U.S. patent application number 15/305639 was filed with the patent office on 2017-02-09 for method for transmitting an explicit signal of layer-2 state variables for d2d communication system and device therefor.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Sunyoung LEE, Seungjune YI.
Application Number | 20170041972 15/305639 |
Document ID | / |
Family ID | 53002528 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170041972 |
Kind Code |
A1 |
YI; Seungjune ; et
al. |
February 9, 2017 |
METHOD FOR TRANSMITTING AN EXPLICIT SIGNAL OF LAYER-2 STATE
VARIABLES FOR D2D COMMUNICATION SYSTEM AND DEVICE THEREFOR
Abstract
The present invention relates to a wireless communication
system. More specifically, the present invention relates to a
method and a device for transmitting an explicit signal of layer-2
state variables for D2D communication system, the method
comprising: generating a configuration message including initial
values of RLC (Radio Link Control) state variables used for an
receiving RLC entity of a peer UE; and transmitting the
configuration message to the peer UE; and transmitting, by a
transmitting RLC entity, RLC PDUs to the receiving RLC entity of
the peer UE by considering the initial values; wherein the
configuration message is transmitted before transmission of the RLC
PDUs using the initial values.
Inventors: |
YI; Seungjune; (Seoul,
KR) ; LEE; Sunyoung; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
53002528 |
Appl. No.: |
15/305639 |
Filed: |
April 3, 2015 |
PCT Filed: |
April 3, 2015 |
PCT NO: |
PCT/KR2015/003361 |
371 Date: |
October 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61982354 |
Apr 22, 2014 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/1896 20130101;
H04L 5/0055 20130101; H04W 76/14 20180201; H04W 92/18 20130101;
H04L 67/1078 20130101; H04W 80/02 20130101 |
International
Class: |
H04W 76/02 20060101
H04W076/02 |
Claims
1-19. (canceled)
20. A method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: receiving a
configuration message including initial values of an PDCP (Packet
Data Convergence Protocol) state variables from a peer UE; setting,
by a receiving PDCP entity, PDCP state variables to the initial
values included in the received configuration message; and
processing PDCP PDUs (Protocol Data Units) received after reception
of the configuration message using the PDCP state variables.
21. The method according to claim 20, wherein the configuration
message is received per radio bearer for D2D (Device to
Device).
22. The method according to claim 20, wherein the configuration
message includes at least one of an initial value of
Next_PDCP_RX_SN or an initial value of RX_HFN. wherein the
Next_PDCP_RX_SN indicates a next expected PDCP SN by a receiver for
a given PDCP entity, and wherein the RX_HFN indicates a HFN value
for the generation of the COUNT value used for the received PDCP
PDUs for a given PDCP entity.
23. The method according to claim 20, wherein the configuration
message is received in different forms of Layer-2 signaling.
24. The method according to claim 20, further comprising:
requesting of the peer UE to transmit the configuration message,
when problem with a received packet is detected.
25. A method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: generating COUNT for
ciphering a first packet; and transmitting MSB (Most Significant
Bit) parts of the COUNT to a peer UE via a direct interface between
the UE and the peer UE.
26. The method according to claim 25, wherein the COUNT is
transmitted using a PDCP (Packet Data Convergence Protocol) PDU
(Protocol Data Unit).
27. A method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: receiving MSB (Most
Significant Bit) parts of COUNT from a peer UE via a direct
interface between the UE and the peer UE; receiving a PDCP (Packet
Data Convergence Protocol) PDU (Protocol Data Unit) from the peer
UE via the direct interface between the UE and the peer UE;
generating COUNT using the MSB parts of the COUNT and a PDCP SN
(Sequence Number) of the received PDCP PDU; and deciphering the
PDCP PDU using the COUNT.
28. The method according to claim 27, wherein PDCP SN is occupied
in LSB parts of the COUNT.
29. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a wireless communication
system and, more particularly, to a method for transmitting an
explicit signal of layer-2 state variables for D2D (Device to
Device) communication system and a device therefor.
BACKGROUND ART
[0002] As an example of a mobile communication system to which the
present invention is applicable, a 3rd Generation Partnership
Project Long Term Evolution (hereinafter, referred to as LTE)
communication system is described in brief.
[0003] FIG. 1 is a view schematically illustrating a network
structure of an E-UMTS as an exemplary radio communication system.
An Evolved Universal Mobile Telecommunications System (E-UMTS) is
an advanced version of a conventional Universal Mobile
Telecommunications System (UMTS) and basic standardization thereof
is currently underway in the 3GPP. E-UMTS may be generally referred
to as a Long Term Evolution (LTE) system. For details of the
technical specifications of the UMTS and E-UMTS, reference can be
made to Release 7 and Release 8 of "3rd Generation Partnership
Project; Technical Specification Group Radio Access Network".
[0004] Referring to FIG. 1, the E-UMTS includes a User Equipment
(UE), eNode Bs (eNBs), and an Access Gateway (AG) which is located
at an end of the network (E-UTRAN) and connected to an external
network. The eNBs may simultaneously transmit multiple data streams
for a broadcast service, a multicast service, and/or a unicast
service.
[0005] One or more cells may exist per eNB. The cell is set to
operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20
MHz and provides a downlink (DL) or uplink (UL) transmission
service to a plurality of UEs in the bandwidth. Different cells may
be set to provide different bandwidths. The eNB controls data
transmission or reception to and from a plurality of UEs. The eNB
transmits DL scheduling information of DL data to a corresponding
UE so as to inform the UE of a time/frequency domain in which the
DL data is supposed to be transmitted, coding, a data size, and
hybrid automatic repeat and request (HARQ)-related information. In
addition, the eNB transmits UL scheduling information of UL data to
a corresponding UE so as to inform the UE of a time/frequency
domain which may be used by the UE, coding, a data size, and
HARQ-related information. An interface for transmitting user
traffic or control traffic may be used between eNBs. A core network
(CN) may include the AG and a network node or the like for user
registration of UEs. The AG manages the mobility of a UE on a
tracking area (TA) basis. One TA includes a plurality of cells.
[0006] Device to device (D2D) communication refers to the
distributed communication technology that directly transfers
traffic between adjacent nodes without using infrastructure such as
a base station. In a D2D communication environment, each node such
as a portable terminal discovers user equipment physically adjacent
thereto and transmits traffic after setting communication session.
In this way, since D2D communication may solve traffic overload by
distributing traffic concentrated into the base station, the D2D
communication may have received attention as the element technology
of the next generation mobile communication technology after 4G.
For this reason, the standard institute such as 3GPP or IEEE has
proceeded to establish the D2D communication standard on the basis
of LTE-A or Wi-Fi, and Qualcomm has developed their own D2D
communication technology.
[0007] It is expected that the D2D communication contributes to
increase throughput of a mobile communication system and create new
communication services. Also, the D2D communication may support
proximity based social network services or network game services.
The problem of link of a user equipment located at a shade zone may
be solved by using a D2D link as a relay. In this way, it is
expected that the D2D technology will provide new services in
various fields.
[0008] The D2D communication technologies such as infrared
communication, ZigBee, radio frequency identification (RFID) and
near field communications (NFC) based on the RFID have been already
used. However, since these technologies support communication only
of a specific object within a limited distance (about 1 m), it is
difficult for the technologies to be regarded as the D2D
communication technologies strictly.
[0009] Although the D2D communication has been described as above,
details of a method for transmitting data from a plurality of D2D
user equipments with the same resource have not been suggested.
DISCLOSURE
Technical Problem
[0010] An object of the present invention devised to solve the
problem lies in a method and device for transmitting an explicit
signal of layer-2 state variables for D2D communication system. The
technical problems solved by the present invention are not limited
to the above technical problems and those skilled in the art may
understand other technical problems from the following
description.
Technical Solution
[0011] The object of the present invention can be achieved by
providing a method for a User Equipment (UE) operating in a
wireless communication system, the method comprising: generating a
configuration message including initial values of RLC (Radio Link
Control) state variables used for an receiving RLC entity of a peer
UE; transmitting the configuration message to the peer UE; and
transmitting, by a transmitting RLC entity, RLC PDUs to the
receiving RLC entity of the peer UE by considering the initial
values, wherein the configuration message is transmitted before
transmission of the RLC PDUs using the initial values.
[0012] Preferably, transmitting, by a transmitting RLC entity, a
first RLC PDU (Protocol Data Unit) to the receiving RLC entity of
the peer UE, wherein RLC SN (Sequence Number) of the first RLC PDU
is set to the initial values, wherein the first RLC PDU is first
transmitted after transmitting the configuration message.
[0013] Preferably, the transmitting RLC entity transmits the RLC
PDUs using a certain values corresponding to the initial values of
RLC state variables used for the receiving RLC entity of the peer
UE.
[0014] Preferably, the configuration message includes at least one
of an initial value of VR(UH) or an initial value of VR(UR), the
wherein the VR(UR) is a received state variable for the UM RLC
entity and holds a value of RLC SN of a earliest UMD PDU that is
still considered for reordering, and the VR(UH) is highest received
state variable for the UM RLC entity and holds a value of RLC SN
following SN of the UMD PDU with the highest SN among received UMD
PDUs.
[0015] Preferably, configuration message is transmitted to the peer
UE multiple times before transmitting any other packets, wherein a
number of transmission of configuration message is configured by an
e-NodeB.
[0016] Preferably, configuration message is transmitted to the peer
UE periodically, wherein periodicity of configuration message
transmission is configured by an e-NodeB
[0017] Preferably, the method further comprises: receiving, from
the peer UE, to request transmission of the configuration message;
and transmitting the configuration message in response to the
request transmission to the peer UE.
[0018] In another aspect of the present invention, provided herein
is a method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: receiving a
configuration message including initial values of an RLC (Radio
Link Control) state variables from a peer UE; setting, by a
receiving RLC entity, RLC state variables to the initial values
included in the received configuration message; and processing RLC
PDUs received after reception of the configuration message using
the RLC state variables.
[0019] Preferably, the method further comprises: requesting of the
peer UE to transmit the configuration message, when problem with a
received packet is detected.
[0020] In another aspect of the present invention, provided herein
is a method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: generating a
configuration message including initial values of PDCP (Packet Data
Convergence Protocol) state variables used for an receiving PDCP
entity of a peer UE; and transmitting the configuration message to
the peer UE; transmitting, by a transmitting PDCP entity, PDCP PDUs
to the receiving PDCP entity of the peer UE by considering the
initial values; wherein the configuration message is transmitted
before transmission of the PDCP PDUs using the initial values.
[0021] In another aspect of the present invention, provided herein
is a method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: receiving a
configuration message including initial values of an PDCP (Packet
Data Convergence Protocol) state variables from a peer UE; setting,
by a receiving PDCP entity, PDCP state variables to the initial
values included in the received configuration message; and
processing PDCP PDUs (Protocol Data Units) received after reception
of the configuration message using the PDCP state variables.
[0022] In another aspect of the present invention, provided herein
is a method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: generating COUNT for
ciphering a first packet; and transmitting MSB (Most Significant
Bit) parts of the COUNT to a peer UE via a direct interface between
the UE and the peer UE.
[0023] In another aspect of the present invention, provided herein
is a method for a User Equipment (UE) operating in a wireless
communication system, the method comprising: receiving MSB (Most
Significant Bit) parts of COUNT from a peer UE via a direct
interface between the UE and the peer UE; receiving a PDCP (Packet
Data Convergence Protocol) PDU (Protocol Data Unit) from the peer
UE via the direct interface between the UE and the peer UE;
generating COUNT using the MSB parts of the COUNT and a PDCP SN
(Sequence Number) of the received PDCP PDU; and deciphering the
PDCP PDU using the COUNT.
[0024] It is to be understood that both the foregoing general
description and the following detailed description of the present
invention are exemplary and explanatory and are intended to provide
further explanation of the invention as claimed.
Advantageous Effects
[0025] According to the present invention, an explicit signal of
layer-2 state variables can be efficiently transmitted in D2D
communication system. It will be appreciated by persons skilled in
the art that that the effects achieved by the present invention are
not limited to what has been particularly described hereinabove and
other advantages of the present invention will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings.
DESCRIPTION OF DRAWINGS
[0026] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention.
[0027] FIG. 1 is a diagram showing a network structure of an
Evolved Universal Mobile Telecommunications System (E-UMTS) as an
example of a wireless communication system;
[0028] FIG. 2A is a block diagram illustrating network structure of
an evolved universal mobile telecommunication system (E-UMTS), and
FIG. 2B is a block diagram depicting architecture of a typical
E-UTRAN and a typical EPC;
[0029] FIG. 3 is a diagram showing a control plane and a user plane
of a radio interface protocol between a UE and an E-UTRAN based on
a 3rd generation partnership project (3GPP) radio access network
standard;
[0030] FIG. 4 is a diagram of an example physical channel structure
used in an E-UMTS system;
[0031] FIG. 5 is a block diagram of a communication apparatus
according to an embodiment of the present invention;
[0032] FIG. 6 is an example of default data path for a normal
communication;
[0033] FIGS. 7-8 are examples of data path scenarios for a
proximity communication;
[0034] FIG. 9 is a conceptual diagram illustrating for a
non-roaming reference architecture;
[0035] FIG. 10 is a conceptual diagram illustrating for a Layer 2
Structure for Sidelink;
[0036] FIG. 11a is a conceptual diagram illustrating for User-Plane
protocol stack for ProSe Direct Communication, and FIG. 11b is
Control-Plane protocol stack for ProSe Direct Communication;
[0037] FIG. 12 is a conceptual diagram illustrating for a PC5
interface for ProSe Direct Discovery;
[0038] FIG. 13 is a conceptual diagram illustrating for model of
two unacknowledged mode peer entities;
[0039] FIGS. 14a to 14f are conceptual diagrams illustrating for
UMD PDU;
[0040] FIG. 15 is a conceptual diagram for functional view of a
PDCP entity;
[0041] FIGS. 16a and 16b are conceptual diagrams for PDCP Data PDU
format for DRBs; and
[0042] FIGS. 17 and 18 are conceptual diagrams for transmitting an
explicit signal of layer-2 state variables for D2D communication
according to embodiments of the present invention.
BEST MODE
[0043] Universal mobile telecommunications system (UMTS) is a 3rd
Generation (3G) asynchronous mobile communication system operating
in wideband code division multiple access (WCDMA) based on European
systems, global system for mobile communications (GSM) and general
packet radio services (GPRS). The long-term evolution (LTE) of UMTS
is under discussion by the 3rd generation partnership project
(3GPP) that standardized UMTS.
[0044] The 3GPP LTE is a technology for enabling high-speed packet
communications. Many schemes have been proposed for the LTE
objective including those that aim to reduce user and provider
costs, improve service quality, and expand and improve coverage and
system capacity. The 3G LTE requires reduced cost per bit,
increased service availability, flexible use of a frequency band, a
simple structure, an open interface, and adequate power consumption
of a terminal as an upper-level requirement.
[0045] Hereinafter, structures, operations, and other features of
the present invention will be readily understood from the
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. Embodiments described
later are examples in which technical features of the present
invention are applied to a 3GPP system.
[0046] Although the embodiments of the present invention are
described using a long term evolution (LTE) system and a
LTE-advanced (LTE-A) system in the present specification, they are
purely exemplary. Therefore, the embodiments of the present
invention are applicable to any other communication system
corresponding to the above definition. In addition, although the
embodiments of the present invention are described based on a
frequency division duplex (FDD) scheme in the present
specification, the embodiments of the present invention may be
easily modified and applied to a half-duplex FDD (H-FDD) scheme or
a time division duplex (TDD) scheme.
[0047] FIG. 2A is a block diagram illustrating network structure of
an evolved universal mobile telecommunication system (E-UMTS). The
E-UMTS may be also referred to as an LTE system. The communication
network is widely deployed to provide a variety of communication
services such as voice (VoIP) through IMS and packet data.
[0048] As illustrated in FIG. 2A, the E-UMTS network includes an
evolved UMTS terrestrial radio access network (E-UTRAN), an Evolved
Packet Core (EPC) and one or more user equipment. The E-UTRAN may
include one or more evolved NodeB (eNodeB) 20, and a plurality of
user equipment (UE) 10 may be located in one cell. One or more
E-UTRAN mobility management entity (MME)/system architecture
evolution (SAE) gateways 30 may be positioned at the end of the
network and connected to an external network.
[0049] As used herein, "downlink" refers to communication from
eNodeB 20 to UE 10, and "uplink" refers to communication from the
UE to an eNodeB. UE 10 refers to communication equipment carried by
a user and may be also referred to as a mobile station (MS), a user
terminal (UT), a subscriber station (SS) or a wireless device.
[0050] FIG. 2B is a block diagram depicting architecture of a
typical E-UTRAN and a typical EPC.
[0051] As illustrated in FIG. 2B, an eNodeB 20 provides end points
of a user plane and a control plane to the UE 10. MME/SAE gateway
30 provides an end point of a session and mobility management
function for UE 10. The eNodeB and MME/SAE gateway may be connected
via an S1 interface.
[0052] The eNodeB 20 is generally a fixed station that communicates
with a UE 10, and may also be referred to as a base station (BS) or
an access point. One eNodeB 20 may be deployed per cell. An
interface for transmitting user traffic or control traffic may be
used between eNodeBs 20.
[0053] The MME provides various functions including NAS signaling
to eNodeBs 20, NAS signaling security, AS Security control, Inter
CN node signaling for mobility between 3GPP access networks, Idle
mode UE Reachability (including control and execution of paging
retransmission), Tracking Area list management (for UE in idle and
active mode), PDN GW and Serving GW selection, MME selection for
handovers with MME change, SGSN selection for handovers to 2G or 3G
3GPP access networks, Roaming, Authentication, Bearer management
functions including dedicated bearer establishment, Support for PWS
(which includes ETWS and CMAS) message transmission. The SAE
gateway host provides assorted functions including Per-user based
packet filtering (by e.g. deep packet inspection), Lawful
Interception, UE IP address allocation, Transport level packet
marking in the downlink, UL and DL service level charging, gating
and rate enforcement, DL rate enforcement based on APN-AMBR. For
clarity MME/SAE gateway 30 will be referred to herein simply as a
"gateway," but it is understood that this entity includes both an
MME and an SAE gateway.
[0054] A plurality of nodes may be connected between eNodeB 20 and
gateway 30 via the S1 interface. The eNodeBs 20 may be connected to
each other via an X2 interface and neighboring eNodeBs may have a
meshed network structure that has the X2 interface.
[0055] As illustrated, eNodeB 20 may perform functions of selection
for gateway 30, routing toward the gateway during a Radio Resource
Control (RRC) activation, scheduling and transmitting of paging
messages, scheduling and transmitting of Broadcast Channel (BCCH)
information, dynamic allocation of resources to UEs 10 in both
uplink and downlink, configuration and provisioning of eNodeB
measurements, radio bearer control, radio admission control (RAC),
and connection mobility control in LTE ACTIVE state. In the EPC,
and as noted above, gateway 30 may perform functions of paging
origination, LTE-IDLE state management, ciphering of the user
plane, System Architecture Evolution (SAE) bearer control, and
ciphering and integrity protection of Non-Access Stratum (NAS)
signaling.
[0056] The EPC includes a mobility management entity (MME), a
serving-gateway (S-GW), and a packet data network-gateway (PDN-GW).
The MME has information about connections and capabilities of UEs,
mainly for use in managing the mobility of the UEs. The S-GW is a
gateway having the E-UTRAN as an end point, and the PDN-GW is a
gateway having a packet data network (PDN) as an end point.
[0057] FIG. 3 is a diagram showing a control plane and a user plane
of a radio interface protocol between a UE and an E-UTRAN based on
a 3GPP radio access network standard. The control plane refers to a
path used for transmitting control messages used for managing a
call between the UE and the E-UTRAN. The user plane refers to a
path used for transmitting data generated in an application layer,
e.g., voice data or Internet packet data.
[0058] A physical (PHY) layer of a first layer provides an
information transfer service to a higher layer using a physical
channel. The PHY layer is connected to a medium access control
(MAC) layer located on the higher layer via a transport channel.
Data is transported between the MAC layer and the PHY layer via the
transport channel. Data is transported between a physical layer of
a transmitting side and a physical layer of a receiving side via
physical channels. The physical channels use time and frequency as
radio resources. In detail, the physical channel is modulated using
an orthogonal frequency division multiple access (OFDMA) scheme in
downlink and is modulated using a single carrier frequency division
multiple access (SC-FDMA) scheme in uplink.
[0059] The MAC layer of a second layer provides a service to a
radio link control (RLC) layer of a higher layer via a logical
channel. The RLC layer of the second layer supports reliable data
transmission. A function of the RLC layer may be implemented by a
functional block of the MAC layer. A packet data convergence
protocol (PDCP) layer of the second layer performs a header
compression function to reduce unnecessary control information for
efficient transmission of an Internet protocol (IP) packet such as
an IP version 4 (IPv4) packet or an IP version 6 (IPv6) packet in a
radio interface having a relatively small bandwidth.
[0060] A radio resource control (RRC) layer located at the bottom
of a third layer is defined only in the control plane. The RRC
layer controls logical channels, transport channels, and physical
channels in relation to configuration, re-configuration, and
release of radio bearers (RBs). An RB refers to a service that the
second layer provides for data transmission between the UE and the
E-UTRAN. To this end, the RRC layer of the UE and the RRC layer of
the E-UTRAN exchange RRC messages with each other.
[0061] One cell of the eNB is set to operate in one of bandwidths
such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or
uplink transmission service to a plurality of UEs in the bandwidth.
Different cells may be set to provide different bandwidths.
[0062] Downlink transport channels for transmission of data from
the E-UTRAN to the UE include a broadcast channel (BCH) for
transmission of system information, a paging channel (PCH) for
transmission of paging messages, and a downlink shared channel
(SCH) for transmission of user traffic or control messages. Traffic
or control messages of a downlink multicast or broadcast service
may be transmitted through the downlink SCH and may also be
transmitted through a separate downlink multicast channel
(MCH).
[0063] Uplink transport channels for transmission of data from the
UE to the E-UTRAN include a random access channel (RACH) for
transmission of initial control messages and an uplink SCH for
transmission of user traffic or control messages. Logical channels
that are defined above the transport channels and mapped to the
transport channels include a broadcast control channel (BCCH), a
paging control channel (PCCH), a common control channel (CCCH), a
multicast control channel (MCCH), and a multicast traffic channel
(MTCH).
[0064] FIG. 4 is a view showing an example of a physical channel
structure used in an E-UMTS system. A physical channel includes
several subframes on a time axis and several subcarriers on a
frequency axis. Here, one subframe includes a plurality of symbols
on the time axis. One subframe includes a plurality of resource
blocks and one resource block includes a plurality of symbols and a
plurality of subcarriers. In addition, each subframe may use
certain subcarriers of certain symbols (e.g., a first symbol) of a
subframe for a physical downlink control channel (PDCCH), that is,
an L1/L2 control channel. In FIG. 4, an L1/L2 control information
transmission area (PDCCH) and a data area (PDSCH) are shown. In one
embodiment, a radio frame of 10 ms is used and one radio frame
includes 10 subframes. In addition, one subframe includes two
consecutive slots. The length of one slot may be 0.5 ms. In
addition, one subframe includes a plurality of OFDM symbols and a
portion (e.g., a first symbol) of the plurality of OFDM symbols may
be used for transmitting the L1/L2 control information. A
transmission time interval (TTI) which is a unit time for
transmitting data is 1 ms.
[0065] A base station and a UE mostly transmit/receive data via a
PDSCH, which is a physical channel, using a DL-SCH which is a
transmission channel, except a certain control signal or certain
service data. Information indicating to which UE (one or a
plurality of UEs) PDSCH data is transmitted and how the UE receive
and decode PDSCH data is transmitted in a state of being included
in the PDCCH.
[0066] For example, in one embodiment, a certain PDCCH is
CRC-masked with a radio network temporary identity (RNTI) "A" and
information about data is transmitted using a radio resource "B"
(e.g., a frequency location) and transmission format information
"C" (e.g., a transmission block size, modulation, coding
information or the like) via a certain subframe. Then, one or more
UEs located in a cell monitor the PDCCH using its RNTI information.
And, a specific UE with RNTI "A" reads the PDCCH and then receive
the PDSCH indicated by B and C in the PDCCH information.
[0067] FIG. 5 is a block diagram of a communication apparatus
according to an embodiment of the present invention.
[0068] The apparatus shown in FIG. 5 can be a user equipment (UE)
and/or eNB adapted to perform the above mechanism, but it can be
any apparatus for performing the same operation.
[0069] As shown in FIG. 5, the apparatus may comprises a
DSP/microprocessor (110) and RF module (transceiver; 135). The
DSP/microprocessor (110) is electrically connected with the
transceiver (135) and controls it. The apparatus may further
include power management module (105), battery (155), display
(115), keypad (120), SIM card (125), memory device (130), speaker
(145) and input device (150), based on its implementation and
designer's choice.
[0070] Specifically, FIG. 5 may represent a UE comprising a
receiver (135) configured to receive a request message from a
network, and a transmitter (135) configured to transmit the
transmission or reception timing information to the network. These
receiver and the transmitter can constitute the transceiver (135).
The UE further comprises a processor (110) connected to the
transceiver (135: receiver and transmitter).
[0071] Also, FIG. 5 may represent a network apparatus comprising a
transmitter (135) configured to transmit a request message to a UE
and a receiver (135) configured to receive the transmission or
reception timing information from the UE. These transmitter and
receiver may constitute the transceiver (135). The network further
comprises a processor (110) connected to the transmitter and the
receiver. This processor (110) may be configured to calculate
latency based on the transmission or reception timing
information.
[0072] Recently, Proximity-based Service (ProSe) has been discussed
in 3GPP. The ProSe enables different UEs to be connected (directly)
each other (after appropriate procedure(s), such as
authentication), through eNB only (but not further through Serving
Gateway (SGW)/Packet Data Network Gateway (PDN-GW, PGW)), or
through SGW/PGW. Thus, using the ProSe, device to device direct
communication can be provided, and it is expected that every
devices will be connected with ubiquitous connectivity. Direct
communication between devices in a near distance can lessen the
load of network. Recently, proximity-based social network services
have come to public attention, and new kinds of proximity-based
applications can be emerged and may create new business market and
revenue. For the first step, public safety and critical
communication are required in the market. Group communication is
also one of key components in the public safety system. Required
functionalities are: Discovery based on proximity, Direct path
communication, and Management of group communications.
[0073] Use cases and scenarios are for example: i)
Commercial/social use, ii) Network offloading, iii) Public Safety,
iv) Integration of current infrastructure services, to assure the
consistency of the user experience including reachability and
mobility aspects, and v) Public Safety, in case of absence of
EUTRAN coverage (subject to regional regulation and operator
policy, and limited to specific public-safety designated frequency
bands and terminals)
[0074] FIG. 6 is an example of default data path for communication
between two UEs. With reference to FIG. 6, even when two UEs (e.g.,
UE1, UE2) in close proximity communicate with each other, their
data path (user plane) goes via the operator network. Thus a
typical data path for the communication involves eNB(s) and/or
Gateway(s) (GW(s)) (e.g., SGW/PGW).
[0075] FIGS. 7 and 8 are examples of data path scenarios for a
proximity communication. If wireless devices (e.g., UE1, UE2) are
in proximity of each other, they may be able to use a direct mode
data path (FIG. 7) or a locally routed data path (FIG. 8). In the
direct mode data path, wireless devices are connected directly each
other (after appropriate procedure(s), such as authentication),
without eNB and SGW/PGW. In the locally routed data path, wireless
devices are connected each other through eNB only.
[0076] FIG. 9 is a conceptual diagram illustrating for a
non-roaming reference architecture.
[0077] PC1 to PC 5 represent interfaces. PC1 is a reference point
between a ProSe application in a UE and a ProSe App server. It is
used to define application level signaling requirements. PC 2 is a
reference point between the ProSe App Server and the ProSe
Function. It is used to define the interaction between ProSe App
Server and ProSe functionality provided by the 3GPP EPS via ProSe
Function. One example may be for application data updates for a
ProSe database in the ProSe Function. Another example may be data
for use by ProSe App Server in interworking between 3GPP
functionality and application data, e.g. name translation. PC3 is a
reference point between the UE and ProSe Function. It is used to
define the interaction between UE and ProSe Function. An example
may be to use for configuration for ProSe discovery and
communication. PC4 is a reference point between the EPC and ProSe
Function. It is used to define the interaction between EPC and
ProSe Function. Possible use cases may be when setting up a
one-to-one communication path between UEs or when validating ProSe
services (authorization) for session management or mobility
management in real time.
[0078] PC5 is a reference point between UE to UE used for control
and user plane for discovery and communication, for relay and
one-to-one communication (between UEs directly and between UEs over
LTE-Uu). Lastly, PC6 is a reference point may be used for functions
such as ProSe Discovery between users subscribed to different
PLMNs.
[0079] EPC (Evolved Packet Core) includes entities such as MME,
S-GW, P-GW, PCRF, HSS etc. The EPC here represents the E-UTRAN Core
Network architecture. Interfaces inside the EPC may also be
impacted albeit they are not explicitly shown in FIG. 9.
[0080] Application servers, which are users of the ProSe capability
for building the application functionality, e.g. in the Public
Safety cases they can be specific agencies (PSAP) or in the
commercial cases social media. These applications are defined
outside the 3GPP architecture but there may be reference points
towards 3GPP entities. The Application server can communicate
towards an application in the UE.
[0081] Applications in the UE use the ProSe capability for building
the application functionality. Example may be for communication
between members of Public Safety groups or for social media
application that requests to find buddies in proximity. The ProSe
Function in the network (as part of EPS) defined by 3GPP has a
reference point towards the ProSe App Server, towards the EPC and
the UE.
[0082] The functionality may include but not restricted to e.g.:
[0083] Interworking via a reference point towards the 3rd party
Applications [0084] Authorization and configuration of the UE for
discovery and Direct communication [0085] Enable the functionality
of the EPC level ProSe discovery [0086] ProSe related new
subscriber data and/handling of data storage; also handling of
ProSe identities; [0087] Security related functionality [0088]
Provide Control towards the EPC for policy related functionality
[0089] Provide functionality for charging (via or outside of EPC,
e.g. offline charging)
[0090] Especially, the following identities are used for ProSe
Direct Communication: [0091] Source Layer-2 ID identifies a sender
of a D2D packet at PC5 interface. The Source Layer-2 ID is used for
identification of the receiver RLC UM entity; [0092] Destination
Layer-2 ID identifies a target of the D2D packet at PC5 interface.
The Destination Layer-2 ID is used for filtering of packets at the
MAC layer. The Destination Layer-2 ID may be a broadcast, groupcast
or unicast identifier; and [0093] SA L1 ID identifier in Scheduling
Assignment (SA) at PC5 interface. SA L1 ID is used for filtering of
packets at the physical layer. The SA L1 ID may be a broadcast,
groupcast or unicast identifier.
[0094] No Access Stratum signaling is required for group formation
and to configure Source Layer-2 ID and Destination Layer-2 ID in
the UE. This information is provided by higher layers.
[0095] In case of groupcast and unicast, the MAC layer will convert
the higher layer ProSe ID (i.e. ProSe Layer-2 Group ID and ProSe UE
ID) identifying the target (Group, UE) into two bit strings of
which one can be forwarded to the physical layer and used as SA L1
ID whereas the other is used as Destination Layer-2 ID. For
broadcast, L2 indicates to L1 that it is a broadcast transmission
using a pre-defined SA L1 ID in the same format as for group- and
unicast.
[0096] FIG. 10 is a conceptual diagram illustrating for a Layer 2
structure for Sidelink.
[0097] The Sidelink is UE to UE interface for ProSe direct
communication and ProSe Direct Discovery. Corresponds to the PC5
interface. The Sidelink comprises ProSe Direct Discovery and ProSe
Direct Communication between UEs. The Sidelink uses uplink
resources and physical channel structure similar to uplink
transmissions. However, some changes, noted below, are made to the
physical channels. E-UTRA defines two MAC entities; one in the UE
and one in the E-UTRAN. These MAC entities handle the following
transport channels additionally, i) sidelink broadcast channel
(SL-BCH), ii) sidelink discovery channel (SL-DCH) and iii) sidelink
shared channel (SL-SCH). [0098] Basic transmission scheme: the
Sidelink transmission uses the same basic transmission scheme as
the UL transmission scheme. However, sidelink is limited to single
cluster transmissions for all the sidelink physical channels.
Further, sidelink uses a 1 symbol gap at the end of each sidelink
sub-frame. [0099] Physical-layer processing: the Sidelink physical
layer processing of transport channels differs from UL transmission
in the following steps:
[0100] i) Scrambling: for PSDCH and PSCCH, the scrambling is not
UE-specific;
[0101] ii) Modulation: 64 QAM is not supported for Sidelink. [0102]
Physical Sidelink control channel: PSCCH is mapped to the Sidelink
control resources. PSCCH indicates resource and other transmission
parameters used by a UE for PSSCH. [0103] Sidelink reference
signals: for PSDCH, PSCCH and PS SCH demodulation, reference
signals similar to uplink demodulation reference signals are
transmitted in the 4th symbol of the slot in normal CP and in the
3rd symbol of the slot in extended cyclic prefix. The Sidelink
demodulation reference signals sequence length equals the size
(number of sub-carriers) of the assigned resource. For PSDCH and
PSCCH, reference signals are created based on a fixed base
sequence, cyclic shift and orthogonal cover code. [0104] Physical
channel procedure: for in-coverage operation, the power spectral
density of the sidelink transmissions can be influenced by the
eNB.
[0105] FIG. 11a is a conceptual diagram illustrating for User-Plane
protocol stack for ProSe Direct Communication, and FIG. 11b is
Control-Plane protocol stack for ProSe Direct Communication.
[0106] FIG. 11a shows the protocol stack for the user plane, where
PDCP, RLC and MAC sublayers (terminate at the other UE) perform the
functions listed for the user plane (e.g. header compression, HARQ
retransmissions). The PC5 interface consists of PDCP, RLC, MAC and
PHY as shown in FIG. 11a.
[0107] User plane details of ProSe Direct Communication: i) MAC sub
header contains LCIDs (to differentiate multiple logical channels),
ii) The MAC header comprises a Source Layer-2 ID and a Destination
Layer-2 ID, iii) At MAC Multiplexing/demultiplexing, priority
handling and padding are useful for ProSe Direct communication, iv)
RLC UM is used for ProSe Direct communication, v) Segmentation and
reassembly of RLC SDUs are performed, vi) A receiving UE needs to
maintain at least one RLC UM entity per transmitting peer UE, vii)
An RLC UM receiver entity does not need to be configured prior to
reception of the first RLC UM data unit, and viii) U-Mode is used
for header compression in PDCP for ProSe Direct Communication.
[0108] FIG. 11b shows the protocol stack for the control plane,
where RRC, RLC, MAC, and PHY sublayers (terminate at the other UE)
perform the functions listed for the control plane. A D2D UE does
not establish and maintain a logical connection to receiving D2D
UEs prior to a D2D communication.
[0109] FIG. 12 is a conceptual diagram illustrating for a PC5
interface for ProSe Direct Discovery.
[0110] ProSe Direct Discovery is defined as the procedure used by
the ProSe-enabled UE to discover other ProSe-enabled UE(s) in its
proximity using E-UTRA direct radio signals via PC5.
[0111] Radio Protocol Stack (AS) for ProSe Direct Discovery is
shown in FIG. 12.
[0112] The AS layer performs the following functions: [0113]
Interfaces with upper layer (ProSe Protocol): The MAC layer
receives the discovery information from the upper layer (ProSe
Protocol). The IP layer is not used for transmitting the discovery
information. [0114] Scheduling: The MAC layer determines the radio
resource to be used for announcing the discovery information
received from upper layer. [0115] Discovery PDU generation: The MAC
layer builds the MAC PDU carrying the discovery information and
sends the MAC PDU to the physical layer for transmission in the
determined radio resource. No MAC header is added.
[0116] There are two types of resource allocation for discovery
information announcement. [0117] Type 1: A resource allocation
procedure where resources for announcing of discovery information
are allocated on a non UE specific basis, further characterized by:
i) The eNB provides the UE(s) with the resource pool configuration
used for announcing of discovery information. The configuration may
be signalled in SIB, ii) The UE autonomously selects radio
resource(s) from the indicated resource pool and announce discovery
information, iii) The UE can announce discovery information on a
randomly selected discovery resource during each discovery period.
[0118] Type 2: A resource allocation procedure where resources for
announcing of discovery information are allocated on a per UE
specific basis, further characterized by: i) The UE in
RRC_CONNECTED may request resource(s) for announcing of discovery
information from the eNB via RRC, ii) The eNB assigns resource(s)
via RRC, iii) The resources are allocated within the resource pool
that is configured in UEs for monitoring.
[0119] For UEs in RRC_IDLE, the eNB may select one of the following
options: [0120] The eNB may provide a Type 1 resource pool for
discovery information announcement in SIB. UEs that are authorized
for Prose Direct Discovery use these resources for announcing
discovery information in RRC_IDLE. [0121] The eNB may indicate in
SIB that it supports D2D but does not provide resources for
discovery information announcement. UEs need to enter RRC Connected
in order to request D2D resources for discovery information
announcement.
[0122] For UEs in RRC_CONNECTED, [0123] A UE authorized to perform
ProSe Direct Discovery announcement indicates to the eNB that it
wants to perform D2D discovery announcement. [0124] The eNB
validates whether the UE is authorized for ProSe Direct Discovery
announcement using the UE context received from MME. [0125] The eNB
may configure the UE to use a Type 1 resource pool or dedicated
Type 2 resources for discovery information announcement via
dedicated RRC signaling (or no resource). [0126] The resources
allocated by the eNB are valid until a) the eNB de-configures the
resource(s) by RRC signaling or b) the UE enters IDLE. (FFS whether
resources may remain valid even in IDLE).
[0127] Receiving UEs in RRC_IDLE and RRC_CONNECTED monitor both
Type 1 and Type 2 discovery resource pools as authorized. The eNB
provides the resource pool configuration used for discovery
information monitoring in SIB. The SIB may contain discovery
resources used for announcing in neighbor cells as well.
[0128] FIG. 13 is a conceptual diagram illustrating for model of
two unacknowledged mode peer entities.
[0129] In UM (Unacknowledged Mode), in-sequence delivery to higher
layers is provided, but no retransmissions of missing PDUs are
requested. UM is typically used for services such as VoIP where
error-free delivery is of less importance compared to short
delivery time. TM (Transparent Mode), although supported, is only
used for specific purposes such as random access.
[0130] Unacknowledged mode (UM) supports segmentation/reassembly
and in-sequence delivery, but not retransmissions. This mode is
used when error-free delivery is not required, for example
voice-over IP, or when retransmissions cannot be requested, for
example broadcast transmissions on MTCH and MCCH using MBSFN.
[0131] When a transmitting UM RLC entity forms UMD PDUs from RLC
SDUs, the transmitting UM RLC entity may i) segment and/or
concatenate the RLC SDUs so that the UMD PDUs fit within the total
size of RLC PDU(s) indicated by lower layer at the particular
transmission opportunity notified by lower layer; and ii) include
relevant RLC headers in the UMD PDU.
[0132] When a receiving UM RLC entity receives UMD PDUs, the
receiving UM RLC entity may i) detect whether or not the UMD PDUs
have been received in duplication, and discard duplicated UMD PDUs;
ii) reorder the UMD PDUs if they are received out of sequence; iii)
detect the loss of UMD PDUs at lower layers and avoid excessive
re-ordering delays; iv) reassemble RLC SDUs from the reordered UMD
PDUs (not accounting for RLC PDUs for which losses have been
detected) and deliver the RLC SDUs to upper layer in ascending
order of the RLC SN; and v) discard received UMD PDUs that cannot
be reassembled into a RLC SDU due to loss at lower layers of an UMD
PDU which belonged to the particular RLC SDU.
[0133] At the time of RLC re-establishment, the receiving UM RLC
entity may reassemble RLC SDUs from the UMD PDUs that are received
out of sequence and deliver them to upper layer, if possible; ii)
discard any remaining UMD PDUs that could not be reassembled into
RLC SDUs; and iii) initialize relevant state variables and stop
relevant timers.
[0134] The receiving UM RLC entity may maintain a reordering window
according to state variable VR(UH) as follows:
[0135] i) a SN falls within the reordering window if
(VR(UH)-UM_Window_Size).ltoreq.SN<VR(UH);
[0136] ii) a SN falls outside of the reordering window
otherwise.
[0137] When receiving an UMD PDU from lower layer, the receiving UM
RLC entity may either discard the received UMD PDU or place it in
the reception buffer.
[0138] If the received UMD PDU was placed in the reception buffer,
the receiving UM RLC may update state variables, reassemble and
deliver RLC SDUs to upper layer and start/stop t-Reordering as
needed.
[0139] When t-Reordering expires, the receiving UM RLC entity may
update state variables, reassemble and deliver RLC SDUs to upper
layer and start t-Reordering as needed
[0140] When an UMD PDU with SN=x is received from lower layer, the
receiving UM RLC entity may discard the received UMD PDU, if
VR(UR)<x<VR(UH) and the UMD PDU with SN=x has been received
before; or if (VR(UH)-UM_Window_Size).ltoreq.x<VR(UR).
[0141] Else, the receiving UM RLC entity may place the received UMD
PDU in the reception buffer.
[0142] When an UMD PDU with SN=x is placed in the reception buffer,
the receiving UM RLC entity may update VR(UH) to x+1 and reassemble
RLC SDUs from any UMD PDUs with SN that falls outside of the
reordering window, remove RLC headers when doing so and deliver the
reassembled RLC SDUs to upper layer in ascending order of the RLC
SN if not delivered before, if x falls outside of the reordering
window.
[0143] If VR(UR) falls outside of the reordering window, the
receiving UM RLC entity may set VR(UR) to
(VR(UH)-UM_Window_Size).
[0144] If the reception buffer contains an UMD PDU with SN=VR(UR),
the receiving UM RLC entity may update VR(UR) to the SN of the
first UMD PDU with SN>current VR(UR) that has not been received;
and reassemble RLC SDUs from any UMD PDUs with SN<updated
VR(UR), remove RLC headers when doing so and deliver the
reassembled RLC SDUs to upper layer in ascending order of the RLC
SN if not delivered before;
[0145] If t-Reordering is running and VR(UX).ltoreq.VR(UR); or if
t-Reordering is running and VR(UX) falls outside of the reordering
window and VR(UX) is not equal to VR(UH), the receiving UM RLC
entity may stop and reset t-Reordering.
[0146] If t-Reordering is not running (includes the case when
t-Reordering is stopped due to actions above) and VR(UH)>VR(UR),
the receiving UM RLC entity may start t-Reordering, and set VR(UX)
to VR(UH).
[0147] When t-Reordering expires, the receiving UM RLC entity may
update VR(UR) to the SN of the first UMD PDU with SN.gtoreq.VR(UX)
that has not been received; and reassemble RLC SDUs from any UMD
PDUs with SN<updated VR(UR), remove RLC headers when doing so
and deliver the reassembled RLC SDUs to upper layer in ascending
order of the RLC SN if not delivered before.
[0148] If VR(UH)>VR(UR), the receiving UM RLC entity may start
t-Reordering, and set VR(UX) to VR(UH).
[0149] Each transmitting UM RLC entity shall maintain the following
state variables above mentioned:
[0150] a) VT(US): this state variable holds the value of the SN to
be assigned for the next newly generated UMD PDU. It is initially
set to 0, and is updated whenever the UM RLC entity delivers an UMD
PDU with SN=VT(US).
[0151] Each receiving UM RLC entity shall maintain the following
state variables above mentioned:
[0152] a) VR(UR)--UM receive state variable: this state variable
holds the value of the SN of the earliest UMD PDU that is still
considered for reordering. It is initially set to 0.
[0153] b) VR(UX)--UM t-Reordering state variable: this state
variable holds the value of the SN following the SN of the UMD PDU
which triggered t-Reordering.
[0154] c) VR(UH)--UM highest received state variable: this state
variable holds the value of the SN following the SN of the UMD PDU
with the highest SN among received UMD PDUs, and it serves as the
higher edge of the reordering window. It is initially set to 0.
[0155] FIGS. 14a to 14f are conceptual diagrams illustrating for
UMD PDU.
[0156] FIG. 14a is a diagram for a UMD PDU with 5 bit SN, FIG. 14b
is a diagram for a UMD PDU with 10 bit SN, FIG. 14c is a diagram
for a UMD PDU with 5 bit SN (Odd number of LIs, i.e. K=1, 3, 5, . .
. ), FIG. 14d is a diagram for a UMD PDU with 5 bit SN (Even number
of LIs, i.e. K=2, 4, 6, . . . ), FIG. 14e is a UMD PDU with 10 bit
SN (Odd number of LIs, i.e. K=1, 3, 5, . . . ), and FIG. 14f is a
diagram for a UMD PDU with 10 bit SN (Even number of LIs, i.e. K=2,
4, 6, . . . ).
[0157] UMD PDU consists of a Data field and an UMD PDU header. UMD
PDU header consists of a fixed part (fields that are present for
every UMD PDU) and an extension part (fields that are present for
an UMD PDU when necessary). The fixed part of the UMD PDU header
itself is byte aligned and consists of a FI, an E and a SN. The
extension part of the UMD PDU header itself is byte aligned and
consists of E(s) and LI(s).
[0158] An UM RLC entity is configured by RRC to use either a 5 bit
SN or a 10 bit SN. When the 5 bit SN is configured, the length of
the fixed part of the UMD PDU header is one byte. When the 10 bit
SN is configured, the fixed part of the UMD PDU header is identical
to the fixed part of the AMD PDU header, except for D/C, RF and P
fields all being replaced with R1 fields. The extension part of the
UMD PDU header is identical to the extension part of the AMD PDU
header (regardless of the configured SN size).
[0159] An UMD PDU header consists of an extension part only when
more than one Data field elements are present in the UMD PDU, in
which case an E and a LI are present for every Data field element
except the last. Furthermore, when an UMD PDU header consists of an
odd number of LI(s), four padding bits follow after the last
LI.
[0160] In the definition of each field in FIG. 14a to FIG. 14f, the
bits in the parameters are represented in which the first and most
significant bit is the left most bit and the last and least
significant bit is the rightmost bit. Unless mentioned otherwise,
integers are encoded in standard binary encoding for unsigned
integers. [0161] Data field: The Data field elements are mapped to
the Data field in the order which they arrive to the RLC entity at
the transmitter. The granularity of the Data field size is one
byte; and the maximum Data field size is the maximum TB size minus
the sum of minimum MAC PDU header size and minimum RLC PDU header
size. A UMD PDU segment is mapped to the Data field. Zero RLC SDU
segments and one or more RLC SDUs, one or two RLC SDU segments and
zero or more RLC SDUs; the RLC SDU segments are either mapped to
the beginning or the end of the Data field, a RLC SDU or RLC SDU
segment larger than 2047 octets can only be mapped to the end of
the Data field. When there are two RLC SDU segments, they belong to
different RLC SDUs. [0162] Sequence number (SN) field: the SN field
indicates the sequence number of the corresponding UMD or AMD PDU.
For an AMD PDU segment, the SN field indicates the sequence number
of the original AMD PDU from which the AMD PDU segment was
constructed from. The sequence number is incremented by one for
every UMD or AMD PDU. Length is 5 bits or 10 bits (configurable)
for UMD PDU. [0163] Extension bit (E) field: Length is 1 bit. The E
field indicates whether Data field follows or a set of E field and
LI field follows. The interpretation of the E field is provided in
Table 1 and Table 2.
TABLE-US-00001 [0163] TABLE 1 Value Description 0 Data field
follows from the octet following the fixed part of the header 1 A
set of E field and LI field follows from the octet following the
fixed part of the header
TABLE-US-00002 TABLE 2 Value Description 0 Data field follows from
the octet following the LI field following this E field 1 A set of
E field and LI field follows from the bit following the LI field
following this E field
[0164] Length Indicator (LI) field: Length is 11 bits. The LI field
indicates the length in bytes of the corresponding Data field
element present in the RLC data PDU delivered/received by an UM or
an AM RLC entity. The first LI present in the RLC data PDU header
corresponds to the first Data field element present in the Data
field of the RLC data PDU, the second LI present in the RLC data
PDU header corresponds to the second Data field element present in
the Data field of the RLC data PDU, and so on. The value 0 is
reserved. [0165] Framing Info (FI) field: Length is 2 bits. The FI
field indicates whether a RLC SDU is segmented at the beginning
and/or at the end of the Data field. Specifically, the FI field
indicates whether the first byte of the Data field corresponds to
the first byte of a RLC SDU, and whether the last byte of the Data
field corresponds to the last byte of a RLC SDU. The interpretation
of the FI field is provided in Table 3.
TABLE-US-00003 [0165] TABLE 3 Value Description 00 First byte of
the Data field corresponds to the first byte of a RLC SDU. Last
byte of the Data field corresponds to the last byte of a RLC SDU.
01 First byte of the Data field corresponds to the first byte of a
RLC SDU. Last byte of the Data field does not correspond to the
last byte of a RLC SDU. 10 First byte of the Data field does not
correspond to the first byte of a RLC SDU. Last byte of the Data
field corresponds to the last byte of a RLC SDU. 11 First byte of
the Data field does not correspond to the first byte of a RLC SDU.
Last byte of the Data field does not correspond to the last byte of
a RLC SDU.
[0166] FIG. 15 is a conceptual diagram for functional view of a
PDCP entity.
[0167] The PDCP entities are located in the PDCP sublayer. Several
PDCP entities may be defined for a UE. Each PDCP entity carrying
user plane data may be configured to use header compression. Each
PDCP entity is carrying the data of one radio bearer. In this
version of the specification, only the robust header compression
protocol (ROHC), is supported. Every PDCP entity uses at most one
ROHC compressor instance and at most one ROHC decompressor
instance. A PDCP entity is associated either to the control plane
or the user plane depending on which radio bearer it is carrying
data for.
[0168] FIG. 15 represents the functional view of the PDCP entity
for the PDCP sublayer, it should not restrict implementation. For
RNs, integrity protection and verification are also performed for
the u-plane.
[0169] UL Data Transfer Procedures:
[0170] At reception of a PDCP SDU from upper layers, the UE may
start a discard timer associated with the PDCP SDU. For a PDCP SDU
received from upper layers, the UE may associate a PDCP SN
(Sequence Number) corresponding to Next_PDCP_TX_SN to the PDCP SDU,
perform header compression of the PDCP SDU, perform integrity
protection and ciphering using COUNT based on TX_HFN and the PDCP
SN associated with this PDCP SDU, increment the Next_PDCP_TX_SN by
one, and submit the resulting PDCP Data PDU to lower layer.
[0171] If the Next_PDCP_TX_SN is greater than Maximum_PDCP_SN, the
Next_PDCP_TX_SN is set to `0` and TX_HFN is incremented by one.
[0172] DL Data Transfer Procedures:
[0173] For DRBs mapped on RLC UM, at reception of a PDCP Data PDU
from lower layers, if received PDCP SN<Next_PDCP_RX_SN, the UE
may increment RX_HFN by one, and decipher the PDCP Data PDU using
COUNT based on RX_HFN and the received PDCP SN. And the UE may set
Next_PDCP_RX_SN to the received PDCP SN+1. If
Next_PDCP_RX_SN>Maximum_PDCP_SN, the UE may set Next_PDCP_RX_SN
to 0, and increment RX_HFN by one.
[0174] The UE may perform header decompression (if configured) of
the deciphered PDCP Data PDU, and deliver the resulting PDCP SDU to
upper layer.
[0175] FIGS. 16a and 16b are conceptual diagrams for PDCP Data PDU
format for DRBs.
[0176] FIG. 16a shows the format of the PDCP Data PDU when a 12 bit
SN length is used. This format is applicable for PDCP Data PDUs
carrying data from DRBs mapped on RLC AM or RLC UM.
[0177] And the FIG. 16b shows the format of the PDCP Data PDU when
a 7 bit SN length is used. This format is applicable for PDCP Data
PDUs carrying data from DRBs mapped on RLC UM.
[0178] The receiving side of each PDCP entity may maintain the
following state variables:
[0179] a) Next_PDCP_RX_SN: The variable Next_PDCP_RX_SN indicates
the next expected PDCP SN by the receiver for a given PDCP entity.
At establishment of the PDCP entity, the UE shall set
Next_PDCP_RX_SN to 0.
[0180] b) RX_HFN: the variable RX_HFN indicates the HFN value for
the generation of the COUNT value used for the received PDCP PDUs
for a given PDCP entity. At establishment of the PDCP entity, the
UE shall set RX_HFN to 0.
[0181] c) Last_Submitted_PDCP_RX_SN: for PDCP entities for DRBs
mapped on RLC AM the variable Last_Submitted_PDCP_RX_SN indicates
the SN of the last PDCP SDU delivered to the upper layers. At
establishment of the PDCP entity, the UE shall set
Last_Submitted_PDCP_RX_SN to Maximum_PDCP_SN.
[0182] In D2D communication, the UM RLC entity and the PDCP entity
are established in the receiver side when the receiver receives the
first RLC UMD PDU from the transmitter. At establishment, according
to the prior art, the related state variables in the RLC entity
(i.e. VR(UR) and VR(UH)) and PDCP entity (i.e. Next_PDCP_RX_SN and
RX_HFN) are initialized to zero. However, this behavior causes
following problems in RLC and PDCP, respectively.
[0183] In case of RLC entity, one of the current functions of the
RLC UM entity is to perform re-ordering and duplicate detection.
The RLC entity may discard received UMD PDUs if any of the
conditions are met, if VR(UR)<x<VR(UH) and the UMD PDU with
SN=x has been received before; or if
(VR(UH)-UM_Window_Size).ltoreq.x<VR(UR).
[0184] Given the fact that a receiving UE can join/re-join the data
reception from a transmitting source at any point in time, there is
a possibility that the SN of the received packet will fall within
the discard window and is incorrectly discarded. The probability of
discarding packets will depend on the window size. For example,
when a UE first sets up the receiving RLC entity, VR(UR) and VR(UH)
are initially set to zero. The window size is set to 512 for a 10
bit SN. According to the formula above if the SN of the first
received packet is between 512 and 1023 then the UE would discard
the packet. The UE will continue discarding packets until a packet
between 0 and 511 is received.
[0185] In case of PDCP entity, one of the current functions of the
PDCP entity is to perform deciphering of the received PDCP SDU. The
deciphering is performed based on the HFN and received PDCP SN. The
HFN is increased by one when the PDCP SN wraps around.
[0186] The receiving UE establishes the PDCP entity when the first
RLC UMD PDU is received from a transmitting UE, in which case the
RX_HFN and Next_PDCP_RX_SN are initialized to zero. However, given
the fact that a receiving UE can join/re-join the data reception
from a transmitting source at any point in time, there is a
possibility that the HFN is already increased to a certain value
depending on the number of PDCP SN wrap around. If the HFN is
desynchronized between the transmitter and the receiver, the
receiver cannot decipher the received PDCP PDU correctly, and the
communication will fail.
[0187] FIG. 17 is a conceptual diagram for transmitting an explicit
signal of layer-2 state variables for D2D communication according
to embodiments of the present invention.
[0188] For the robust initialization of state variables, it is
invented that an explicit signal, say configuration message
including initial values of RLC or PDCP state variables, is
transmitted from the transmitter to the receiver. The receiver
initializes the RLC and PDCP state variables according to the
received configuration message.
[0189] In case of RLC entity, when the transmitting RLC entity
generates the configuration message including initial values of RLC
state variables used for an receiving RLC entity of a peer UE
(S1701).
[0190] The transmitting RLC entity transmits the configuration
message to the peer UE (S1703) and RLC PDUs to the receiving RLC
entity of the peer UE by considering the initial values
(S1705).
[0191] Preferably, the configuration message is transmitted before
transmission of the RLC PDUs using the initial values.
[0192] Preferably, the configuration message includes at least one
of an initial value of VR(UH) or an initial value of VR(UR), and
the VR(UR) is a received state variable for the UM RLC entity and
holds a value of RLC SN of a earliest UMD PDU that is still
considered for reordering, and the VR(UH) is highest received state
variable for the UM RLC entity and holds a value of RLC SN
following SN of the UMD PDU with the highest SN among received UMD
PDUs.
[0193] Preferably, the configuration message is transmitted to the
peer UE multiple times before transmitting any other packets,
wherein the number of transmissions of configuration message is
configured by an e-NodeB.
[0194] Preferably, the configuration message is transmitted to the
peer UE periodically, wherein periodicity of configuration message
transmission is configured by an e-NodeB.
[0195] When the transmitting UE transmits a first RLC PDU to the
receiving RLC entity of the peer UE, RLC SN (Sequence Number) of
the first RLC PDU can be set to the initial values. The first RLC
PDU is first transmitted after transmitting the configuration
message.
[0196] Preferably, the transmitting RLC entity transmits the RLC
PDUs using a certain values corresponding to the initial values of
RLC state variables used for the receiving RLC entity of the peer
UE.
[0197] Preferably, the configuration message can be transmitted in
different forms of L2 signaling; MAC Control Element, RLC Control
PDU, or PDCP Control PDU.
[0198] Preferably, the configuration message can be transmitted per
radio bearer for D2D (Device to Device).
[0199] When the receiving RLC entity receives a configuration
message including initial values of RLC state variables from a
transmitting RLC entity of a peer UE (S1705), the receiving RLC
entity sets RLC state variables to the initial values included in
the received configuration message (S1707). And the receiving RLC
entity processes RLC PDUs received after reception of the
configuration message using the RLC state variables (S1709).
[0200] Optionally, when the receiving RLC entity detects problem
with the received packet (e.g. keep discarding in RLC entity or
keep failing header decompression in PDCP entity), the receiving
RLC entity can request of the transmitting RLC entity of the peer
UE to transmit the configuration message. At that time, the
transmitting RLC entity can transmits the configuration message in
response to the request transmission to the receiving RLC
entity.
[0201] In PDCP mapped on UM RLC, two state variables need to be
considered, i.e. RX_HFN and Next_PDCP_RX_SN. As per current
specification, they are all initialized to 0 at PDCP entity
establishment.
[0202] The RX_HFN is maintained in the receiver internally, and it
should be synchronized to the TX_HFN. The RX_HFN is updated (i.e.
incremented) depending on the comparison result between received
PDCP SN and Next_PDCP_RX_SN, as above mentioned.
[0203] Therefore, if deciphering is performed in PDCP layer for D2D
communication, the state variables RX_HFN and Next_PDCP_RX_SN
should be initialized to defined values or initialized based on a
defined rule in order to maintain the synchronization of HFN values
between the transmitter and the receiver.
[0204] As explained before, the RX_HFN is maintained in the
receiver internally. Thus, the receiver does not know the correct
RX_HFN value when the receiving PDCP entity is established. Two
options can be considered for synchronization of HFN values. [0205]
Option1. The transmitter transmits the current HFN value to the
receiver via e.g. a PDCP Control PDU using the configuration
message. [0206] Option2. The 32 bit COUNT value is attached to
every PDCP Data PDU.
[0207] In case of Option 1, there are similar with case of RLC
entity described in FIG. 17.
[0208] In case of PDCP entity, when the transmitting PDCP entity
generates the configuration message including initial values of
PDCP state variables used for an receiving PDCP entity of a peer UE
(S1701).
[0209] The transmitting PDCP entity transmits the configuration
message to the peer UE (S1703) and PDCP PDUs to the receiving PDCP
entity of the peer UE by considering the initial values
(S1705).
[0210] Preferably, the configuration message is transmitted before
transmission of the PDCP PDUs using the initial values.
[0211] Preferably, the configuration message includes at least one
of an initial Next_PDCP_RX_SN or an initial value of RX_HFN, and
the Next_PDCP_RX_SN indicates a next expected PDCP SN by a receiver
for a given PDCP entity, and the RX_HFN indicates a HFN value for
the generation of the COUNT value used for the received PDCP PDUs
for a given PDCP entity.
[0212] Preferably, the configuration message is transmitted to the
peer UE multiple times before transmitting any other packets,
wherein a number of transmission of configuration message is
configured by an e-NodeB.
[0213] Preferably, the configuration message is transmitted to the
peer UE periodically, wherein periodicity of configuration message
transmission is configured by an e-NodeB.
[0214] When the transmitting UE transmits a first PDCP PDU to the
receiving PDCP entity of the peer UE, PDCP SN of the first PDCP PDU
can be set to the initial values. The first PDCP PDU is first
transmitted after transmitting the configuration message.
[0215] Preferably, the transmitting PDCP entity transmits the PDCP
PDUs using a certain values corresponding to the initial values of
PDCP state variables used for the receiving PDCP entity of the peer
UE.
[0216] Preferably, the configuration message can be transmitted in
different forms of L2 signaling; MAC Control Element, RLC Control
PDU, or PDCP Control PDU.
[0217] Preferably, the configuration message can be transmitted per
radio bearer for D2D (Device to Device).
[0218] When the receiving PDCP entity receives a configuration
message including initial values of PDCP state variables from a
transmitting PDCP entity of a peer UE (S1705), the receiving PDCP
entity sets PDCP state variables to the initial values included in
the received configuration message (S1707). And the receiving PDCP
entity processes PDCP PDUs received after reception of the
configuration message using the PDCP state variables (S1709).
[0219] Optionally, when the receiving PDCP entity detects problem
with the received packet (e.g. keep discarding in RLC entity or
keep failing header decompression in PDCP entity), the receiving
PDCP entity can request of the transmitting PDCP entity of the peer
UE to transmit the configuration message. At that time, the
transmitting PDCP entity can transmits the configuration message in
response to the request transmission to the receiving PDCP
entity.
[0220] Option 2 is explained in FIG. 18.
[0221] FIG. 18 is a conceptual diagram for transmitting an explicit
signal of layer-2 state variables for D2D communication according
to embodiments of the present invention.
[0222] Option2 is more robust solution than Option1 by adding whole
COUNT value to each PDCP Data PDU.
[0223] The transmitting PDCP entity generates COUNT for ciphering a
first packet (S1801). And the transmitting PDCP entity transmits
MSB parts of the COUNT to a receiving PDCP entity of the peer UE
via a direct interface between the UE and the peer UE (S1803).
[0224] Preferably, the MSB parts of the COUNT may be PTK ID. Thus,
zeroth-order of COUNT to 15th of COUNT are set to PTK ID, and PDCP
SN is input into 16th of COUNT to 31st of COUNT.
[0225] The PTK (ProSe Traffic Key) identity may be set to a unique
value in the sending UE that has not been previously used together
with the same PGK and PGK identity in the UE. A 16-bit counter in
association with the Group Identity, PGK identity and the Group
Member Identity may be used as the PTK identity. Every time a new
PTK needs to be derived, the PTK Identity counter is
incremented.
[0226] When the receiving PDCP entity receives the MSB parts of the
COUNT and a PDCP PDU (S1805), the receiving PDCP entity generates
COUNT using the MSB parts of the COUNT and a PDCP SN of the
received PDCP PDU (S1807).
[0227] Preferably, the PDCP SN is occupied in LSB parts of the
COUNT.
[0228] And then the receiving PDCP deciphers the PDCP PDU using the
COUNT (S1809).
[0229] The embodiments of the present invention described
hereinbelow are combinations of elements and features of the
present invention. The elements or features may be considered
selective unless otherwise mentioned. Each element or feature may
be practiced without being combined with other elements or
features. Further, an embodiment of the present invention may be
constructed by combining parts of the elements and/or features.
Operation orders described in embodiments of the present invention
may be rearranged. Some constructions of any one embodiment may be
included in another embodiment and may be replaced with
corresponding constructions of another embodiment. It is obvious to
those skilled in the art that claims that are not explicitly cited
in each other in the appended claims may be presented in
combination as an embodiment of the present invention or included
as a new claim by subsequent amendment after the application is
filed.
[0230] In the embodiments of the present invention, a specific
operation described as performed by the BS may be performed by an
upper node of the BS. Namely, it is apparent that, in a network
comprised of a plurality of network nodes including a BS, various
operations performed for communication with an MS may be performed
by the BS, or network nodes other than the BS. The term `eNB` may
be replaced with the term `fixed station`, `Node B`, `Base Station
(BS)`, `access point`, etc.
[0231] The above-described embodiments may be implemented by
various means, for example, by hardware, firmware, software, or a
combination thereof.
[0232] In a hardware configuration, the method according to the
embodiments of the present invention may be implemented by one or
more Application Specific Integrated Circuits (ASICs), Digital
Signal Processors (DSPs), Digital Signal Processing Devices
(DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate
Arrays (FPGAs), processors, controllers, microcontrollers, or
microprocessors.
[0233] In a firmware or software configuration, the method
according to the embodiments of the present invention may be
implemented in the form of modules, procedures, functions, etc.
performing the above-described functions or operations. Software
code may be stored in a memory unit and executed by a processor.
The memory unit may be located at the interior or exterior of the
processor and may transmit and receive data to and from the
processor via various known means.
[0234] Those skilled in the art will appreciate that the present
invention may be carried out in other specific ways than those set
forth herein without departing from the spirit and essential
characteristics of the present invention. The above embodiments are
therefore to be construed in all aspects as illustrative and not
restrictive. The scope of the invention should be determined by the
appended claims and their legal equivalents, not by the above
description, and all changes coming within the meaning and
equivalency range of the appended claims are intended to be
embraced therein.
INDUSTRIAL APPLICABILITY
[0235] While the above-described method has been described
centering on an example applied to the 3GPP LTE system, the present
invention is applicable to a variety of wireless communication
systems in addition to the 3GPP LTE system.
* * * * *