IEEE C80216m-08/993r1

Project / IEEE 802.16 Broadband Wireless Access Working Group <
Title / Consideration about Interaction of HARQ and ARQ
Date Submitted / 2008-9-05
Source(s) / Taegon Kong, Youngsoo Yuk,
Ronny Yongho Kim and Kiseon Ryu
LG Electronics Inc. / E-mail:{tgkong, sixs,ronnykim, ksryu}@lge.com
Re: / MAC: Data Plane; in response to the TGm Call for Contributions and Comments 802.16m-08/033 for Session 57
Abstract / This contribution covers the considerations about the Interaction of HARQ and ARQ with the redesign of ARQ
Purpose / To be discussed and adopted by TGm for use in the IEEE 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.
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:
and <
Further information is located at < and <

Consideration about Interaction of HARQ and ARQ

Taegon Kong, Youngsoo Yuk, Ronny YonghoKim, Kiseon Ryu

LG Electronics

1.Introduction

In the legacy 802.16 system, Automatic Repeat reQuest (ARQ) and Hybrid ARQ areprovided for a reliable communication. In order to meet the data plane latency requirement and enhance the system performance, it is desirable to enhance the ARQ and HARQ performance. By employing simple ARQ and HARQ interaction, ARQ performance can be improved substantially. In order to design ARQ state machine with consideration of interaction with HARQ, it is required to understand the HARQ process. In this contribution, we propose to use HARQ and ARQ interaction and related procedures. More specifically, because there is a problem in receiver side in interaction between ARQ and HARQ, changes in ARQ state machine considering the interaction in the receiver side is proposed.

2.Problem Definition

In the interaction of ARQ and HARQ, HARQ functional block shall transmit “Local ACK” and “Local NACK” to ARQ module. However when “Local NACK” is received from the HARQ function block, ARQ functional block shall change its state accordingly. In addition to the interaction operation in the transmitter side, the ARQ function in the receiver side shall consider Local NACK as well.

Figure 1. Unnecessary retransmission generated by Local NACK and ARQ timeout in the receiver

When there is no “Local NACK” in the receiver side, unnecessary retransmission might occur which incur resource wastage. The Fig 1. shows an example of such a problem. When the number of retransmission reaches predefined maximum number, the Hybrid ARQ in the transmitter generates a signal and sends it to the ARQ at the transmitter. The ARQ in the transmitter regards it as a retransmission request from the ARQ at the receiver and retransmitsthe negative acknowledged packet. While the retransmission packet is being delivered, the ARQ waiting timerat the receiver expires and goes into the waiting state again after transmitting an ARQ NACK. When the transmitter ARQ receives the ARQ NACK, it retransmits the packet again to the receiver ARQ. This kind of problem is caused because there is no local ACK/NACK signaling consideration in the receiver ARQ.

3.Description of Proposed Interaction between ARQ and HARQ

In order to alleviate the problem, HARQ in the transmitter and the receiver shall transmit Local NACK and ACK and ARQ state machine in the receiver shall employ ARQ timer reset.As shown in the Fig. 2, upon reception of the local NACK, the ARQ state machine in the receiver shall reset the ARQ timer and turn into the waiting state. This prevents the premature ARQ timer expiry in case of existence of local NACK/ACK.

Figure 2. ARQ Reset Procedure

4.Conclusion

With the introduction of an interaction between ARQ and Hybrid ARQ, the existing ARQ state machine shall be redesigned.In this contribution, we proposed to use local ACK/NACK in both the transmitter and the receiver and employ anARQ timer reset scheme in order to prevent unnecessary retransmission.

Text Proposal for the IEEE802.16m SDD

======Start of Proposed Text ======

10. Medium Access Control Sub-Layer

10.2.3HARQ and ARQ Interactions

HARQ functional block in receiver and transmitter provides local ACK and NACK to ARQ functional block in order to work tightly with ARQ functional block. ARQ block’s state machine changes with consideration of local ACK /NACK.

10.2.3.x Local NACK between HARQ and ARQ

In the event of transmitting and receiving the NACK between HARQ functional blocks, local NACK is delivered to the ARQ function blocks in the receiver and the transmitter. ARQ operation such as ARQ window size negotiation, ARQ block size negotiation, and Retransmission timer, in both the receiver side and the transmitter side shall consider the interaction with HARQ functional block.

======End of Proposed Text ======