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Hybrid ARQ Operation for IEEE 802.16m

IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number:

IEEE C802.16m-08/454Date Submitted:

2008-05-05Source:

Sungkyung Kim, Kwangjae Lim, Sungcheol Chang, Voice: +82-42-860-6448Seokheon Cho, Jungim Kim, Chulsik Yoon E-mail: {cyrano, kjlim, scchang, csyoon}@etri.re.krETRI161 Gajeong-dong Yusong-gu Daejeon, Korea

*<http://standards.ieee.org/faqs/affiliationFAQ.html>Venue:

EEE 802.16 Session #55, Macau, ChinaBase Contribution:

IEEE C802.16m-08/454Purpose:

To discuss and adopt the proposed text in the next revision of the 802.16m SDDNotice:

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.

Release:The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that

this contribution may be made public by IEEE 802.16.

Patent Policy:The contributor is familiar with the IEEE-SA Patent Policy and Procedures:

<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.

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Contents

• HARQ Mode• HARQ Signaling• HARQ Operation• HARQ in Persistent Allocation• HARQ Support for MAC PDU retransmission

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HARQ Mode

• Comparison among the HARQ Operation Modes

• 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.

Synchronous non-adaptive

Synchronous adaptive

Asynchronous non-adaptive

Asynchronous 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

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HARQ Signaling

• Required HARQ Operation parameters– 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 non-adaptive mode

• None

– 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.

Tx Side Rx Side

Connection set-up

HARQ type, Maximum number of retransmssions

HARQ signaling for HARQ set-up

New HARQ burst (1)

HARQ CH ID(x), toggle bit(0), SPID(IR case), MCS, allocated resource region

Retx. HARQ burst (1)

Asynchronous mode indication

HARQ Feedback Delay

HARQ Feedback (NAK)Synchronous HARQ interval

Retx. HARQ burst (1)

HARQ Feedback (NAK)

HARQ Feedback DelaySynchronous HARQ interval

HARQ CH ID(x), toggle bit(0), SPID(IR case), MCS, allocated resource region

HARQ signaling for new transmission

HARQ signaling for change of HARQ mode

HARQ signaling for asynchronous retransmssion

HARQ Feedback (ACK)

HARQ Feedback Delay

New HARQ burst (2)

HARQ CH ID(x), toggle bit(1), SPID(IR case), MCS, allocated resource region

HARQ signaling for new transmission

[The Example for HARQ signaling]

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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

– The Example of FDD

0 1

Synchronous Mode

Synchronous non-adaptive

New transmission

Asynchronous mode indication

2

Synchronous HARQ subframe (N+M*X)={0,8,16..}

X-subframes

DL UL Asynchronous Mode

Y(0)=5, Y(3)=3

UL HARQ Feedback Channel

0

Synchronous Mode

X subframes

Synchronous non-adaptive

Asynchronous mode indication

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New transmission

Asynchronous Mode

Synchronous HARQ subframe (N+M*X)={0,8,16..} Y(0)=3, Y(3)=3

[DL]

[UL]

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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 HARQ Feedback– Physical channel vs. MAC signaling

Physical DL Feedback channel MAC signaling via MAP

CRC included 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

0 21

Synchronous Mode

X subframes

Synchronous non-adaptive

Synchronous adaptive

New transmissionChange of

allocated regionAsynchronous

mode indication

NACK indication

MAP UL HARQ burstHARQ Feedback

asynchronous

Synchronous HARQ subframe (N+M*X)={5,13,21,29,..}

DL UL

Y(5)=6, Y(6)=5

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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

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[ Downlink PA with HARQ Operation]

Synchronous retransmission

N frame

2

Asynchronous retransmission

Asynchronous retransmission

New transmission (HARQ CH ID :x)

10 3

N+1 frame N+2 frame N+3 frame N+4 frame N+5 frame N+6 frame N+7 frame

New transmission (HARQ CH ID :Y)

HARQ CH ID:X, toggle bit(0), SPID(IR case), MCS, allocated resource region

NAK NAK NAK NAK NAK

HARQ CH ID:X, toggle bit(0), SPID(IR case), MCS, allocated resource region

Asynchronous retransmission

ACKSynchronous

retransmission

2

HARQ CH ID:Y, toggle bit(0), SPID(IR case), MCS, allocated resource region

ACK

- The number of synchronous retransmission (N) = 1

Persistent Allocation Period

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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.

0

MAP UL HARQ Feedback Channel

Feedback error (NACK à ACK)

HARQ Feedback Message

HARQ CH ID, frame number

0

Fast Retransmission

0

New transmission(HARQ CH ID: X, toggle bit:0)

N frame N+1 frame N+2 frame

RX failure

NAKRX

failure

NAK NAK

Maximum retransmission: 2

1 2

RX failure

RX failure

NAK

New transmission(HARQ CH ID: X, toggle bit:1)

New transmission(HARQ CH ID: X, toggle bit:0)

HARQ burst

HARQ TX side: Notification of Maximum retransmission failure

HARQ RX side: Generation of an HARQ feedback message

No

Bur

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no

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Fast Retransmission

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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.