U.S. patent application number 17/570378 was filed with the patent office on 2022-06-30 for method and apparatus for improving retransmission scheduling of sidelink communication in a wireless communication system.
The applicant listed for this patent is ASUSTek Computer Inc.. Invention is credited to Wei-Yu Chen.
Application Number | 20220210815 17/570378 |
Document ID | / |
Family ID | |
Filed Date | 2022-06-30 |
United States Patent
Application |
20220210815 |
Kind Code |
A1 |
Chen; Wei-Yu |
June 30, 2022 |
METHOD AND APPARATUS FOR IMPROVING RETRANSMISSION SCHEDULING OF
SIDELINK COMMUNICATION IN A WIRELESS COMMUNICATION SYSTEM
Abstract
Methods and apparatuses for improving retransmission scheduling
of sidelink communications are disclosed herein. In one method, a
first device monitors a down control signal for scheduling sidelink
resource. The first device performs a sidelink transmission for a
second device based on a first sidelink grant allocated by a base
station. The first device determines a retransmission need of the
sidelink transmission based on a Hybrid Automatic Repeat Request
(HARQ) feedback of the sidelink transmission from the second
device. The first device transmits a retransmission indication for
the retransmission need to the base station. The first device
starts or restarts a timer upon the transmission of the
retransmission indication, wherein the timer is used for
controlling a period of monitoring a downlink control resource
set.
Inventors: |
Chen; Wei-Yu; (Taipei City,
TW) |
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Applicant: |
Name |
City |
State |
Country |
Type |
ASUSTek Computer Inc. |
Taipei City 112 |
|
TW |
|
|
Appl. No.: |
17/570378 |
Filed: |
January 6, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16797577 |
Feb 21, 2020 |
11252753 |
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17570378 |
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62808482 |
Feb 21, 2019 |
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International
Class: |
H04W 72/12 20060101
H04W072/12; H04W 72/14 20060101 H04W072/14; H04L 1/18 20060101
H04L001/18; H04L 1/08 20060101 H04L001/08; H04L 1/16 20060101
H04L001/16 |
Claims
1. A method of a first device to monitor downlink control signaling
for scheduling sidelink resources, comprising: performing a
sidelink transmission for a second device; determining a
retransmission need of the sidelink transmission based on a
feedback of the sidelink transmission received from the second
device; transmitting a retransmission indication for the
retransmission need to a base station; and starting or restarting a
timer upon the transmission of the retransmission indication,
wherein the timer is used for controlling a round-trip time
(RTT).
2. The method of claim 1, wherein the sidelink transmission for the
second device is based on a first sidelink grant allocated by the
base station.
3. The method of claim 1, wherein the feedback is a Hybrid
Automatic Repeat Request (HARQ) feedback.
4. The method of claim 3, wherein the HARQ feedback is received
from the second device through a sidelink interface.
5. The method of claim 3, further comprising: transmitting the
retransmission indication to the base station if the first device
does not receive the HARQ feedback from the second device.
6. The method of claim 3, further comprising: transmitting the
retransmission indication to the base station if the HARQ feedback
from the second device indicates a reception failure of the
sidelink transmission.
7. The method of claim 1, wherein the timer is a RTT timer for
sidelink.
8. The method of claim 1, wherein the downlink control signaling
includes a Physical Downlink Control Channel (PDCCH) or a
coreset.
9. The method of claim 1, wherein the downlink control signaling
includes a set of PDCCH occasions.
10. The method of claim 1, wherein the timer is used for triggering
start of a retransmission timer for sidelink, and for controlling a
period of monitoring a downlink control resource set.
11. A first device configured to monitor downlink control signaling
for scheduling sidelink resources, comprising: a memory; and a
processor operatively coupled to the memory, wherein the processor
is configured to execute program code to: perform a sidelink
transmission for a second device; determine a retransmission need
of the sidelink transmission based on a feedback of the sidelink
transmission received from the second device; transmit a
retransmission indication for the retransmission need to a base
station; and start or restart a timer upon the transmission of the
retransmission indication, wherein the timer is used for
controlling a round-trip time (RTT).
12. The first device of claim 11, wherein the sidelink transmission
for the second device is based on a first sidelink grant allocated
by the base station.
13. The first device of claim 11, wherein the feedback is a Hybrid
Automatic Repeat Request (HARQ) feedback.
14. The first device of claim 13, wherein the HARQ feedback is
received from the second device through a sidelink interface.
15. The first device of claim 13, wherein the processor is further
configured to execute program code to: transmit the retransmission
indication to the base station if the first device does not receive
the HARQ feedback from the second device.
16. The first device of claim 13, wherein the processor is further
configured to execute program code to: transmit the retransmission
indication to the base station if the HARQ feedback from the second
device indicates a reception failure of the sidelink
transmission.
17. The first device of claim 11, wherein the timer is a RTT timer
for sidelink.
18. The first device of claim 11, wherein the downlink control
signaling includes a Physical Downlink Control Channel (PDCCH) or a
coreset.
19. The first device of claim 11, wherein the downlink control
signaling includes a set of PDCCH occasions.
20. The first device of claim 11, wherein the timer is used for
triggering start of a retransmission timer for sidelink, and for
controlling a period of monitoring a downlink control resource set.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present Application is a continuation of U.S. patent
application Ser. No. 16/797,577, filed Feb. 21, 2020, which claims
priority to and the benefit of U.S. Provisional Patent Application
Ser. No. 62/808,482, filed Feb. 21, 2019; with the entire
disclosures of each referenced application fully incorporated
herein by reference.
FIELD
[0002] This disclosure generally relates to wireless communication
networks, and more particularly, to a method and apparatus for
improving retransmission scheduling of sidelink communication in a
wireless communication system.
BACKGROUND
[0003] With the rapid rise in demand for communication of large
amounts of data to and from mobile communication devices,
traditional mobile voice communication networks are evolving into
networks that communicate with Internet Protocol (IP) data packets.
Such IP data packet communication can provide users of mobile
communication devices with voice over IP, multimedia, multicast and
on-demand communication services.
[0004] An exemplary network structure is an Evolved Universal
Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can
provide high data throughput in order to realize the above-noted
voice over IP and multimedia services. A new radio technology for
the next generation (e.g., 5G) is currently being discussed by the
3GPP standards organization. Accordingly, changes to the current
body of 3GPP standard are currently being submitted and considered
to evolve and finalize the 3GPP standard.
SUMMARY
[0005] In one method, a first device monitors a down control signal
for scheduling sidelink resource. The first device performs a
sidelink transmission for a second device based on a first sidelink
grant allocated by a base station. The first device determines a
retransmission need of the sidelink transmission based on a Hybrid
Automatic Repeat Request (HARQ) feedback of the sidelink
transmission from the second device. The first device transmits a
retransmission indication for the retransmission need to the base
station. The first device starts or restarts a timer upon the
transmission of the retransmission indication, wherein the timer is
used for controlling a period of monitoring a downlink control
resource set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows a diagram of a wireless communication system
according to one exemplary embodiment.
[0007] FIG. 2 is a block diagram of a transmitter system (also
known as access network) and a receiver system (also known as user
equipment or UE) according to one exemplary embodiment.
[0008] FIG. 3 is a functional block diagram of a communication
system according to one exemplary embodiment.
[0009] FIG. 4 is a functional block diagram of the program code of
FIG. 3 according to one exemplary embodiment.
[0010] FIG. 5 is a reproduction of FIG. 6.1.3.1a-1 showing Sidelink
BSR and Truncated Sidelink BSR MAC control element for even N taken
from 3GPP TS 36.321-f30.
[0011] FIG. 6 is a reproduction of FIG. 6.1.3.1a-2: Sidelink BSR
and Truncated Sidelink BSR MAC control element for odd N taken from
3GPP TS 36.321-f30.
[0012] FIG. 7 is a reproduction of FIG. 6.1.6-1 showing
R/R/E/LCID/F/L MAC subheader taken from 3GPP TS 36.321-f30.
[0013] FIG. 8 is a reproduction of FIG. 6.1.6-2 showing R/R/E/LCID
MAC subheader taken from 3GPP TS 36.321-f30.
[0014] FIG. 9 is a reproduction of FIG. 6.1.6-3 showing SL-SCH MAC
subheader for V="0001" and "0010" taken from 3GPP TS
36.321-f30.
[0015] FIG. 10 is a reproduction of FIG. 6.1.6-3a showing SL-SCH
MAC subheader for V=''0011'' taken from 3GPP TS 36.321-f30.
[0016] FIG. 11 is a reproduction of FIG. 6.1.6-4 showing an
"Example of MAC PDU consisting of MAC header, MAC SDUs and padding"
taken from 3GPP TS 36.321-f30.
[0017] FIG. 12 illustrates an issue of NR V2X sidelink with
DRX.
[0018] FIG. 13 illustrates one exemplary embodiment showing a long
enough inactivity timer.
[0019] FIG. 14 illustrates one exemplary embodiment showing a start
or restart of an inactivity timer for transmitting a feedback of a
sidelink transmission to BS.
[0020] FIG. 15 is a flow diagram for one exemplary embodiment from
the perspective of a User Equipment (UE).
DETAILED DESCRIPTION
[0021] The exemplary wireless communication systems and devices
described below employ a wireless communication system, supporting
a broadcast service. Wireless communication systems are widely
deployed to provide various types of communication such as voice,
data, and so on. These systems may be based on code division
multiple access (CDMA), time division multiple access (TDMA),
orthogonal frequency division multiple access (OFDMA), 3GPP LTE
(Long Term Evolution) wireless access, 3GPP LTE-A or LTE-Advanced
(Long Term Evolution Advanced), 3GPP2 UMB (Ultra Mobile Broadband),
WiMax, 3GPP NR (New Radio) wireless access for 5G, or some other
modulation techniques.
[0022] In particular, the exemplary wireless communication systems
devices described below may be designed to support one or more
standards such as the standard offered by a consortium named "3rd
Generation Partnership Project" referred to herein as 3GPP,
including: TS 36.321-f30; RAN1 #94 chairman's note; TS 38.321-f40;
TS 38.321-f40; and RAN1 #adhoc1901 Chairman's Note. The standards
and documents listed above are hereby expressly incorporated by
reference in their entirety.
[0023] FIG. 1 shows a multiple access wireless communication system
according to one embodiment of the invention. An access network 100
(AN) includes multiple antenna groups, one including 104 and 106,
another including 108 and 110, and an additional including 112 and
114. In FIG. 1, only two antennas are shown for each antenna group,
however, more or fewer antennas may be utilized for each antenna
group. Access terminal 116 (AT) is in communication with antennas
112 and 114, where antennas 112 and 114 transmit information to
access terminal 116 over forward link 120 and receive information
from access terminal 116 over reverse link 118. Access terminal
(AT) 122 is in communication with antennas 106 and 108, where
antennas 106 and 108 transmit information to access terminal (AT)
122 over forward link 126 and receive information from access
terminal (AT) 122 over reverse link 124. In a FDD system,
communication links 118, 120, 124 and 126 may use different
frequency for communication. For example, forward link 120 may use
a different frequency then that used by reverse link 118.
[0024] Each group of antennas and/or the area in which they are
designed to communicate is often referred to as a sector of the
access network. In the embodiment, antenna groups each are designed
to communicate to access terminals in a sector of the areas covered
by access network 100.
[0025] In communication over forward links 120 and 126, the
transmitting antennas of access network 100 may utilize beamforming
in order to improve the signal-to-noise ratio of forward links for
the different access terminals 116 and 122. Also, an access network
using beamforming to transmit to access terminals scattered
randomly through its coverage causes less interference to access
terminals in neighboring cells than an access network transmitting
through a single antenna to all its access terminals.
[0026] An access network (AN) may be a fixed station or base
station used for communicating with the terminals and may also be
referred to as an access point, a Node B, a base station, an
enhanced base station, an evolved Node B (eNB), a network node, a
network, or some other terminology. An access terminal (AT) may
also be called user equipment (UE), a wireless communication
device, terminal, access terminal or some other terminology.
[0027] FIG. 2 is a simplified block diagram of an embodiment of a
transmitter system 210 (also known as the access network) and a
receiver system 250 (also known as access terminal (AT) or user
equipment (UE) in a MIMO system 200. At the transmitter system 210,
traffic data for a number of data streams is provided from a data
source 212 to a transmit (TX) data processor 214.
[0028] In one embodiment, each data stream is transmitted over a
respective transmit antenna. TX data processor 214 formats, codes,
and interleaves the traffic data for each data stream based on a
particular coding scheme selected for that data stream to provide
coded data.
[0029] The coded data for each data stream may be multiplexed with
pilot data using OFDM techniques. The pilot data is typically a
known data pattern that is processed in a known manner and may be
used at the receiver system to estimate the channel response. The
multiplexed pilot and coded data for each data stream is then
modulated (i.e., symbol mapped) based on a particular modulation
scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data
stream to provide modulation symbols. The data rate, coding, and
modulation for each data stream may be determined by instructions
performed by processor 230.
[0030] The modulation symbols for all data streams are then
provided to a TX MIMO processor 220, which may further process the
modulation symbols (e.g., for OFDM). TX MIMO processor 220 then
provides N.sub.T modulation symbol streams to N.sub.T transmitters
(TMTR) 222a through 222t. In certain embodiments, TX MIMO processor
220 applies beamforming weights to the symbols of the data streams
and to the antenna from which the symbol is being transmitted.
[0031] Each transmitter 222 receives and processes a respective
symbol stream to provide one or more analog signals, and further
conditions (e.g., amplifies, filters, and upconverts) the analog
signals to provide a modulated signal suitable for transmission
over the MIMO channel. N.sub.T modulated signals from transmitters
222a through 222t are then transmitted from N.sub.T antennas 224a
through 224t, respectively.
[0032] At receiver system 250, the transmitted modulated signals
are received by N.sub.R antennas 252a through 252r and the received
signal from each antenna 252 is provided to a respective receiver
(RCVR) 254a through 254r. Each receiver 254 conditions (e.g.,
filters, amplifies, and down converts) a respective received
signal, digitizes the conditioned signal to provide samples, and
further processes the samples to provide a corresponding "received"
symbol stream.
[0033] An RX data processor 260 then receives and processes the
N.sub.R received symbol streams from N.sub.R receivers 254 based on
a particular receiver processing technique to provide N.sub.T
"detected" symbol streams. The RX data processor 260 then
demodulates, deinterleaves, and decodes each detected symbol stream
to recover the traffic data for the data stream. The processing by
RX data processor 260 is complementary to that performed by TX MIMO
processor 220 and TX data processor 214 at transmitter system
210.
[0034] A processor 270 periodically determines which pre-coding
matrix to use (discussed below). Processor 270 formulates a reverse
link message comprising a matrix index portion and a rank value
portion.
[0035] The reverse link message may comprise various types of
information regarding the communication link and/or the received
data stream. The reverse link message is then processed by a TX
data processor 238, which also receives traffic data for a number
of data streams from a data source 236, modulated by a modulator
280, conditioned by transmitters 254a through 254r, and transmitted
back to transmitter system 210.
[0036] At transmitter system 210, the modulated signals from
receiver system 250 are received by antennas 224, conditioned by
receivers 222, demodulated by a demodulator 240, and processed by a
RX data processor 242 to extract the reserve link message
transmitted by the receiver system 250. Processor 230 then
determines which pre-coding matrix to use for determining the
beamforming weights then processes the extracted message.
[0037] Turning to FIG. 3, this figure shows an alternative
simplified functional block diagram of a communication device
according to one embodiment of the invention. As shown in FIG. 3,
the communication device 300 in a wireless communication system can
be utilized for realizing the UEs (or ATs) 116 and 122 in FIG. 1 or
the base station (or AN) 100 in FIG. 1, and the wireless
communications system is preferably the LTE system or the NR
system. The communication device 300 may include an input device
302, an output device 304, a control circuit 306, a central
processing unit (CPU) 308, a memory 310, a program code 312, and a
transceiver 314. The control circuit 306 executes the program code
312 in the memory 310 through the CPU 308, thereby controlling an
operation of the communications device 300. The communications
device 300 can receive signals input by a user through the input
device 302, such as a keyboard or keypad, and can output images and
sounds through the output device 304, such as a monitor or
speakers. The transceiver 314 is used to receive and transmit
wireless signals, delivering received signals to the control
circuit 306, and outputting signals generated by the control
circuit 306 wirelessly. The communication device 300 in a wireless
communication system can also be utilized for realizing the AN 100
in FIG. 1.
[0038] FIG. 4 is a simplified block diagram of the program code 312
shown in FIG. 3 in accordance with one embodiment of the invention.
In this embodiment, the program code 312 includes an application
layer 400, a Layer 3 portion 402, and a Layer 2 portion 404, and is
coupled to a Layer 1 portion 406. The Layer 3 portion 402 generally
performs radio resource control. The Layer 2 portion 404 generally
performs link control. The Layer 1 portion 406 generally performs
physical connections.
[0039] Sidelink resource allocation and utilization mechanism in
current MAC specification is disclosed in 3GPP TS36.321-f30 and is
quoted below:
5.4.4 Scheduling Request
[0040] The Scheduling Request (SR) is used for requesting UL-SCH
resources for new transmission. When an SR is triggered, it shall
be considered as pending until it is cancelled. All pending SR(s)
shall be cancelled and sr-ProhibitTimer and ssr-ProhibitTimer shall
be stopped when a MAC PDU is assembled and this PDU includes a BSR
which contains buffer status up to (and including) the last event
that triggered a BSR (see subclause 5.4.5), or, if all pending
SR(s) are triggered by Sidelink BSR, when a MAC PDU is assembled
and this PDU includes a Sidelink BSR which contains buffer status
up to (and including) the last event that triggered a Sidelink BSR
(see subclause 5.14.1.4), or, if all pending SR(s) are triggered by
Sidelink BSR, when upper layers configure autonomous resource
selection, or when the UL grant(s) can accommodate all pending data
available for transmission. If the MAC entity has resources for SR
configured on only one of SPUCCH and PUCCH, that SR resource is
valid for all logical channels. If the MAC entity has resources for
SR configured on both PUCCH and SPUCCH, MAC entity shall consider
all logical channels that have triggered an SR (and at
retxBSR-Timer expiry, MAC entity shall consider all logical
channels, belonging to a LCG, with data available for
transmission): [0041] PUCCH resources for SR are valid if
logicalChannelSr-Restriction is not configured, or if logical
ChannelSr-Restriction allows SR on PUCCH, for any of the logical
channels; [0042] SPUCCH resources for SR are valid if
logicalChannelSr-Restriction is not configured, or if
logicalChannelSr-Restriction allows SR on SPUCCH, for any of the
logical channels. If an SR is triggered and there is no other SR
pending, the MAC entity shall set the SR_COUNTER and the
SSR_COUNTER to 0. As long as one SR is pending, the MAC entity
shall for each TTI: [0043] if no UL-SCH resources are available for
a transmission in this TTI: [0044] Except for NB-IoT: [0045] if the
MAC entity has no valid PUCCH nor valid SPUCCH resource for SR
configured in any TTI: [0046] if the MAC entity is a MCG MAC entity
and rach-Skip is not configured; or [0047] if the MAC entity is a
SCG MAC entity and rach-SkipSCG is not configured: [0048] initiate
a Random Access procedure (see subclause 5.1) on the corresponding
SpCell and cancel all pending SRs; [0049] else if this TTI is not
part of a measurement gap or Sidelink Discovery Gap for
Transmission, and if transmission of V2X sidelink communication is
not prioritized in this TTI as described in subclause 5.14.1.2.2:
[0050] if the MAC entity has at least one valid SPUCCH resource for
SR configured for this TTI and if ssr-ProhibitTimer is not running:
[0051] if SSR_COUNTER<dssr-TransMax: increment SSR_COUNTER by 1;
instruct the physical layer to signal the SR on one valid SPUCCH
resource for SR; start the ssr-ProhibitTimer. [0052] else: notify
RRC to release SPUCCH for all serving cells; if the MAC entity has
no valid PUCCH resource for SR configured in any TTI: notify RRC to
release PUCCH for all serving cells; notify RRC to release SRS for
all serving cells; clear any configured downlink assignments and
uplink grants; initiate a Random Access procedure (see subclause
5.1) on the SpCell and cancel all pending SRs. [0053] if the MAC
entity has at least one valid PUCCH resource for SR configured for
this TTI and if sr-ProhibitTimer is not running: [0054] if
SR_COUNTER<dsr-TransMax: increment SR_COUNTER by 1; instruct the
physical layer to signal the SR on one valid PUCCH resource for SR;
start the sr-ProhibitTimer. [0055] else: notify RRC to release
PUCCH and SPUCCH for all serving cells; notify RRC to release SRS
for all serving cells; clear any configured downlink assignments
and uplink grants; initiate a Random Access procedure (see
subclause 5.1) on the SpCell and cancel all pending SRs. [0056] For
NB-IoT: [0057] if the MAC entity has no valid resource for SR
together with acknowledgement of the data in this TTI and no valid
PRACH resource for SR configured in any TTI: [0058] initiate a
Random Access Procedure (see subclause 5.1) and cancel all pending
SRs. [0059] else: [0060] if the MAC entity has valid resource for
SR together with acknowledgement of the data in this TTI: [0061]
instruct the physical layer to signal the SR together with
acknowledgement of the data. [0062] else: [0063] if the MAC entity
has valid PRACH resource for SR configured in this TTI and
sr-ProhibitTimer is not running: instruct the physical layer to
signal the SR on one valid PRACH resource for SR. start the
sr-ProhibitTimer in the subframe containing the last repetition of
the corresponding SR transmission. [0064] NOTE 1: The selection of
which valid PUCCH/SPUCCH resource for SR to signal SR on when the
MAC entity has more than one valid PUCCH/SPUCCH resource for SR in
one TTI or overlapping TTIs is left to UE implementation. [0065]
NOTE 2: SR_COUNTER is incremented for each SR bundle.
sr-ProhibitTimer is started in the first TTI of an SR bundle.
5.7 Discontinuous Reception (DRX)
[0066] The MAC entity may be configured by RRC with a DRX
functionality that controls the UE's PDCCH monitoring activity for
the MAC entity's C-RNTI, TPC-PUCCH-RNTI, TPC-PUSCH-RNTI,
Semi-Persistent Scheduling C-RNTI (if configured), UL
Semi-Persistent Scheduling V-RNTI (if configured), eIMTA-RNTI (if
configured), SL-RNTI (if configured), SL-V-RNTI (if configured),
CC-RNTI (if configured), SRS-TPC-RNTI (if configured), and AUL
C-RNTI (if configured). When in RRC_CONNECTED, if DRX is
configured, the MAC entity is allowed to monitor the PDCCH
discontinuously using the DRX operation specified in this
subclause; otherwise the MAC entity monitors the PDCCH
continuously. When using DRX operation, the MAC entity shall also
monitor PDCCH according to requirements found in other subclauses
of this specification. RRC controls DRX operation by configuring
the timers onDurationTimer, drx-InactivityTimer, drx-Retransmission
Timer (for HARQ processes scheduled using 1 ms TTI, one per DL HARQ
process except for the broadcast process),
drx-RetransmissionTimerShortTTI (for HARQ processes scheduled using
short TTI, one per DL HARQ process), drx-ULRetransmissionTimer (for
HARQ processes scheduled using 1 ms TTI, one per asynchronous UL
HARQ process), drx-ULRetransmissionTimerShortTTI (for HARQ
processes scheduled using short TTI, one per asynchronous UL HARQ
process), the longDRX-Cycle, the value of the drxStartOffset and
optionally the drxShortCycleTimer and shortDRX-Cycle. A HARQ RTT
timer per DL HARQ process (except for the broadcast process) and UL
HARQ RTT Timer per asynchronous UL HARQ process is also defined
(see subclause 7.7). When a DRX cycle is configured, the Active
Time includes the time while: [0067] onDurationTimer or
drx-InactivityTimer or drx-Retransmission Timer or
drx-RetransmissionTimerShortTTI or drx-ULRetransmissionTimer or
drx-ULRetransmissionTimerShortTTI or mac-ContentionResolutionTimer
(as described in subclause 5.1.5) is running; or [0068] a
Scheduling Request is sent on PUCCH/SPUCCH and is pending (as
described in subclause 5.4.4); or [0069] an uplink grant for a
pending HARQ retransmission can occur and there is data in the
corresponding HARQ buffer for synchronous HARQ process; or [0070] a
PDCCH indicating a new transmission addressed to the C-RNTI of the
MAC entity has not been received after successful reception of a
Random Access Response for the preamble not selected by the MAC
entity (as described in subclause 5.1.4); or [0071]
mpdcch-UL-HARQ-ACK-FeedbackConfig is configured and repetitions
within a bundle are being transmitted according to
UL_REPETITION_NUMBER. When DRX is configured, the MAC entity shall
for each subframe: [0072] if a HARQ RTT Timer expires in this
subframe: [0073] if the data of the corresponding HARQ process was
not successfully decoded: [0074] start the drx-Retransmission Timer
or drx-RetransmissionTimerShortTTI for the corresponding HARQ
process; [0075] if NB-IoT, start or restart the
drx-InactivityTimer. [0076] if an UL HARQ RTT Timer expires in this
subframe: [0077] start the drx-ULRetransmissionTimer or
drx-ULRetransmissionTimerShortTTI for the corresponding HARQ
process. [0078] if NB-IoT, start or restart the
drx-InactivityTimer. [0079] if a DRX Command MAC control element or
a Long DRX Command MAC control element is received: [0080] stop
onDurationTimer; [0081] stop drx-InactivityTimer. [0082] if
drx-InactivityTimer expires or a DRX Command MAC control element is
received in this subframe: [0083] if the Short DRX cycle is
configured: [0084] start or restart drxShortCycleTimer; [0085] use
the Short DRX Cycle. [0086] else: [0087] use the Long DRX cycle.
[0088] if drxShortCycleTimer expires in this subframe: [0089] use
the Long DRX cycle. [0090] if a Long DRX Command MAC control
element is received: [0091] stop drxShortCycleTimer; [0092] use the
Long DRX cycle. [0093] If the Short DRX Cycle is used and
[(SFN*10)+subframe number] modulo (shortDRX-Cycle)=(drxStartOffset)
modulo (shortDRX-Cycle); or [0094] if the Long DRX Cycle is used
and [(SFN*10)+subframe number] modulo
(longDRX-Cycle)=drxStartOffset: [0095] if NB-IoT: [0096] if there
is at least one HARQ process for which neither HARQ RTT Timer nor
UL HARQ RTT Timer is running, start onDurationTimer. [0097] else:
[0098] start onDurationTimer. [0099] during the Active Time, for a
PDCCH-subframe, if the subframe is not required for uplink
transmission for half-duplex FDD UE operation, and if the subframe
is not a half-duplex guard subframe [7] and if the subframe is not
part of a configured measurement gap and if the subframe is not
part of a configured Sidelink Discovery Gap for Reception, and for
NB-IoT if the subframe is not required for uplink transmission or
downlink reception other than on PDCCH; or [0100] during the Active
Time, for a subframe other than a PDCCH-subframe and for a UE
capable of simultaneous reception and transmission in the
aggregated cells, if the subframe is a downlink subframe indicated
by a valid eIMTA L1 signalling for at least one serving cell not
configured with schedulingCellId [8] and if the subframe is not
part of a configured measurement gap and if the subframe is not
part of a configured Sidelink Discovery Gap for Reception; or
[0101] during the Active Time, for a subframe other than a
PDCCH-subframe and for a UE not capable of simultaneous reception
and transmission in the aggregated cells, if the subframe is a
downlink subframe indicated by a valid eIMTA L1 signalling for the
SpCell and if the subframe is not part of a configured measurement
gap and if the subframe is not part of a configured Sidelink
Discovery Gap for Reception: [0102] monitor the PDCCH; [0103] if
the PDCCH indicates a DL transmission or if a DL assignment has
been configured for this subframe: [0104] if the UE is an NB-IoT
UE, a BL UE or a UE in enhanced coverage: [0105] start the HARQ RTT
Timer for the corresponding HARQ process in the subframe containing
the last repetition of the corresponding PDSCH reception; [0106]
else: [0107] start the HARQ RTT Timer for the corresponding HARQ
process; [0108] stop the drx-Retransmission Timer or
drx-RetransmissionTimerShortTTI for the corresponding HARQ process.
[0109] if NB-IoT, stop drx-ULRetransmissionTimer for all UL HARQ
processes. [0110] if the PDCCH indicates an UL transmission for an
asynchronous HARQ process or if an UL grant has been configured for
an asynchronous HARQ process for this subframe, or if the PDCCH
indicates an UL transmission for an autonomous HARQ process or;
[0111] if the uplink grant is a configured grant for the MAC
entity's AUL C-RNTI and if the corresponding PUSCH transmission has
been performed in this subframe: [0112] if
mpdcch-UL-HARQ-ACK-FeedbackConfig is not configured; or [0113] if
mpdcch-UL-HARQ-ACK-FeedbackConfig is configured and an UL HARQ-ACK
feedback has not been received on PDCCH until the last repetition
of the corresponding PUSCH transmission [0114] start the UL HARQ
RTT Timer for the corresponding HARQ process in the subframe
containing the last repetition of the corresponding PUSCH
transmission; [0115] stop the drx-ULRetransmissionTimer or
drx-ULRetransmissionTimerShortTTI for the corresponding HARQ
process; [0116] if NB-IoT, stop drx-Retransmission Timer for all DL
HARQ processes. [0117] if the PDCCH indicates a new transmission
(DL, UL or SL): [0118] except for an NB-IoT UE configured with a
single DL and UL HARQ process, start or restart
drx-InactivityTimer. [0119] if the PDCCH indicates a transmission
(DL, UL) for an NB-IoT UE: [0120] if the NB-IoT UE is configured
with a single DL and UL HARQ process: [0121] stop
drx-InactivityTimer. [0122] stop onDurationTimer. [0123] if the
PDCCH indicates an UL HARQ-ACK feedback for an asynchronous UL HARQ
process for a UE configured with mpdcch-UL-HARQ-ACK-FeedbackConfig;
and [0124] if the PUSCH transmission is completed: [0125] stop
drx-ULRetransmissionTimer for all UL HARQ processes. [0126] if the
PDCCH indicates HARQ feedback for one or more HARQ processes for
which UL HARQ operation is autonomous: [0127] stop the
drx-ULRetransmissionTimer for the corresponding HARQ process(es).
[0128] in current subframe n, if the MAC entity would not be in
Active Time considering grants/assignments/DRX Command MAC control
elements/Long DRX Command MAC control elements received and
Scheduling Request sent until and including subframe n-5 when
evaluating all DRX Active Time conditions as specified in this
subclause, type-0-triggered SRS [2] shall not be reported. [0129]
if CQI masking (cqi-Mask) is setup by upper layers: [0130] in
current TTI n, if onDurationTimer would not be running considering
grants/assignments/DRX Command MAC control elements/Long DRX
Command MAC control elements received until and including TTI n-5
when evaluating all DRX Active Time conditions as specified in this
subclause, CQI/PMI/RI/PTI/CRI on PUCCH shall not be reported.
[0131] else: [0132] in current TTI n, if the MAC entity would not
be in Active Time considering grants/assignments/DRX Command MAC
control elements/Long DRX Command MAC control elements received and
Scheduling Request sent until and including TTI n-5 when evaluating
all DRX Active Time conditions as specified in this subclause,
CQI/PMI/RI/PTI/CRI on PUCCH shall not be reported. Regardless of
whether the MAC entity is monitoring PDCCH or not, the MAC entity
receives and transmits HARQ feedback and transmits type-1-triggered
SRS [2] when such is expected. The MAC entity monitors PDCCH
addressed to CC-RNTI for a PUSCH trigger B [2] on the corresponding
SCell even if the MAC entity is not in Active Time. when such is
expected. When the BL UE or the UE in enhanced coverage or NB-IoT
UE receives PDCCH, the UE executes the corresponding action
specified in this subclause in the subframe following the subframe
containing the last repetition of the PDCCH reception where such
subframe is determined by the starting subframe and the DCI
subframe repetition number field in the PDCCH specified in TS36.213
[2], unless explicitly stated otherwise. [0133] NOTE 1: The same
Active Time applies to all activated serving cell(s). [0134] NOTE
2: In case of downlink spatial multiplexing, if a TB is received
while the HARQ RTT Timer is running and the previous transmission
of the same TB was received at least N subframes before the current
subframe (where N corresponds to the HARQ RTT Timer), the MAC
entity should process it and restart the HARQ RTT Timer. [0135]
NOTE 3: The MAC entity does not consider PUSCH trigger B [2] to be
an indication of a new transmission. [0136] NOTE 4: For NB-IoT, for
operation in FDD mode, and for operation in TDD mode with a single
HARQ process, DL and UL transmissions will not be scheduled in
parallel, i.e. if a DL transmission has been scheduled an UL
transmission will not be scheduled until HARQ RTT Timer of the DL
HARQ process has expired (and vice versa).
5.14 SL-SCH Data Transfer
5.14.1 SL-SCH Data Transmission
5.14.1.1 SL Grant Reception and SCI Transmission
[0137] In order to transmit on the SL-SCH the MAC entity must have
at least one sidelink grant. Sidelink grants are selected as
follows for sidelink communication: [0138] if the MAC entity is
configured to receive a single sidelink grant dynamically on the
PDCCH and more data is available in STCH than can be transmitted in
the current SC period, the MAC entity shall: [0139] using the
received sidelink grant determine the set of subframes in which
transmission of SCI and transmission of first transport block occur
according to subclause 14.2.1 of [2]; [0140] consider the received
sidelink grant to be a configured sidelink grant occurring in those
subframes starting at the beginning of the first available SC
Period which starts at least 4 subframes after the subframe in
which the sidelink grant was received, overwriting a previously
configured sidelink grant occurring in the same SC period, if
available; [0141] clear the configured sidelink grant at the end of
the corresponding SC Period; [0142] else, if the MAC entity is
configured by upper layers to receive multiple sidelink grants
dynamically on the PDCCH and more data is available in STCH than
can be transmitted in the current SC period, the MAC entity shall
for each received sidelink grant: [0143] using the received
sidelink grant determine the set of subframes in which transmission
of SCI and transmission of first transport block occur according to
subclause 14.2.1 of [2]; [0144] consider the received sidelink
grant to be a configured sidelink grant occurring in those
subframes starting at the beginning of the first available SC
Period which starts at least 4 subframes after the subframe in
which the sidelink grant was received, overwriting a previously
configured sidelink grant received in the same subframe number but
in a different radio frame as this configured sidelink grant
occurring in the same SC period, if available; [0145] clear the
configured sidelink grant at the end of the corresponding SC
Period; [0146] else, if the MAC entity is configured by upper
layers to transmit using one or multiple pool(s) of resources as
indicated in subclause 5.10.4 of [8] and more data is available in
STCH than can be transmitted in the current SC period, the MAC
entity shall for each sidelink grant to be selected: [0147] if
configured by upper layers to use a single pool of resources:
[0148] select that pool of resources for use; [0149] else, if
configured by upper layers to use multiple pools of resources:
[0150] select a pool of resources for use from the pools of
resources configured by upper layers whose associated priority list
includes the priority of the highest priority of the sidelink
logical channel in the MAC PDU to be transmitted; [0151] NOTE: If
more than one pool of resources has an associated priority list
which includes the priority of the sidelink logical channel with
the highest priority in the MAC PDU to be transmitted, it is left
for UE implementation which one of those pools of resources to
select. [0152] randomly select the time and frequency resources for
SL-SCH and SCI of a sidelink grant from the selected resource pool.
The random function shall be such that each of the allowed
selections [2] can be chosen with equal probability; [0153] use the
selected sidelink grant to determine the set of subframes in which
transmission of SCI and transmission of first transport block occur
according to subclause 14.2.1 of [2]; [0154] consider the selected
sidelink grant to be a configured sidelink grant occurring in those
subframes starting at the beginning of the first available SC
Period which starts at least 4 subframes after the subframe in
which the sidelink grant was selected; [0155] clear the configured
sidelink grant at the end of the corresponding SC Period; [0156]
NOTE: Retransmissions on SL-SCH cannot occur after the configured
sidelink grant has been cleared. [0157] NOTE: If the MAC entity is
configured by upper layers to transmit using one or multiple
pool(s) of resources as indicated in subclause 5.10.4 of [8], it is
left for UE implementation how many sidelink grants to select
within one SC period taking the number of sidelink processes into
account. Sidelink grants are selected as follows for V2X sidelink
communication: [0158] if the MAC entity is configured to receive a
sidelink grant dynamically on the PDCCH and data is available in
STCH, the MAC entity shall: [0159] use the received sidelink grant
to determine the number of HARQ retransmissions and the set of
subframes in which transmission of SCI and SL-SCH occur according
to subclause 14.2.1 and 14.1.1.4A of [2]; [0160] consider the
received sidelink grant to be a configured sidelink grant; [0161]
if the MAC entity is configured by upper layers to receive a
sidelink grant on the PDCCH addressed to SL Semi-Persistent
Scheduling V-RNTI, the MAC entity shall for each SL SPS
configuration: [0162] if PDCCH contents indicate SPS activation:
[0163] use the received sidelink grant to determine the number of
HARQ retransmissions and the set of subframes in which transmission
of SCI and SL-SCH occur according to subclause 14.2.1 and 14.1.1.4A
of [2]; [0164] consider the received sidelink grant to be a
configured sidelink grant; [0165] if PDCCH contents indicate SPS
release: [0166] clear the corresponding configured sidelink grant;
[0167] if the MAC entity is configured by upper layers to transmit
using pool(s) of resources in one or multiple carriers as indicated
in subclause 5.10.13.1 of [8] based on sensing, or partial sensing,
or random selection only if upper layers indicates that
transmissions of multiple MAC PDUs are allowed according to
subclause 5.10.13.1a of [8], and the MAC entity selects to create a
configured sidelink grant corresponding to transmissions of
multiple MAC PDUs, and data is available in STCH associated with
one or multiple carriers, the MAC entity shall for each Sidelink
process configured for multiple transmissions on a selected carrier
according to subclause 5.14.1.5: [0168] if
SL_RESOURCE_RESELECTION_COUNTER=0 and when
SL_RESOURCE_RESELECTION_COUNTER was equal to 1 the MAC entity
randomly selected, with equal probability, a value in the interval
[0, 1] which is above the probability configured by upper layers in
probResourceKeep; or [0169] if neither transmission nor
retransmission has been performed by the MAC entity on any resource
indicated in the configured sidelink grant during the last second;
or [0170] if sl-ReselectAfter is configured and the number of
consecutive unused transmission opportunities on resources
indicated in the configured sidelink grant is equal to
sl-ReselectAfter; or [0171] if there is no configured sidelink
grant; or [0172] if the configured sidelink grant cannot
accommodate a RLC SDU by using the maximum allowed MCS configured
by upper layers in maxMCS-PSSCH and the MAC entity selects not to
segment the RLC SDU; or [0173] NOTE: If the configured sidelink
grant cannot accommodate the RLC SDU, it is left for UE
implementation whether to perform segmentation or sidelink resource
reselection. [0174] if transmission(s) with the configured sidelink
grant cannot fulfil the latency requirement of the data in a
sidelink logical channel according to the associated PPPP, and the
MAC entity selects not to perform transmission(s) corresponding to
a single MAC PDU; or [0175] NOTE: If the latency requirement is not
met, it is left for UE implementation whether to perform
transmission(s) corresponding to single MAC PDU or sidelink
resource reselection. [0176] if a pool of resources is configured
or reconfigured by upper layers for the selected carrier: [0177]
clear the configured sidelink grant, if available; [0178] trigger
the TX carrier (re-)selection procedure as specified in sub-clause
5.14.1.5; [0179] if the carrier is (re-)selected in the Tx carrier
(re-)selection according to sub-clause 5.14.1.5, the following is
performed on the selected carrier: [0180] select one of the allowed
values configured by upper layers in
restrictResourceReservationPeriod and set the resource reservation
interval by multiplying 100 with the selected value; [0181] NOTE:
How the UE selects this value is up to UE implementation. [0182]
randomly select, with equal probability, an integer value in the
interval [5, 15] for the resource reservation interval higher than
or equal to 100 ms, in the interval [10, 30] for the resource
reservation interval equal to 50 ms or in the interval [25, 75] for
the resource reservation interval equal to 20 ms, and set
SL_RESOURCE_RESELECTION_COUNTER to the selected value; [0183]
select the number of HARQ retransmissions from the allowed numbers
that are configured by upper layers in allowedRetxNumberPSSCH
included in pssch-TxConfigList and, if configured by upper layers,
overlapped in allowedRetxNumberPSSCH indicated in
cbr-pssch-TxConfigList for the highest priority of the sidelink
logical channel(s) allowed on the selected carrier and the CBR
measured by lower layers according to [6] if CBR measurement
results are available or the corresponding defaultTxConfigIndex
configured by upper layers if CBR measurement results are not
available; [0184] select an amount of frequency resources within
the range that is configured by upper layers between
minSubchannel-NumberPSSCH and maxSubchannel-NumberPSSCH included in
pssch-TxConfigList and, if configured by upper layers, overlapped
between minSubchannel-NumberPSSCH and maxSubchannel-NumberPSSCH
indicated in cbr-pssch-TxConfigList for the highest priority of the
sidelink logical channel(s) allowed on the selected carrier and the
CBR measured by lower layers according to [6] if CBR measurement
results are available or the corresponding defaultTxConfigIndex
configured by upper layers if CBR measurement results are not
available; [0185] if transmission based on random selection is
configured by upper layers: [0186] randomly select the time and
frequency resources for one transmission opportunity from the
resource pool, according to the amount of selected frequency
resources. The random function shall be such that each of the
allowed selections can be chosen with equal probability; [0187]
else: [0188] randomly select the time and frequency resources for
one transmission opportunity from the resources indicated by the
physical layer according to subclause 14.1.1.6 of [2], according to
the amount of selected frequency resources. The random function
shall be such that each of the allowed selections can be chosen
with equal probability; [0189] use the randomly selected resource
to select a set of periodic resources spaced by the resource
reservation interval for transmission opportunities of SCI and
SL-SCH corresponding to the number of transmission opportunities of
MAC PDUs determined in subclause 14.1.1.4B of [2]; [0190] if the
number of HARQ retransmissions is equal to 1 and there are
available resources left in the resources indicated by the physical
layer that meet the conditions in subclause 14.1.1.7 of [2] for
more transmission opportunities: [0191] randomly select the time
and frequency resources for one transmission opportunity from the
available resources, according to the amount of selected frequency
resources. The random function shall be such that each of the
allowed selections can be chosen with equal probability; [0192] use
the randomly selected resource to select a set of periodic
resources spaced by the resource reservation interval for the other
transmission opportunities of SCI and SL-SCH corresponding to the
number of retransmission opportunities of the MAC PDUs determined
in subclause 14.1.1.4B of [2]; [0193] consider the first set of
transmission opportunities as the new transmission opportunities
and the other set of transmission opportunities as the
retransmission opportunities; [0194] consider the set of new
transmission opportunities and retransmission opportunities as the
selected sidelink grant. [0195] else: [0196] consider the set as
the selected sidelink grant; [0197] use the selected sidelink grant
to determine the set of subframes in which transmissions of SCI and
SL-SCH occur according to subclause 14.2.1 and 14.1.1.4B of [2];
[0198] consider the selected sidelink grant to be a configured
sidelink grant; [0199] else if SL_RESOURCE_RESELECTION_COUNTER=0
and when SL_RESOURCE_RESELECTION_COUNTER was equal to 1 the MAC
entity randomly selected, with equal probability, a value in the
interval [0, 1] which is less than or equal to the probability
configured by upper layers in probResourceKeep: [0200] clear the
configured sidelink grant, if available; [0201] randomly select,
with equal probability, an integer value in the interval [5, 15]
for the resource reservation interval higher than or equal to 100
ms, in the interval [10, 30] for the resource reservation interval
equal to 50 ms or in the interval [25, 75] for the resource
reservation interval equal to 20 ms, and set
SL_RESOURCE_RESELECTION_COUNTER to the selected value; [0202] use
the previously selected sidelink grant for the number of
transmissions of the MAC PDUs determined in subclause 14.1.1.4B of
[2] with the resource reservation interval to determine the set of
subframes in which transmissions of SCI and SL-SCH occur according
to subclause 14.2.1 and 14.1.1.4B of [2]; [0203] consider the
selected sidelink grant to be a configured sidelink grant; [0204]
else, if the MAC entity is configured by upper layers to transmit
using pool(s) of resources in one or multiple carriers as indicated
in subclause 5.10.13.1 of [8], the MAC entity selects to create a
configured sidelink grant corresponding to transmission(s) of a
single MAC PDU, and data is available in STCH associated with one
or multiple carriers, the MAC entity shall for a Sidelink process
on a selected carrier according to subclause 5.14.1.5: [0205]
trigger the TX carrier (re-)selection procedure as specified in
sub-clause 5.14.1.5; [0206] if the carrier is (re-)selected in the
Tx carrier (re-)selection according to sub-clause 5.14.1.5, the
following is performed on the selected carrier: [0207] select the
number of HARQ retransmissions from the allowed numbers that are
configured by upper layers in allowedRetxNumberPSSCH included in
pssch-TxConfigList and, if configured by upper layers, overlapped
in allowedRetxNumberPSSCH indicated in cbr-pssch-TxConfigList for
the highest priority of the sidelink logical channel(s) allowed on
the selected carrier and the CBR measured by lower layers according
to [6] if CBR measurement results are available or the
corresponding defaultTxConfigIndex configured by upper layers if
CBR measurement results are not available; [0208] select an amount
of frequency resources within the range that is configured by upper
layers between minSubchannel-NumberPSSCH and
maxSubchannel-NumberPSSCH included in pssch-TxConfigList and, if
configured by upper layers, overlapped between
minSubchannel-NumberPSSCH and maxSubchannel-NumberPSSCH indicated
in cbr-pssch-TxConfigList for the highest priority of the sidelink
logical channel(s) allowed on the selected carrier and the CBR
measured by lower layers according to [6] if CBR measurement
results are available or the corresponding defaultTxConfigIndex
configured by upper layers if CBR measurement results are not
available;
[0209] if transmission based on random selection is configured by
upper layers: [0210] randomly select the time and frequency
resources for one transmission opportunity of SCI and SL-SCH from
the resource pool, according to the amount of selected frequency
resources. The random function shall be such that each of the
allowed selections can be chosen with equal probability; [0211]
else: [0212] randomly select the time and frequency resources for
one transmission opportunity of SCI and SL-SCH from the resources
indicated by the physical layer according to subclause 14.1.1.6 of
[2], according to the amount of selected frequency resources. The
random function shall be such that each of the allowed selections
can be chosen with equal probability; [0213] if the number of HARQ
retransmissions is equal to 1: [0214] if transmission based on
random selection is configured by upper layers and there are
available resources that meet the conditions in subclause 14.1.1.7
of [2] for one more transmission opportunity: [0215] randomly
select the time and frequency resources for the other transmission
opportunity of SCI and SL-SCH corresponding to additional
transmission of the MAC PDU from the available resources, according
to the amount of selected frequency resources. The random function
shall be such that each of the allowed selections can be chosen
with equal probability; [0216] else, if transmission based on
sensing or partial sensing is configured by upper layers and there
are available resources left in the resources indicated by the
physical layer that meet the conditions in subclause 14.1.1.7 of
[2] for one more transmission opportunity: [0217] randomly select
the time and frequency resources for the other transmission
opportunity of SCI and SL-SCH corresponding to additional
transmission of the MAC PDU from the available resources, according
to the amount of selected frequency resources. The random function
shall be such that each of the allowed selections can be chosen
with equal probability; [0218] consider a transmission opportunity
which comes first in time as the new transmission opportunity and a
transmission opportunity which comes later in time as the
retransmission opportunity; [0219] consider both of the
transmission opportunities as the selected sidelink grant; [0220]
else: [0221] consider the transmission opportunity as the selected
sidelink grant; [0222] use the selected sidelink grant to determine
the subframes in which transmission(s) of SCI and SL-SCH occur
according to subclause 14.2.1 and 14.1.1.4B of [2]; [0223] consider
the selected sidelink grant to be a configured sidelink grant.
[0224] NOTE: For V2X sidelink communication, the UE should ensure
the randomly selected time and frequency resources fulfill the
latency requirement. [0225] NOTE: For V2X sidelink communication,
when there is no overlapping between the chosen configuration(s) in
pssch-TxConfigList and chosen configuration(s) indicated in
cbr-pssch-TxConfigList, it is up to UE implementation whether the
UE transmits and which transmitting parameters the UE uses between
allowed configuration(s) indicated in pssch-TxConfigList and
allowed configuration(s) indicated in cbr-pssch-TxConfigList. The
MAC entity shall for each subframe: [0226] if the MAC entity has a
configured sidelink grant occurring in this subframe: [0227] if
SL_RESOURCE_RESELECTION_COUNTER=1 and the MAC entity randomly
selected, with equal probability, a value in the interval [0, 1]
which is above the probability configured by upper layers in
probResourceKeep: [0228] set the resource reservation interval
equal to 0; [0229] if the configured sidelink grant corresponds to
transmission of SCI: [0230] for V2X sidelink communication in UE
autonomous resource selection: [0231] select a MCS which is, if
configured, within the range that is configured by upper layers
between minMCS-PSSCH and maxMCS-PSSCH included in
pssch-TxConfigList and, if configured by upper layers, overlapped
between minMCS-PSSCH and maxMCS-PSSCH indicated in
cbr-pssch-TxConfigList for the highest priority of the sidelink
logical channel(s) in the MAC PDU and the CBR measured by lower
layers according to [6] if CBR measurement results are available or
the corresponding defaultTxConfigIndex configured by upper layers
if CBR measurement results are not available; [0232] NOTE: MCS
selection is up to UE implementation if the MCS or the
corresponding range is not configured by upper layers. [0233] NOTE:
For V2X sidelink communication, when there is no overlapping
between the chosen configuration(s) included in pssch-TxConfigList
and chosen configuration(s) indicated in cbr-pssch-TxConfigList, it
is up to UE implementation whether the UE transmits and which
transmitting parameters the UE uses between allowed
configuration(s) indicated in pssch-TxConfigList and allowed
configuration(s) indicated in cbr-pssch-TxConfigList. [0234] for
V2X sidelink communication in scheduled resource allocation: [0235]
select a MCS unless it is configured by upper layer; [0236]
instruct the physical layer to transmit SCI corresponding to the
configured sidelink grant; [0237] for V2X sidelink communication,
deliver the configured sidelink grant, the associated HARQ
information and the value of the highest priority of the sidelink
logical channel(s) in the MAC PDU to the Sidelink HARQ Entity for
this subframe; [0238] else if the configured sidelink grant
corresponds to transmission of first transport block for sidelink
communication: [0239] deliver the configured sidelink grant and the
associated HARQ information to the Sidelink HARQ Entity for this
subframe. [0240] NOTE: If the MAC entity has multiple configured
grants occurring in one subframe and if not all of them can be
processed due to the single-cluster SC-FDM restriction, it is left
for UE implementation which one of these to process according to
the procedure above.
5.14.1.2 Sidelink HARQ Operation
5.14.1.2.1 Sidelink HARQ Entity
[0241] The MAC entity is configured by upper layers to transmit
using pool(s) of resources on one or multiple carriers as indicated
in subclause 5.10.13.1 of 3GPP TS 36.331 [8], there is one Sidelink
HARQ Entity at the MAC entity for each carrier for transmission on
SL-SCH, which maintains a number of parallel Sidelink processes.
For sidelink communication, the number of transmitting Sidelink
processes associated with the Sidelink HARQ Entity is defined in
[8]. For V2X sidelink communication, the maximum number of
transmitting Sidelink processes associated with each Sidelink HARQ
Entity is 8. A sidelink process may be configured for transmissions
of multiple MAC PDUs. For transmissions of multiple MAC PDUs, the
maximum number of transmitting Sidelink processes associated with
each Sidelink HARQ Entity is 2. A delivered and configured sidelink
grant and its associated HARQ information are associated with a
Sidelink process. For each subframe of the SL-SCH and each Sidelink
process, the Sidelink HARQ Entity shall: [0242] if a sidelink grant
corresponding to a new transmission opportunity has been indicated
for this Sidelink process and there is SL data, for sidelink
logical channels of ProSe destination associated with this sidelink
grant, available for transmission: [0243] obtain the MAC PDU from
the "Multiplexing and assembly" entity; [0244] deliver the MAC PDU
and the sidelink grant and the HARQ information to this Sidelink
process; [0245] instruct this Sidelink process to trigger a new
transmission. [0246] else, if this subframe corresponds to
retransmission opportunity for this Sidelink process: [0247]
instruct this Sidelink process to trigger a retransmission. [0248]
NOTE: The resources for retransmission opportunities are specified
in subclause 14.2.1 of [2] unless specified in subclause
5.14.1.1.
5.14.1.2.2 Sidelink Process
[0249] The Sidelink process is associated with a HARQ buffer. The
sequence of redundancy versions is 0, 2, 3, 1. The variable
CURRENT_IRV is an index into the sequence of redundancy versions.
This variable is updated modulo 4. New transmissions and
retransmissions either for a given SC period in sidelink
communication or in V2X sidelink communication are performed on the
resource indicated in the sidelink grant as specified in subclause
5.14.1.1 and with the MCS selected as specified in subclause
5.14.1.1. If the sidelink process is configured to perform
transmissions of multiple MAC PDUs for V2X sidelink communication
the process maintains a counter SL_RESOURCE_RESELECTION_COUNTER.
For other configurations of the sidelink process, this counter is
not available. If the Sidelink HARQ Entity requests a new
transmission, the Sidelink process shall: [0250] set CURRENT_IRV to
0; [0251] store the MAC PDU in the associated HARQ buffer; [0252]
store the sidelink grant received from the Sidelink HARQ Entity;
[0253] generate a transmission as described below. If the Sidelink
HARQ Entity requests a retransmission, the Sidelink process shall:
[0254] generate a transmission as described below. To generate a
transmission, the Sidelink process shall: [0255] if there is no
uplink transmission; or if the MAC entity is able to perform uplink
transmissions and transmissions on SL-SCH simultaneously at the
time of the transmission; or if there is a MAC PDU to be
transmitted in this TTI in uplink, except a MAC PDU obtained from
the Msg3 buffer and transmission of V2X sidelink communication is
prioritized over uplink transmission; and [0256] if there is no
Sidelink Discovery Gap for Transmission or no transmission on PSDCH
at the time of the transmission; or, in case of transmissions of
V2X sidelink communication, if the MAC entity is able to perform
transmissions on SL-SCH and transmissions on PSDCH simultaneously
at the time of the transmission: [0257] instruct the physical layer
to generate a transmission according to the stored sidelink grant
with the redundancy version corresponding to the CURRENT_IRV value.
[0258] increment CURRENT_IRV by 1; [0259] if this transmission
corresponds to the last transmission of the MAC PDU: [0260]
decrement SL_RESOURCE_RESELECTION_COUNTER by 1, if available. The
transmission of V2X sidelink communication is prioritized over
uplink transmission if the following conditions are met: [0261] if
the MAC entity is not able to perform uplink transmissions and
transmissions of V2X sidelink communication simultaneously at the
time of the transmission; and [0262] if uplink transmission is not
prioritized by upper layer according to [15]; and [0263] if the
value of the highest priority of the sidelink logical channel(s) in
the MAC PDU is lower than thresSL-TxPrioritization if
thresSL-TxPrioritization is configured.
5.14.1.3 Multiplexing and Assembly
[0264] For PDU(s) associated with one SCI, MAC shall consider only
logical channels with the same Source Layer-2 ID-Destination
Layer-2 ID pair. Multiple transmissions within overlapping SC
periods to different ProSe Destinations are allowed subject to
single-cluster SC-FDM constraint. In V2X sidelink communication,
multiple transmissions for different Sidelink processes are allowed
to be independently performed in different subframes.
5.14.1.3.1 Logical Channel Prioritization
[0265] The Logical Channel Prioritization procedure is applied when
a new transmission is performed. Each sidelink logical channel has
an associated priority which is the PPPP and optionally an
associated PPPR. Multiple sidelink logical channels may have the
same associated priority. The mapping between priority and LCID is
left for UE implementation. If duplication is activated as
specified in 3GPP TS 36.323 [4], the MAC entity shall map different
sidelink logical channels which correspond to the same PDCP entity
in duplication onto different carriers in accordance with 5.14.1.5
or onto different carriers of different carrier set, if configured
by upper layer (3GPP TS 36.331 [8]), based on UE implementation.
The MAC entity shall perform the following Logical Channel
Prioritization procedure either for each SCI transmitted in an SC
period in sidelink communication, or for each SCI corresponding to
a new transmission in V2X sidelink communication: [0266] The MAC
entity shall allocate resources to the sidelink logical channels in
the following steps: [0267] Only consider sidelink logical channels
not previously selected for this SC period and the SC periods (if
any) which are overlapping with this SC period, to have data
available for transmission in sidelink communication; [0268] Only
consider sidelink logical channels which meet the following
conditions: [0269] allowed on the carrier where the SCI is
transmitted for V2X sidelink communication, if the carrier is
configured by upper layers according to 3GPP TS 36.331 [8] and 3GPP
TS 24.386 [15]; [0270] having a priority whose associated
threshCBR-FreqReselection is no lower than the CBR of the carrier
when the carrier is (re-)selected in accordance with 5.14.1.5;
[0271] Exclude sidelink logical channel(s) not allowed on the
carrier where the SCI is transmitted, if duplication is activated
as specified in 3GPP TS 36.323 [4]. [0272] Step 0: Select a ProSe
Destination, having the sidelink logical channel with the highest
priority, among the sidelink logical channels having data available
for transmission and having the same transmission format as the one
selected corresponding to the ProSe Destination; [0273] NOTE: The
sidelink logical channels belonging to the same ProSe Destination
have the same transmission format. [0274] For each MAC PDU
associated to the SCI: [0275] Step 1: Among the sidelink logical
channels belonging to the selected ProSe Destination and having
data available for transmission, allocate resources to the sidelink
logical channel with the highest priority; [0276] Step 2: if any
resources remain, sidelink logical channels belonging to the
selected ProSe Destination are served in decreasing order of
priority until either the data for the sidelink logical channel(s)
or the SL grant is exhausted, whichever comes first. Sidelink
logical channels configured with equal priority should be served
equally. [0277] The UE shall also follow the rules below during the
scheduling procedures above: [0278] the UE should not segment an
RLC SDU (or partially transmitted SDU) if the whole SDU (or
partially transmitted SDU) fits into the remaining resources;
[0279] if the UE segments an RLC SDU from the sidelink logical
channel, it shall maximize the size of the segment to fill the
grant as much as possible; [0280] the UE should maximise the
transmission of data; [0281] if the MAC entity is given a sidelink
grant size that is equal to or larger than 10 bytes (for sidelink
communication) or 11 bytes (for V2X sidelink communication) while
having data available for transmission, the MAC entity shall not
transmit only padding.
5.14.1.3.2 Multiplexing of MAC SDUs
[0282] The MAC entity shall multiplex MAC SDUs in a MAC PDU
according to subclauses 5.14.1.3.1 and 6.1.6.
5.14.1.4 Buffer Status Reporting
[0283] The sidelink Buffer Status reporting procedure is used to
provide the serving eNB with information about the amount of
sidelink data available for transmission in the SL buffers
associated with the MAC entity. RRC controls BSR reporting for the
sidelink by configuring the two timers periodic-BSR-TimerSL and
retx-BSR-TimerSL. Each sidelink logical channel belongs to a ProSe
Destination. Each sidelink logical channel is allocated to an LCG
depending on the priority and optionally the PPPR of the sidelink
logical channel, and the mapping between LCG ID and priority and
optionally the mapping between LCG ID and PPPR which are provided
by upper layers in logicalChGroupinfoList [8]. LCG is defined per
ProSe Destination. A sidelink Buffer Status Report (BSR) shall be
triggered if any of the following events occur: [0284] if the MAC
entity has a configured SL-RNTI or a configured SL-V-RNTI: [0285]
SL data, for a sidelink logical channel of a ProSe Destination,
becomes available for transmission in the RLC entity or in the PDCP
entity (the definition of what data shall be considered as
available for transmission is specified in [3] and [4]
respectively) and either the data belongs to a sidelink logical
channel with higher priority than the priorities of the sidelink
logical channels which belong to any LCG belonging to the same
ProSe Destination and for which data is already available for
transmission, or there is currently no data available for
transmission for any of the sidelink logical channels belonging to
the same ProSe Destination, in which case the Sidelink BSR is
referred below to as "Regular Sidelink BSR"; [0286] UL resources
are allocated and number of padding bits remaining after a Padding
BSR has been triggered is equal to or larger than the size of the
Sidelink BSR MAC control element containing the buffer status for
at least one LCG of a ProSe Destination plus its subheader, in
which case the Sidelink BSR is referred below to as "Padding
Sidelink BSR"; [0287] retx-BSR-TimerSL expires and the MAC entity
has data available for transmission for any of the sidelink logical
channels, in which case the Sidelink BSR is referred below to as
"Regular Sidelink BSR"; [0288] periodic-BSR-TimerSL expires, in
which case the Sidelink BSR is referred below to as "Periodic
Sidelink BSR"; [0289] else: [0290] An SL-RNTI or an SL-V-RNTI is
configured by upper layers and SL data is available for
transmission in the RLC entity or in the PDCP entity (the
definition of what data shall be considered as available for
transmission is specified in [3] and [4] respectively), in which
case the Sidelink BSR is referred below to as "Regular Sidelink
BSR".
For Regular and Periodic Sidelink BSR:
[0290] [0291] if the number of bits in the UL grant is equal to or
larger than the size of a Sidelink BSR containing buffer status for
all LCGs having data available for transmission plus its subheader:
[0292] report Sidelink BSR containing buffer status for all LCGs
having data available for transmission; [0293] else report
Truncated Sidelink BSR containing buffer status for as many LCGs
having data available for transmission as possible, taking the
number of bits in the UL grant into consideration.
For Padding Sidelink BSR:
[0293] [0294] if the number of padding bits remaining after a
Padding BSR has been triggered is equal to or larger than the size
of a Sidelink BSR containing buffer status for all LCGs having data
available for transmission plus its subheader: [0295] report
Sidelink BSR containing buffer status for all LCGs having data
available for transmission; [0296] else report Truncated Sidelink
BSR containing buffer status for as many LCGs having data available
for transmission as possible, taking the number of bits in the UL
grant into consideration. If the Buffer Status reporting procedure
determines that at least one Sidelink BSR has been triggered and
not cancelled: [0297] if the MAC entity has UL resources allocated
for new transmission for this TTI and the allocated UL resources
can accommodate a Sidelink BSR MAC control element plus its
subheader as a result of logical channel prioritization: [0298]
instruct the Multiplexing and Assembly procedure to generate the
Sidelink BSR MAC control element(s); [0299] start or restart
periodic-BSR-TimerSL except when all the generated Sidelink BSRs
are Truncated Sidelink BSRs; [0300] start or restart
retx-BSR-TimerSL; [0301] else if a Regular Sidelink BSR has been
triggered: [0302] if an uplink grant is not configured: [0303] a
Scheduling Request shall be triggered. A MAC PDU shall contain at
most one Sidelink BSR MAC control element, even when multiple
events trigger a Sidelink BSR by the time a Sidelink BSR can be
transmitted in which case the Regular Sidelink BSR and the Periodic
Sidelink BSR shall have precedence over the padding Sidelink BSR.
The MAC entity shall restart retx-BSR-TimerSL upon reception of an
SL grant. All triggered regular Sidelink BSRs shall be cancelled in
case the remaining configured SL grant(s) valid for this SC Period
can accommodate all pending data available for transmission in
sidelink communication or in case the remaining configured SL
grant(s) valid can accommodate all pending data available for
transmission in V2X sidelink communication. All triggered Sidelink
BSRs shall be cancelled in case the MAC entity has no data
available for transmission for any of the sidelink logical
channels. All triggered Sidelink BSRs shall be cancelled when a
Sidelink BSR (except for Truncated Sidelink BSR) is included in a
MAC PDU for transmission. All triggered Sidelink BSRs shall be
cancelled, and retx-BSR-TimerSL and periodic-BSR-TimerSL shall be
stopped, when upper layers configure autonomous resource selection.
The MAC entity shall transmit at most one Regular/Periodic Sidelink
BSR in a TTI. If the MAC entity is requested to transmit multiple
MAC PDUs in a TTI, it may include a padding Sidelink BSR in any of
the MAC PDUs which do not contain a Regular/Periodic Sidelink BSR.
All Sidelink BSRs transmitted in a TTI always reflect the buffer
status after all MAC PDUs have been built for this TTI. Each LCG
shall report at the most one buffer status value per TTI and this
value shall be reported in all Sidelink BSRs reporting buffer
status for this LCG. [0304] NOTE: A Padding Sidelink BSR is not
allowed to cancel a triggered Regular/Periodic Sidelink BSR. A
Padding Sidelink BSR is triggered for a specific MAC PDU only and
the trigger is cancelled when this MAC PDU has been built.
6.1.3.1a Sidelink BSR MAC Control Elements
[0305] Sidelink BSR and Truncated Sidelink BSR MAC control elements
consist of one Destination Index field, one LCG ID field and one
corresponding Buffer Size field per reported target group. The
Sidelink BSR MAC control elements are identified by MAC PDU
subheaders with LCIDs as specified in table 6.2.1-2. They have
variable sizes. For each included group, the fields are defined as
follows (FIGS. 6.1.3.1a-1 and 6.1.3.1a-2): [0306] Destination
Index: The Destination Index field identifies the ProSe Destination
or the destination for V2X sidelink communication. The length of
this field is 4 bits. The value is set to the index of the
destination reported in destinationInfoList for sidelink
communication or is set to one index among index(es) associated to
same destination reported in v2x-DestinationInfoList for V2X
sidelink communication. If multiple such lists are reported, the
value is indexed sequentially across all the lists in the same
order as specified in [8]; [0307] LCG ID: The Logical Channel Group
ID field identifies the group of logical channel(s) which buffer
status is being reported. The length of the field is 2 bits; [0308]
Buffer Size: The Buffer Size field identifies the total amount of
data available across all logical channels of a LCG of a ProSe
Destination after all MAC PDUs for the TTI have been built. The
amount of data is indicated in number of bytes. It shall include
all data that is available for transmission in the RLC layer and in
the PDCP layer; the definition of what data shall be considered as
available for transmission is specified in [3] and [4]
respectively. The size of the RLC and MAC headers are not
considered in the buffer size computation. The length of this field
is 6 bits. The values taken by the Buffer Size field are shown in
Table 6.1.3.1-1; [0309] R: Reserved bit, set to "0". Buffer Sizes
of LCGs are included in decreasing order of the highest priority of
the sidelink logical channel belonging to the LCG irrespective of
the value of the Destination Index field. FIG. 5 (a reproduction of
FIG. 6.1.3.1a-1: Sidelink BSR and Truncated Sidelink BSR MAC
control element for even N). FIG. 6 (a reproduction of FIG.
6.1.3.1a-2: Sidelink BSR and Truncated Sidelink BSR MAC control
element for odd N).
6.1.6 Mac Pdu (Sl-Sch)
[0310] A MAC PDU consists of a MAC header, one or more MAC Service
Data Units (MAC SDU), and optionally padding; as described in FIG.
6.1.6-4. Both the MAC header and the MAC SDUs are of variable
sizes. A MAC PDU header consists of one SL-SCH subheader, one or
more MAC PDU subheaders; each subheader except SL-SCH subheader
corresponds to either a MAC SDU or padding. The SL-SCH subheader
consists of the seven header fields V/R/R/R/R/SRC/DST. A MAC PDU
subheader consists of the six header fields R/R/E/LCID/F/L but for
the last subheader in the MAC PDU. The last subheader in the MAC
PDU consists solely of the four header fields R/R/E/LCID. A MAC PDU
subheader corresponding to padding consists of the four header
fields R/R/E/LCID. FIG. 7 (a reproduction of FIG. 6.1.6-1:
R/R/E/LCID/F/L MAC subheader). FIG. 8 (a reproduction of FIG.
6.1.6-2: R/R/E/LCID MAC subheader). FIG. 9 (a reproduction of FIG.
6.1.6-3: SL-SCH MAC subheader for V="0001" and "0010"). FIG. 10 (a
reproduction of FIG. 6.1.6-3a: SL-SCH MAC subheader for
V=''0011''). MAC PDU subheaders have the same order as the
corresponding MAC SDUs and padding. Padding occurs at the end of
the MAC PDU, except when single-byte or two-byte padding is
required. Padding may have any value and the MAC entity shall
ignore it. When padding is performed at the end of the MAC PDU,
zero or more padding bytes are allowed. When single-byte or
two-byte padding is required, one or two MAC PDU subheaders
corresponding to padding are placed after the SL-SCH subheader and
before any other MAC PDU subheader. A maximum of one MAC PDU can be
transmitted per TB. FIG. 11 (a reproduction of FIG. 6.1.6-4:
Example of MAC PDU consisting of MAC header, MAC SDUs and
padding).
[0311] In 3GPP TS 38.321-f40, Scheduling Request (SR), Buffer
Status Reporting (BSR), and Discontinuous Reception (DRX) mechanism
in New Radio (NR) is quoted below:
5.4.4 Scheduling Request
[0312] The Scheduling Request (SR) is used for requesting UL-SCH
resources for new transmission. The MAC entity may be configured
with zero, one, or more SR configurations. An SR configuration
consists of a set of PUCCH resources for SR across different BWPs
and cells. For a logical channel, at most one PUCCH resource for SR
is configured per BWP. Each SR configuration corresponds to one or
more logical channels. Each logical channel may be mapped to zero
or one SR configuration, which is configured by RRC. The SR
configuration of the logical channel that triggered the BSR
(subclause 5.4.5) (if such a configuration exists) is considered as
corresponding SR configuration for the triggered SR. RRC configures
the following parameters for the scheduling request procedure:
[0313] sr-ProhibitTimer (per SR configuration); [0314] sr-TransMax
(per SR configuration). The following UE variables are used for the
scheduling request procedure: [0315] SR_COUNTER (per SR
configuration). If an SR is triggered and there are no other SRs
pending corresponding to the same SR configuration, the MAC entity
shall set the SR_COUNTER of the corresponding SR configuration to
0. When an SR is triggered, it shall be considered as pending until
it is cancelled. All pending SR(s) triggered prior to the MAC PDU
assembly shall be cancelled and each respective sr-ProhibitTimer
shall be stopped when the MAC PDU is transmitted and this PDU
includes a Long or Short BSR MAC CE which contains buffer status up
to (and including) the last event that triggered a BSR (see
subclause 5.4.5) prior to the MAC PDU assembly. All pending SR(s)
shall be cancelled and each respective sr-ProhibitTimer shall be
stopped when the UL grant(s) can accommodate all pending data
available for transmission. Only PUCCH resources on a BWP which is
active at the time of SR transmission occasion are considered
valid. As long as at least one SR is pending, the MAC entity shall
for each pending SR: [0316] 1> if the MAC entity has no valid
PUCCH resource configured for the pending SR: [0317] 2> initiate
a Random Access procedure (see subclause 5.1) on the SpCell and
cancel the pending SR. [0318] 1> else, for the SR configuration
corresponding to the pending SR: [0319] 2> when the MAC entity
has an SR transmission occasion on the valid PUCCH resource for SR
configured; and [0320] 2> if sr-ProhibitTimer is not running at
the time of the SR transmission occasion; and [0321] 2> if the
PUCCH resource for the SR transmission occasion does not overlap
with a measurement gap; and [0322] 2> if the PUCCH resource for
the SR transmission occasion does not overlap with a UL-SCH
resource: [0323] 3> if SR_COUNTER<sr-TransMax: [0324] 4>
increment SR_COUNTER by 1; [0325] 4> instruct the physical layer
to signal the SR on one valid PUCCH resource for SR; [0326] 4>
start the sr-ProhibitTimer. [0327] 3> else: [0328] 4> notify
RRC to release PUCCH for all Serving Cells; [0329] 4> notify RRC
to release SRS for all Serving Cells; [0330] 4> clear any
configured downlink assignments and uplink grants; [0331] 4>
clear any PUSCH resources for semi-persistent CSI reporting; [0332]
4> initiate a Random Access procedure (see subclause 5.1) on the
SpCell and cancel all pending SRs. [0333] NOTE 1: The selection of
which valid PUCCH resource for SR to signal SR on when the MAC
entity has more than one overlapping valid PUCCH resource for the
SR transmission occasion is left to UE implementation. [0334] NOTE
2: If more than one individual SR triggers an instruction from the
MAC entity to the PHY layer to signal the SR on the same valid
PUCCH resource, the SR_COUNTER for the relevant SR configuration is
incremented only once. The MAC entity may stop, if any, ongoing
Random Access procedure due to a pending SR which has no valid
PUCCH resources configured, which was initiated by MAC entity prior
to the MAC PDU assembly. Such a Random Access procedure may be
stopped when the MAC PDU is transmitted using a UL grant other than
a UL grant provided by Random Access Response, and this PDU
includes a BSR MAC CE which contains buffer status up to (and
including) the last event that triggered a BSR (see subclause
5.4.5) prior to the MAC PDU assembly, or when the UL grant(s) can
accommodate all pending data available for transmission.
5.4.5 Buffer Status Reporting
[0335] The Buffer Status reporting (BSR) procedure is used to
provide the serving gNB with information about UL data volume in
the MAC entity. RRC configures the following parameters to control
the BSR: [0336] periodicBSR-Timer; [0337] retxBSR-Timer; [0338]
logicalChannelSR-DelayTimerApplied; [0339]
logicalChannelSR-DelayTimer; [0340] logicalChannelSR-Mask; [0341]
logicalChannelGroup. Each logical channel may be allocated to an
LCG using the logicalChannelGroup. The maximum number of LCGs is
eight. The MAC entity determines the amount of UL data available
for a logical channel according to the data volume calculation
procedure in TSs 38.322 [3] and 38.323 [4]. A BSR shall be
triggered if any of the following events occur: [0342] UL data, for
a logical channel which belongs to an LCG, becomes available to the
MAC entity; and either [0343] this UL data belongs to a logical
channel with higher priority than the priority of any logical
channel containing available UL data which belong to any LCG; or
[0344] none of the logical channels which belong to an LCG contains
any available UL data. in which case the BSR is referred below to
as `Regular BSR`; [0345] UL resources are allocated and number of
padding bits is equal to or larger than the size of the Buffer
Status Report MAC CE plus its subheader, in which case the BSR is
referred below to as `Padding BSR`; [0346] retxBSR-Timer expires,
and at least one of the logical channels which belong to an LCG
contains UL data, in which case the BSR is referred below to as
`Regular BSR`; [0347] periodicBSR-Timer expires, in which case the
BSR is referred below to as `Periodic BSR`. [0348] NOTE: When
Regular BSR triggering events occur for multiple logical channels
simultaneously, each logical channel triggers one separate Regular
BSR. For Regular BSR, the MAC entity shall: [0349] 1> if the BSR
is triggered for a logical channel for which
logicalChannelSR-DelayTimerApplied is configured by upper layers:
[0350] 2> start or restart the logicalChannelSR-DelayTimer.
[0351] 1> else: [0352] 2> if running, stop the
logicalChannelSR-DelayTimer. For Regular and Periodic BSR, the MAC
entity shall: [0353] 1> if more than one LCG has data available
for transmission when the MAC PDU containing the BSR is to be
built: [0354] 2> report Long BSR for all LCGs which have data
available for transmission. [0355] 1> else: [0356] 2> report
Short BSR.
For Padding BSR:
[0356] [0357] 1> if the number of padding bits is equal to or
larger than the size of the Short BSR plus its subheader but
smaller than the size of the Long BSR plus its subheader: [0358]
2> if more than one LCG has data available for transmission when
the BSR is to be built: [0359] 3> if the number of padding bits
is equal to the size of the Short BSR plus its subheader: [0360]
4> report Short Truncated BSR of the LCG with the highest
priority logical channel with data available for transmission.
[0361] 3> else: [0362] 4> report Long Truncated BSR of the
LCG(s) with the logical channels having data available for
transmission following a decreasing order of the highest priority
logical channel (with or without data available for transmission)
in each of these LCG(s), and in case of equal priority, in
increasing order of LCGID. [0363] 2> else: [0364] 3> report
Short BSR. [0365] 1> else if the number of padding bits is equal
to or larger than the size of the Long BSR plus its subheader:
[0366] 2> report Long BSR for all LCGs which have data available
for transmission. For BSR triggered by retxBSR-Timer expiry, the
MAC entity considers that the logical channel that triggered the
BSR is the highest priority logical channel that has data available
for transmission at the time the BSR is triggered. The MAC entity
shall: [0367] 1> if the Buffer Status reporting procedure
determines that at least one BSR has been triggered and not
cancelled: [0368] 2> if UL-SCH resources are available for a new
transmission and the UL-SCH resources can accommodate the BSR MAC
CE plus its subheader as a result of logical channel
prioritization: [0369] 3> instruct the Multiplexing and Assembly
procedure to generate the BSR MAC CE(s); [0370] 3> start or
restart periodicBSR-Timer except when all the generated BSRs are
long or short Truncated BSRs; [0371] 3> start or restart
retxBSR-Timer. [0372] 2> if a Regular BSR has been triggered and
logicalChannelSR-DelayTimer is not running: [0373] 3> if there
is no UL-SCH resource available for a new transmission; or [0374]
3> if the MAC entity is configured with configured uplink
grant(s) and the Regular BSR was triggered for a logical channel
for which logicalChannelSR-Mask is set to false; or 3> if the
UL-SCH resources available for a new transmission do not meet the
LCP mapping restrictions (see subclause 5.4.3.1) configured for the
logical channel that triggered the BSR: [0375] 4> trigger a
Scheduling Request. [0376] NOTE: UL-SCH resources are considered
available if the MAC entity has an active configuration for either
type of configured uplink grants, or if the MAC entity has received
a dynamic uplink grant, or if both of these conditions are met. If
the MAC entity has determined at a given point in time that UL-SCH
resources are available, this need not imply that UL-SCH resources
are available for use at that point in time. A MAC PDU shall
contain at most one BSR MAC CE, even when multiple events have
triggered a BSR. The Regular BSR and the Periodic BSR shall have
precedence over the padding BSR. The MAC entity shall restart
retxBSR-Timer upon reception of a grant for transmission of new
data on any UL-SCH. All triggered BSRs may be cancelled when the UL
grant(s) can accommodate all pending data available for
transmission but is not sufficient to additionally accommodate the
BSR MAC CE plus its subheader. All BSRs triggered prior to MAC PDU
assembly shall be cancelled when a MAC PDU is transmitted and this
PDU includes a Long or Short BSR MAC CE which contains buffer
status up to (and including) the last event that triggered a BSR
prior to the MAC PDU assembly. [0377] NOTE: MAC PDU assembly can
happen at any point in time between uplink grant reception and
actual transmission of the corresponding MAC PDU. BSR and SR can be
triggered after the assembly of a MAC PDU which contains a BSR MAC
CE, but before the transmission of this MAC PDU. In addition, BSR
and SR can be triggered during MAC PDU assembly.
5.7 Discontinuous Reception (DRX)
[0378] The MAC entity may be configured by RRC with a DRX
functionality that controls the UE's PDCCH monitoring activity for
the MAC entity's C-RNTI, CS-RNTI, INT-RNTI, SFI-RNTI, SP-CSI-RNTI,
TPC-PUCCH-RNTI, TPC-PUSCH-RNTI, and TPC-SRS-RNTI. When using DRX
operation, the MAC entity shall also monitor PDCCH according to
requirements found in other subclauses of this specification. When
in RRC_CONNECTED, if DRX is configured, for all the activated
Serving Cells, the MAC entity may monitor the PDCCH discontinuously
using the DRX operation specified in this subclause; otherwise the
MAC entity shall monitor the PDCCH continuously. RRC controls DRX
operation by configuring the following parameters: [0379]
drx-onDurationTimer: the duration at the beginning of a DRX Cycle;
[0380] drx-SlotOffset: the delay before starting the
drx-onDurationTimer; [0381] drx-InactivityTimer: the duration after
the PDCCH occasion in which a PDCCH indicates a new UL or DL
transmission for the MAC entity; [0382] drx-RetransmissionTimerDL
(per DL HARQ process except for the broadcast process): the maximum
duration until a DL retransmission is received; [0383]
drx-RetransmissionTimerUL (per UL HARQ process): the maximum
duration until a grant for UL retransmission is received; [0384]
drx-LongCycleStartOffset: the Long DRX cycle and drx-StartOffset
which defines the subframe where the Long and Short DRX Cycle
starts; [0385] drx-ShortCycle (optional): the Short DRX cycle;
[0386] drx-ShortCycleTimer (optional): the duration the UE shall
follow the Short DRX cycle; [0387] drx-HARQ-RTT-TimerDL (per DL
HARQ process except for the broadcast process): the minimum
duration before a DL assignment for HARQ retransmission is expected
by the MAC entity; [0388] drx-HARQ-RTT-TimerUL (per UL HARQ
process): the minimum duration before a UL HARQ retransmission
grant is expected by the MAC entity. When a DRX cycle is
configured, the Active Time includes the time while: [0389]
drx-onDurationTimer or drx-InactivityTimer or
drx-RetransmissionTimerDL or drx-RetransmissionTimerUL or
ra-ContentionResolutionTimer (as described in subclause 5.1.5) is
running; or [0390] a Scheduling Request is sent on PUCCH and is
pending (as described in subclause 5.4.4); or [0391] a PDCCH
indicating a new transmission addressed to the C-RNTI of the MAC
entity has not been received after successful reception of a Random
Access Response for the Random Access Preamble not selected by the
MAC entity among the contention-based Random Access Preamble (as
described in subclause 5.1.4). When DRX is configured, the MAC
entity shall: [0392] 1> if a MAC PDU is received in a configured
downlink assignment: [0393] 2> start the drx-HARQ-RTT-TimerDL
for the corresponding HARQ process in the first symbol after the
end of the corresponding transmission carrying the DL HARQ
feedback; [0394] 2> stop the drx-RetransmissionTimerDL for the
corresponding HARQ process. [0395] 1> if a MAC PDU is
transmitted in a configured uplink grant: [0396] 2> start the
drx-HARQ-RTT-TimerUL for the corresponding HARQ process in the
first symbol after the end of the first repetition of the
corresponding PUSCH transmission; [0397] 2> stop the
drx-RetransmissionTimerUL for the corresponding HARQ process.
[0398] 1> if a drx-HARQ-RTT-TimerDL expires: [0399] 2> if the
data of the corresponding HARQ process was not successfully
decoded: [0400] 3> start the drx-RetransmissionTimerDL for the
corresponding HARQ process in the first symbol after the expiry of
drx-HARQ-RTT-TimerDL. [0401] 1> if a drx-HARQ-RTT-TimerUL
expires: [0402] 2> start the drx-RetransmissionTimerUL for the
corresponding HARQ process in the first symbol after the expiry of
drx-HARQ-RTT-TimerUL. [0403] 1> if a DRX Command MAC CE or a
Long DRX Command MAC CE is received: [0404] 2> stop
drx-onDurationTimer; [0405] 2> stop drx-InactivityTimer. [0406]
1> if drx-InactivityTimer expires or a DRX Command MAC CE is
received: [0407] 2> if the Short DRX cycle is configured: [0408]
3> start or restart drx-ShortCycleTimer in the first symbol
after the expiry of drx-InactivityTimer or in the first symbol
after the end of DRX Command MAC CE reception; [0409] 3> use the
Short DRX Cycle. [0410] 2> else: [0411] 3> use the Long DRX
cycle. [0412] 1> if drx-ShortCycleTimer expires: [0413] 2>
use the Long DRX cycle. [0414] 1> if a Long DRX Command MAC CE
is received: [0415] 2> stop drx-ShortCycleTimer; [0416] 2>
use the Long DRX cycle. [0417] 1> if the Short DRX Cycle is
used, and [(SFN.times.10)+subframe number] modulo
(drx-ShortCycle)=(drx-StartOffset) modulo (drx-ShortCycle); or
[0418] 1> if the Long DRX Cycle is used, and
[(SFN.times.10)+subframe number] modulo (drx-LongCycle)=drx-Start
Offset: [0419] 2> start drx-onDurationTimer after drx-SlotOffset
from the beginning of the subframe. [0420] 1> if the MAC entity
is in Active Time: [0421] 2> monitor the PDCCH; [0422] 2> if
the PDCCH indicates a DL transmission: [0423] 3> start the
drx-HARQ-RTT-TimerDL for the corresponding HARQ process in the
first symbol after the end of the corresponding transmission
carrying the DL HARQ feedback; [0424] 3> stop the
drx-RetransmissionTimerDL for the corresponding HARQ process.
[0425] 2> if the PDCCH indicates a UL transmission: [0426] 3>
start the drx-HARQ-RTT-TimerUL for the corresponding HARQ process
in the first symbol after the end of the first repetition of the
corresponding PUSCH transmission; [0427] 3> stop the
drx-RetransmissionTimerUL for the corresponding HARQ process.
[0428] 2> if the PDCCH indicates a new transmission (DL or UL):
[0429] 3> start or restart drx-InactivityTimer in the first
symbol after the end of the PDCCH reception. [0430] 1> in
current symbol n, if the MAC entity would not be in Active Time
considering grants/assignments/DRX Command MAC CE/Long DRX Command
MAC CE received and Scheduling Request sent 4 ms prior to symbol n
when evaluating all DRX Active Time conditions as specified in this
subclause: [0431] 2> not transmit periodic SRS and
semi-persistent SRS defined in TS 38.214 [7]. [0432] 1> if CSI
masking (csi-Mask) is setup by upper layers: [0433] 2> in
current symbol n, if onDurationTimer would not be running
considering grants/assignments/DRX Command MAC CE/Long DRX Command
MAC CE received 4 ms prior to symbol n when evaluating all DRX
Active Time conditions as specified in this subclause: [0434] 3>
not report CSI on PUCCH. [0435] 1> else: [0436] 2> in current
symbol n, if the MAC entity would not be in Active Time considering
grants/assignments/DRX Command MAC CE/Long DRX Command MAC CE
received and Scheduling Request sent 4 ms prior to symbol n when
evaluating all DRX Active Time conditions as specified in this
subclause: [0437] 3> not report CSI on PUCCH and semi-persistent
CSI on PUSCH. Regardless of whether the MAC entity is monitoring
PDCCH or not, the MAC entity transmits HARQ feedback, aperiodic CSI
on PUSCH, and aperiodic SRS defined in TS 38.214 [7] when such is
expected. The MAC entity needs not to monitor the PDCCH if it is
not a complete PDCCH occasion (e.g. the Active Time starts or ends
in the middle of a PDCCH occasion).
[0438] In RAN1 #94 chairman's note, the agreements of NR
Vehicle-to-Everything (V2X) are discussed and quoted below:
Agreements:
[0439] At least two sidelink resource allocation modes are defined
for NR-V2X sidelink communication [0440] Mode 1: Base station
schedules sidelink resource(s) to be used by UE for sidelink
transmission(s) [0441] Mode 2: UE determines (i.e. base station
does not schedule) sidelink transmission resource(s) within
sidelink resources configured by base station/network or
pre-configured sidelink resources
Notes:
[0441] [0442] eNB control of NR sidelink and gNB control of LTE
sidelink resources will be separately considered in corresponding
agenda items. [0443] Mode-2 definition covers potential sidelink
radio-layer functionality or resource allocation sub-modes (subject
to further refinement including merging of some or all of them)
where [0444] a) UE autonomously selects sidelink resource for
transmission [0445] b) UE assists sidelink resource selection for
other UE(s) [0446] c) UE is configured with NR configured grant
(type-1 like) for sidelink transmission [0447] d) UE schedules
sidelink transmissions of other UEs RAN1 to continue study details
of resource allocation modes for NR-V2X sidelink communication
[0448] In RAN1 #adohoc1901, the agreements for how a UE to request
sidelink resource for retransmission are discussed and quoted
below:
Agreements:
[0449] It is supported that in mode 1 for unicast, the in-coverage
UE sends an indication to gNB to indicate the need for
retransmission [0450] At least PUCCH is used to report the
information [0451] If feasible, RAN1 reuses PUCCH defined in Rel-15
[0452] The gNB can also schedule re-transmission resource [0453]
FFS transmitter UE and/or receiver UE [0454] If receiver UE, the
indication is in the form of HARQ ACK/NAK [0455] If transmitter UE,
FFS
[0456] Some or all of the following terminology and assumption may
be used hereafter. [0457] BS: a network central unit or a network
node in NR which is used to control one or multiple TRPs which are
associated with one or multiple cells. Communication between BS and
TRP(s) is via fronthaul. BS may be referred to as central unit
(CU), eNB, gNB, or NodeB. [0458] TRP: a transmission and reception
point provides network coverage and directly communicates with UEs.
TRP may be referred to as distributed unit (DU) or network node.
[0459] Cell: a cell is composed of one or multiple associated TRPs,
i.e. coverage of the cell is composed of coverage of all associated
TRP(s). One cell is controlled by one BS. Cell may be referred to
as TRP group (TRPG). [0460] For network side: [0461] Downlink
timing of TRPs in the same cell are synchronized. [0462] RRC layer
of network side is in BS. For UE side: [0463] There are at least
two UE (RRC) states: connected state (or called active state) and
non-connected state (or called inactive state or idle state).
Inactive state may be an additional state or belong to connected
state or non-connected state.
[0464] Based on the current RAN1 design, a UE performing a sidelink
unicast communication will support HARQ feedback in a sidelink
interface. In other words, a Transmit (Tx) UE will monitor HARQ
feedback from a Receive (Rx) UE after the Tx UE performed a
sidelink transmission to the Rx UE. Based on the HARQ feedback
result, the Tx UE may need to use the sidelink resource to perform
a retransmission for the sidelink transmission to the Rx UE again
through the sidelink interface.
[0465] Currently, in the RAN1 discussion, the Tx UE (i.e., Mode 1
UE) may need to transmit an indication to the base station to
indicate the need for retransmission. In the discussion, the
indication could be one or more HARQ feedbacks for indicating
whether a transmission of a sidelink grant is successful or
unsuccessful. And it would be possible for a UE to receive another
sidelink grant or a sidelink grant for retransmission for
responding to such indication/HARQ feedback. Based on current New
Radio (NR) Discontinuous Reception (DRX) design or LTE
Vehicle-to-Everything (V2X) design, the UE may stay in a DRX period
and will not receive any downlink control signaling from the Base
Station (BS). In such case, the BS may need to wait until the next
on-duration period to schedule the another Sidelink (SL) grant or
the SL grant for retransmission as shown in FIG. 12. The gray area
is the delay time that the UE will not monitor the downlink control
channel (e.g., Physical Downlink Control Channel (PDCCH), coreset,
and/or a PDCCH occasion).
[0466] Considering the possible DRX configuration, another SL grant
or the SL grant for retransmission may not be able to satisfy the
latency requirement of data included in the sidelink transmission.
Although the BS could improve latency by configuring a short DRX
period to the UE, the UE could suffer from a longer awaking time
and increase unnecessary power consumption.
[0467] The following methods address this issue. As those skilled
in the art will appreciate, one or more of the following methods
may be applied at the same time.
[0468] According to one method, a new active time for monitoring a
sidelink grant and/or a sidelink grant for retransmission after/in
response to transmitting a feedback of the sidelink transmission to
a BS for indicating the need for retransmission. In this method,
the UE starts monitoring a sidelink grant and/or a sidelink grant
for retransmission after/in response to the UE transmitting a
feedback of a sidelink transmission. In one method, the BS
configures whether the UE should start monitoring sidelink grants.
In one method, the start timing of the monitoring period is
configured by a BS (e.g., controlled by a timer or a counter).
Alternatively, the start timing of the monitoring period is
predefined or preconfigured. In addition, the UE monitors the
sidelink grant and/or the sidelink grant for retransmission within
a monitoring period. In one method, the monitoring period is
controlled by a timer or a counter. In one method, a length of the
monitoring period is configured by a BS. Alternatively, the length
of the monitoring period is preconfigured or predefined in the
UE.
[0469] In one embodiment, the UE starts/triggers a sidelink
retransmission timer after the UE transmits the feedback of a
sidelink transmission (e.g., a retransmission request indication)
to the BS. In one method, the UE will start a Round-Trip Time (RTT)
timer (for sidelink) after the transmission feedback of the
sidelink transmission and before start of the sidelink
retransmission timer. In one method, the RTT timer (for sidelink)
is used for triggering/starting the sidelink retransmission timer
and the sidelink retransmission timer is triggered/started by the
UE after the RTT timer expires. In one method, a length of the RTT
timer is configured by a BS. Alternatively, the length of the RTT
timer is predefined. In another method, the RTT timer is maintained
in a per UE manner. Alternatively, the RTT timer is maintained in
per sidelink HARQ process manner. In one method, the RTT timer is
different and/or independent from a RTT timer used for uplink
and/or downlink. Alternatively, the RTT timer is the same timer or
the shared same value as the RTT timer used for the uplink HARQ
process. In one method, the sidelink retransmission timer is
different and/or independent from a retransmission timer used for
uplink and/or downlink. Alternatively, the sidelink retransmission
timer is the same timer or the shared same value as the
retransmission timer used for the uplink HARQ process.
[0470] Alternatively, the UE directly starts the sidelink
retransmission timer in response to the transmission of the
feedback of the sidelink transmission to the BS.
[0471] In another method, the sidelink retransmission timer is
maintained in a per UE manner. Alternatively, the sidelink
retransmission timer is maintained in a per sidelink HARQ process
manner. Alternatively, the sidelink retransmission timer is a per
sidelink HARQ process used for sidelink unicast communication or
for a sidelink communication which needs HARQ feedback.
[0472] In another embodiment, a new condition for starting or
restarting an inactivity timer (e.g. drx-InactivityTimer) is
defined. In another method, the feedback of the sidelink
transmission could start or restart the inactivity timer and keep
the UE monitoring the PDCCH for sidelink grant and/or sidelink
grant for retransmission. In another method, a UE starts or
restarts the inactivity timer when the UE receives a sidelink grant
for retransmission. Accordingly, the UE can prolong the possible
scheduling time for the base station. In one method, the
above-mentioned inactivity timer is the drx-InactivityTimer
disclosed in 3GPP TS 38.321-f40. Alternatively, the above-mentioned
inactivity-timer is another inactivity-timer for the sidelink. An
example for the embodiment is shown in FIG. 14. After the UE
performs a transmission of a retransmission request indication
(e.g., the feedback for the sidelink transmission) to the BS, the
UE starts the inactivity timer again.
[0473] For above methods and/or embodiment, the UE starts the timer
and/or monitors the downlink control channel (e.g., coreset and/or
PDCCH occasion) if the feedback of the sidelink transmission
indicates a Negative Acknowledgement (NACK) or the need of a
retransmission. Alternatively, the UE starts the timer and/or
monitors downlink control channel (e.g. coreset and/or PDCCH
occasion) regardless of the content of the feedback to the BS.
[0474] According to another method, the UE uses a Scheduling
Request (SR) transmission for indicating the need for
retransmission. The SR transmission is used for requesting a
sidelink grant and/or a sidelink grant for retransmission (instead
of the uplink grant). After the UE performs the SR for a sidelink
grant and/or a sidelink grant for retransmission, the UE will start
to monitor the downlink control channel (used for scheduling the
sidelink grant and/or the sidelink grant for retransmission). In
another method, the UE has no pending SR associated with the SR
transmission.
[0475] Alternatively, if we treat a SR for the sidelink resource by
the Medium Access Control (MAC) entity following the procedure of
the SR for the uplink grant, based on current specification, the UE
starts monitoring the PDCCH after the UE performs a SR transmission
(for uplink) to the base station. On the other hand, the SR
transmission is triggered by a pending SR. The pending SR is
usually triggered by a Buffer Status Report (BSR) or a sidelink
BSR. The pending SR will be cancelled when a MAC Protocol Data Unit
(PDU) is assembled. The PDU includes a Sidelink BSR which contains
a buffer status up to (and including) the last event that triggered
a Sidelink BSR. However, if the pending SR for triggering the SR
transmission is triggered by the retransmission request (or the
HARQ NACK received in the sidelink interface) instead of a
triggered sidelink BSR, then the pending SR will not be cancelled
in any cases. And the pending SR will continuously trigger the SR
transmission and the caused problem.
[0476] For the pending SR not triggered by the sidelink BSR, some
possible ways for cancelling the pending SR are listed as follows.
In one method, the pending SR of the SR transmission is cancelled
when the UE receives a sidelink grant. In another method, the
pending SR of the SR transmission is cancelled when the UE receives
a sidelink grant for retransmission. In one method, the pending SR
of the SR transmission is cancelled when the UE receives a sidelink
grant corresponding to the sidelink transmission which triggered
the pending SR. In one method, the pending SR of the SR
transmission is cancelled when the Transfer Block (TB), which needs
retransmission, is discarded, flushed, or overwritten.
[0477] In one method, the correspondence between a sidelink grant
(or a sidelink for retransmission) and the sidelink transmission
being performed is determined by a sidelink HARQ process ID/index.
Alternatively, the correspondence between a sidelink grant (or a
sidelink for retransmission) and the sidelink transmission being
performed is determined by the reception timing of the sidelink
grant (or a sidelink for retransmission). Alternatively, the
correspondence between a sidelink grant (or a sidelink for
retransmission) and the sidelink transmission being performed is
determined by a field or an indication included in the sidelink
grant (or a sidelink for retransmission). Alternatively, the
correspondence between a sidelink grant (or a sidelink for
retransmission) and the sidelink transmission being performed is
determined by a transport block size indicated by the sidelink
grant (or a sidelink for retransmission).
[0478] In one method, a UE starts or restarts an Inactive timer
when the UE receives a sidelink grant for retransmission. By this
way, it can prolong the possible scheduling time for the base
station.
[0479] In one method, the UE performs the SR transmission (for
sidelink) if the UE receives a NACK in a sidelink interface for a
sidelink transmission or the UE does not receive a HARQ feedback
corresponding to a sidelink transmission (which needs HARQ feedback
in sidelink interface) in a sidelink interface. Alternatively, the
UE performs the SR transmission (for sidelink) regardless of the
HARQ feedback result in the sidelink interface for a sidelink
transmission. The UE performs the SR transmission (for sidelink) if
the SR transmission needs a HARQ feedback result in the sidelink
interface or the UE is configured with or allocated with
resource(s) for performing the SR transmission.
[0480] In one method, the UE monitors the downlink control channel
(e.g., PDCCH, PDCCH occasion, and/or coreset) in response to
performing the SR transmission (for sidelink) if the HARQ feedback
result in the sidelink interface is a NACK or a Discontinuous
Transmission (DTX) (i.e., receives no HARQ feedback).
[0481] According to another method, the a dedicated coreset/PDCCH
monitoring occasion is allocated to receive a sidelink grant and/or
sidelink grant retransmission. In NR, a concept called coreset is
defined. A coreset is designed to limit a specific control resource
set for a UE to perform decode. A smaller control resource set can
reduce decoding overload in a UE, and a larger control resource set
could let a BS schedule more transmissions for improving data
rates. A similar concept is a PDCCH monitoring occasion. The fewer
PDCCH monitoring occasions can reduce a UE's power consumption, and
more PDCCH monitoring occasions can reduce scheduling latency.
[0482] In this method, a UE will be allocated to one or multiple
coresets and/or sets of PDCCH monitoring occasions for monitoring a
sidelink grant and/or a sidelink grant for retransmission. The
balance between power consumption and data rates could be
controlled by a BS by determining the size of coreset and/or the
amount of PDCCH occasions. Alternatively, the UE is allocated one
or multiple coresets and/or one or more sets of PDCCH monitoring
occasions for monitoring a sidelink grant or a sidelink grant for
retransmission.
[0483] In one method, the UE starts monitoring one or multiple
coresets and/or set of PDCCH monitoring occasions in response to
the transmission of the retransmission request indication to the
BS.
[0484] In one method, if the coreset(s) and/or PDCCH occasion(s)
are not shared with Uu scheduling, a UE applies another
Discontinuous Reception (DRX) mechanism for the coresets and/or
PDCCH occasion for controlling the power consumption and decoding
complexity. In one method, the DRX mechanism means the same
procedure with different configurations (e.g., length of timer,
start offset, DRX period).
[0485] In another method, the UE does not apply the DRX mechanism
to the PDCCH monitoring of the sidelink grant and/or sidelink grant
for retransmission. In one method, the UE does not apply the DRX
mechanism to a Radio Network Temporary Identifier (RNTI) used for
scheduling sidelink grant and/or sidelink grant for retransmission.
In one method, one or multiple coresets and/or one or multiple sets
of PDCCH occasions of the sidelink grant are separated from the
coresets and/or PDCCH occasion sets used for Uu scheduling (e.g. UL
grant, DL assignment). Alternatively, the coreset(s) and/or PDCCH
occasion set(s) of the sidelink grant are shared or are the same as
the coreset and/or PDCCH occasions used for Uu scheduling (e.g. UL
grant, DL assignment). By removing DRX, the UE could always be able
to receive a sidelink grant and/or sidelink grant for
retransmission. In one method, one or multiple coresets and/or one
or multiple set of the PDCCH occasions of the sidelink grant for
retransmission are separated from the coresets and/or the PDCCH
occasion sets used for Uu scheduling (e.g. UL grant, DL
assignment).
[0486] In another method, the Inactivity timer is configured with a
large enough value for covering any scheduling delay from a new
transmission until retransmission. In this method, the network
(e.g., BS) will need to allocate a long enough timer value to cover
any potential future scheduling. Following LTE V2X design, a UE
will start or restart an inactivity timer in response to receiving
a sidelink grant for a new transmission. In order to prevent
issues, the network could allocate a long enough inactivity timer
value for scheduling a potential sidelink grant for retransmission
or another sidelink grant. The time relationship is shown in FIG.
13. As shown in FIG. 13, the inactivity timer is longer than a
whole round trip transmission and the processing time in the
sidelink interface. The gray area is the time for the network to
schedule a potential sidelink grant for retransmission or another
sidelink grant. More specifically, the inactivity timer is longer
than the maximum time for a whole round trip transmission and the
processing time for a sidelink transmission which needs the
sidelink HARQ feedback in the sidelink interface plus the
processing and transmission delay for the retransmission request
indication.
[0487] In another method, the UE starts to monitor a downlink
control channel when receiving HARQ feedback from another device in
a sidelink interface. After a first UE performs a sidelink
transmission to a second UE through a sidelink interface, the first
UE monitors a HARQ feedback for the sidelink transmission in the
sidelink interface. The first UE needs to transmit a feedback
and/or a retransmission request indication to a BS for indicating
whether the sidelink transmission needs a retransmission. Since
issues may be caused by not monitoring a downlink control channel,
the first UE starts monitoring the downlink control channel when
the first UE determines that the HARQ feedback result for the
sidelink transmission in the sidelink interface. More specifically,
the first UE determines the HARQ feedback as a NACK if the first UE
receives the NACK from the second UE. The first UE determines the
HARQ feedback as an ACK if the first UE receives the ACK from the
second UE. The first UE determines the HARQ feedback as a NACK or
DTX if the first UE does not receive a corresponding HARQ feedback
from the second UE.
[0488] In one method, the first UE starts monitoring the downlink
control channel when the first UE determines the HARQ feedback
result for the sidelink transmission in the sidelink interface as a
NACK or DTX. Alternatively, the first UE starts monitoring the
downlink control channel regardless of the HARQ feedback
result.
[0489] In one method, the UE transmits the feedback and/or the
retransmission request indication to the BS if the UE determines
the HARQ feedback result as a NACK or DTX. Alternatively, the UE
transmits the feedback and/or the retransmission request indication
to the BS regardless of the HARQ feedback result, but the contents
of or the format of the feedback and/or the retransmission request
indication will be different depending on the HARQ feedback
result.
[0490] For some of the above-disclosed methods, the UE is in
RRC_CONNECTED. In one method, the UE is configured with a network
scheduling mode (i.e., mode 1). In one method, the UE is configured
with a dual mode (i.e., both mode 1 and mode 2). In one method, the
sidelink grant and the sidelink grant for retransmission have
different Downlink Control Information (DCI) format. Alternatively,
the sidelink grant and the sidelink grant for retransmission share
the same DCI format. In one method, the sidelink transmission is or
includes a sidelink data transmission (e.g., SL-SCH, data belongs
to SL logical channel). In one method, the sidelink transmission is
a sidelink unicast transmission. Alternatively, the sidelink
transmission is a sidelink groupcast transmission. In one method,
the sidelink transmission includes a sidelink control information
transmission.
[0491] According to one exemplary method for a first device to
monitor down control signal for scheduling sidelink resource, the
includes: performing a sidelink transmission to a second device
based on a first sidelink grant allocated by a base station;
determining a retransmission need of the sidelink transmission
based on a first sidelink resource used for monitoring feedback of
the sidelink transmission from the second device; transmitting a
retransmission indication for the retransmission need to the base
station; and monitoring a downlink control resource set in response
to the transmission of the retransmission indication.
[0492] In another exemplary method, the sidelink transmission is an
unicast transmission.
[0493] In another exemplary method, the sidelink transmission needs
to receive HARQ feedback from the second device through sidelink
interface.
[0494] In another exemplary method, the first sidelink grant
allocates a second sidelink resource for the sidelink
transmission.
[0495] In another exemplary method, the first sidelink grant
allocates a first uplink resource for the transmission of the
retransmission indication.
[0496] In another exemplary method, the first sidelink resource is
determined by the second sidelink resource.
[0497] In another exemplary method, the first device transmits the
retransmission indication to the base station if the UE does not
receive the feedback from the second device.
[0498] In another exemplary method, the first device transmits the
retransmission indication to the base station if the feedback from
the second device indicates reception failure of the sidelink
transmission.
[0499] In another exemplary method, the first device starts or
restarts a timer in response to the transmission of the
retransmission indication, wherein the timer is used for
controlling period of the monitoring.
[0500] In another exemplary method, the timer is an
Inactivity-timer (e.g. drx-InactivityTimer).
[0501] In another exemplary method, the timer is a new timer
different from the Inactivity-timer (i.e. drx-InactivityTimer).
[0502] In another exemplary method, the downlink control resource
set is a PDCCH channel.
[0503] In another exemplary method, the downlink control resource
set includes a set of PDCCH occasion(s).
[0504] In another exemplary method, the downlink control resource
set is a coreset.
[0505] In another exemplary method for a first device to monitor
down control signal for scheduling sidelink resource, the method
includes: performing a sidelink transmission to a second device
based on a first sidelink grant allocated by a base station;
determining a retransmission need of the sidelink transmission
based on a first sidelink resource used for monitoring feedback of
the sidelink transmission from the second device; transmitting a
retransmission indication for the retransmission need to the base
station; starting a first timer in response to transmission of the
retransmission indication; and monitoring a downlink control
resource set after the first timer expires.
[0506] In another exemplary method, the sidelink transmission is an
unicast transmission.
[0507] In another exemplary method, the sidelink transmission needs
to receive a HARQ feedback from the second device through a
sidelink interface.
[0508] In another exemplary method, the first sidelink grant
allocates a second sidelink resource for the sidelink
transmission.
[0509] In another exemplary method, the first sidelink grant
allocates a first uplink resource for the transmission of the
retransmission indication.
[0510] In another exemplary method, the first sidelink resource is
determined by the second sidelnk resource.
[0511] In another exemplary method, the first device transmits the
retransmission indication to the base station if the UE does not
receive the feedback from the second device.
[0512] In another exemplary method, the first device transmits the
retransmission indication to the base station if the feedback from
the second device indicates reception failure of the sidelink
transmission.
[0513] In another exemplary method, the first timer is a timer for
not monitoring the downlink control resource set.
[0514] In another exemplary method, the first timer is a timer for
determining when to start a second timer.
[0515] In another exemplary method, the first timer is a RTT timer
(for a sidelink).
[0516] In another exemplary method, the first timer is a timer for
a sidelink HARQ process.
[0517] In another exemplary method, the first device starts a
second timer when monitoring the downlink control resource set.
[0518] In another exemplary method, the first device starts a
second timer when the first timer expires.
[0519] In another exemplary method, the second timer is used for
controlling a period of the monitoring.
[0520] In another exemplary method, the second timer is a timer for
a sidelink HARQ process.
[0521] In another exemplary method, the second timer is a
retransmission timer (for a sidelink).
[0522] In another exemplary method, the downlink control resource
set is a PDCCH channel.
[0523] In another exemplary method, the downlink control resource
set includes a set of PDCCH occasion(s).
[0524] In another exemplary method, the downlink control resource
set is a coreset.
[0525] In another exemplary method, the first device receives a
second sidelink grant when monitoring the control resource set; and
uses the second sidelink grant to perform a retransmission of the
sidelink transmission to the second device.
[0526] In another exemplary method for a first device to monitor
down control signal for scheduling sidelink resource, the method
includes: triggering a SR for a retransmission need of a sidelink
transmission; performing a SR transmission for the SR to a base
station; cancelling the SR when receiving a scheduling for the
sidelink transmission; stop performing SR transmission for the SR
after the SR is cancelled.
[0527] In another exemplary method, the sidelink transmission is an
unicast transmission.
[0528] In another exemplary method, the SR is associated with a
first SR configuration.
[0529] In another exemplary method, the association between the SR
and the first SR configuration is configured by the base
station.
[0530] In another exemplary method, the scheduling for the sidelink
transmission is a sidelink grant.
[0531] In another exemplary method, the scheduling for the sidelink
transmission is a sidelink grant for retransmission.
[0532] In another exemplary method, the first device determines the
sidelink grant for retransmission is the scheduling for the
sidelink transmission based on a HARQ process Index/ID indicated in
the sidelink grant.
[0533] In another exemplary method, the first device determines the
sidelink grant for retransmission is the scheduling for the
sidelink transmission based on a received timing of the sidelink
grant for retransmission.
[0534] In another exemplary method, the first device determines the
sidelink grant for retransmission is the scheduling for the
sidelink transmission based on a field in the sidelink grant for
retransmission.
[0535] In another exemplary method, the first device determines the
sidelink grant for retransmission is the scheduling for the
sidelink transmission based on a transport block size field in the
sidelink grant for retransmission.
[0536] In another exemplary method, the first device does not
cancel the SR when the first device receives a first sidelink grant
for a new transmission.
[0537] In another exemplary method, the first device does not
cancel the SR when the first device receives a second sidelink
grant for retransmission, wherein the second sidelink grant is not
for the sidelink transmission.
[0538] FIG. 15 is a flow chart 1500 according to one exemplary
embodiment from the perspective of a first device such as, but not
limited to, a UE, wherein the first device monitors a down control
signal for scheduling sidelink resource. In step 1505, the first
device performs a sidelink transmission for a second device based
on a first sidelink grant allocated by a base station. In step
1510, the first device determines a retransmission need of the
sidelink transmission based on a Hybrid Automatic Repeat Request
(HARQ) feedback of the sidelink transmission from the second
device. In step 1515, the first device transmits a retransmission
indication for the retransmission need to the base station. In step
1520, the first device starts or restarts a timer upon the
transmission of the retransmission indication, wherein the timer is
used for controlling a period of monitoring a downlink control
resource set.
[0539] In another method, the sidelink transmission needs to
receive the HARQ feedback from the second device through a sidelink
interface.
[0540] In another method, the first device transmits the
retransmission indication to the base station if the first device
does not receive the HARQ feedback from the second device.
[0541] In another method, the first device transmits the
retransmission indication to the base station if the HARQ feedback
from the second device indicates a reception failure of the
sidelink transmission.
[0542] In another method, the timer is a drx-InactivityTimer or a
drx-RetransmissionTimerSL.
[0543] In another method, the downlink control resource set is a
Physical Dowlink Control Channel (PDCCH) or a coreset.
[0544] In another method, the downlink control resource set
includes a set of PDCCH occasions.
[0545] As those skilled in the art will appreciate, the various
disclosed embodiments and/or methods may be combined to form new
embodiments and/or methods.
[0546] Referring back to FIGS. 3 and 4, in one embodiment, the
device 300 includes a program code 312 stored in memory 310,
wherein the device 300 monitors a down control signal for
scheduling sidelink resource. The CPU 308 could execute program
code 312 to (i) perform a sidelink transmission for a second device
based on a first sidelink grant allocated by a base station, (ii)
determine a retransmission need of the sidelink transmission based
on a Hybrid Automatic Repeat Request (HARD) feedback of the
sidelink transmission from the second device, (iii) transmit a
retransmission indication for the retransmission need to the base
station, (iv) start or restart a timer upon the transmission of the
retransmission indication, wherein the timer is used for
controlling a period of monitoring a downlink control resource
set.
[0547] Furthermore, the CPU 308 can execute the program code 312 to
perform all of the above-described actions and steps or others
methods described herein.
[0548] The above-disclosed methods allow a UE to be immediately
scheduled by a base station for sidelink retransmission needs.
[0549] Various aspects of the disclosure have been described above.
It should be apparent that the teachings herein may be embodied in
a wide variety of forms and that any specific structure, function,
or both being disclosed herein is merely representative. Based on
the teachings herein one skilled in the art should appreciate that
an aspect disclosed herein may be implemented independently of any
other aspects and that two or more of these aspects may be combined
in various ways. For example, an apparatus may be implemented or a
method may be practiced using any number of the aspects set forth
herein. In addition, such an apparatus may be implemented or such a
method may be practiced using other structure, functionality, or
structure and functionality in addition to or other than one or
more of the aspects set forth herein. As an example of some of the
above concepts, in some aspects concurrent channels may be
established based on pulse repetition frequencies. In some aspects
concurrent channels may be established based on pulse position or
offsets. In some aspects concurrent channels may be established
based on time hopping sequences.
[0550] Those of skill in the art would understand that information
and signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0551] Those of skill would further appreciate that the various
illustrative logical blocks, modules, processors, means, circuits,
and algorithm steps described in connection with the aspects
disclosed herein may be implemented as electronic hardware (e.g., a
digital implementation, an analog implementation, or a combination
of the two, which may be designed using source coding or some other
technique), various forms of program or design code incorporating
instructions (which may be referred to herein, for convenience, as
"software" or a "software module"), or combinations of both. To
clearly illustrate this interchangeability of hardware and
software, various illustrative components, blocks, modules,
circuits, and steps have been described above generally in terms of
their functionality. Whether such functionality is implemented as
hardware or software depends upon the particular application and
design constraints imposed on the overall system. Skilled artisans
may implement the described functionality in varying ways for each
particular application, but such implementation decisions should
not be interpreted as causing a departure from the scope of the
present disclosure.
[0552] In addition, the various illustrative logical blocks,
modules, and circuits described in connection with the aspects
disclosed herein may be implemented within or performed by an
integrated circuit ("IC"), an access terminal, or an access point.
The IC may comprise a general purpose processor, a digital signal
processor (DSP), an application specific integrated circuit (ASIC),
a field programmable gate array (FPGA) or other programmable logic
device, discrete gate or transistor logic, discrete hardware
components, electrical components, optical components, mechanical
components, or any combination thereof designed to perform the
functions described herein, and may execute codes or instructions
that reside within the IC, outside of the IC, or both. A general
purpose processor may be a microprocessor, but in the alternative,
the processor may be any conventional processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0553] It is understood that any specific order or hierarchy of
steps in any disclosed process is an example of a sample approach.
Based upon design preferences, it is understood that the specific
order or hierarchy of steps in the processes may be rearranged
while remaining within the scope of the present disclosure. The
accompanying method claims present elements of the various steps in
a sample order, and are not meant to be limited to the specific
order or hierarchy presented.
[0554] The steps of a method or algorithm described in connection
with the aspects disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module (e.g., including
executable instructions and related data) and other data may reside
in a data memory such as RAM memory, flash memory, ROM memory,
EPROM memory, EEPROM memory, registers, a hard disk, a removable
disk, a CD-ROM, or any other form of computer-readable storage
medium known in the art. A sample storage medium may be coupled to
a machine such as, for example, a computer/processor (which may be
referred to herein, for convenience, as a "processor") such the
processor can read information (e.g., code) from and write
information to the storage medium. A sample storage medium may be
integral to the processor. The processor and the storage medium may
reside in an ASIC. The ASIC may reside in user equipment. In the
alternative, the processor and the storage medium may reside as
discrete components in user equipment. Moreover, in some aspects
any suitable computer-program product may comprise a
computer-readable medium comprising codes relating to one or more
of the aspects of the disclosure. In some aspects a computer
program product may comprise packaging materials.
[0555] While the invention has been described in connection with
various aspects, it will be understood that the invention is
capable of further modifications. This application is intended to
cover any variations, uses or adaptation of the invention
following, in general, the principles of the invention, and
including such departures from the present disclosure as come
within the known and customary practice within the art to which the
invention pertains.
* * * * *