HARQ Soft Buffer Management for 802.16m Document Number: C802.16m-08/1328 Date Submitted: 2008-10-31 Source: Yih-Shen Chen, Kelvin Chou, I-Kang Fu, and Paul Cheng Voice: +886-3-5670766 E-mail: yihshen.chen@mediatek.com, IK.Fu@mediatek.com, Paul.Cheng@mediatek.com MediaTek Inc. Venue: 802.16m-08/040, “Call for Contributions and Comments on Project 802.16m System Description Document (SDD)” - TGm SDD: Other Base Contribution: This is the base contribution Purpose: To be discussed and adopted by TGm for the P802.16m 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: <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 >.

Introduction Asynchronous mode is adopted in DL HARQ transmission Maximum retransmission delay Maximum number of retransmissions Maximum number of HARQ processes ACK/NACK delay Each erroneous HARQ burst is discarded after maximal retry Aggregation mode is more efficient for soft buffer utilization Problem: In case of DL-MAP (USCCH) lost, misperception/inconsistency of buffer state between MS and BS occurs [1] the retry count in the BS and MS is different “Maximum retransmission delay” parameter can be applied to solve the problem [1] TWG HARQ CC #1 meeting minutes

Lost-of-MAP Issue for Asynchronous DL-HARQ (1/2) ~ without “maximal retransmission delay” When DL-MAP is lost, the DL HARQ transmission status is unknown for MS MS has no idea whether a DL_HARQ_IE is assigned Soft buffer overflow: new HARQ burst is received while occupied soft buffer is not released

Lost-of-MAP Issue for Asynchronous DL-HARQ (2/2) ~ with “maximal retransmission delay” Increase retry count when the time delay exceeds “maximum retransmission delay” Discard the burst from soft buffer when retry count reaches maximal retransmission number

Text Proposal [Insert the following section at the end of 10.2.1.1 HARQ timing and protocol] “HARQ retry count is increased by one if maximal retransmission delay time is reached. Discard un-decodable packets from soft buffer if retry count exceeds maximal retransmission count.”