Transcript IEEE C802.16m-08/454

Hybrid ARQ Operation for IEEE 802.16m
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16m-08/454
Date Submitted:
2008-05-05
Source:
Sungkyung Kim, Kwangjae Lim, Sungcheol Chang,
Seokheon Cho, Jungim Kim, Chulsik Yoon
ETRI
161 Gajeong-dong Yusong-gu Daejeon, Korea
Voice: +82-42-860-6448
E-mail: {cyrano, kjlim, scchang, csyoon}@etri.re.kr
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Venue:
EEE 802.16 Session #55, Macau, China
Base Contribution:
IEEE C802.16m-08/454
Purpose:
To discuss and adopt the proposed text in the next revision of the 802.16m SDD
Notice:
This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in
the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material
contained herein.
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Contents
•
•
•
•
•
HARQ Mode
HARQ Signaling
HARQ Operation
HARQ in Persistent Allocation
HARQ Support for MAC PDU retransmission
2
HARQ Mode
•
•
Comparison among the HARQ Operation
Synchronous
Asynchronous
Asynchronous
Modes Synchronous
non-adaptive
adaptive
non-adaptive
adaptive
Retransmission timing
fixed
fixed
Not-fixed
Not-fixed
Retransmission format
fixed
dynamic
fixed
Dynamic
Required retransmission
signaling
Implicit
signaling
Explicit
signaling
Explicit
signaling
Explicit
signaling
MAP overhead
low
high
high
high
flexibility
low
medium
medium
high
We propose the synchronous non-adaptive HARQ mode as a
default mechanism by reason of low MAP overhead. Also,
HARQ mode can be changed to the asynchronous adaptive
scheme in order to get the scheduling gain or/and to support
the flexibility of resource allocation.
3
HARQ Signaling
• Required HARQ Operation parameters
[The Example for HARQ signaling]
– Per Network entry or/and Connection set-up
• HARQ type: CC, IR, CC-IR, etc.
• The number of maximum retransmissions in
synchronous mode
– Per New transmission of HARQ burst
• HARQ CH ID, toggle bit, SPID (IR case),
MCS, Allocated resource region.
– Per Retransmission in synchronous nonadaptive mode
Tx Side
Rx Side
Connection set-up
HARQ type, Maximum number of retransmssions
HARQ signaling
for HARQ set-up
HARQ CH ID(x), toggle bit(0), SPID(IR case), MCS,
allocated resource region
New HARQ burst (1)
HARQ signaling for
new transmission
HARQ Feedback Delay
Synchronous
HARQ interval
HARQ Feedback (NAK)
Retx. HARQ burst (1)
HARQ Feedback Delay
Synchronous
HARQ interval
• None
HARQ Feedback (NAK)
Asynchronous mode indication
HARQ signaling for
change of HARQ mode
HARQ CH ID(x), toggle bit(0), SPID(IR case), MCS,
allocated resource region
HARQ signaling for
asynchronous retransmssion
– Per HARQ mode change
• Asynchronous mode indication
– Per Retransmission in asynchronous adaptive
mode
• HARQ CH ID, toggle bit, SPID (IR case),
MCS or shortened adaptive transmission
format, allocated resource region.
Retx. HARQ burst (1)
HARQ Feedback Delay
HARQ Feedback (ACK)
HARQ CH ID(x), toggle bit(1), SPID(IR case), MCS,
allocated resource region
New HARQ burst (2)
HARQ signaling for
new transmission
4
DL HARQ Operation
• DL HARQ timing diagram
– Synchronous HARQ subframe : N+M*X
– Fixed or described HARQ feedback subframe: Y({N+M*X}%8)
(N: subframe index of new transmission. M: the number of retransmission trials. X:
synchronous HARQ interval, Y(K): HARQ feedback delay in K- subframe transmission)
– The Example of TDD
New
transmission
Asynchronous
mode indication
Synchronous ModeDL
0
Asynchronous Mode
UL
1
2
X-subframes
Synchronous
non-adaptive
Synchronous HARQ subframe (N+M*X)={0,8,16..}
Y(0)=5, Y(3)=3
– The Example of FDD
New
transmission
Synchronous HARQ subframe (N+M*X)={0,8,16..} Y(0)=3, Y(3)=3
Asynchronous
mode indication
Synchronous Mode
[DL]
Asynchronous Mode
UL HARQ Feedback Channel
0
1
2
X subframes
[UL]
Synchronous
non-adaptive
5
UL HARQ Operation
• UL HARQ timing diagram
– Synchronous HARQ subframe : N+M*X
– Fixed or described HARQ feedback subframe: Y({N+M*X}%8)
– The Example of TDD (5:3)
DL
Synchronous
non-adaptive
NACK
indication
New transmission
UL
Change of
allocated region
Asynchronous
mode indication
Synchronous Mode
0
1
asynchronous
2
X subframes
Synchronous HARQ subframe (N+M*X)={5,13,21,29,..} Y(5)=6, Y(6)=5
MAP
HARQ Feedback
Synchronous
adaptive
UL HARQ burst
• DL HARQ Feedback
– Physical channel vs. MAC signaling
Physical DL Feedback channel
MAC signaling via MAP
No
Yes
Error cases
• ACK to NAK error: collision owing to
synchronous retransmission
• NAK to ACK error: data loss & resource waste
Failure of reception: Resource
waste
Flexibility
Low
high
CRC included
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HARQ in PA
• Persistent Allocation for VoIP
– Fixed MCS and Fixed Allocated resource region.
– HARQ signaling in PA
• Explicit HARQ CH ID allocation for new transmission
• The number of synchronous retransmissions (N=0, 1, 2, ..)
– The MS with low link budget may need more synchronous retransmissions without the
additional MAP overhead.
• Resource allocation for asynchronous retransmission
– The Example of Persistent Allocation with HARQ operation in downlink
New transmission
(HARQ CH ID :x)
Persistent Allocation Period
N+1 frame
N+2 frame
N frame
0
1
NAK
NAK
Synchronous
retransmission
HARQ CH ID:X, toggle bit(0), SPID(IR
case), MCS, allocated resource region
HARQ CH ID:X, toggle bit(0), SPID(IR
case), MCS, allocated resource region
New transmission
(HARQ CH ID :Y)
N+3 frame
N+4 frame
2
N+5 frame
0
NAK
Asynchronous
retransmission
1
NAK
HARQ CH ID:Y, toggle bit(0), SPID(IR
case), MCS, allocated resource region
N+6 frame
N+7 frame
3
NAK
Synchronous
Asynchronous
retransmission
retransmission
- The number of synchronous retransmission (N) = 1
[ Downlink PA with HARQ Operation]
2
ACK
ACK
Asynchronous
retransmission
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HARQ Support for MAC PDU
Retransmission
• HARQ-assisted Fast Retransmission
– Purpose:
• To Recover the data loss owing to NAK to ACK Feedback Error and/or transmission failure
by exceed in maximum retransmission.
• To reduce the long retransmission delay with ARQ scheme.
– Operation:
• HARQ TX Side: Fast notification of maximum retransmission failure.
• HARQ RX Side: Delivery of HARQ Feedback Message (Report for HARQ ACK to NAK
error or/and HARQ Max. retransmission failure) to the TX side.
New transmission
(HARQ CH ID: X, toggle bit:0)
N frame
HARQ TX side: Notification of
Maximum retransmission failure
Fast Retransmission
N+2 frame
N+1 frame
1
0
New transmission
(HARQ CH ID: X, toggle bit:1)
Feedback error
(NACK à ACK)
0
2
New transmission
(HARQ CH ID: X, toggle bit:0)
Fast Retransmission
0
RX
failure
NAK
RX
failure
NAK
RX
failure
NAK
Maximum retransmission: 2
MAP
HARQ burst
UL HARQ Feedback Channel
HARQ Feedback Message
RX
failure
NAK
No Burst and no
asynchronous change
indication
HARQ CH ID,
frame number
HARQ RX side: Generation of an
HARQ feedback message
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Proposed Text (1)
•
X.x. Hybrid ARQ Operations
X.x.1 Basic Principles
The HARQ scheme is basically a stop-and-wait protocol and supports multiple HARQ channels.
Synchronous non-adaptive HARQ mode is used as a default scheme on both downlink HARQ and
uplink HARQ in order to reduce downlink control overhead. Moreover, on purpose to enhance the
scheduling gain and to support the flexibility of resource allocation, HARQ retransmission mode can
be switched to asynchronous adaptive HARQ mode. To support optional asynchronous adaptive
HARQ mode per HARQ burst, explicit signaling or implicit signaling is needed.
For the HARQ operations the following parameters are considered:
- HARQ type (CC, IR, CC-IR, etc.)
- HARQ mode (synchronous non-adaptive, asynchronous adaptive)
- HARQ CH ID
- Toggle bit (new burst indication)
- SPID (Redundancy version of IR)
- MCS or Shortened adaptive HARQ transmission format
- Allocated resource region
- the number of maximum retransmissions
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Proposed Text (2)
For downlink HARQ operations, uplink HARQ feedback information (ACK/NAK) shall be
transmitted through a physical uplink feedback channel.
X.x.2 HARQ Operations for Persistent Allocation
For Persistent Allocation, HARQ CH ID shall be explicitly signaled. The number of maximum
synchronous retransmissions (N) is fixed during the persistent allocation (N=0, 1, 2, ..).
Xx3 HARQ support for fast MAC PDU retransmission
Owing to the errors of the physical HARQ feedback channel and failure of maximum retransmission,
data loss and resource waste can be generated on both downlink and uplink transmissions.
To recover data loss and to reduce retransmission delay, HARQ feedback information can be used by
the TX side. Moreover, cross-operations between HARQ and ARQ can be supported on both
downlink HARQ and uplink HARQ.
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