred to an upper layer, the RLC
SN being greater than the current RX_Next_Reassembly value. [0442]
Reassemble UMD PDUs having RLC SNs that are smaller than the
updated RX_Next_Reassembly value into RLC SDUs, remove RLC headers,
and transfer the reassembled RLC SDUs to the upper layer in
ascending order of the RLC SNs when the reassembled RLC SDUs have
never previously been transferred to the upper layer. [0443] When
the RLC SN of the x value is out of the RLC reassembly window,
[0444] Update a RX_Next_Highest variable to x+1. [0445] When the
in-order delivery function is not set, [0446] Discard all data
corresponding to RLC SNs being out of the RLC reassembly window.
[0447] Reassemble UMD PDUs having the RLC SNs being out of the RLC
reassembly window into RLC SDUs, remove RLC headers, and transfer
the reassembled RLC SDUs to the upper layer in ascending order of
the RLC SNs when the reassembled RLC SDUs have never previously
been transferred to the upper layer. [0448] When the
RX_Next_Reassembly value is out of the RLC reassembly window,
[0449] Set the RX_Next_Reassembly variable to the RLC SN of the
first data (or data having the lowest RLC SN among the data having
the great RLC SNs) among the data neither yet reassembled nor
transferred to the upper layer, the RLC SN being equal to or
greater than the current RX_Next_Highest-UM_Window_Size value.
[0450] When the RLC reassembly timer is being driven, [0451] When a
RX_Timer_Trigger value is equal to or smaller than the
RX_Next_Reassumbly value, [0452] Or, when the RX_Timer_Trigger
value is out of the RLC reassembly window and the RX_Timer_Trigger
value is not equal to the RX_Next_Highest value, [0453] Or, when
the RX_Next_Highest value is equal to a RX_Next_Reassembly+1 value
and there is no segment lost before a final byte of all segments
currently received for a RLC SDU having the RX_Next_Reassembly
value as a RLC SN, [0454] Stop and initialize the RLC reassembly
timer. [0455] When the RLC reassembly timer is not driven
(including a case in which the RLC reassembly timer stops according
to a procedure), [0456] When the RX_Next_Highest value is greater
than a RX_Next_Reassumbly+1 value, [0457] Or, when the
RX_Next_Highest value is equal to the RX_Next_Reassumbly+1 value
and there is at least one segment lost before a final byte of all
segments currently received for a RLC SDU having the
RX_Next_Reassembly value as a RLC SN, [0458] Start the RLC
reassembly timer, and [0459] Set the RX_Timer_Trigger variable to
the RX_Next_Highest value.
[0460] When the RLC reassembly timer is expired in the
above-described procedure, the reception RLC layer may operate as
follows. [0461] Update the RX_Next_Reassembly variable to an RLC SN
of first data (or data having a lowest RLC SN) not yet reassembled,
the RLC SN being equal to or greater than the RX_Timer_Trigger
value. [0462] When the in-order delivery function is not set,
[0463] Discard all segments having RLC SNs that are smaller than
the updated RX_Next_Reassembly value. [0464] Reassemble UMD PDUs
having RLC SNs that are smaller than the updated RX_Next_Reassembly
value into RLC SDUs, remove RLC headers, and transfer the
reassembled RLC SDUs to the upper layer in ascending order of the
RLC SNs when the reassembled RLC SDUs have never previously been
transferred to the upper layer. [0465] When the RX_Next_Highest
value is greater than a RX_Next_Reassumbly+1 value, [0466] Or, when
the RX_Next_Highest value is equal to the RX_Next_Reassumbly+1
value and there is at least one segment lost before a final byte of
all segments currently received for a RLC SDU having the
RX_Next_Reassembly value as a RLC SN, [0467] Start the RLC
reassembly timer, and [0468] Set the RX_Timer_Trigger variable to
the RX_Next_Highest value.
[0469] FIGS. 2IA and 21B shows RLC header formats that may be
applied in the 2-1 embodiment which are the operations of the
reception RLC layer in which the RLC UM mode according to an
embodiment of the disclosure is set.
[0470] Referring to FIG. 2I, in the 2-1 embodiment which are the
operations of the reception RLC layer in which the RLC UM mode
according to an embodiment of the disclosure is set, when the
in-order delivery function is not set, the transmission RLC layer
may apply, when transmitting data (RLC SDU or RLC PDU) as complete
data without segmenting the RLC SDU, a RLC header 2i-05 to the data
and transmit the data in the case that a 6-bit RLC SN has been set
in the RLC layer. The RLC header 2i-05 includes a SI field
(indicating the complete data, a first segment, a final segment, or
a middle segment being neither the first segment nor the final
segment) without an RLC SN. However, when the transmission RLC
layer segments a RLC SDU and transmits segments, the transmission
RLC layer may apply a RLC header 2i-10 including a RLC SN and a SI
field to a first segment and transmit the first segment, and apply
a RLC header 2i-20 including a RLC SN, a SI field, and a SO field
(indicating a first byte segmented from the RLC SDU) to a middle or
final segment and transmit the middle or final segment.
[0471] Also, when the in-order delivery function is not set, the
transmission RLC layer may apply, when transmitting data (RLC SDU
or RLC PDU) as complete data without separating the RLC SDU, the
RLC header 2i-05 including a SI field in the data without a RLC SN
to the data and transmit the data, in the case in which a 12-bit
RLC SN has been set in the RLC layer. However, when the
transmission RLC layer segments a RLC SDU and transmits segments,
the transmission RLC layer may apply a RLC header 2i-15 including a
RLC SN and a SI field in the first segment and transmit the first
segment, and apply a RLC header 2i-25 including a RLC SN, a SI
field, and a SO field (indicating a first byte segmented from the
RLC SDU) to the middle or final segment and transmit the middle or
final segment.
[0472] In the 2-1 embodiment which are the operations of the
reception RLC layer in which the RLC UM mode according to an
embodiment of the disclosure is set, when the in-order delivery
function is set, the transmission RLC layer may apply, when
transmitting data (RLC SDU or RLC PDU) as complete data without
segmenting the RLC SDU, a RLC header 2i-10 including a RLC SN and a
SI field (indicating the complete data, a first segment, a final
segment, or a middle segment being neither the first segment nor
the final segment) to the data and transmit the data, in the case
that a 6-bit RLC SN has been set in the RLC layer, such that the
reception RLC layer is capable of ordering the data. However, when
the transmission RLC layer segments a RLC SDU and transmits
segments, the transmission RLC layer may apply the RLC header
including a RLC SN and a SI field to the first segment and transmit
the first segment, and apply the RLC header 2i-20 including a RLC
SN, a SI field, and a SO field (indicating a first byte segmented
from the RLC SDU) to the middle or final segment and transmit the
middle or final segment.
[0473] According to another method, in the 2-1 embodiment which are
the operations of the reception RLC layer in which the RLC UM mode
according to an embodiment of the disclosure is set, when the
in-order delivery function is set, the transmission RLC layer may
apply, when transmitting data (RLC SDU or RLC PDU) as complete data
without segmenting the RLC SDU, a RLC header 2i-30 including a RLC
SN to the data and transmit the data, in the case that a 6-bit RLC
SN has been set in the RLC layer such that the reception RLC layer
is capable of ordering the data. The RLC header 2i-30 includes a
12-bit RLC SN and a SI field (indicating the complete data, a first
segment, a final segment, or a middle segment being neither the
first segment nor the final segment), a 1-bit I field, defined by
the transmission RLC layer, indicating that the in-order delivery
function is capable of being set or applied. That is, the
transmission RLC layer may change a length of an RLC SN from 6 bits
to 12 bits, and indicate the in-order delivery function with a
1-bit indicator. However, when the transmission RLC layer segments
an RLC SDU and transmits segments, the transmission RLC layer may
apply the RLC header 2i-30 to a first segment and transmit the
first segment. The RLC header includes an RLC SN, a SI field and a
1-bit I field, defined by the transmission RLC layer, including an
indication representing that the in-order delivery function is
capable of being set or applied. Also, the transmission RLC layer
may apply an RLC header 2i-35 to a middle or final segment and
transmit the middle or final segment. The RLC header 2i-35 includes
a RLC SN, a SI field, a SO field (indicating a first byte segmented
from a RLC SDU), and a 1-bit I field, defined by the transmission
RLC layer, including an indication representing that the in-order
delivery function may be set or applied.
[0474] Also, when the in-order delivery function is set, the
transmission RLC layer may apply, when transmitting data (RLC SDU
or RLC PDU) as complete data without segmenting the RLC SDU, the
RLC header 2i-15 including a RLC SN and a SI field and transmit the
data, in the case that a 12-bit RLC SN has been set in the RLC
layer. However, when the transmission RLC layer segments a RLC SDU
and transmits segments, the transmission RLC layer may apply the
RLC header 2i-15 including a RLC SN and a SI field to the first
segment and transmit the first segment, and may apply the RLC
header 2i-25 including a RLC SN, a SI field, and a SO field
(indicating a first byte segmented from a RLC SDU) to the middle or
final segment and transmit the middle or final segment.
[0475] According to another method, when the in-order delivery
function is set, the transmission RLC layer may apply, when
transmitting data (RLC SDU or RLC PDU) as complete data without
segmenting the RLC SDU, the RLC header 2i-30 to the data and
transmit the data, in the case that a 12-bit RLC SN has been set in
the RLC layer. The RLC header 2i-30 includes an RLC SN, a SI field,
and a 1-bit I field, defined by the transmission RLC layer,
including an indication representing that the in-order delivery
function is capable of being set or applied. However, when the
transmission RLC layer segments a RLC SDU and transmits segments,
the transmission RLC layer may apply the RLC header 2i-30 including
a RLC SN, a SI field, and a 1-bit I field, defined by the
transmission RLC layer, including an indication representing that
the in-order delivery function is capable of being set or applied
to the first segment and transmit the first segment, and apply the
RLC header 2i-35 including a RLC SN, a SI field, a SO field
(indicating a first byte segmented from a RLC SDU), and a 1-bit I
field, defined by the transmission RLC layer, including an
indication representing that the in-order delivery function is
capable of being set or applied to the middle or final segment and
transmit the middle or final segment.
[0476] According to an embodiment of the disclosure, the
transmission RLC layer may define a I field in a header format of
2i-05, set the I field to 0 like a header format of 2i-40, and then
apply the header format of 2i-40 to a RLC SDU not segmented in the
case that the in-order delivery function is not set.
[0477] Also, when the in-order delivery function is set or
activated, the transmission RLC layer may configure an RLC header
format including the I field according to an embodiment of the
disclosure and transmit data including the RLC header format. When
the in-order delivery function is set or activated, the reception
RLC layer may check the I field to identify an RLC SN, and order
the received data. The reception RLC layer may immediately
reassemble a RLC PDU of which an I field value is 0 without
applying the in-order delivery function to the RLC PDU although the
in-order delivery function is set, remove a RLC header, and then
transfer the resultant RLC PDU to an upper layer (because the RLC
PDU is data transmitted before the in-order delivery function is
set).
[0478] Detailed operations of a 2-2 embodiment when the reception
RLC layer according to an embodiment of the disclosure operates in
the RLC AM mode may be as follows. In the RLC AM mode, the RLC
layer may implement an ARQ function, receive an RLC status report
(indicating successful data transfer with an RLC SN) from a
receiving terminal, and retransmit data not successfully
transmitted, thereby preventing data loss.
[0479] First, in the RLC AM mode, variables that are used for a
window operation of the reception RLC layer may be defined as
follows. [0480] RX_Next: status variable indicating an RLC SN
following a highest or final RLC SN among completely received data
which is capable of being reassembled [0481]
RX_Next_Status_Trigger: status variable indicating an RLC SN
following an RLC SN triggering the RLC assembly timer [0482]
RX_Next_Highest: status variable indicating an RLC SN following a
highest RLC SN among received data [0483] RX_Next_Highest_Status:
status variable indicating a highest RLC SN (for example, an RLC SN
following a highest RLC SN successfully received) that may be
indicated as ACK_SN in an RLC status report when the RLC status
report is configured
[0484] When the reception RLC layer receives an AMD PDU including y
to z bytes of an RLC SDU having an RLC SN of a x value from a lower
layer, the reception RLC layer may operate as follows. [0485] When
the RLC SN of the x value of the received AMD PDU is out of an RLC
reception window, [0486] When an AMD PDU including y to z bytes of
an RLC SDU having the RLC SN of the x value has been previously
received, [0487] Discard the received AMD PDU. [0488] Otherwise,
[0489] Store the received AMD PDU in the reception buffer. [0490]
When a portion or segment included in the AMD PDU has been
previously received, [0491] Consider that the portion or segment
included in the AMD PDU has been received in duplicate and discard
the portion or segment.
[0492] The reception RLC layer may operate in regard of the AMD PDU
stored in the buffer in the above-described procedure, as follows.
That is, when the AMD PDU having the RLC SN of the x value is
stored in the buffer, the reception RLC layer may operate as
follows. [0493] When the x value of the RLC SN is equal to or
greater than a RX_Next_Highest value, [0494] Update the
RX_Next_Highest value to x+1 [0495] When all bytes of an RLC SDU
corresponding to the x value of the RLC SN are received, [0496]
When the in-order delivery function is not set, [0497] Reassemble
data or segments corresponding to the x value of the RLC SN to
configure an RLC SDU, remove an RLC header, and then transfer the
reassembled RLC SDU to an upper layer, [0498] When the x value is
equal to a RX_Next_Reassembly value, [0499] Update a
RX_Highest_Status variable to an RLC SN of first data (having a
lowest RLC SN) which is greater than the RX_Highest_Status value
and of which all bytes are not yet completely received. [0500] When
the x value is equal to a RX_Next value, [0501] update a RX_Next
variable to an RLC SN of first data (having a lowest RLC SN) which
is greater than the RX_Next value and of which all bytes are not
yet completely received. [0502] Reassemble AMD PDUs having RLC SNs
that are smaller than the updated RX_Next value into RLC SDUs,
remove RLC headers, and transfer the reassembled RLC SDUs to the
upper layer in ascending order of the RLC SNs when the reassembled
RLC SDUs have never previously been transferred to the upper
layer.
[0503] When the RLC reassembly timer is being driven, [0504] When a
RX_Next_Status_Trigger value is equal to the RX_Next value, [0505]
Or, when the RX_Next_Status_Trigger value is equal to a RX_Next+1
value and there is no segment lost before a final byte of all
segments currently received for a RLC SDU having the RX_Next value
as a RLC SN, [0506] Or, when the RX_Next_Status_Trigger value is
out of an RLC reception window and the RX_Next_Status_Trigger value
is not equal to a RX_Next+AM_Window_Size value, [0507] Stop and
initialize the RLC reassembly timer. [0508] When the RLC reassembly
time is not driven (including a case in which the RLC reassembly
timer stops according to a procedure), [0509] When the
RX_Next_Highest value is greater than the RX_Next+1 value, [0510]
Or, when the RX_Next_Highest value is equal to the RX_Next+1 value
and there is at least one segment lost before a final byte of all
segments currently received for a RLC SDU having the RX_Next value
as a RLC SN, [0511] Start the RLC reassembly timer, and [0512] Set
the RX_Next_Status_Trigger variable to the RX_Next_Highest
value.
[0513] When the RLC reassembly timer is expired in the
above-described procedure, the reception RLC layer may operate as
follows. [0514] Update the RX_Highest_Status variable to an RLC SN
of first data (data having a lowest RLC SN) not yet completely
received, the RLC SN being equal to or greater than the
RX_Next_Status_Trigger value. [0515] When the RX_Next_Highest value
is greater than the RX_Next+1 value, [0516] Or, when the
RX_Next_Highest value is equal to the RX_Next+1 value and there is
at least one segment lost before a final byte of all segments
currently received for a RLC SDU having the RX_Next value as a RLC
SN, [0517] Start the RLC reassembly timer, and [0518] Set the
RX_Timer_Status_Trigger variable to the RX_Next_Highest value.
[0519] FIG. 2J shows RLC header formats that may be applied in the
2-2 embodiment which are operations of the reception RLC layer in
which the RLC AM mode according to an embodiment of the disclosure
is set.
[0520] Referring to FIG. 2J, in the 2-2 embodiment which are
operations of the reception RLC layer in which the RLC AM mode
according to an embodiment of the disclosure is set, when the
transmission RLC layer transmits data (RLC SDU or RLC PDU) as
complete data without segmenting the RLC SDU or when the
transmission RLC layer transmits a first segment segmented from the
RLC SDU, the transmission RLC layer may apply, in the case that a
12-bit RLC SN has been set in the RLC layer, a RLC header 2j-05
including a RLC SN and a SI field (indicating the complete data,
the first segment, a final segment, or a middle segment being
neither the first segment nor the final segment) to the data and
transmit the data. However, when the transmission RLC layer
segments a RLC SDU and transmits segments, the transmission RLC
layer may apply a RLC header 2j-15 including a RLC SN, a SI field,
and a SO field (indicating a first byte segmented from the RLC SDU)
to the middle or final segment and transmit the middle or final
segment.
[0521] Also, in the 2-2 embodiment which are the operations of the
reception RLC layer in which the RLC AM mode according to an
embodiment of the disclosure is set, when the transmission RLC
layer transmits data (RLC SDU or RLC PDU) as complete data without
segmenting the RLC SDU or when the transmission RLC layer transmits
a first segment segmented from the RLC SDU, the transmission RLC
layer may apply, in the case that a 18-bit RLC SN has been set in
the RLC layer, a RLC header 2j-10 including a RLC SN and a SI field
(indicating the complete data, the first segment, a final segment,
or a middle segment being neither the first segment nor the final
segment) to the data and transmit the data. However, when the
transmission RLC layer segments a RLC SDU and transmits segments,
the transmission RLC layer may apply a RLC header 2j-20 including a
RLC SN, a SI field, and a SO field (indicating a first byte
segmented from the RLC SDU) to the middle or final segment and
transmit the middle or final segment.
[0522] In the 2-2 embodiment which are the operations of the
reception RLC layer in which the RLC AM mode according to an
embodiment of the disclosure is set, because a RLC SN is included
in each data unlike the RLC UM mode, the same RLC headers shown in
FIG. 2J may be applied to both a case that the in-order delivery
function is set and a case that the in-order delivery function is
not set, according to lengths of RLC SNs, as described above. That
is, in the RLC AM mode, the same RLC header format may be applied
and used regardless of whether or not the in-order delivery
function is set, unlike the RLC UM mode. According to another
method, the transmission RLC layer may define a 1-bit indicator
like the RLC UM mode to indicate that the in-order delivery
function is set, and define and use an RLC header format.
[0523] FIG. 2K shows operations of a reception RLC layer of a UE
according to an embodiment of the disclosure.
[0524] Referring to FIG. 2K, the reception RLC layer (2k-01) of the
UE may receive data from a lower layer, in operation 2k-05.
[0525] The UE may determine whether the in-order delivery function
is set, based on the received data, in operation 2k-10.
[0526] When the in-order delivery function is set, the UE may apply
the above-described 2-1 embodiment to the RLC UM mode in
consideration of a RLC header, and apply the above-described 2-2
embodiment to the RLC AM mode in consideration of a RLC header, in
operation 2k-20. For example, the UE may activate the in-order
delivery function to order and process the received data and
transfer the resultant data to an upper layer.
[0527] When the in-order delivery function is not set, the UE may
apply the 1-1 embodiment or the 2-1 embodiment for the reception
RLC layer to the RLC UM mode in consideration of a RLC header, and
apply the 1-2 embodiment or the 2-2 embodiment for the reception
RLC layer to the RLC AM mode in consideration of a RLC header, in
operation 2k-15. For example, the UE may process the received data
and transfer the processed data to the upper layer according to the
out-of-order delivery function.
[0528] FIG. 2L shows a structure of a UE or a wireless node to
which an embodiment of the disclosure may be applied.
[0529] Referring to FIG. 2L, the UE may include an RF processor
2l-10, a baseband processor 2l-20, a storage device 2l-30, and a
controller 2l-40. However, an internal structure of the UE is not
limited to the embodiment shown in FIG. 2L, and the UE may include
more or less components than those shown in FIG. 2L. The RF
processor 2l-10 may perform a function for transmitting and
receiving signals through a wireless channel, such as band
conversion, amplification, etc. of signals. That is, the RF
processor 2l-10 may up-convert a baseband signal provided from the
baseband processor 2l-20 into a RF band signal, transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through the antenna into a baseband signal. For example,
the RF processor 2l-10 may include a transmission filter, a
reception filter, an amplifier, a mixer, an oscillator, a DAC, an
ADC, etc. In FIG. 2I, a single antenna is shown, however, the UE
may include a plurality of antennas. Also, the RF processor 2l-10
may include a plurality of RF chains. Furthermore, the RF processor
2l-10 may perform beamforming. For beamforming, the RF processor
2l-10 may adjust phases and magnitudes of signals that are
transmitted/received through the plurality of antennas or antenna
elements. Also, the RF processor 2l-10 may perform MIMO, and when
MIMO is performed, the RF processor 2l-10 may receive several
layers. The RF processor 2l-10 may perform sweeping of a received
beam by appropriately setting the plurality of antennas or antenna
elements according to a control of the controller 2l-40, or may
adjust a direction and width of a received beam such that the
received beam coordinates with a beam that is to be
transmitted.
[0530] The baseband processor 2l-20 may perform a function of
conversion between baseband signals and bit streams according to a
physical layer specification of a system. For example, upon data
transmission, the baseband processor 2l-20 may encipher and
modulate a transmission bit stream to generate complex symbols.
Also, upon data reception, the baseband processor 2l-20 may
demodulate and decipher a baseband signal provided from the RF
processor 2l-10 to restore a reception bit stream. For example,
according to an OFDM method, upon data transmission, the baseband
processor 2l-20 may encipher and modulate a transmission bit stream
to generate complex symbols, map the complex symbols to
subcarriers, and then construct OFDM symbols through IFFT and CP
insertion. Also, upon data reception, the baseband processor 2l-20
may segment a baseband signal provided from the RF processor 2l-10
in units of OFDM symbols, restore signals mapped to subcarriers
through FFT, and then restore a reception bit stream through
demodulation and deciphering.
[0531] The baseband processor 2l-20 and the RF processor 2l-10 may
transmit and receive signals as described above. Accordingly, the
baseband processor 2l-20 and the RF processor 2l-10 are also
referred to as a transmitter, a receiver, a transceiver, or a
communicator. Furthermore, at least one of the baseband processor
2l-20 or the RF processor 2l-10 may include a plurality of
communication modules to support a plurality of different radio
access technologies. Also, at least one of the baseband processor
2l-20 or the RF processor 2l-10 may include different communication
modules to process signals of different frequency bands. For
example, the different radio access technologies may include a LET
network, a NR network, etc. Also, the different frequency bands may
include a SHF (e.g., 2.1 GHz and 1 GHz) band and a mm wave (e.g.,
60 GHz) band. The UE may transmit/receive a signal to/from a gNB by
using the baseband processor 2l-20 and the RF processor 2l-10,
wherein the signal may include control information and data.
[0532] The storage device 2l-30 may store data, such as basic
programs, application programs, and configuration information, for
operations of the UE. The storage device 2l-30 may provide the
stored data according to a request from the controller 2l-40. The
storage device 2l-30 may be configured with storage media, such as
ROM, RAM, a hard disc, CD-ROM, DVD, and the like, or a combination
of such storage media. Also, the storage device 2l-30 may be
configured with a plurality of memories.
[0533] The controller 2l-40 may control overall operations of the
UE. For example, the controller 2l-40 may transmit and receive
signals through the baseband processor 2l-20 and the RF processor
2l-10. Also, the controller 2l-40 may write data in the storage
device 2l-30 or read data from the storage device 2l-30. To write
or read data, the controller 2l-40 may include at least one
processor. For example, the controller 2l-40 may include a
communication processor CP for performing control for
communication, and an application processor AP for controlling an
upper layer of an application program, etc. Also, the controller
2l-40 may include multiple connection processor 2l-42 for
processing multiple connections. Also, the controller 2l-40 may
control the UE to perform a method for processing communication
data described above. Also, at least one component of the UE may be
implemented as a single chip.
[0534] FIG. 2M shows a block configuration of a TRP or a wireless
node in a wireless communication system according to an embodiment
of the disclosure.
[0535] Referring to FIG. 2M, a gNB (also, referred to as a TRP or a
wireless node) may include a RF processor 2m-10, a baseband
processor 2m-20, a backhaul communicator 2m-30, a storage device
2m-40, and a controller 2m-50. However, an internal structure of
the gNB is not limited to the embodiment shown in FIG. 2M, and the
gNB may include more or less components than those shown in FIG.
2M.
[0536] The RF processor 2m-10 may perform a function for
transmitting and receiving signals through a wireless channel, such
as band conversion, amplification, etc. of signals. That is, the RF
processor 2m-10 may up-convert a baseband signal provided from the
baseband processor 2m-20 into a RF band signal, transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through the antenna into a baseband signal. For example,
the RF processor 2m-10 may include a transmission filter, a
reception filter, an amplifier, a mixer, an oscillator, a DAC, an
ADC, etc. In FIG. 2M, a single antenna is shown, however, the gNB
may include a plurality of antennas. Also, the RF processor 2m-10
may include a plurality of RF chains. Furthermore, the RF processor
2m-10 may perform beamforming. For beamforming, the RF processor
2m-10 may adjust phases and magnitudes of signals that are
transmitted/received through the plurality of antennas or antenna
elements. The RF processor 2m-10 may perform downlink MIMO by
transmitting one or more layers.
[0537] The baseband processor 2m-20 may perform a function of
conversion between baseband signals and bit streams according to a
physical layer specification of first radio access technology. For
example, upon data transmission, the baseband processor 2m-20 may
encipher and modulate a transmission bit stream to generate complex
symbols. Also, upon data reception, the baseband processor 2m-20
may demodulate and decipher a baseband signal provided from the RF
processor 2m-10 to restore a reception bit stream. For example,
according to the OFDM method, upon data transmission, the baseband
processor 2m-20 may encipher and modulate a transmission bit stream
to generate complex symbols, map the complex symbols to
subcarriers, and then construct OFDM symbols through IFFT and CP
insertion. Also, upon data reception, the baseband processor 2m-20
may segment a baseband signal provided from the RF processor 2m-10
in units of OFDM symbols, restore signals mapped to subcarriers
through FFT, and then restore a reception bit stream through
demodulation and deciphering. The baseband processor 2m-20 and the
RF processor 2m-10 may transmit and receive signals as described
above. Accordingly, the baseband processor 2m-20 and the RF
processor 2m-10 are also referred to as a transmitter, a receiver,
a transceiver, or a wireless communicator. The gNB may
transmit/receive a signal to/from the UE by using the baseband
processor 2m-20 and the RF processor 2m-10, wherein the signal may
include control information and data.
[0538] The communicator 2m-30 may provide an interface for
communicating with other nodes in a network.
[0539] The storage device 2m-40 may store data, such as basic
programs, application programs, and configuration information, for
operations of the gNB. Particularly, the storage device 2m-40 may
store information about a bearer assigned to a UE connected to the
gNB, a measurement result reported from the connected UE, etc.
Also, the storage device 2m-40 may store information that is used
as a determination criterion about whether to provide multiple
connections to the UE or whether to release multiple connections to
the UE. Also, the storage device 2m-40 may provide the stored data
according to a request from the controller 2m-50. The storage
device 2m-40 may be configured with storage media, such as ROM,
RAM, a hard disc, CD-ROM, DVD, and the like, or a combination of
such storage media. Also, the storage device 2m-40 may be
configured with a plurality of memories.
[0540] The controller 2m-50 may control overall operations of the
gNB. For example, the controller 2m-50 may transmit and receive
signals through the baseband processor 2m-20 and the RF processor
2m-10 or through the backhaul communicator 2m-30. Also, the
controller 2m-50 may write data in the storage device 2m-40 or read
data from the storage device 2m-40. To write or read data, the
controller 2m-50 may include at least one processor. Also, the
controller 2m-50 may include multiple connection processor 2m-52
for processing multiple connections. For example, the controller
2m-50 may control the gNB such that the UE may perform a method for
performing communication data as described above. Also, at least
one component in the gNB may be implemented as a single chip.
[0541] The methods according to the embodiments of the disclosure
described in claims or specification thereof may be implemented in
hardware, software, or a combination of hardware and software.
[0542] When the methods are implemented in software, a
computer-readable storage medium storing at least one program
(software module) may be provided. The at least one program stored
in the computer-readable storage medium may be configured for
execution by at least one processor within an electronic device.
The at least one program may include instructions that cause the
electronic device to execute the methods according to the
embodiments of the disclosure described in the claims or
specification thereof.
[0543] The program (software module or software) may be stored in
RAM, a non-volatile memory including a flash memory, ROM, an
electrically erasable programmable ROM (EEPROM), a magnetic disc
storage device, CD-ROM, DVDs or other types of optical storage
devices, and a magnetic cassette. Alternatively, the program may be
stored in a memory that is configured as a combination of some or
all of the memories. A plurality of such memories may be
included.
[0544] Furthermore, the program may be stored in an attachable
storage device that may be accessed through communication networks
such as the Internet, Intranet, a local area network (LAN), a wide
LAN (WLAN), and a storage area network (SAN) or a communication
network configured in a combination thereof. The storage device may
access a device performing the embodiments of the disclosure
through an external port. Further, a separate storage device on the
communication network may also access the device performing the
embodiments of the disclosure.
[0545] In the embodiments of the disclosure, a component included
in the disclosure is expressed in a singular or plural form
depending on the described embodiments of the disclosure. However,
singular or plural expressions are selected to be suitable for the
presented situations for convenience, and the disclosure is not
limited to the singular or plural form. A component expressed in a
plural form may be configured as a single component, or a component
expressed in a singular form may be configured as a plurality of
components.
[0546] The disclosed embodiments provide an apparatus and method
capable of effectively providing a service to a mobile
communication system.
[0547] Meanwhile, the embodiments of the disclosure disclosed in
the present specification and the drawings are specific examples
intended to easily describe the technical content of the disclosure
and help understanding the disclosure, not intended to limit the
scope of the disclosure. That is, it is apparent to those skilled
in the art that other modified examples based on the technical
spirit of the disclosure may be executed. Also, the embodiments may
be combined and used as needed. For example, some parts of the
embodiments of the disclosure may be combined to operate the gNB
and UE. Also, the embodiments of the disclosure may be applied to
other communication systems, and other modified examples based on
the technical concept of the embodiments may also be executed.
[0548] Although the present disclosure has been described with
various embodiments, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications as fall
within the scope of the appended claims.
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