U.S. patent application number 16/186185 was filed with the patent office on 2019-05-09 for method and apparatus for transmitting and receiving signals in wireless communication system.
The applicant listed for this patent is Samsung Electronics Co., Ltd. Invention is credited to Jae Hyuk JANG, Seung Ri JIN, Dong gun KIM, Sang Bum KIM, Soeng Hun KIM, Alexander SAYENKO.
Application Number | 20190141773 16/186185 |
Document ID | / |
Family ID | 66327955 |
Filed Date | 2019-05-09 |
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United States Patent
Application |
20190141773 |
Kind Code |
A1 |
KIM; Dong gun ; et
al. |
May 9, 2019 |
METHOD AND APPARATUS FOR TRANSMITTING AND RECEIVING SIGNALS IN
WIRELESS COMMUNICATION SYSTEM
Abstract
A method, performed by a user equipment (UE), of transmitting
and receiving signals in a wireless communication system, according
to an embodiment, includes receiving a logical channel release
request from a next-generation node B (gNB), determining a logical
channel to release, an operation mode of the logical channel to
release, and whether a packet data convergence protocol (PDCP)
layer apparatus connected to the logical channel is re-established,
based on the logical channel release request, and performing PDCP
data recovery based on the determination result.
Inventors: |
KIM; Dong gun; (Suwon-si,
KR) ; KIM; Sang Bum; (Suwon-si, KR) ; KIM;
Soeng Hun; (Suwon-si, KR) ; SAYENKO; Alexander;
(Suwon-si, KR) ; JANG; Jae Hyuk; (Suwon-si,
KR) ; JIN; Seung Ri; (Suwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd |
Suwon-si |
|
KR |
|
|
Family ID: |
66327955 |
Appl. No.: |
16/186185 |
Filed: |
November 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 80/02 20130101;
H04W 76/27 20180201; H04W 76/34 20180201; H04W 76/19 20180201; H04W
72/1284 20130101; H04W 88/02 20130101; H04W 76/30 20180201 |
International
Class: |
H04W 76/19 20060101
H04W076/19; H04W 76/30 20060101 H04W076/30 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2017 |
KR |
10-2017-0148448 |
Nov 16, 2017 |
KR |
10-2017-0153117 |
Claims
1. A method, performed by a user equipment (UE), of transmitting
and receiving signals in a wireless communication system, the
method comprising: receiving a logical channel release request from
a next-generation node B (gNB); determining a logical channel to
release, an operation mode of the logical channel to release, and
whether a packet data convergence protocol (PDCP) layer apparatus
connected to the logical channel is re-established based on the
logical channel release request; and performing PDCP data recovery
based on the determination result.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
U.S.C. .sctn. 119 to Korean Patent Application No. 10-2017-0153117
filed on Nov. 16, 2017 and to Korean Patent Application No.
10-2017-0148448 filed on Nov. 9, 2017 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 wireless communication systems,
and more particularly, to methods and apparatuses for transmitting
and receiving signals in wireless communication systems.
2. Description of Related Art
[0003] To meet the increase in demand for wireless data traffic
after the commercialization of 4G communication systems,
considerable efforts have been made to develop improved 5G
communication systems or pre-5G communication systems. This is one
reason why `5G communication systems` or `pre-5G communication
systems` are called `beyond 4G network communication systems` or
`post Long Term Evolution (LTE) systems`. In order to achieve a
high data rate, 5G communication systems are being developed to be
implemented in a super-high frequency band (millimeter wave
(mmWave)), e.g., a band of 60 GHz. In order to reduce path loss in
such a super-high frequency band and to increase a propagation
distance of electric waves in 5G communication systems, various
technologies such as beamforming, massive multiple input multiple
output (massive MIMO), full dimensional MIMO (FD-MIMO), array
antennas, analog beamforming, and large scale antennas are being
studied. In order to improve system networks for 5G communication
systems, various technologies such as evolved small cells, advanced
small cells, cloud radio access networks (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. In addition, for 5G communication systems, advanced
coding modulation (ACM) technologies such as hybrid frequency shift
keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and
sliding window superposition coding (SWSC) and advanced access
technologies such as filter bank multi-carrier (FBMC),
non-orthogonal multiple access (NOMA), and sparse code multiple
access (SCMA) have been developed.
[0004] The Internet has evolved from a human-based connection
network, where humans create and consume information, to the
Internet of things (IoT), where distributed elements such as
objects exchange information with each other to process the
information. Internet of everything (IoE) technology, in which the
IoT technology is combined with, for example, technology for
processing big data through connection with a cloud server, is
being newly provided. In order to implement the IoT, various
technological elements such as a sensing technology, wired/wireless
communication and network infrastructures, a service interface
technology, and a security technology are used. In recent years,
technologies related to sensor networks for connecting objects,
machine-to-machine (M2M) communication, and machine type
communication (MTC) have been studied. In the IoT environment,
intelligent Internet technology (IT) services may be provided to
collect and analyze data obtained from connected objects and thus
to create new values in human life. As existing information
technology (IT) and various industries converge and combine with
each other, the IoT may be applied to various fields such as smart
homes, smart buildings, smart cities, smart cars or connected cars,
smart grids, health care, smart home appliances, and advanced
medical services.
[0005] Various attempts are being made to apply 5G communication
systems to the IoT network. For example, technologies related to
sensor networks, M2M communication, MTC, etc. are implemented by
using beamforming, MIMO, array antennas, etc. Application of a
cloud RAN as the above-described big data processing technology may
be an example of convergence of the 5G communication technology and
the IoT technology.
[0006] As one of various technologies capable of satisfying
increasing demands for large-capacity data communication, a method
of providing multiple connections has been disclosed. For example,
multiple connections may be provided using multiple carriers
according to a carrier aggregation (CA) technique for LTE systems.
As such, users may use more resources to receive services. In
addition, the LTE systems may provide various services including
broadcast services such as multimedia broadcast multicast service
(MBMS).
SUMMARY
[0007] Unequal uplink and downlink service areas may occur in
wireless communication systems. In this case, an uplink or downlink
service area may be limited or reduced to avoid service quality
deterioration and thus the service area may not be efficiently
used.
[0008] In wireless communication systems, dual connectivity may be
used to transmit more data at high speed in downlinks and uplinks
or used to transmit data in duplicate to increase reliability. Dual
connectivity may be configured for multiple bearers. Therefore, a
procedure for changing a bearer type from a split bearer using dual
connectivity to a normal bearer (e.g., a master cell group (MCG)
bearer or a secondary cell group (SCG) bearer) or releasing each
SCG bearer using dual connectivity by independently releasing
logical channels of the split bearer or the SCG bearer is used.
[0009] In uplinks of wireless communication systems, since user
equipment (UE) has a physically small size and a high frequency
band and a wide bandwidth are not easily usable as an uplink
frequency band, a bottleneck phenomenon may occur in uplink
transmission resources compared to downlink transmission resources.
In addition, since the maximum Tx power level of the UE is less
than the maximum Tx power level of an evolved node B (eNB) or a
next-generation node B (gNB), a problem of reduction in coverage
for uplink data transmission may occur.
[0010] In accordance with an aspect of the disclosure, a method,
performed by a user equipment (UE), of transmitting and receiving
signals in a wireless communication system includes receiving a
logical channel release request from a next-generation node B
(gNB), determining a logical channel to release, an operation mode
of the logical channel to release, and whether a packet data
convergence protocol (PDCP) layer apparatus connected to the
logical channel is re-established, based on the logical channel
release request, and performing PDCP data recovery based on the
determination result.
[0011] 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.
[0012] 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.
[0013] 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
[0014] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0015] FIG. 1A is a diagram illustrating the structure of a new
radio (NR) system;
[0016] FIG. 1B includes conceptual diagrams illustrating a method
of using an additional uplink frequency according to an
embodiment;
[0017] FIG. 1C is a diagram illustrating uplink and downlink
service areas in a NR system;
[0018] FIG. 1D illustrates flowcharts of methods of performing cell
selection in consideration of an additional uplink frequency,
according to embodiments;
[0019] FIG. 1E is a flowchart illustrating an operation of
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment;
[0020] FIG. 1F is a flowchart illustrating a user equipment (UE)
operation for performing cell selection in consideration of an
additional uplink frequency, according to an embodiment;
[0021] FIG. 1G is a flowchart illustrating a UE operation for
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment;
[0022] FIG. 1H is a flowchart illustrating a UE operation for
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment;
[0023] FIG. 2A is a flowchart illustrating an operation of
configuring an additional uplink frequency, according to an
embodiment;
[0024] FIG. 2B is a flowchart illustrating a UE operation for
configuring an additional uplink frequency, according to an
embodiment;
[0025] FIG. 3A is a diagram illustrating the structure of a Long
Term Evolution (LTE) system to which the present disclosure is
applicable;
[0026] FIG. 3B is a diagram illustrating a radio protocol
architecture of an LTE system to which the present disclosure is
applicable;
[0027] FIG. 3C is a diagram illustrating the structure of a NR
system to which the present disclosure is applicable;
[0028] FIG. 3D is a diagram illustrating a radio protocol
architecture of a NR system to which the present disclosure is
applicable;
[0029] FIG. 3E is a diagram illustrating dual connectivity bearers
or multi-connectivity bearers configurable for a UE, to which dual
connectivity or multi-connectivity is applied, in a NR system,
according to an embodiment;
[0030] FIG. 3F is a flowchart illustrating a procedure, performed
by a next-generation node B (gNB), for configuring one of various
bearers described in relation to FIG. 3E, for a UE by using a RRC
message and sending a RRC message to release logical channels of
the configured bearer when the UE establishes connection, according
to an embodiment;
[0031] FIG. 3G is a flowchart illustrating a UE operation when a UE
receives a logical channel release request from a gNB, according to
an embodiment;
[0032] FIG. 4A is a flowchart illustrating a procedure, performed
by a gNB, for instructing whether to perform uplink data
compression (UDC), when a UE establishes a connection with a
network, according to an embodiment;
[0033] FIG. 4B is a diagram illustrating a procedure and a data
configuration for performing UDC, according to an embodiment;
[0034] FIG. 4C is a diagram illustrating a UDC method according to
an embodiment;
[0035] FIG. 4D is a diagram illustrating a UDC header according to
an embodiment;
[0036] FIGS. 4E and 4F are diagrams illustrating a procedure for
defining a new field capable of reducing overhead, in a packet data
convergence protocol (PDCP) header and configuring a PDCP packet
data unit (PDU) by using the new field, according to
embodiments;
[0037] FIG. 4G is a flowchart illustrating a transmitter (UE)
operation for performing a UDC method capable of reducing overhead,
according to an embodiment;
[0038] FIG. 4H is a flowchart illustrating a receiver (gNB)
operation for performing a UDC method capable of reducing overhead,
according to an embodiment;
[0039] FIG. 4I illustrates a block diagram of a UE according to an
embodiment;
[0040] FIG. 4J illustrates a block diagram of a gNB according to an
embodiment;
[0041] FIG. 5 is a flowchart illustrating a handover procedure
according to an embodiment;
[0042] FIG. 6 is a flowchart illustrating a UE operation for
performing handover, according to an embodiment;
[0043] FIG. 7 is a flowchart illustrating a scheduling request
procedure according to an embodiment; and
[0044] FIG. 8 is a flowchart illustrating a UE operation for
requesting scheduling.
DETAILED DESCRIPTION
[0045] FIGS. 1A through 8, 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.
[0046] In the following description of the present disclosure,
detailed descriptions of known functions and configurations
incorporated herein will be omitted when it may make the subject
matter of the present disclosure unclear. The terms used in the
specification are defined in consideration of functions used in the
present disclosure, and may be changed according to the intent or
conventionally used methods of operators and users. Accordingly,
definitions of the terms should be understood on the basis of the
entire description of the present specification.
[0047] Hereinafter, the present disclosure will be described in
detail by explaining embodiments of the disclosure with reference
to the attached drawings. Like reference numerals in the drawings
denote like elements. Expressions such as "at least one of," when
preceding a list of elements, modify the entire list of elements
and do not modify the individual elements of the list.
[0048] Terms identifying access nodes, terms indicating network
entities, terms indicating messages, terms indicating interfaces
between network entities, terms indicating various types of
identification information, and so on that are used in the
following description are exemplified for convenience of
explanation. Accordingly, the present disclosure is not limited to
terms to be described below and other terms indicating objects
having the equivalent technical meanings may be used.
[0049] Hereinafter, for convenience of explanation, the present
disclosure uses terms and names that are defined in the 3rd
Generation Partnership Project Long Term Evolution (3GPP LTE).
However, the present disclosure is not limited to the terms and
names but may be equally applied to systems following other
standards. Herein, for convenience of explanation, the terms
evolved node B (eNB) and next-generation node B (gNB) may be used
interchangeably. That is, a base station described as an eNB may
indicate a gNB, or vice versa.
[0050] FIG. 1A is a diagram illustrating the structure of a new
radio (NR) system.
[0051] Referring to FIG. 1A, a radio access network of the NR
system may include a new radio node B (NR NB, NR gNB, or gNB) 1a-10
and an AMF (or new radio core network (NR CN) or next-generation
core network (NG CN)) 1a-05. New radio user equipment (NR UE) 1a-15
may access an external network via the gNB 1a-10 and the AMF
1a-05.
[0052] In FIG. 1A, the gNB 1a-10 corresponds to an evolved node B
(eNB) of a legacy Long Term Evolution (LTE) system. The gNB 1a-10
is connected to the NR UE 1a-15 through radio channels and may
provide superior services compared to a legacy node B (1a-20).
Since all user traffic data is serviced through shared channels in
the NR system, an apparatus for collating buffer status information
of UEs, available Tx power status information, channel status
information, etc. and performing scheduling is used and the gNB
1a-10 may serve as such an apparatus. A single gNB may generally
control multiple cells. A bandwidth greater than the maximum
bandwidth of legacy LTE may be given to achieve high speed data
transmission, compared to the existing LTE system, and beamforming
technology may be added to radio access technology such as
orthogonal frequency-division multiplexing (OFDM). Adaptive
modulation & coding (AMC) may also be used to determine a
modulation scheme and a channel coding rate in accordance with a
channel status of the NR UE 1a-15. The AMF 1a-05 may perform
functions such as mobility support, bearer setup, and quality of
service (QoS) setup. The AMF 1a-05 is an apparatus for performing a
mobility management function and various control functions for the
NR UE 1a-15 and may be connected to multiple gNBs. The NR system
may cooperate with the legacy LTE system, and the AMF 1a-05 may be
connected to a mobility management entity (MME) 1a-25 through a
network interface. The MME 1a-25 may be connected to a legacy eNB
1a-30. The NR UE 1a-15 supporting LTE-NR dual connectivity may be
connected to and transmit and receive data to and from the gNB
1a-10 and the eNB 1a-30 (1a-35).
[0053] FIG. 1B includes conceptual diagrams illustrating a method
of using an additional uplink frequency according to an
embodiment.
[0054] In some cases, uplink and downlink service areas of a mobile
communication system may not equal. The unequal service areas may
occur due to different uplink and downlink channel characteristics
or due to a limitation of the maximum Tx power level or a
structural limitation of a Tx antenna of a UE. In general, the
downlink service area may be wider than the uplink service area.
For example, in a time-division duplex (TDD) system of 3.5 GHz, a
downlink service area 1b-05 is wider than an uplink service area
1b-10. In this case, a first UE 1b-20 has no problem in receiving
uplink and downlink services, but a second UE 1b-25 may have a
problem in transmitting uplink data to a gNB 1b-15. Therefore, to
solve the problem due to unequal service areas, a valid downlink
service area may be reduced to be equal to the uplink service area.
That is, although a wider downlink service area is providable, to
reduce the problem due to unequal service areas, the downlink
service area is reduced to be equal to the uplink service area.
[0055] In a NR system, to solve a limitation of performance due to
unequal service areas, a UE may use an uplink frequency
corresponding to a wider service area. For example, an uplink
frequency 1b-30 of 1.8 GHz may be provided to a UE in addition to
an uplink frequency 1b-35 of 3.5 GHz. The additional uplink
frequency is called a supplementary uplink (SUL) frequency. Based
on frequency characteristics, a radio range increases in a lower
frequency range. Thus, 1.8 GHz, which is lower than 3.5 GHz, may
provide a wider service area. Therefore, a second UE 1b-50 may
successfully transmit data to a gNB 1b-40 by using the uplink
frequency 1b-30 of 1.8 GHz.
[0056] Irrespective of the service area problem, since both uplink
frequencies of 1.8 GHz and 3.5 GHz are available to a first UE
1b-45, the first UE 1b-45 may select and use one of 1.8 GHz and 3.5
GHz to avoid congestion of uplink traffic. In this case, the
additional uplink frequency may be a LTE frequency.
[0057] Both a NR uplink frequency and a SUL frequency may be
configured for UE, and uplink data such as physical uplink shared
channel (PUSCH) data may be transmitted on only one uplink at a
time. Physical uplink control channel (PUCCH) data may also be
transmitted on only one uplink at a time, and the uplink for PUCCH
transmission may be the same as or different from the uplink for
PUSCH transmission.
[0058] A gNB supporting SUL may provide a first threshold value
used to determine an uplink for attempting random access, to UEs in
a cell by using system information. A UE supporting SUL may
calculate a reference signal received power (RSRP) by measuring a
sync signal block (SSB) broadcasted by the gNB on a downlink, and
compare the RSRP to the first threshold value. When a measured
downlink channel quality is lower than the first threshold value,
the UE may select a SUL frequency as the uplink for attempting
random access. When the measured downlink channel quality is not
lower than the first threshold value, the UE may perform random
access at a NR uplink frequency.
[0059] FIG. 1C is a diagram illustrating uplink and downlink
service areas in a NR system.
[0060] A problem of unequal uplink and downlink service areas in a
mobile communication system has been described above. The problem
of unequal service areas may influence cell selection. In the
mobile communication system, cell selection refers to an operation
of selecting a cell to be camped on by a UE in a standby mode. The
UE may select a cell by determining whether the UE satisfies
S-criteria. The UE may monitor whether a paging message is received
from the selected cell, and perform random access to access the
selected cell. For example, a first UE 1c-10 is located inside
uplink and downlink service areas and thus has no problem in
selecting a cell. However, a second UE 1c-15 may be located inside
a downlink service area 1c-20 but outside an uplink service area
1c-25. This may mean that a signal of the second UE 1c-15 does not
reach a gNB 1c-05 although the maximum Tx power level of the second
UE 1c-15 is used. The S-criteria applicable to the NR system may
include S-criteria for LTE. The S-criteria for LTE are as described
below. In this case, the second UE 1c-15 does not satisfy the
S-criteria and may not select a cell.
[0061] [Inequality 1]
[0062] Srxlev>0 AND Squal>0
[0063] where:
Srxlev=Q.sub.rxlevmeas-(Q.sub.rxlevmin+Q.sub.rxlevminoffset)-Pcompensati-
on-Qoffset.sub.temp
Squal=Q.sub.qualmeas-(Q.sub.qualmin+Q.sub.qualminoffset)-Qoffset.sub.tem-
p
[0064] where:
TABLE-US-00001 TABLE 1 S-Criteria Parameters Srxlev Cell selection
RX level value (dB) Squal Cell selection quality value (dB)
Qoffset.sub.temp Offset temporarily applied to a cell as specified
in [3] (dB) Q.sub.rxlevmeas Measured cell RX level value (RSRP)
Q.sub.qualmeas Measured cell quality value (RSRQ) Q.sub.rxlevmin
Minimum required RX level in the cell (dBm) Q.sub.qualmin Minimum
required quality level in the cell (dB) Q.sub.rxlevminoffset Offset
to the signaled Q.sub.rxlevmin taken into account in the Srxlev
evaluation as a result of a periodic search for a higher priority
PLMN while camped normally in a VPLMN [5] Q.sub.qualminoffset
Offset to the signaled Q.sub.qualmin taken into account in the
Squal evaluation as a result of a periodic search for a higher
priority PLMN while camped normally in a VPLMN [5] Pcompensation If
the UE supports the additionalPmax in the NS-PmaxList, if present,
in SIB1, SIB3 and SIB5: [Expression 2]max(P.sub.EMAX1
-P.sub.PowerClass, 0) - (min(P.sub.EMAX2, P.sub.PowerClass) -
min(P.sub.EMAX1, P.sub.PowerClass)) (dB); else: [Expression
3]max(P.sub.EMAX1 -P.sub.PowerClass, 0) (dB) P.sub.EMAX1, Maximum
TX power level an UE may use when transmitting on the P.sub.EMAX2
uplink in the cell (dBm) defined as P.sub.EMAX in TS 36.101 [33].
P.sub.EMAX1 and P.sub.EMAX2 are obtained from the p-Max and the
NS-PmaxList respectively in SIB1, SIB3 and SIB5 as specified in TS
36.331 [3]. P.sub.PowerClass Maximum RF output power of the UE
(dBm) according to the UE power class as defined in TS 36.101
[33]
[0065] The S-criteria will now be described in detail. To provide a
wider service area to a UE supporting a higher maximum Tx power
level, an additional cell selection parameter is defined and
Pcompensation is revised. Mobile carriers tend to configure a
Q_rxlevmin value in accordance with an uplink service area. For
example, the Q_rxlevmin value is configured in such a manner that a
UE having a maximum Tx power level of 17 dBm may select a
corresponding cell. From Rel-10, UEs having higher maximum Tx power
levels of 20 dBm and 23 dBm may be supported and wider service
areas may be provided to the UEs.
[0066] In the 3GPP standards, new P_EMAX2 applicable by UEs is
adopted and the definition of Pcompensation is revised to have a
positive value when, for example,
P_PowerClass.gtoreq.P_EMAX2>P_EMAX1.
[0067] Compared to a NR uplink frequency, a SUL frequency 1c-30 is
located in a lower frequency range and thus may provide a wider
uplink service area. Therefore, UE supporting SUL may select a cell
in consideration of a SUL service area. A cell which is not
selectable in consideration of a NR uplink service area may be
selected in consideration of the SUL service area.
[0068] An embodiment proposes a method of performing a cell
selection operation in consideration of a SUL service area. In this
regard, a gNB provides a new cell selection parameter and a UE may
determine whether the S-criteria are satisfied, by using the new
cell selection parameter.
[0069] FIG. 1D illustrates flowcharts of methods of performing cell
selection in consideration of an additional uplink frequency,
according to embodiments.
[0070] In a first method of initializing a cell selection operation
considering an additional uplink frequency, it may be determined
whether both a gNB and a UE support SUL technology (1d-05). Whether
both the gNB and the UE support SUL technology will be described in
relation to a first criterion. When the first criterion is
satisfied, the UE may perform a cell selection operation in
consideration of influence of SUL (1d-15).
[0071] A criterion that a measured downlink channel quality needs
to be lower than a first threshold value may be added to the first
criterion. As described above, the UE may perform random access at
the SUL frequency only when the downlink channel quality is lower
than the first threshold value. Therefore, the additional criterion
may be further considered. When the first criterion is not
satisfied, the UE may perform a cell selection operation of LTE or
a cell selection operation not considering influence of SUL
(1d-10). The cell selection operation considering influence of SUL
will be described below. The UE may determine whether the gNB
supports SUL, by receiving a SUL-related parameter broadcasted by
the gNB.
[0072] In a second method of initializing a cell selection
operation considering an additional uplink frequency, the UE
initially performs a cell selection operation of LTE or a cell
selection operation not considering influence of SUL (1d-20). It
may be determined whether the S-criteria are satisfied and thus a
cell is selected in the cell selection operation (1d-25). When the
S-criteria are satisfied and thus the cell is selected, the UE may
camp on the cell. Otherwise, when the S-criteria are not satisfied,
the UE may determine whether the first criterion is satisfied
(1d-30). When the first criterion is satisfied, the UE may perform
a cell selection operation in consideration of influence of SUL
(1d-40). Otherwise, when the first criterion is not satisfied, the
UE may search for another cell (1d-35).
[0073] FIG. 1E is a flowchart illustrating an operation of
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment.
[0074] UE 1e-05 may be powered on (1e-15) and then scan
radio-frequency (RF) channels in a band supportable based on UE
capability (1e-20). However, the above description merely
corresponds to an example and, alternatively, the UE 1e-05 may scan
pre-stored RF channels. The UE 1e-05 may find a frequency
corresponding to the highest signal power among the channels
(1e-25). The UE 1e-05 may receive system information broadcasted by
a certain gNB 1e-10, at the frequency (1e-30). The system
information may include cell selection parameters.
[0075] When the gNB 1e-10 supports SUL function, the system
information may also include a SUL-related cell selection
parameter. The SUL-related cell selection parameter differs
depending on embodiments and will be described below together with
the embodiments. The UE 1e-05 may perform a cell selection
operation by using the first or second method. For example, when
the UE 1e-05 supports SUL function, a cell selection operation
considering influence of SUL may be performed (1e-35). That is,
whether to perform cell selection may be determined by substituting
the SUL-related cell selection parameter in an expression of the
S-criteria. When the expression of the S-criteria is satisfied and
a corresponding cell is ultimately regarded as a suitable cell in
further consideration of public land mobile network (PLMN)
selection and barring, the UE 1e-05 may camp on the cell
(1e-40).
[0076] FIG. 1F is a flowchart illustrating a UE operation for
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment.
[0077] In an embodiment, a UE may receive a first NS-PmaxList, a
second NS-PmaxList, a first P_EMAX1, and a second P_EMAX1 which are
broadcasted as system information from a gNB (1f-05). In this case,
the system information may include, for example, at least one of
remaining minimum system information (RMSI) and other system
information (OSI).
[0078] The NS-PmaxList may include one or more P-Max values and one
or more additionalSpectrumEmission values. The P-Max value included
in the NS-PmaxList may correspond to P_EMAX2 of [Expression 2]. The
ASN.1 format of the NS-PmaxList shown below is captured from the
ASN.1 of LTE for reference. It is regarded that a similar ASN.1
format will be defined for a NR system.
TABLE-US-00002 NS-PmaxList information element -- ASN1START
NS-PmaxList-r10 ::= SEQUENCE (SIZE (1..maxNS-Pmax-r10)) OF
NS-PmaxValue- r10 NS-PmaxValue-r10 ::= SEQUENCE {
additionalPmax-r10 P-Max OPTIONAL, -- Need OP
additionalSpectrumEmission AdditionalSpectrumEmission } --
ASN1STOP
[0079] In an embodiment, the first NS-PmaxList and first P_EMAX1
values may be determined in consideration of influence of SUL. The
second NS-PmaxList and second P_EMAX1 values may be determined
similarly to those of LTE. That is, the P_EMAX1 value may generally
indicate the lowest maximum Tx power level value applicable in a
cell, although the definition thereof is variable. In this case,
propagation characteristics of a NR uplink frequency will be
considered. For a UE supporting a higher maximum Tx power level,
the second NS-PmaxList values may be provided. In general, the
P_EMAX2 value included in the NS-PmaxList is greater than the
P_EMAX1 value. As such, when the maximum Tx power level value of
the UE is greater than the P_EMAX1 value, [Expression 2] may have a
negative value and, ultimately, [Inequality 1] may be satisfied. An
increase in the maximum Tx power level of the UE may lead to an
increase in an uplink service area, and [Expression 2] may expand
an entire cell service area based on expansion of the uplink
service area. Considering SUL for cell selection means that the
uplink service area is expanded.
[0080] Thus, the effect thereof equals the effect of an increase in
the maximum Tx power level of the UE. Therefore, in the present
disclosure, the first NS-PmaxList and first P_EMAX1 values may be
determined to be less than the second NS-PmaxList and second
P_EMAX1 values by a value .alpha.. In this case, the value .alpha.
may be determined in consideration of a difference in service area
or propagation characteristics between a NR uplink frequency and a
SUL frequency. For example, a difference in path loss between the
NR uplink frequency and the SUL frequency may be configured as the
value .alpha.. The effect thereof equals the effect of an increase
in the maximum Tx power level of the UE.
[0081] When the first criterion is satisfied, the UE may determine
whether [Inequality 1] is satisfied, by substituting the first
NS-PmaxList and first P_EMAX1 values in [Expression 2] (1f-10).
When [Inequality 1] is satisfied, the UE may select a corresponding
cell. When the first criterion is not satisfied, the UE may
determine whether [Inequality 1] is satisfied, by substituting the
first NS-PmaxList and first P_EMAX1 values in [Expression 2]
(1f-15). When [Inequality 1] is satisfied, the UE may select a
corresponding cell.
[0082] Although an embodiment is described above based on the first
method, the first method is merely an example and the second method
may also be applicable.
[0083] FIG. 1G is a flowchart for describing a UE operation for
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment.
[0084] In an embodiment, a UE may receive, from a gNB, a second
NS-PmaxList and a second P_EMAX1, which are similar to those of
LTE, as system information and further receive a value .alpha.
indicating a difference in service area or propagation
characteristics between a NR uplink frequency and a SUL frequency
(1g-05). In this case, the system information may include, for
example, at least one of remaining minimum system information
(RMSI) and other system information (OSI). For example, a
difference in path loss between the NR uplink frequency and the SUL
frequency may be configured as the value .alpha..
[0085] The value .alpha. may be configured as a difference between
Q_rxlevmin and a first threshold value. In this case, the gNB does
not additionally provide the a value as the system information. The
Q_rxlevmin value indicates the minimum required Rx level in a
corresponding cell (e.g., RSRP).
[0086] When the first criterion is satisfied, the UE may determine
whether [Inequality 1] is satisfied, by substituting values
obtained by subtracting the value .alpha. from the second
NS-PmaxList and second P_EMAX1 values, in [Expression 2] (1g-10).
Alternatively, the UE may determine whether [Inequality 1] is
satisfied, by substituting a value obtained by adding the value
.alpha. to the maximum Tx power level value of the UE (e.g.,
P_PowerClass) in [Expression 2]. The effect of the preprocessing
operation using the value .alpha. equals the effect of an increase
in the maximum Tx power level of the UE due to influence of the SUL
frequency. When [Inequality 1] is satisfied, the UE may select a
cell. When the first criterion is not satisfied, the UE may
determine whether [Inequality 1] is satisfied, by substituting the
second NS-PmaxList and second P_EMAX1 values in [Expression 2]
(1g-15). When [Inequality 1] is satisfied, the UE may select a
cell.
[0087] Although an embodiment is described above based on the first
method, the second method may also be applicable.
[0088] FIG. 1H is a flowchart illustrating a UE operation for
performing cell selection in consideration of an additional uplink
frequency, according to an embodiment.
[0089] In an embodiment, a UE may receive a Q_rxlevmin value
considering influence of SUL, as system information from a gNB
(1h-05). In this case, the system information may include, for
example, at least one of remaining minimum system information
(RMSI) and other system information (OSI). For example, a
difference between the Q_rxlevmin value and an existing Q_rxlevmin
value is a difference in service area or propagation
characteristics between a NR uplink frequency and a SUL frequency.
Alternatively, the gNB may provide the difference value.
[0090] When the first criterion is satisfied, the UE may determine
whether [Inequality 1] is satisfied, by using the Q_rxlevmin value
considering the influence of SUL (1h-10). When [Inequality 1] is
satisfied, the UE may select a corresponding cell. When the first
criterion is not satisfied, the UE may determine whether
[Inequality 1] is satisfied, by using the existing Q_rxlevmin value
(1h-15). When [Inequality 1] is satisfied, the UE may select a
corresponding cell.
[0091] Although an embodiment is described above based on the first
method, the second method may also be applicable.
[0092] FIG. 2A is a flowchart illustrating an operation of
configuring an additional uplink frequency, according to an
embodiment.
[0093] A UE 2a-05 may receive system information from a gNB 2a-10
(2a-15). The system information may include servingCellConfigCommon
information element (IE). The IE may include configuration
information about a NR uplink frequency and a SUL frequency. The
configuration information may include random-access channel (RACH),
PUCCH, and PUSCH configuration information to be applied to the SUL
frequency as well as the NR uplink frequency, and frequency
information of the SUL frequency, e.g., information about a center
frequency, a bandwidth, and a frequency band to which the SUL
frequency belongs. The configuration information is cell-specific
information shared by all UEs in a cell.
[0094] The gNB 2a-10 supporting SUL may provide a first threshold
value used to determine an uplink for attempting random access, to
the UEs in the cell by using the system information. The UE 2a-05
supporting SUL may calculate a reference signal received power
(RSRP) by measuring a sync signal block (SSB) broadcasted by the
gNB 2a-10 on a downlink, and compare the RSRP to the first
threshold value.
[0095] When a measured downlink channel quality is lower than the
first threshold value, the UE 2a-05 may select the SUL frequency as
the uplink for attempting random access (2a-20). Otherwise, the UE
2a-05 may perform random access at the NR uplink frequency.
[0096] The UE 2a-05 may transmit a preamble on the selected uplink
(2a-25). The gNB 2a-10 having successfully received the preamble
may transmit a random access response (RAR) message to the UE 2a-05
(2a-30). When the NR uplink frequency is used to transmit the
preamble and transmission of the preamble fails after a preset
number of retransmission attempts, the UE 2a-05 may change the
uplink for attempting random access, to the SUL frequency and then
re-attempt to transmit the preamble. When transmission of the
preamble also fails at the SUL frequency after a preset number of
retransmission attempts, the UE 2a-05 may report random access
failure to an upper layer, e.g., a non-access stratum (NAS).
According to another example, the UE 2a-05 may re-perform the
operation of determining the uplink for attempting random access,
and attempt random access through the re-determined uplink.
Information about whether to additionally attempt random access
through another uplink and information about the number of
retransmission attempts may be signaled by the gNB 2a-10 by using
the system information.
[0097] The RAR message includes uplink synchronization information
and, when the RAR message is received, the UE 2a-05 may start a
timeAlignmentTimer (2a-35). The PAR message may include scheduling
information used to transmit a subsequent message, e.g., msg3.
[0098] The UE 2a-05 may transmit the msg3 message to the gNB 2a-10
by using a radio resource indicated by the scheduling information
(2a-40). The msg3 message may include a radio resource control
(RRC) Request message. This message may include a connection
request and cause value information indicating a cause of the
request.
[0099] The gNB 2a-10 having successfully received the msg3 message
may transmit a msg4 message to the UE 2a-05 (2a-45). The msg4
message may include a RRC Setup message. The RRC Setup message may
include UE-specific configuration information. The configuration
information may include PUCCH, PUSCH, and sounding reference symbol
(SRS) configuration information about the uplink used for random
access. When the uplink used for random access is the SUL
frequency, the SUL frequency is regarded as having already been
configured for the UE 2a-05, and the gNB 2a-10 provides at least
SRS configuration information about the NR uplink frequency to the
UE 2a-05. The SRS configuration information about the NR uplink
frequency is used to allow the gNB 2a-10 to check a channel status
of the NR uplink frequency during data transmission at the SUL
frequency. The gNB 2a-10 may provide all types of uplink
configuration information about the NR uplink frequency to the UE
2a-05. This is enabled when the NR uplink frequency has a
sufficient channel quality, in order to use the two uplink
frequencies in turn through layer 1 (L1) signaling. Therefore,
there may be two methods of using SUL.
[0100] According to a first method of using SUL, all types of
uplink configuration information may be provided on an uplink and
both PUCCH and PUSCH data may be transmitted on the uplink. Only
SRS configuration information may be provided on another uplink and
a channel quality status thereof may be monitored. When the channel
quality status of the other uplink is good, additional
configuration information may be provided and PUCCH and PUSCH data
may be transmitted on the other uplink.
[0101] According to a second method of using SUL, all types of
uplink configuration information may be provided on two uplinks and
an uplink for PUSCH transmission may be designated through L1
signaling. PUCCH transmission is determined through RRC signaling,
and PUCCH and PUSCH data does not always need to be transmitted on
the same uplink. However, a default uplink for PUSCH transmission
is the same as an uplink for PUCCH transmission.
[0102] In response to the RRC Setup message, the UE 2a-05 may
transmit a RRC Setup Complete message to the gNB 2a-10 (2a-50). The
RRC Setup Complete message may include a NAS container. When the UE
2a-05 has data to be transmitted to a core network (e.g., an AMF),
the UE 2a-05 may transmit the data by using the NAS container. The
AMF having received the information may report capability
information of the UE 2a-05 to the gNB 2a-10. The capability
information is collected by the AMF from the UE 2a-05 at a previous
access. At an initial access, the AMF may not have the capability
information of the UE 2a-05.
[0103] Therefore, in this case, the gNB 2a-10 requests the
capability information from the UE 2a-05 (2a-55). The gNB 2a-10 may
forward, to the AMF, the capability information reported from the
UE 2a-05. The capability information may include information
indicating whether the UE 2a-05 supports SUL, and SUL-supportable
frequency range or frequency band information. Although the gNB
2a-10 supports SUL function, when a SUL frequency does not belong
to a frequency range or frequency band supported by the UE 2a-05,
the gNB 2a-10 may regard the UE 2a-05 as not supporting SUL.
[0104] The gNB 2a-10 may transmit a SUL-related RRC signal for the
following purposes (2a-60).
[0105] First, when a SUL frequency is not yet configured, a RRC
signal may be transmitted to configure the SUL frequency. In this
case, according to the first or second method of using SUL, all
types of uplink configuration information may be provided or at
least SRS configuration information may be provided at the SUL
frequency. In general, the uplink configuration information
includes RACH, PUSCH, PUCCH, and SRS configuration information,
physical layer configuration information such as antenna, channel
quality information (CQI), and power control information, media
access control (MAC) layer configuration information, radio bearer
setup information, etc.
[0106] Second, a RRC signal may be transmitted to change an uplink
for PUCCH transmission. The uplink for PUCCH transmission is an
uplink used for random access by default. The gNB 2a-10 may change
the uplink for PUCCH transmission, by using the RRC signal. Uplink
configuration information about the uplink for PUCCH transmission
is provided to the UE 2a-05 in advance or simultaneously with a
change of PUCCH.
[0107] Third, a RRC signal may be transmitted to release a SUL
operation. When the SUL operation is released, the UE 2a-05 removes
all types of configuration information of the SUL frequency. The
gNB 2a-10 may release an uplink while maintaining the SUL
operation. For example, the gNB 2a-10 which uses the second method
of using SUL may be switched to the first method of using SUL. In
this case, the UE 2a-05 removes configuration information of the
released uplink but retains SRS configuration information.
[0108] The gNB 2a-10 may instruct the UE 2a-05 to perform random
access through a certain uplink, by using a physical downlink
control channel (PDCCH) order (2a-65) or after certain RRC
signaling in order to provide a timing for uplink synchronization
or configuration information application.
[0109] Two uplinks may be configured in a SUL operation and
different timerAlignmentTimers may be configured for the uplinks
(2a-70). A timer may be started or re-started in a random access
operation or when uplink synchronization information of a Timing
Advance Command MAC Control Element (TAC MAC CE) is received. The
UE 2a-05 regards uplink synchronization as having been achieved,
until the timer is expired. When the timer is expired, the UE 2a-05
regards uplink synchronization as having not been achieved.
Therefore, before the timer is expired, random access is performed
again or a TAC MAC CE is received. According to another method,
although two uplinks are configured, only one timerAlignmentTimer
may be used and a criterion for (re)starting the timer is changed.
For example, when a new uplink is configured, the gNB 2a-10 may
give an instruction to perform random access or may provide a TAC
MAC CE for synchronization through the new uplink. In this case,
the timer may be restarted.
[0110] When a single gNB 2a-10 uses a NR uplink frequency and a SUL
frequency, synchronizations of the two uplinks may be equal or very
similar. Therefore, the gNB 2a-10 may provide, to the UE 2a-05,
information indicating whether individual uplink synchronization
processes are used. For example, when a single timerAlignmentTimer
is configured, the synchronizations of the two uplinks are regarded
as being equal. Otherwise, when individual timerAlignmentTimers are
configured for the uplinks, the synchronizations of the two uplinks
are regarded as being different and thus individual synchronization
processes are used.
[0111] In the second method of using SUL, when the gNB 2a-10
decides to switch an uplink (2a-75), the gNB 2a-10 may transmit a
L1 signal to the UE 2a-05 (2a-80). The UE 2a-05 having received the
L1 signal may transmit PUSCH data on an uplink indicated by the L1
signal (2a-85).
[0112] FIG. 2B is a flowchart illustrating a UE operation for
configuring an additional uplink frequency, according to an
embodiment.
[0113] In operation 2b-05, a UE may receive system information from
a gNB. The system information may include servingCellConfigCommon
IE. The IE may include configuration information about a NR uplink
frequency and a SUL frequency.
[0114] In operation 2b-10, when a measured downlink channel quality
(e.g., Down Link RSRP) is lower than a first threshold value, the
UE may select the SUL frequency as an uplink for attempting random
access. Otherwise, the UE may select the NR uplink frequency.
[0115] In operation 2b-15, the UE may transmit a preamble on the
selected uplink.
[0116] In operation 2b-20, the UE may receive a RAR message.
[0117] In operation 2b-25, the UE may transmit a Msg3 message
including a RRC Request message.
[0118] In operation 2b-30, the UE may receive a Msg4 message
including a RRC Setup message. The configuration information may
include PUCCH, PUSCH, and sounding reference symbol (SRS)
configuration information about the uplink used for random access.
When the uplink used for random access is the SUL frequency, the
SUL frequency is regarded as having already been configured for the
UE, and the gNB provides at least SRS configuration information
about the NR uplink frequency to the UE.
[0119] In operation 2b-35, the UE may transmit a RRC Setup Complete
message. The RRC Setup Complete message may include a NAS
container. When the UE has data to be transmitted to a core network
(e.g., an AMF), the UE may transmit the data by using the NAS
container. The AMF having received the information may report
capability information of the UE to the gNB.
[0120] In operation 2b-40, the UE may report capability information
of the UE upon request by the gNB.
[0121] In operation 2b-45, the UE may transmit a SUL-related RRC
signal for the following purposes.
[0122] First, when a SUL frequency is not yet configured, a RRC
signal may be transmitted to configure the SUL frequency. Second, a
RRC signal may be transmitted to change an uplink for PUCCH
transmission. Third, a RRC signal may be transmitted to release a
SUL operation.
[0123] In operation 2b-50, the UE may perform random access through
a certain uplink based on a PDCCH order.
[0124] In operation 2b-55, the UE may receive a L1 signal.
[0125] In operation 2b-60, the UE may transmit PUSCH data on an
uplink indicated by the L1 signal.
[0126] FIG. 3A is a diagram illustrating the structure of an LTE
system to which the present disclosure is applicable.
[0127] Referring to FIG. 3A, a radio access network of the LTE
system may include evolved nodes B (ENBs) or nodes B 3a-05, 3a-10,
3a-15, and 3a-20, a mobility management entity (MME) 3a-25, and a
serving-gateway (S-GW) 3a-30. A user equipment (UE) 3a-35 may
access an external network via the ENBs 3a-05, 3a-10, 3a-15, and
3a-20 and the S-GW 3a-30.
[0128] In FIG. 3A, each of the ENBs 3a-05, 3a-10, 3a-15, and 3a-20
corresponds to a legacy node B of a universal mobile
telecommunications system (UMTS). Each ENB is connected to the UE
3a-35 through radio channels and may perform complex functions
compared to a legacy node B. Since all user traffic data including
real-time services such as voice over Internet protocol (VoIP) is
serviced through shared channels in the LTE system, an apparatus
for collating buffer status information of UEs, available Tx power
status information, channel status information, etc. and performing
scheduling is used and each of the ENBs 3a-05, 3a-10, 3a-15, and
3a-20 may serve as such an apparatus. A single ENB may generally
control multiple cells. For example, the LTE system may use radio
access technology such as orthogonal frequency-division
multiplexing (OFDM) at a bandwidth of 20 MHz to achieve a data rate
of 100 Mbps. The LTE system may also use adaptive modulation &
coding (AMC) to determine a modulation scheme and a channel coding
rate in accordance with a channel status of the UE 3a-35. The S-GW
3a-30 is an apparatus for providing data bearers and may configure
or release the data bearers under the control of the MME 3a-25. The
MME 3a-25 is an apparatus for performing a mobility management
function and various control functions for the UE 3a-35 and may be
connected to the ENBs 3a-05, 3a-10, 3a-15, and 3a-20.
[0129] FIG. 3B is a diagram illustrating a radio protocol
architecture of an LTE system to which the present disclosure is
applicable.
[0130] Referring to FIG. 3B, the radio protocol architecture of the
LTE system may include packet data convergence protocol (PDCP)
layers 3b-05 and 3b-40, radio link control (RLC) layers 3b-10 and
3b-35, and media access control (MAC) layers 3b-15 and 3b-30
respectively for a UE and an eNB. The PDCP layer 3b-05 or 3b-40 is
in charge of IP header compression/decompression, etc. Main
functions of the PDCP layer 3b-05 or 3b-40 are summarized below.
[0131] Header compression and decompression: robust header
compression (ROHC) only [0132] Transfer of user data [0133]
In-sequence delivery of upper layer packet data units (PDUs) at
PDCP re-establishment procedure for RLC AM (Acknowledged Mode)
[0134] For split bearers in DC (only support for RLC AM): PDCP PDU
routing for transmission and PDCP PDU reordering for reception
[0135] Duplicate detection of lower layer SDUs at PDCP
re-establishment procedure for RLC AM [0136] Retransmission of PDCP
SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP
data-recovery procedure, for RLC AM [0137] Ciphering and
deciphering [0138] Timer-based SDU discard in uplink
[0139] The RLC layer 3b-10 or 3b-35 may perform, for example, an
automatic repeat request (ARQ) operation by reconfiguring PDCP PDUs
to an appropriate size. Main functions of the RLC layer 3b-10 or
3b-35 are summarized below. [0140] Transfer of upper layer PDUs
[0141] Error Correction through ARQ (only for AM data transfer)
[0142] Concatenation, segmentation and reassembly of RLC SDUs (only
for UM and AM data transfer) [0143] Re-segmentation of RLC data
PDUs (only for AM data transfer) [0144] Reordering of RLC data PDUs
(only for UM and AM data transfer) [0145] Duplicate detection (only
for UM and AM data transfer) [0146] Protocol error detection (only
for AM data transfer) [0147] RLC SDU discard (only for UM and AM
data transfer) [0148] RLC re-establishment
[0149] The MAC layer 3b-15 or 3b-30 may be connected to multiple
RLC layer apparatuses configured for a single UE and may multiplex
RLC PDUs into a MAC PDU and demultiplex the RLC PDUs from the MAC
PDU. Main functions of the MAC layer 3b-15 or 3b-30 are summarized
below. [0150] Mapping between logical channels and transport
channels [0151] 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
[0152] Scheduling information reporting [0153] Error correction
through HARQ [0154] Priority handling between logical channels of
one UE [0155] Priority handling between UEs by means of dynamic
scheduling [0156] MBMS service identification [0157] Transport
format selection [0158] Padding
[0159] A physical (PHY) layer 3b-20 or 3b-25 may channel-code and
modulate upper layer data into OFDM symbols and transmit the OFDM
symbols through a radio channel, or demodulate OFDM symbols
received through a radio channel and channel-decode and deliver the
OFDM symbols to an upper layer.
[0160] FIG. 3C is a diagram illustrating the structure of a NR
system to which the present disclosure is applicable.
[0161] Referring to FIG. 3C, a radio access network of the NR (or
5G) system may include a new radio node B (NR NB, NR gNB, or gNB)
3c-10 and a new radio core network (NR CN) 3c-05. A new radio user
equipment (NR UE) 3c-15 may access an external network via the NR
gNB 3c-10 and the NR CN 3c-05.
[0162] In FIG. 3C, the NR gNB 3c-10 may correspond to an evolved
node B (eNB) of a legacy LTE system. The NR gNB 3c-10 is connected
to the NR UE 3c-15 through radio channels and may provide superior
services compared to a legacy node B. Since all user traffic data
is serviced through shared channels in the NR system, an apparatus
for collating buffer status information of UEs, available Tx power
status information, channel status information, etc. and performing
scheduling is used and the NR gNB 3c-10 may serve as such an
apparatus. A single NR gNB may generally control multiple
cells.
[0163] Currently, a bandwidth greater than the maximum bandwidth of
LTE may be given to achieve an ultrahigh data rate, and beamforming
technology may be added to radio access technology such as
orthogonal frequency-division multiplexing (OFDM). Adaptive
modulation & coding (AMC) may also be used to determine a
modulation scheme and a channel coding rate in accordance with a
channel status of the NR UE 3c-15. The NR CN 3c-05 may perform
functions such as mobility support, bearer setup, and quality of
service (QoS) setup. The NR CN 3c-05 is an apparatus for performing
a mobility management function and various control functions for
the NR UE 3c-15 and may be connected to multiple gNBs. The NR
system may cooperate with the legacy LTE system, and the NR CN
3c-05 may be connected to a mobility management entity (MME) 3c-25
through a network interface. The MME 3c-25 may be connected to a
legacy eNB 3c-30.
[0164] FIG. 3D is a diagram illustrating a radio protocol
architecture of a NR system to which the present disclosure is
applicable.
[0165] Referring to FIG. 3D, the radio protocol architecture of the
NR system may include NR PDCP layers 3d-05 and 3d-40, NR RLC layers
3d-10 and 3d-35, NR MAC layers 3d-15 and 3d-30 respectively for a
UE and a NR eNB.
[0166] Main functions of the NR PDCP layer 3d-05 or 3d-40 may
include some of the following functions. [0167] Header compression
and decompression: ROHC only [0168] Transfer of user data [0169]
In-sequence delivery of upper layer PDUs [0170] Out-of-sequence
delivery of upper layer PDUs [0171] PDCP PDU reordering for
reception [0172] Duplicate detection of lower layer SDUs [0173]
Retransmission of PDCP SDUs [0174] Ciphering and deciphering [0175]
Timer-based SDU discard in uplink
[0176] The reordering function of the NR PDCP layer apparatus 3d-05
or 3d-40 refers to a function of reordering PDCP PDUs received from
a lower layer, on a PDCP sequence number (SN) basis and may include
a function of delivering the reordered data to an upper layer in
order or out of order, a function of recording lost PDCP PDUs by
reordering the PDCP PDUs, a function of reporting status
information of the lost PDCP PDUs to a transmitter, and a function
of requesting to retransmit the lost PDCP PDUs.
[0177] Main functions of the NR RLC layer 3d-10 or 3d-35 may
include at least some of the following functions. [0178] Transfer
of upper layer PDUs [0179] In-sequence delivery of upper layer PDUs
[0180] Out-of-sequence delivery of upper layer PDUs [0181] Error
Correction through ARQ [0182] Concatenation, segmentation and
reassembly of RLC SDUs [0183] Re-segmentation of RLC data PDUs
[0184] Reordering of RLC data PDUs [0185] Duplicate detection
[0186] Protocol error detection [0187] RLC SDU discard [0188] RLC
re-establishment
[0189] The in-sequence delivery function of the NR RLC layer
apparatus 3d-10 or 3d-35 refers to a function of delivering RLC
service data units (SDUs) received from a lower layer, to an upper
layer in order and may include a function of reassembling multiple
RLC SDUs segmented from a RLC SDU and delivering the RLC SDU when
the segmented RLC SDUs are received. The in-sequence delivery
function may include at least one of a function of reordering
received RLC PDUs on a RLC SN or PDCP SN basis, a function of
recording lost RLC PDUs by reordering the RLC PDUs, and a function
of reporting status information of the lost RLC PDUs to a
transmitter. The in-sequence delivery function may include a
function of requesting to retransmit the lost RLC PDUs and a
function of delivering only RLC SDUs previous to a lost RLC SDU, to
the upper layer in order, when the lost RLC SDU exists. The
in-sequence delivery function may include a function of delivering
all RLC SDUs received before a timer is started, to the upper layer
in order, although a lost RLC SDU exists, when a certain timer is
expired, or a function of delivering all RLC SDUs received up to a
current time, to the upper layer in order, although a lost RLC SDU
exists, when a certain timer is expired.
[0190] The NR RLC layer apparatus 3d-10 or 3d-35 may process the
RLC PDUs in order of reception (in order of arrival regardless of
sequence numbers) and deliver the RLC PDUs to a PDCP layer
apparatus out of order (out-of sequence delivery), and reassemble
segments received or stored in a buffer, into a whole RLC PDU and
process and deliver the RLC PDU to the PDCP layer apparatus. The NR
RLC layer apparatus 3d-10 or 3d-35 may not have a concatenation
function, and the concatenation function may be performed by the NR
MAC layer apparatus 3d-15 or 3d-30 or be replaced with a
multiplexing function of the NR MAC layer apparatus 3d-15 or
3d-30.
[0191] The out-of-sequence delivery function of the NR RLC layer
apparatus 3d-10 or 3d-35 may refer to a function of delivering the
RLC SDUs received from the lower layer, to the upper layer out of
order. The out-of-sequence delivery function may include a function
of reassembling multiple RLC SDUs segmented from a RLC SDU and
delivering the RLC SDU when the segmented RLC SDUs are received.
The out-of-sequence delivery function may include a function of
storing RLC SNs or PDCP SNs of received RLC PDUs and recording lost
RLC PDUs by ordering the RLC PDUs.
[0192] The NR MAC layer apparatus 3d-15 or 3d-30 may be connected
to multiple NR RLC layer apparatuses configured for a single UE,
and main functions of the NR MAC layer apparatus 3d-15 or 3d-30 may
include at least some of the following functions. [0193] Mapping
between logical channels and transport channels [0194]
Multiplexing/demultiplexing of MAC SDUs [0195] Scheduling
information reporting [0196] Error correction through HARQ [0197]
Priority handling between logical channels of one UE [0198]
Priority handling between UEs by means of dynamic scheduling [0199]
MBMS service identification [0200] Transport format selection
[0201] Padding
[0202] A NR PHY layer apparatus 3d-20 or 3d-25 may channel-code and
modulate upper layer data into OFDM symbols and transmit the OFDM
symbols through a radio channel. The NR PHY layer apparatus 3d-20
or 3d-25 may demodulate OFDM symbols received through a radio
channel and channel-decode and deliver the OFDM symbols to an upper
layer.
[0203] The present disclosure proposes a procedure in which a UE
compresses uplink data and a gNB decompresses the data in a
wireless communication system, and a method of solving
decompression failure, e.g., a method of supporting a data
transception procedure in which a transmitter compresses data and a
receiver decompresses the data. The method proposed by the present
disclosure may also be applied to a procedure in which a gNB
compresses downlink data directed to a UE and the UE receives and
decompresses the compressed downlink data. As described above,
since a transmitter transmits compressed data, more data may be
transmitted and coverage may be improved.
[0204] In the present disclosure, dual connectivity refers to a
technology by which a UE simultaneously accesses a master cell
group (MCG) of a master gNB and a secondary cell group (SCG) of a
secondary gNB and transmit and receive data to and from the two
gNBs. Dual connectivity may be easily extended to
multi-connectivity. That is, using multi-connectivity, a UE may
simultaneously access a master gNB and multiple secondary gNBs and
transmit and receive data to and from the gNBs, or may
simultaneously access multiple master gNBs and multiple secondary
gNBs and transmit and receive data to and from the gNBs.
[0205] The present disclosure is described in relation to dual
connectivity for convenience of explanation and may be easily
extended to multi-connectivity.
[0206] FIG. 3E is a diagram illustrating dual connectivity bearers
or multi-connectivity bearers configurable for a UE 3e-01, to which
dual connectivity or multi-connectivity is applied, in a NR system,
according to an embodiment.
[0207] In FIG. 3E, the UE 3e-01 may be configured to have dual
connectivity by a gNB, may be dual-connected to a master gNB 3e-02
and a secondary gNB 3e-03, and may configure various bearers based
on bearer setup information or logical channel configuration
information configured by the master gNB 3e-02 or the secondary gNB
3e-03. The UE 3e-01 may configure a MCG bearer showing that a RLC
layer apparatus operates in a RLC unacknowledged mode (UM) as
indicated by 3e-05. The UE 3e-01 may configure a MCG bearer showing
that a RLC layer apparatus operates in a RLC acknowledged mode (AM)
as indicated by 3e-10, or configure a MCG split bearer showing that
a PDCP layer apparatus is in a MCG and RLC layer apparatuses
operate in a RLC UM mode as indicated by 3e-15. The UE 3e-01 may
configure a MCG split bearer showing that a PDCP layer apparatus is
in a MCG and RLC layer apparatuses operate in a RLC AM mode as
indicated by 3e-20.
[0208] The UE 3e-01 may configure a SCG split bearer showing that a
PDCP layer apparatus is in a SCG and RLC layer apparatuses operate
in a RLC UM mode as indicated by 3e-25. The UE 3e-01 may configure
a SCG split bearer showing that a PDCP layer apparatus is in a SCG
and RLC layer apparatuses operate in a RLC AM mode as indicated by
3e-30. The UE 3e-01 may configure a SCG bearer showing that a RLC
layer apparatus operates in a RLC UM mode as indicated by 3e-35, or
configure a SCG bearer showing that a RLC layer apparatus operates
in a RLC AM mode as indicated by 3e-40.
[0209] Among the above-described bearers, the MCG or SCG split
bearer showing that RLC layer apparatuses operate in a RLC AM mode
has a structure useful for high-speed data transmission, and the
MCG or SCG split bearer showing that RLC layer apparatuses operate
in a RLC UM mode has a structure useful for packet duplication.
[0210] FIG. 3F is a flowchart illustrating a procedure, performed
by a gNB, for configuring one of the various bearers described
above in relation to FIG. 3E, for a UE by using a RRC message and
sending a RRC message to release logical channels of the configured
bearer when the UE establishes connection, according to an
embodiment.
[0211] In FIG. 3F, when the UE for transmitting and receiving data
in a RRC connected mode does not perform data transmission or
reception due to any reason or for a certain period, the gNB may
send a RRCConnectionRelease message to the UE to switch the UE to a
RRC idle mode (3f-01). When the UE that has not established a
connection with the gNB (hereinafter referred to as an idle mode
UE) has data to be transmitted, the UE may perform a RRC connection
establishment procedure with the gNB.
[0212] The UE may achieve reverse transmission synchronization with
the gNB through a random access procedure and transmit a
RRCConnectionRequest message to the gNB (3f-05). The
RRCConnectionRequest message may include a UE identifier, an
establishmentCause, etc.
[0213] The gNB may transmit a RRCConnectionSetup message such that
the UE establishes a RRC connection (3f-10). The RRCConnectionSetup
message may include logical channel configuration information or
bearer setup information, and thus, the MCG bearer showing that a
RLC layer apparatus operates in a RLC UM mode, the MCG bearer
showing that a RLC layer apparatus operates in a RLC AM mode, the
MCG split bearer showing that RLC layer apparatuses operate in a
RLC AM mode, the MCG split bearer showing that RLC layer
apparatuses operate in a RLC UM mode, the SCG bearer showing that a
RLC layer apparatus operates in a RLC UM mode, the SCG bearer
showing that a RLC layer apparatus operates in a RLC AM mode, the
SCG split bearer showing that RLC layer apparatuses operate in a
RLC AM mode, or the SCG split bearer showing that RLC layer
apparatuses operate in a RLC UM mode, which is described above in
relation to FIG. 3E, may be configured for the UE.
[0214] The RRCConnectionSetup message may include CellGroupConfig
IE containing a CellGroupID and logicalchannel-ToReleaseList
information such that the UE may be instructed as to which logical
channels of which cell group to release. When the CellGroupID is
not included in the CellGroupConfig IE, a master cell group may not
be designated. The RRCConnectionSetup message may include a
secondary cell group release message containing a
SecondaryCellGroupToReleaseList and a CellGroupID and SCG
configuration information containing logicalchannel-ToReleaseList
information such that the UE may be instructed as to which logical
channels of which secondary cell group to release.
[0215] The RRCConnectionSetup message may include RRC connection
configuration information. A RRC connection may also be called a
signaling radio bearer (SRB) and may be used to transmit and
receive a RRC message as a control message between the UE and the
gNB.
[0216] The RRC connected UE may transmit a
RRCConnetionSetupComplete message to the gNB (3f-15). When the gNB
does not know of or desires to check capability of the currently
connected UE, the gNB may send a UE capability inquiry message. The
UE may send a UE capability report message. The UE capability
report message may include an indicator indicating whether the UE
is capable of using uplink data compression (UDC). The
RRCConnetionSetupComplete message may include a control message
such as a SERVICE REQUEST message for requesting an MME to
configure bearers for a certain service by the UE.
[0217] The gNB may transmit the SERVICE REQUEST message included in
the RRCConnetionSetupComplete message, to the MME (3f-20), and the
MME may determine whether to provide the service requested by the
UE.
[0218] Upon determining to provide the service requested by the UE,
the MME may transmit an INITIAL CONTEXT SETUP REQUEST message to
the gNB (3f-25). The INITIAL CONTEXT SETUP REQUEST message may
include quality of service (QoS) information to be applied to
configure data radio bearers (DRBs) and security information to be
applied to the DRBs (e.g., a security key or a security
algorithm).
[0219] The gNB may exchange a SecurityModeCommand message (3f-30)
and a SecurityModeComplete message (3f-35) with the UE to configure
a security mode. After the security mode is completely configured,
the gNB may transmit a RRCConnectionReconfiguration message to the
UE (3f-40). The RRCConnectionReconfiguration message may include
logical channel configuration information or bearer setup
information and thus, the MCG bearer showing that a RLC layer
apparatus operates in a RLC UM mode, the MCG bearer showing that a
RLC layer apparatus operates in a RLC AM mode, the MCG split bearer
showing that RLC layer apparatuses operate in a RLC AM mode, the
MCG split bearer showing that RLC layer apparatuses operate in a
RLC UM mode, the SCG bearer showing that a RLC layer apparatus
operates in a RLC UM mode, the SCG bearer showing that a RLC layer
apparatus operates in a RLC AM mode, the SCG split bearer showing
that RLC layer apparatuses operate in a RLC AM mode, or the SCG
split bearer showing that RLC layer apparatuses operate in a RLC UM
mode, which is described above in relation to FIG. 3E, may be
configured for the UE.
[0220] The RRCConnectionReconfiguration message may include
CellGroupConfig IE containing a CellGroupID and
logicalchannel-ToReleaseList information such that the UE may be
instructed as to which logical channels of which cell group to
release. When the CellGroupID is not included in the
CellGroupConfig IE, a master cell group may not be designated. The
RRCConnectionReconfiguration message may include a secondary cell
group release message containing a SecondaryCellGroupToReleaseList
and a CellGroupID and SCG configuration information containing
logicalchannel-ToReleaseList information such that the UE may be
instructed as to which logical channels of which secondary cell
group to release.
[0221] The RRCConnectionReconfiguration message may include DRB
setup information for processing user data and the UE may configure
DRBs by using the DRB setup information and transmit a
RRCConnectionReconfigurationComplete message to the gNB
(3f-45).
[0222] The gNB having completely configured the DRBs with the UE
may transmit an INITIAL CONTEXT SETUP COMPLETE message to the MME
(3f-50) and the MME having received the INITIAL CONTEXT SETUP
COMPLETE message may exchange an S1 BEARER SETUP message and an S1
BEARER SETUP RESPONSE message with an S-GW to configure S1 bearers
(3f-55 and 3f-60). The S1 bearers are data transmission connections
established between the S-GW and the gNB and may correspond to the
DRBs one-to-one. When the above-described operations are all
completed, the UE may transmit and receive data to and from the gNB
and the S-GW (3f-65 and 3f-70). As described above, a general data
transmission procedure includes three steps of RRC connection
setup, security setup, and DRB setup.
[0223] The gNB may transmit a RRCConnectionReconfiguration message
to the UE to renew, add, or change the RRC connection due to any
reason (3f-75). The RRCConnectionReconfiguration message may
include logical channel configuration information or bearer setup
information and thus, the MCG bearer showing that a RLC layer
apparatus operates in a RLC UM mode, the MCG bearer showing that a
RLC layer apparatus operates in a RLC AM mode, the MCG split bearer
showing that RLC layer apparatuses operate in a RLC AM mode, the
MCG split bearer showing that RLC layer apparatuses operate in a
RLC UM mode, the SCG bearer showing that a RLC layer apparatus
operates in a RLC UM mode, the SCG bearer showing that a RLC layer
apparatus operates in a RLC AM mode, the SCG split bearer showing
that RLC layer apparatuses operate in a RLC AM mode, or the SCG
split bearer showing that RLC layer apparatuses operate in a RLC UM
mode, which is described above in relation to FIG. 3E, may be
configured for the UE.
[0224] The RRCConnectionReconfiguration message may include
CellGroupConfig IE containing a CellGroupID and
logicalchannel-ToReleaseList information such that the UE may be
instructed as to which logical channels of which cell group to
release. When the CellGroupID is not included in the
CellGroupConfig IE, a master cell group may not be designated. The
RRCConnectionReconfiguration message may include a secondary cell
group release message containing a SecondaryCellGroupToReleaseList
and a CellGroupID and SCG configuration information containing
logicalchannel-ToReleaseList information such that the UE may be
instructed as to which logical channels of which secondary cell
group to release.
[0225] In a NR system according to an embodiment, the gNB may
configure, for the UE, the various bearers described above in
relation to FIG. 3E by using the RRC message indicated by 3f-10,
3f-40, or 3f-75 in FIG. 3F. The gNB may change types of the bearers
configured as described above in relation to FIG. 3E, by using the
RRC message indicated by 3f-10, 3f-40, or 3f-75. For example, the
bearer type may be changed to the MCG bearer indicated by 3e-05 by
releasing logical channels (a RLC layer apparatus and a MAC layer
apparatus) corresponding to a SCG of the MCG split bearer showing
that RLC layer apparatuses operate in a RLC UM mode as indicated by
3e-15, changed to the MCG bearer indicated by 3e-10 by releasing
logical channels (a RLC layer apparatus and a MAC layer apparatus)
corresponding to a SCG of the MCG split bearer showing that RLC
layer apparatuses operate in a RLC AM mode as indicated by 3e-20,
changed to the SCG bearer indicated by 3e-35 by releasing logical
channels (a RLC layer apparatus and a MAC layer apparatus)
corresponding to a MCG of the SCG split bearer showing that RLC
layer apparatuses operate in a RLC UM mode as indicated by 3e-25,
or changed to the SCG bearer indicated by 3e-40 by releasing
logical channels (a RLC layer apparatus and a MAC layer apparatus)
corresponding to a MCG of the SCG split bearer showing that RLC
layer apparatuses operate in a RLC AM mode as indicated by
3e-30.
[0226] The present disclosure proposes a method of releasing a
logical channel of a bearer in an NR system.
[0227] An embodiment for releasing a logical channel of a bearer in
the present disclosure is as described below.
[0228] A gNB may instruct a UE as to which logical channel of which
cell group to release, by using the RRC message indicated by 3f-10,
3f-40, or 3f-75 in FIG. 3F and including CellGroupConfig IE
containing a CellGroupID and logicalchannel-ToReleaseList
information. When the CellGroupID is not included in the
CellGroupConfig IE, a master cell group may not be designated. When
instructed by the gNB as to which logical channel of which bearer
of which cell group to release, the UE may perform a logical
channel release procedure on the instructed logical channel.
[0229] Logical Channel Release Method Based on Cell Group
Configuration
[0230] The network configures the UE with a Master Cell Group (MCG)
and zero or one or more Secondary Cell Groups (SCG). For EN-DC, the
MSG is configured as specified in TS 36.331. The network provides
the configuration parameters for a cell group in the
CellGroupsConfig IE. If the CellGroupConfig does not contain the
cellGroupId, it applies for the MCG. Otherwise, it applies for an
SCG [0231] if the CellGroupConfig contains the
logicalChannel-ToReleaseList: [0232] perform Logical Channel
Release
[0233] An embodiment for releasing a logical channel of a bearer in
the present disclosure is as described below.
[0234] A gNB may instruct a UE as to which logical channel of which
secondary cell group to release, by using the RRC message indicated
by 3f-10, 3f-40, or 3f-75 in FIG. 3F and including a secondary cell
group release message containing a SecondaryCellGroupToReleaseList
and a CellGroupID and SCG configuration information containing
logicalchannel-ToReleaseList information. When instructed by the
gNB as to which logical channel of which bearer of which cell group
to release, the UE may perform a logical channel release procedure
on the instructed logical channel.
[0235] Logical Channel Release Method based on Secondary Cell Group
Release
[0236] The UE shall [0237] for each CellGroupld in the
SecondaryCellGroupToReleaseList: [0238] reset SCG MAC, if
configured; [0239] for each logical channel that is part of the SCG
configuration: [0240] *perform logical channel release procedure
[0241] release the entire SCG configuration;
[0242] A logical channel release procedure is performed in various
embodiments for releasing a logical channel of a bearer. The
logical channel release procedure will now be described in
detail.
[0243] An embodiment of a logical channel release procedure in a NR
system according to the present disclosure is as described
below.
[0244] When UE configuration information including a
logicalChannel-ToReleaseList containing a LogicalChannelIdentity is
received using the RRC message indicated by 3f-10, 3f-40, or 3f-75
in FIG. 3F, that is, when instructed to release a logical channel
is received according to various embodiments for releasing a
logical channel of a bearer, a UE may perform the following
operations. [0245] release the RLC entity or entities (includes
discarding all pending RLC PDUs and RLC SDUs) [0246] trigger the
associated PDCP entity to perform data recovery [0247] release the
DTCH logical channel [0248] Logical Channel Release Procedure
[0249] The UE shall: [0250] for each LogicalChannelIdentity value
included in the logicalChannel-ToReleaseList that is part of the
current UE configuration (LCH release), or [0251] for each
LogicalChannelIdentity value that is to be released as the result
of full configuration option: [0252] release the RLC entity or
entities (includes discarding all pending RLC PDUs and RLC SDUs);
[0253] trigger the associated PDCP entity to perform data recovery
[0254] release the DTCH logical channel.
[0255] An embodiment of a logical channel release procedure in a NR
system according to the present disclosure is as described
below.
[0256] When UE configuration information including a
logicalChannel-ToReleaseList containing a LogicalChannelIdentity is
received using the RRC message indicated by 3f-10, 3f-40, or 3f-75
in FIG. 3F, that is, when instructed to release a logical channel
is received according to various embodiments for releasing a
logical channel of a bearer, a UE performs the following
operations. [0257] release the RLC entity or entities (includes
discarding all pending RLC PDUs and RLC SDUs) [0258] if the RLC
entity (or RLC entities) is(are) RLC AM entity (or RLC AM
entities), trigger the associated PDCP entity to perform data
recovery [0259] release the DTCH logical channel
[0260] Logical Channel Release Procedure
[0261] The UE shall: [0262] for each LogicalChannelIdentity value
included in the logicalChannel-ToReleaseList that is part of the
current UE configuration (LCH release), or [0263] for each
LogicalChannelIdentity value that is to be released as the result
of full configuration option: [0264] release the RLC entity or
entities (includes discarding all pending RLC PDUs and RLC SDUs);
[0265] if the RLC entity (or RLC entities) is(are) RLC AM entity
(or RLC AM entities), trigger the associated PDCP entity to perform
data recovery [0266] release the DTCH logical channel.
[0267] In an embodiment of a logical channel release procedure,
when the RLC layer apparatus operates in a RLC UM mode, although
data loss occurs, data recovery is not required and thus PDCP data
recovery may not be unnecessarily performed. That is, since the RLC
UM mode allows data loss and is sensitive to a delay, performing
PDCP data recovery only in the RLC AM mode is suitable to satisfy
service requirements and is more efficient.
[0268] An embodiment of a logical channel release procedure in a NR
system according to the present disclosure is as described
below.
[0269] When UE configuration information including a
logicalChannel-ToReleaseList containing a LogicalChannelIdentity is
received using the RRC message indicated by 3f-10, 3f-40, or 3f-75
in FIG. 3F, that is, when instructed to release a logical channel
is received according to various embodiments for releasing a
logical channel of a bearer, a UE may perform the following
operations. [0270] release the RLC entity or entities (includes
discarding all pending RLC PDUs and RLC SDUs) [0271] if the RLC
entity (or RLC entities) is(are) RLC AM entity (or RLC AM entities)
and if the associated PDCP entity is neither released nor
re-established, trigger the associated PDCP entity to perform data
recovery [0272] release the DTCH logical channel
[0273] Logical Channel Release Procedure
[0274] The UE shall: [0275] for each LogicalChannelIdentity value
included in the logicalChannel-ToReleaseList that is part of the
current UE configuration (LCH release), or [0276] for each
LogicalChannelIdentity value that is to be released as the result
of full configuration option: [0277] release the RLC entity or
entities (includes discarding all pending RLC PDUs and RLC SDUs);
[0278] if the RLC entity (or RLC entities) is(are) RLC AM entity
(or RLC AM entities) and if the associated PDCP entity is neither
released nor re-established, trigger the associated PDCP entity to
perform data recovery [0279] release the DTCH logical channel.
[0280] In an embodiment of a logical channel release procedure, if
the RLC layer apparatus operates in a RLC UM mode, although data
loss occurs, data recovery is not required and thus PDCP data
recovery may not be unnecessarily performed. When the associated
PDCP layer apparatus is released or re-established, PDCP data
recovery may not be performed. In other words, when the PDCP layer
apparatus is released or re-established, since all pending data are
discarded and a buffer is initialized, retransmission or data
recovery may not be performed. That is, when the associated PDCP
layer apparatus is neither released nor re-established and when the
RLC AM layer apparatus (or RLC AM layer apparatuses) is released or
re-established, PDCP data recovery may not be performed.
[0281] A PDCP data recovery procedure is performed in various
embodiments of a logical channel release procedure.
[0282] The present disclosure proposes an efficient PDCP data
recovery procedure in a NR system as described below.
[0283] When a PDCP data recovery request for a radio bearer or an
associated logical channel, a PDCP layer apparatus of a UE may
perform the following operations. [0284] if the radio bearer is
configured by upper layers to send a PDCP status report in the
uplink (statusReportRequired), compile a status report and submit
it to lower layers as the first PDCP PDU for the transmission;
[0285] perform retransmission of all the PDCP PDUs previously
submitted to re-established or released AM RLC entity in ascending
order of the associated COUNT values from the first PDCP PDU for
which the successful delivery has not been confirmed by lower
layers.
[0286] PDCP Data Recovery Procedure
[0287] When upper layers request a PDCP Data Recovery for a radio
bearer, the UE shall: [0288] if the radio bearer is configured by
upper layers to send a PDCP status report in the uplink
(statusReportRequired), compile a status report and submit it to
lower layers as the first PDCP PDU for the transmission; [0289]
perform retransmission of all the PDCP PDUs previously submitted to
re-established or released AM RLC entity in ascending order of the
associated COUNT values from the first PDCP PDU for which the
successful delivery has not been confirmed by lower layers.
[0290] FIG. 3G is a flowchart illustrating a UE operation when a UE
receives a logical channel release request from a gNB, according to
an embodiment.
[0291] In FIG. 3G, the UE may receive a logical channel release
request from the gNB according to, for example, the various
embodiments for releasing a logical channel of a bearer
(3g-05).
[0292] When the logical channel release request is received, the UE
may identify which logical channel of which bearer of which cell
group to release, and determine whether a RLC layer apparatus
corresponding to the logical channel operates in a RLC AM mode and
whether a PDCP layer apparatus connected to the logical channel is
neither re-established nor released (3g-10).
[0293] When the RLC layer apparatus corresponding to the logical
channel operates in a RLC AM mode and when the PDCP layer apparatus
connected to the logical channel is neither re-established nor
released, the PDCP layer apparatus may perform PDCP data recovery
(3g-15). Otherwise, the PDCP layer apparatus may not perform PDCP
data recovery (3g-20).
[0294] The present disclosure proposes a procedure in which a UE
compresses uplink data and a gNB decompresses the data in a
wireless communication system, a certain header format therefor,
and a method of solving decompression failure, e.g., a method of
supporting a data transception procedure in which a transmitter
compresses data and a receiver decompresses the data. The present
disclosure may also be applied to a procedure in which a gNB
compresses downlink data directed to a UE and the UE receives and
decompresses the compressed downlink data. As described above,
since a transmitter transmits compressed data, more data may be
transmitted and coverage may be improved.
[0295] FIG. 4A is a flowchart illustrating a procedure, performed
by a gNB, for instructing whether to perform uplink data
compression (UDC), when a UE establishes a connection with a
network, according to an embodiment.
[0296] FIG. 4A illustrates a procedure in which a gNB requests UDC
when a UE in a RRC idle mode or a RRC inactive (or
lightly-connected) mode is switched to a RRC connected mode and
establishes a connection with a network.
[0297] In FIG. 4A, when the UE for transmitting and receiving data
in a RRC connected mode does not perform data transmission or
reception due to any reason or for a certain period, the gNB may
send a RRCConnectionRelease message to the UE to switch the UE to a
RRC idle mode (4a-01). When the UE that has not established a
connection with the gNB (hereinafter referred to as an idle mode
UE) has data to be transmitted, the UE may perform a RRC connection
establishment procedure with the gNB.
[0298] The UE may achieve reverse transmission synchronization with
the gNB through a random access procedure and transmit a
RRCConnectionRequest message to the gNB (4a-05). The
RRCConnectionRequest message may include a UE identifier, an
establishmentCause, etc.
[0299] The gNB may transmit a RRCConnectionSetup message such that
the UE establishes a RRC connection (4a-10). The RRCConnectionSetup
message may include information indicating whether to use UDC per
logical channel (LogicalChannelConfig), per bearer, or per PDCP
layer apparatus (PDCP-Config). Specifically, the RRCConnectionSetup
message may provide information indicating whether to use UDC only
for which IP or QoS flow, for each logical channel, bearer, or PDCP
layer apparatus (or service data adaptation protocol (SDAP) layer
apparatus). As another example, using the RRCConnectionSetup
message, information about an IP or QoS flow to use or not to use
UDC may be provided to the SDAP layer apparatus such that the SDAP
layer apparatus may instruct the PDCP layer apparatus whether to
use or not to use UDC for each QoS flow. As another example,
through the RRCConnectionSetup message, the PDCP layer apparatus
may autonomously check each QoS flow (based on configuration
information provided by the gNB) and determine whether to apply or
not to apply UDC.
[0300] When instructed to use UDC, a pre-defined library or
dictionary ID to be used for UDC, a buffer size to be used for UDC,
etc. may be provided.
[0301] The RRCConnectionSetup message may include an uplink data
decompression setup or release command. When configured to use UDC,
it may be configured with a RLC AM bearer (a lossless mode due to
an ARQ function or a retransmission function) and may not be
configured with a header compression protocol (e.g., a robust
header compression (ROHC) protocol). The RRCConnectionSetup message
may include RRC connection configuration information. A RRC
connection may also be called a signaling radio bearer (SRB) and
may be used to transmit and receive a RRC message as a control
message between the UE and the gNB.
[0302] The RRC connected UE may transmit a
RRCConnetionSetupComplete message to the gNB (4a-15). When the gNB
does not know of or desires to check capability of the currently
connected UE, the gNB may send a UE capability inquiry message. The
UE may send a UE capability report message. The UE capability
report message may include an indicator indicating whether the UE
is capable of using UDC.
[0303] The RRCConnetionSetupComplete message may include a control
message such as a SERVICE REQUEST message for requesting an MME to
configure bearers for a certain service for the UE. The gNB may
transmit the SERVICE REQUEST message included in the
RRCConnetionSetupComplete message, to the MME (4a-20), and the MME
may determine whether to provide the service requested by the
UE.
[0304] Upon determining to provide the service requested by the UE,
the MME may transmit an INITIAL CONTEXT SETUP REQUEST message to
the gNB (4a-25). The INITIAL CONTEXT SETUP REQUEST message may
include QoS information to be applied to configure data radio
bearers (DRB) and security information to be applied to the DRBs
(e.g., a security key or a security algorithm).
[0305] The gNB may exchange a SecurityModeCommand message (4a-30)
and a SecurityModeComplete message (4a-35) with the UE to configure
a security mode. After the security mode is completely configured,
the gNB may transmit a RRCConnectionReconfiguration message to the
UE (4a-40). The RRCConnectionReconfiguration message may include
information indicating whether to use UDC per logical channel
(LogicalChannelConfig), per bearer, or per PDCP layer apparatus
(PDCP-Config). Specifically, the RRCConnectionReconfiguration
message may provide information indicating whether to use UDC only
for which IP or QoS flow, for each logical channel, bearer, or PDCP
layer apparatus (or service data adaptation protocol (SDAP) layer
apparatus). As another example, using the
RRCConnectionReconfiguration message, information about an IP or
QoS flow to use or not to use UDC may be provided to the SDAP layer
apparatus such that the SDAP layer apparatus may instruct the PDCP
layer apparatus whether to use or not to use UDC for each QoS flow.
As another example, through the RRCConnectionReconfiguration
message, the PDCP layer apparatus may autonomously check each QoS
flow (based on configuration information provided by the gNB) and
determine whether to apply or not to apply UDC.
[0306] When instructed to use UDC, a pre-defined library or
dictionary ID to be used for UDC, a buffer size to be used for UDC,
etc. may be provided. The RRCConnectionReconfiguration message may
include an uplink data decompression setup or release command. When
configured to use UDC, it may be configured with a RLC AM bearer (a
lossless mode due to an ARQ function or a retransmission function)
and may not be configured with a header compression protocol (e.g.,
a ROHC protocol). The RRCConnectionReconfiguration message may
include DRB setup information for processing user data and the UE
may configure DRBs by using the DRB setup information and transmit
a RRCConnectionReconfigurationComplete message to the gNB
(4a-45).
[0307] The gNB having completely configured the DRBs with the UE
may transmit an INITIAL CONTEXT SETUP COMPLETE message to the MME
(4a-50) and the MME having received the INITIAL CONTEXT SETUP
COMPLETE message may exchange an S1 BEARER SETUP message and an S1
BEARER SETUP RESPONSE message with an S-GW to configure S1 bearers
(4a-55 and 4a-60). The S1 bearers are data transmission connections
established between the S-GW and the gNB and may correspond to the
DRBs one-to-one. When the above-described operations are all
completed, the UE may transmit and receive data to and from the gNB
and the S-GW (4a-65 and 4a-70). As described above, a general data
transmission procedure includes three steps of RRC connection
setup, security setup, and DRB setup. The gNB may transmit a
RRCConnectionReconfiguration message to the UE to renew, add, or
change the RRC connection due to any reason (4a-75). The
RRCConnectionReconfiguration message may include information
indicating whether to use UDC per logical channel
(LogicalChannelConfig), per bearer, or per PDCP layer apparatus
(PDCP-Config). Specifically, the RRCConnectionReconfiguration
message may provide information indicating whether to use UDC only
for which IP or QoS flow, for each logical channel, bearer, or PDCP
layer apparatus (or service data adaptation protocol (SDAP) layer
apparatus). As another example, using the
RRCConnectionReconfiguration message, information about an IP or
QoS flow to use or not to use UDC may be provided to the SDAP layer
apparatus such that the SDAP layer apparatus may instruct the PDCP
layer apparatus whether to use or not to use UDC for each QoS
flow.
[0308] As another example, the PDCP layer apparatus may
autonomously check each QoS flow (based on configuration
information provided by the gNB) and determine whether to apply or
not to apply UDC.
[0309] When instructed to use UDC, a pre-defined library or
dictionary ID to be used for UDC, a buffer size to be used for UDC,
etc. may be provided. The RRCConnectionReconfiguration message may
include an uplink data decompression setup or release command. When
configured to use UDC, it may be configured with a RLC AM bearer (a
lossless mode due to an ARQ function or a retransmission function)
and may not be configured with a header compression protocol (e.g.,
a ROHC protocol).
[0310] FIG. 4B is a diagram illustrating a procedure and a data
configuration for performing UDC, according to an embodiment.
[0311] In FIG. 4B, uplink data 4b-05 may include data corresponding
to services such as video upload, photo upload, web browser, and
voice over LTE (VoLTE). Data generated by an application layer
apparatus may be processed by a network data transmission layer
such as a TCP/IP or UDP layer to configure headers 4b-10 and 4b-15
and may be delivered to a PDCP layer apparatus. When a PDCP SDU is
received from an upper layer, the PDCP layer apparatus may perform
the following operations.
[0312] When the RRC message indicated by 4a-10, 4a-40, or 4a-75 in
FIG. 4A indicates to use UDC for the PDCP layer apparatus, the PDCP
layer apparatus may perform UDC on the PDCP SDU as indicated by
4b-20 to compress the uplink data, configure a UDC header (a header
for the compressed uplink data 4b-20) 4b-25, perform ciphering,
perform integrity protection when configured, and configure a PDCP
header 4b-30, thereby generating a PDCP PDU. The PDCP layer
apparatus includes a UDC compression/decompression layer apparatus
and may determine whether to perform UDC on each data unit as
indicated by the RRC message and use the UDC
compression/decompression layer apparatus. In a transmitter, a Tx
PDCP layer apparatus may perform data compression by using a UDC
compression layer apparatus and, in a receiver, a Rx PDCP layer
apparatus may perform data decompression by using a UDC
decompression layer apparatus.
[0313] The above-described procedure of FIG. 4B may be used not
only to compress the uplink data by a UE but also to compress
downlink data. The above description related to the uplink data may
be equally applied to the downlink data.
[0314] FIG. 4C is a diagram illustrating a UDC method according to
an embodiment.
[0315] FIG. 4C illustrates a DEFLATE-based UDC algorithm which is a
lossless compression algorithm. According to the DEFLATE-based UDC
algorithm, basically, uplink data may be compressed using a
combination of an LZ77 algorithm and Huffman coding algorithm.
According to the LZ77 algorithm, an operation of finding repeated
occurrences of data within a sliding window is performed, and when
the repeated occurrences within the sliding window are found, data
compression is performed by expressing the repeated data within the
sliding window as a location and length thereof. The sliding window
is called a buffer in the UDC method and may be set to 8 kilobytes
or 32 kilobytes. That is, the sliding window or the buffer may
record 8,192 or 32,768 characters, find repeated occurrences of
data, and perform data compression by expressing the repeated data
as a location and length thereof. Therefore, since the LZ77
algorithm is a sliding window scheme, that is, since subsequent
data is coded immediately after previously coded data is updated in
a buffer, successive data may have correlations therebetween.
[0316] Thus, the subsequent data may be normally decoded only when
the previously coded data is normally decoded. The codes compressed
and expressed as the location and length by using the LZ77
algorithm is compressed once again by using the Huffman coding
algorithm. According to the Huffman coding algorithm, repeated
characters may be found and data compression may be performed once
again by assigning the shortest code to the most frequent character
and assigning the longest code to the least frequent character. The
Huffman coding algorithm is a prefix coding algorithm and is an
optimal coding scheme by which all codes are uniquely
decodable.
[0317] As described above, a transmitter may encode raw data 4c-05
by using the LZ77 algorithm (4c-10), update a buffer 4c-15, and
configure a UDC header by generating checksum bits for the content
(or data) of the buffer. The checksum bits may be used by a
receiver to determine validity of a buffer status. The transmitter
may compress the codes encoded using the LZ77 algorithm, by using
the Huffman coding algorithm (4c-20), and transmit the compressed
data as uplink data (4c-25).
[0318] The receiver may perform a decompression procedure on the
compressed data received from the transmitter, in an inverse manner
to that of the transmitter. That is, the receiver may perform
Huffman decoding (4c-30), update a buffer (4c-35), and check
validity of the updated buffer, based on the checksum bits of the
UDC header. Upon determining that the checksum bits have no error,
the receiver may decompress the data by performing decoding using
the LZ77 algorithm (4c-40) to reconstruct the raw data and deliver
the decompressed data to an upper layer (4c-45).
[0319] As described above, since the LZ77 algorithm is a sliding
window scheme, that is, since subsequent data is coded immediately
after previously coded data is updated in a buffer, successive data
may have correlations therebetween. Thus, the subsequent data may
be normally decoded only when the previously coded data is normally
decoded. Therefore, a Rx PDCP layer apparatus may check PDCP
sequence numbers of a PDCP header, check a UDC header (check an
indicator indicating whether data compression is or is not
performed), and decompress compressed UDC data in ascending order
of the PDCP sequence numbers.
[0320] A procedure for configuring UDC for a UE by a gNB and a
procedure for performing UDC by the UE are as described below.
[0321] The gNB may configure or release UDC for a bearer or a
logical channel which configures a RLC AM mode for the UE, by using
the RRC message indicated by 4a-10, 4a-40, or 4a-75 in FIG. 4A. The
gNB may reset a UDC apparatus (or protocol) of a PDCP layer
apparatus of the UE, by using the RRC message. Resetting the UDC
apparatus (or protocol) means that a UDC buffer for uplink data
compression of the UE is reset, and is used to achieve
synchronization between the UDC buffer of the UE and a UDC buffer
for uplink data decompression of the gNB. To reset the buffer of
the UDC apparatus, an existing PDCP control PDU may be modified or
a new PDCP control PDU may be defined and a transmitter (gNB) may
reset a UDC buffer of a receiver (UE) by using the PDCP control PDU
instead of the RRC message to achieve synchronization for user data
compression and decompression between the transmitter and the
receiver.
[0322] Using the RRC message, whether to perform uplink data
compression may be determined per bearer, per logical channel, or
per PDCP layer apparatus. Specifically, whether to perform or not
to perform uplink data decompression may be configured per IP (or
QoS) flow in each bearer, logical channel, or PDCP layer
apparatus.
[0323] For the configuration per QoS flow, the PDCP layer apparatus
may configure an indicator or information to indicate for which QoS
flow to perform uplink data decompression and for which QoS flow
not to perform uplink data decompression. The configuration per QoS
flow may be provided to a SDAP layer apparatus other than the PDCP
layer apparatus such that the SDAP layer apparatus may instruct the
PDCP layer apparatus whether to perform or not to perform uplink
data decompression for each QoS flow when the QoS flow is mapped to
a bearer.
[0324] Using the RRC message, the gNB may configure a PDCP discard
timer value for the UE. In this case, for the PDCP discard timer
value, a PDCP discard timer value for data to which UDC is not
applied and a PDCP discard timer value for data to which UDC is
applied may be separately configured.
[0325] When configured to perform UDC for a certain bearer, logical
channel, or PDCP layer apparatus (or for any QoS flows of the
certain bearer, logical channel, or PDCP layer apparatus) by using
the RRC message, the UE may reset a buffer in a UDC apparatus of
the PDCP layer apparatus in accordance with the configuration and
prepare a UDC procedure. When a PDCP SDU is received from an upper
layer and when configured to perform UDC for the PDCP layer
apparatus, the UE may perform UDC on the received PDCP SDU.
[0326] When configured to perform UDC only for certain QoS flows of
the PDCP layer apparatus, the UE may determine whether to perform
UDC by checking an instruction of an upper SDAP layer or QoS flow
identities, and perform UDC. When UDC is performed and the buffer
is updated in accordance with the UDC compression, the UE may
configure a UDC buffer. When UDC is performed, the PDCP SDU
received from the upper layer may be compressed into UDC data
(e.g., a UDC block) having a smaller size.
[0327] The UE may configure a UDC header for the compressed UDC
data. The UDC header may include an indicator indicating whether
UDC is or is not performed. For example, a 1-bit indicator of the
UDC header may have a value 0 indicating that UDC is applied, or a
value 1 indicating that UDC is not applied.
[0328] UDC may not be applied because an upper layer (e.g., an
application layer) has already performed data compression such
that, although the PDCP layer apparatus performs UDC, a very low
compression ratio may be obtained and processing load of a
transmitter may unnecessarily increase due to the compression
procedure, or because the PDCP SDU received from the upper layer
does not have a repeated data structure and thus may not be
compressed using the UDC method (e.g., the DEFLATE algorithm).
[0329] When UDC is performed on the PDCP SDU received from the
upper layer and the UDC buffer is updated, the Rx PDCP layer
apparatus may calculate checksum bits and include the calculated
checksum bits in the UDC buffer to check validity of the updated
UDC buffer. Herein, the checksum bits have a certain length, e.g.,
4 bits.
[0330] The UE may perform integrity protection on data to which
uplink data decompression is applied or not applied, when integrity
protection is configured for the data, perform ciphering, and
deliver the data to a lower layer.
[0331] FIG. 4D is a diagram illustrating a UDC header 4d-05
according to an embodiment.
[0332] In FIG. 4D, when UDC is applied (when UDC is performed), a
PDCP PDU may include a PDCP header, the UDC header 4d-05, and a
compressed UDC data block. The UDC header 4d-05 may have a size of
1 byte and may include an F field 4d-10, an R field 4d-15, and
checksum bits 4d-20.
[0333] In the UDC header 4d-05, the F field 4d-10 is a field
indicating whether UDC is applied or not applied to the UDC data
block. For example, the F field 4d-10 may indicate whether UDC is
performed or not performed. That is, a Tx PDCP layer apparatus may
set the F field 4d-10 to be, for example, 1 when a PDCP SDU is
received from an upper layer and UDC is applied thereto, and may
set the F field 4d-10 to be 0 when UDC is applied thereto. UDC may
not be applied because an upper layer (e.g., an application layer)
has already performed data compression such that, although the PDCP
layer apparatus performs UDC, a very low compression ratio may be
obtained and processing load of a transmitter may unnecessarily
increase due to the compression procedure. The PDCP layer apparatus
may determine whether to apply UDC, by receiving instruction
information for each IP or QoS flow from a SDAP layer apparatus, or
the PDCP layer apparatus or a UDC apparatus may determine whether
to apply UDC to each IP or QoS flow based on configuration
information included in a RRC message provided by a gNB.
[0334] The R bits 4d-15 of FIG. 4D are reserved bits and may be
defined and used to indicate whether to reset a UDC buffer, whether
to use current data to update the UDC buffer, or whether to use a
pre-defined dictionary.
[0335] The checksum bits 4d-20 of FIG. 4D may be used to check
validity of the content of a Tx UDC buffer used when a transmitter
applies UDC, as described above. When a receiver decompresses
compressed UDC data, the receiver may calculate and use checksum
bits to check validity of the content of a Rx UDC buffer. The
checksum bits 4d-20 may have a length of 4 bits or may have a
longer length to increase accuracy of checking validity.
[0336] FIGS. 4E and 4F are diagrams illustrating a procedure for
defining a new field capable of reducing overhead, in a PDCP header
and configuring a PDCP PDU by using the new field, according to
embodiments.
[0337] As illustrated in FIG. 4E, a new U field 4e-10 may be
defined in a PDCP header 4e-05. The U field 4e-10 may indicate
whether UDC is applied to a PDCP SDU of the PDCP PDU. The U field
4e-10 may indicate whether a UDC header exists in the PDCP SDU. The
reason why a 1-bit indicator of the PDCP header 4e-05 indicates
whether UDC is applied and whether a UDC header exists is because,
when an upper layer (e.g., an application layer) has already
performed data compression, that is, when the upper layer already
has a compression function, although a PDCP layer apparatus
performs UDC, a very low compression ratio may be obtained and
processing load of a transmitter may unnecessarily increase due to
the compression procedure.
[0338] The PDCP layer apparatus may determine whether to apply UDC,
by receiving instruction information for each IP or QoS flow from a
SDAP layer apparatus, or the PDCP layer apparatus or a UDC
apparatus may determine whether to apply UDC to each IP or QoS flow
based on configuration information included in a RRC message
provided by a gNB.
[0339] In FIG. 4F, when UDC is not applied to upper layer data
4f-15, a Tx PDCP layer apparatus 4f-01 for which UDC is configured
may set the U field of a PDCP header 4f-20 to be 0 (or 1) and omit
a UDC header. Otherwise, when UDC is applied to upper layer data
4f-05, the Tx PDCP layer apparatus 4f-01 for which UDC is
configured may set the U field of a PDCP header 4f-10 to be 1 (or
0) and configure and insert a UDC header. Therefore, when the U
field of the PDCP header is set to be 0, a Rx PDCP layer apparatus
may determine that no UDC header exists and may omit a UDC process,
i.e., uplink data decompression, on the PDCP SDU. Otherwise, when
the U field of the PDCP header is set to be 1, the Rx PDCP layer
apparatus may determine that a UDC header exists, read the UDC
header of the PDCP SDU, check validity of a buffer by using
checksum bits of the UDC header, and perform uplink data
decompression on the other part of the PDCP SDU to reconstruct raw
data.
[0340] Therefore, when data is transmitted from a transmitter to a
receiver and a PDCP PDU is configured for the PDCP SDU to which UDC
is not applied, the 1-bit U field 4e-10 of the PDCP header 4e-05 of
FIG. 4E may indicate that no UDC header exists and that UDC is not
applied, a UDC header may be omitted, and thus 1-byte overhead may
be saved. The U field may be used only when UDC is configured for a
bearer, a logical channel, or a PDCP layer apparatus and may be
used as a reserved field or another function field when UDC is not
configured.
[0341] FIG. 4G is a flowchart illustrating a transmitter (UE)
operation for performing a UDC method capable of reducing overhead,
according to an embodiment.
[0342] In FIG. 4G, a Tx PDCP layer apparatus 4g-01 of the UE for
which UDC is configured may receive upper layer data (4g-05) and
determine whether to apply UDC (4g-10). Herein, the PDCP layer
apparatus 4g-01 may determine whether to apply UDC, by receiving
instruction information for each IP or QoS flow from a SDAP layer
apparatus, or the PDCP layer apparatus 4g-01 or a UDC apparatus may
determine whether to apply UDC to each IP or QoS flow, based on
configuration information included in a RRC message provided by a
gNB.
[0343] When UDC is not applied to the upper layer data, a U field
of a PDCP header may be set to be 0 (or 1) and a UDC header may be
omitted (4g-20). When UDC is applied to the upper layer data, the U
field of the PDCP header may be set to be 1 (or 0) and a UDC header
may be configured and inserted (4g-15).
[0344] FIG. 4H is a flowchart illustrating a receiver (gNB)
operation for performing a UDC method capable of reducing overhead,
according to an embodiment.
[0345] In FIG. 4H, when lower layer data is received (4h-05), a Rx
PDCP layer apparatus 4h-01 of the gNB may determine whether UDC is
applied, by using a 1-bit indicator of a PDCP header (4h-10). When
a U field of the PDCP header is set to be 0, the Rx PDCP layer
apparatus of the gNB may determine that no UDC header exists, and
omit a UDC process, i.e., uplink data decompression, on a PDCP SDU
(4h-20).
[0346] Otherwise, when the U field of the PDCP header is set to be
1, the Rx PDCP layer apparatus of the gNB may determine that a UDC
header exists, read the UDC header of the PDCP SDU, check validity
of a buffer by using checksum bits of the UDC header, and perform
uplink data decompression on the other part of the PDCP SDU to
reconstruct raw data (4h-15).
[0347] Using the 1-bit indicator of the PDCP header according to an
embodiment, data to which UDC is applied by a transmitter and data
to which UDC is not applied may be independently processed. For
example, independent PDCP sequence numbers may be assigned to the
data to which UDC is applied and the data to which UDC is not
applied. That is, using the 1-bit indicator of the PDCP header, the
receiver may operate independent Rx windows of the PDCP layer
apparatus, independent window variables, and independent timers for
the data to which UDC is applied and the data to which UDC is not
applied
[0348] Alternatively, common PDCP sequence numbers may be assigned
to the data to which UDC is applied and the data to which UDC is
not applied, and a receiver may distinguish between the data to
which UDC is applied and the data to which UDC is not applied, by
using a 1-bit indicator of a header (e.g., a PDCP header or a UDC
header) to independently process the data, and deliver the
independently processed data to an upper layer in order of being
processed. In this case, the receiver may deliver the data to which
UDC is applied, to the upper layer in ascending order of the PDCP
sequence numbers, and deliver the data to which UDC is not applied,
to the upper layer in ascending order of the PDCP sequence
numbers
[0349] That is, when the Rx PDCP layer of the receiver delivers
data to the upper layer, the Rx PDCP layer does not merely deliver
the data in ascending order of PDCP sequence numbers and may
distinguish between data to which UDC is applied and data to which
UDC is not applied, deliver the data to which UDC is applied, to
the upper layer in ascending order of PDCP sequence numbers, and
deliver the data to which UDC is not applied, to the upper layer in
ascending order of PDCP sequence numbers.
[0350] FIG. 4I illustrates a block diagram of a UE according to an
embodiment.
[0351] Referring to FIG. 4I, the UE may include a radio frequency
(RF) processor 4i-10, a baseband processor 4i-20, a storage 4i-30,
and a controller 4i-40. The above-mentioned elements are merely
examples and elements of the UE are not limited thereto.
[0352] The RF processor 4i-10 may perform functions for
transmitting and receiving signals through radio channels, e.g.,
band conversion and amplification of signals. The RF processor
4i-10 may up-convert a baseband signal provided from the baseband
processor 4i-20, into a RF band signal and then transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through an antenna, into a baseband signal. For example,
the RF processor 4i-10 may include a Tx filter, a Rx filter, an
amplifier, a mixer, an oscillator, a digital-to-analog convertor
(DAC), and an analog-to-digital convertor (ADC). Although only a
single antenna is illustrated in FIG. 4I, the UE may include
multiple antennas. The RF processor 4i-10 may include multiple RF
chains. The RF processor 4i-10 may perform beamforming. For
beamforming, the RF processor 4i-10 may adjust phases and sizes of
signals transmitted or received through multiple antennas or
antenna elements. The RF processor 4i-10 may perform MIMO and may
receive data of multiple layers in the MIMO operation. The RF
processor 4i-10 may perform Rx beam sweeping by appropriately
configuring multiple antennas or antenna elements, or adjust a
direction and a beam width of the Rx beam to coordinate with the Tx
beam, under the control of the controller 4i-40.
[0353] The baseband processor 4i-20 may convert between a baseband
signal and a bitstream based on physical layer specifications of a
system. For example, for data transmission, the baseband processor
4i-20 may generate complex symbols by encoding and modulating a Tx
bitstream. For data reception, the baseband processor 4i-20 may
reconstruct a Rx bitstream by demodulating and decoding a baseband
signal provided from the RF processor 4i-10. For example, according
to an orthogonal frequency-division multiplexing (OFDM) scheme, for
data transmission, the baseband processor 4i-20 may generate
complex symbols by encoding and modulating a Tx bitstream, map the
complex symbols to subcarriers, and then configure OFDM symbols by
performing inverse fast Fourier transformation (IFFT) and inserting
a cyclic prefix (CP). For data reception, the baseband processor
4i-20 may segment a baseband signal provided from the RF processor
4i-10, into OFDM symbol units, reconstruct signals mapped to
subcarriers by performing fast Fourier transformation (FFT), and
then reconstruct a Rx bitstream by demodulating and decoding the
signals.
[0354] The baseband processor 4i-20 and the RF processor 4i-10 may
transmit and receive signals as described above. As such, the
baseband processor 4i-20 and the RF processor 4i-10 may also be
called transmitters, receivers, transceivers, or communication
units. At least one of the baseband processor 4i-20 and the RF
processor 4i-10 may include multiple communication modules to
support different multiple radio access technologies. At least one
of the baseband processor 4i-20 and the RF processor 4i-10 may
include multiple communication modules to process signals of
different frequency bands. For example, the different radio access
technologies may include a LTE network and a NR network. The
different frequency bands may include a super-high frequency (SHF)
(e.g., 2.5 GHz or 5 Ghz) band and a millimeter wave (mmWave) (e.g.,
60 GHz) band.
[0355] The storage 4i-30 may store data such as basic programs,
application programs, and configuration information for the
above-described operations of the UE. The storage 4i-30 may provide
the stored data upon request by the controller 4i-40.
[0356] The controller 4i-40 may control overall operations of the
UE. For example, the controller 4i-40 may transmit and receive
signals through the baseband processor 4i-20 and the RF processor
4i-10. The controller 4i-40 may record and read data on or from the
storage 4i-30. In this regard, the controller 4i-40 may include at
least one processor. For example, the controller 4i-40 may include
a communication processor (CP) for controlling communications and
an application processor (AP) for controlling an upper layer such
as an application program.
[0357] The controller 4i-40 may include a multi-connectivity
processor 4i-42 for operation in a multi-connectivity mode. For
example, the controller 4i-40 may control the UE to perform a UE
operation according to the afore-described embodiment.
[0358] According to an embodiment of the present disclosure, the UE
may receive DRB setup information and scheduling request (SR)
transmission configuration information from a gNB, request
scheduling by transmitting a SR according to the afore-described
embodiment, and transmit data by receiving allocation of uplink
resources from the gNB.
[0359] FIG. 4J illustrates a block diagram of a gNB according to an
embodiment.
[0360] Referring to FIG. 4J, the gNB may include a RF processor
4j-10, a baseband processor 4j-20, a backhaul communication unit
4j-30, a storage 4j-40, and a controller 4j-50. The above-mentioned
elements are merely examples and elements of the gNB are not
limited thereto.
[0361] The RF processor 4j-10 may perform functions for
transmitting and receiving signals through radio channels, e.g.,
band conversion and amplification of signals. The RF processor
4j-10 may up-convert a baseband signal provided from the baseband
processor 4j-20, into a RF band signal and then transmit the RF
band signal through an antenna, and down-convert an RF band signal
received through an antenna, into a baseband signal. For example,
the RF processor 4j-10 may include a Tx filter, a Rx filter, an
amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only
a single antenna is illustrated in FIG. 4J, the gNB may include
multiple antennas. The RF processor 4j-10 may include multiple RF
chains. The RF processor 4j-10 may perform beamforming. For
beamforming, the RF processor 4j-10 may adjust phases and sizes of
signals transmitted or received through multiple antennas or
antenna elements. The RF processor 4j-10 may perform downlink MIMO
by transmitting data of one or more layers.
[0362] The baseband processor 4j-20 may convert between a baseband
signal and a bitstream based on physical layer specifications of a
wireless communication system. For example, for data transmission,
the baseband processor 4j-20 may generate complex symbols by
encoding and modulating a Tx bitstream. For data reception, the
baseband processor 4j-20 may reconstruct a Rx bitstream by
demodulating and decoding a baseband signal provided from the RF
processor 4j-10. For example, according to an OFDM scheme, for data
transmission, the baseband processor 4j-20 may generate complex
symbols by encoding and modulating a Tx bitstream, map the complex
symbols to subcarriers, and then configure OFDM symbols by
performing IFFT and inserting a CP. For data reception, the
baseband processor 4j-20 may segment a baseband signal provided
from the RF processor 4j-10, into OFDM symbol units, reconstruct
signals mapped to subcarriers by performing FFT, and then
reconstruct a Rx bitstream by demodulating and decoding the
signals. The baseband processor 4j-20 and the RF processor 4j-10
may transmit and receive signals as described above. As such, the
baseband processor 4j-20 and the RF processor 4j-10 may also be
called transmitters, receivers, transceivers, communication units,
or wireless communication units.
[0363] The backhaul communication unit 4j-30 may provide an
interface for communicating with other nodes in a network. The
backhaul communication unit 4j-30 may transform a bitstream to be
transmitted from the gNB to another node, e.g., a secondary node B
or a core network, into a physical signal, or transform a physical
signal received from another node, into a bitstream.
[0364] The storage 4j-40 may store data such as basic programs,
application programs, and configuration information for operations
of the gNB. Specifically, the storage 4j-40 may store information
about bearers configured for a connected UE, a measurement report
transmitted from the connected UE, etc. The storage 4j-40 may store
criteria information used to determine whether to provide or
release multi-connectivity to or from the UE. The storage 4j-40 may
provide the stored data upon request by the controller 4j-50.
[0365] The controller 4j-50 may control overall operations of the
gNB. For example, the controller 4j-50 may transmit and receive
signals through the baseband processor 4j-20, the RF processor
4j-10, and the backhaul communication unit 4j-30. The controller
4j-50 may record and read data on or from the storage 4j-40. In
this regard, the controller 4j-50 may include at least one
processor. The controller 4j-50 my include a multi-connectivity
processor 4j-52 for operation in a multi-connectivity mode.
[0366] FIG. 5 is a flowchart illustrating a handover procedure
according to an embodiment.
[0367] Referring to FIG. 5, a UE 505 reports to a gNB 510 that the
UE 505 supports SUL (515). Information indicating whether the UE
505 supports SUL and information about a supported SUL frequency
band are transmitted as SUL capability information. The gNB 510 may
activate at least one of a NR uplink and a SUL for the UE 505. The
UE 505 achieves uplink synchronization by performing random access
through the activated uplink. The gNB 510 provides PUCCH
configuration information for one uplink by using a radio resource
control (RRC) signal. For scheduling, the gNB 510 provides downlink
control information (DCI) indicating for which uplink a UL grant is
given.
[0368] The gNB 510 provides, to the UE 505, configuration
information instructing to measure neighboring frequencies or
cells. That is, the gNB 510 transmits measurement configuration
information to the UE 505 (520). The UE 505 measures the
neighboring frequencies or cells based on the measurement
configuration information (525). The UE 505 transmits a measurement
report to the gNB 510 (530). The gNB 510 decides whether to perform
handover (HO) for the UE 505, based on the measurement report
(535).
[0369] The UE 505 receives handover configuration information from
the gNB 510 (540). The handover configuration information includes
mobility control information. The handover configuration
information includes at least one of NR uplink and SUL
configuration information of a target cell and random access radio
resource information to be applied by the target cell.
[0370] The NR uplink and SUL configuration information of the
target cell includes information about a center frequency and a
bandwidth of a NR uplink frequency band of the target cell, and a
center frequency and a bandwidth of a SUL frequency band of the
target cell. Specifically, the center frequency may be a center
frequency of a cell-defining SSB.
[0371] In the present disclosure, the random access radio resource
information is provided by at least one of the NR uplink and the
SUL. When a source gNB decides handover for a certain UE, the
source gNB transmits a handover preparation request message to the
target cell. The handover preparation request message includes the
SUL capability information of the UE 505. For example, the SUL
capability information includes information indicating whether the
UE 505 supports SUL and information about a supported SUL frequency
band.
[0372] The target cell transmits random access configuration
information to be applied by the target cell, to the source gNB.
When the random access configuration information corresponds to the
SUL, the target cell transmits the random access configuration
information to the source gNB.
[0373] In addition, when the random access radio resource
information applied to the SUL of the target cell is provided, the
target cell provides information indicating that the random access
radio resource information is dedicated to the SUL. The random
access radio resource information may include ID information of a
preamble, time and frequency information used to transmit the
preamble, and Tx power information of the preamble.
[0374] The UE 505 selects one uplink for attempting random access,
according to a certain rule (545). For example, according to the
certain rule, the NR uplink may always be selected first, or the
SUL may be selected when a reference signal received power (RSRP)
of the target cell is lower than a preset threshold value. The
threshold value is provided to the UE 505 by using a RRC signal.
For example, the threshold value may be included in the handover
configuration information transmitted to the UE 505.
[0375] Alternatively, when the configuration information is
provided for the two uplinks, the NR uplink and the SUL, the gNB
510 may also provide information indicating which of the NR uplink
and the SUL is used first. The UE 505 performs random access to the
target cell (550). When the random access ultimately fails (555),
the UE 505 attempts random access again by using radio resources of
the other uplink (560).
[0376] As another example, the UE 505 selects an uplink for
attempting preamble transmission, based on the RSRP. When, the RSRP
is lower than the preset threshold value, the UE 505 selects the
SUL. Otherwise, the UE 505 selects the NR uplink. The threshold
value is provided to the UE 505 by using system information or a
dedicated RRC signal.
[0377] FIG. 6 is a flowchart illustrating a UE operation for
performing handover, according to an embodiment.
[0378] Referring to FIG. 6, in operation 605, a UE receives, from a
gNB, configuration information instructing to measure neighboring
frequencies or cells. In operation 610, the UE measures the
neighboring frequencies or cells based on the measurement
configuration. In operation 615, the UE transmits a measurement
report to the gNB.
[0379] In operation 620, the UE receives handover configuration
information from the gNB. In operation 625, the UE selects one of
uplinks of a target cell and performs random access through the
uplink. In operation 630, when the random access ultimately fails,
the UE attempts random access again by using radio resources of the
other uplink.
[0380] FIG. 7 is a flowchart illustrating a scheduling request
procedure according to an embodiment.
[0381] Referring to FIG. 7, a UE 705 reports, to a gNB 710, UE
capability information indicating that the UE 705 supports SUL
(715). Information indicating whether the UE 705 supports SUL and
information about a supported SUL frequency band are transmitted as
SUL capability information. The gNB 710 may activate a NR uplink, a
SUL, or both for the UE 705. The UE 705 achieves uplink
synchronization by performing random access through the activated
uplink. The gNB 710 provides PUCCH configuration information for
one uplink by using a RRC signal. For scheduling, the gNB 710
provides DCI indicating for which uplink a UL grant is given. The
gNB 710 provides NR uplink and SUL configuration information to the
UE 705 (720).
[0382] The UE 705 performs random access to achieve uplink
synchronization (725). The gNB 710 transmits a layer 1 (L1) signal
indicating to use which of a NR uplink and a SUL for data
transmission (730). The L1 signal corresponds to configuration
information inserted by a physical layer and the configuration
information is included in DCI of a PDCCH or a control resource set
(CORESET). The L1 signal is decoded by a physical layer of a
receiver, and thus is used when rapid transmission of information
or an accurate application timing of received information is
required.
[0383] For example, the gNB 710 configures the NR uplink for data
transmission by using the L1 signal. The UE 705 identifies lack of
uplink radio resources for a buffer status report (BSR) at a
certain timing (735). The UE 705 transmits an SR to the gNB 710 to
transmit the BSR (740). The UE 705 identifies transmission failure
of the SR (745). The UE 705 switches to the SUL and performs random
access to the gNB 710 (750).
[0384] As another example, the UE 705 selects an uplink for
attempting SR transmission, based on a RSRP. The UE 705 selects the
SUL when the RSRP is lower than a preset threshold value, and
selects the NR uplink when the RSRP is equal to or higher than the
preset threshold value. The threshold value is provided to the UE
705 by using system information or a dedicated RRC signal.
[0385] When transmission of the SR is attempted multiple times
through the SUL but fails, the UE 705 triggers random access
through an uplink determined based on a certain rule. For example,
the SUL may be selected or an uplink for attempting preamble
transmission is selected based on the RSRP. The UE 705 selects the
SUL when the RSRP is lower than the preset threshold value, or
selects the NR uplink otherwise. The threshold value is provided to
the UE 705 by using system information or a dedicated RRC
signal.
[0386] FIG. 8 is a flowchart illustrating a UE operation for
requesting scheduling.
[0387] Referring to FIG. 8, in operation 805, a UE receives NR
uplink and SUL configuration information from a gNB. In operation
810, the UE receives, from the gNB, an L1 signal indicating to use
a NR uplink for data transmission. In operation 815, the UE
transmits data through the indicated NR uplink.
[0388] In operation 820, the UE identifies lack of uplink radio
resources for a BSR at a certain timing. In operation 825, the UE
transmits an SR to the gNB to transmit the BSR. In operation 830,
the UE identifies transmission failure of the SR. The UE switches
to a SUL and performs random access to the gNB.
[0389] It should be understood that embodiments described herein
should be considered in a descriptive sense only and not for
purposes of limitation. Descriptions of features or aspects within
each embodiment should typically be considered as available for
other similar features or aspects in other embodiments. The
afore-described embodiments may operate in combination when
required. For example, a gNB (or eNB) and a UE may operate
according to a combination of parts of the embodiments. Although
the embodiments have been described on the basis of a NR system,
modifications thereof based on the technical aspects of the
embodiments are applicable to other systems such as
frequency-division duplex (FDD) and time-division duplex (TDD) LTE
systems.
[0390] According to the present disclosure, the performance of
communications may be improved by solving a problem of unequal
uplink and downlink service areas in a wireless communication
system.
[0391] The present disclosure proposes a procedure for changing a
bearer type from a split bearer using dual connectivity to a normal
bearer (e.g., a master cell group (MCG) bearer or a secondary cell
group (SCG) bearer) or releasing each SCG bearer using dual
connectivity by independently releasing logical channels of the
split bearer or the SCG bearer. As such, since the bearer type is
freely changeable, signaling overhead due to configuration or
reconfiguration of the bearer type may be reduced and transfer
delay may be reduced.
[0392] The present disclosure also proposes a procedure for
compressing or decompressing data when user equipment (UE)
transmits uplink data or an evolved node B (eNB) or a
next-generation node B (gNB) transmits downlink data to the UE in a
wireless communication system. As such, since overhead is reduced,
more data may be transmitted and coverage may be improved.
[0393] 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.
* * * * *