1. Slide 1 802.16m HARQ Document Number: C802.16m-08/340 Date Submitted: 2008-05-05 Source: Sean McBeath, Juejun Liu, Jianmin LuVoice: Huawei TechnologiesE-mail: {smcbeath, juejunliu, lujianmin}@huawei.com Fang Huiyingfang.huiying@zte.com.cn ZTE Dong Xiaolu, Du Ying{dongxiaolu, duying}@mail.ritt.com.cn CATR * http://standards.ieee.org/faqs/affiliationFAQ.html Venue: IEEE 802.16m-08/016r1: Call for Contributions on Project 802.16m System Description Document (SDD). Target topic: Hybrid ARQ (protocol and timing). Base Contribution: None Purpose: Discussion and approval by TGm for 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. 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. Slide 2 Introduction For HARQ, there are three main scheduling options: dynamic scheduling (802.16e), semi-persistent scheduling (802.16 Rev. 2), and persistent scheduling, all of which are illustrated on the next slide. In these slides, we focus on the following two issues - Timing associated with transmission of acknowledgement information Applies to all three scheduling options - HARQ timing for persistent scheduling

3. Slide 3 HARQ Scheduling Options Dynamic Scheduling Variable Semi-Persistent Scheduling time Pre-Defined ResourceDynamic Resource Persistent Scheduling (Synchronous HARQ) HARQ RTT 1 st HARQ Transmission of Packet 1 1 st HARQ Transmission of Packet 2 Variable

4. Slide 4 Minimum Processing Time For DL traffic, the MS requires a minimum amount of time to decode a burst before transmitting acknowledgement information. In these slides, we use a value of 3 subframes. Receive Packet Transmit Acknowledgement Information Minimum Processing Time

5. Slide 5 Minimum Scheduling Time For DL traffic, the BS requires a minimum amount of time to process acknowledgement information before transmitting a subsequent packet or a HARQ retransmission. In these slides, we use a value of 2 subframes. Transmit Subsequent Packet or HARQ Retransmission Receive Acknowledgement Information Minimum Scheduling Time

6. Slide 6 Timing of Acknowledgement Information For each TDD ratio, for each subframe, the timing relationship between the reception of the packet and the transmission of acknowledgement information should be predefined. The example above represents the 5:3 TDD ratio. This relationship should exist for dynamic scheduling, semi-persistent scheduling, and persistent scheduling.

7. Slide 7 Overview of Synchronous HARQ With asymmetric TDD, the period associated with synchronous HARQ cannot be the same for all mobile stations or cannot be the same for all time In the following slides, we present two timing options for synchronous HARQ

8. Slide 8 Synchronous HARQ Option 1 A B C D E F A B C D E F

9. Slide 9 Synchronous HARQ Option 2 A B C D E F A B C D E F

10. Slide 10 VoIP Timing Diagram for Synchronous HARQ Option 1 VoIP Packet Arrival Rate (No Jitter) Transmission Opportunities

11. Slide 11 VoIP Timing Diagram for Synchronous HARQ Option 2 VoIP Packet Arrival Rate (No Jitter) Transmission Opportunities

12. Slide 12 Tradeoffs Advantages of Option 1 - More straightforward scheduler implementation - DRX cycles are periodic - Lower minimum HARQ timing Disadvantages of Option 1 - HARQ timing is not consistent for all assignments Advantages of Option 2 - Lower average HARQ timing - HARQ timing is consistent for all assignments Disadvantages for Option 2 - Less straightforward scheduler implementation - DRX cycles are not periodic - Small time difference between jitter free VoIP packet arrival rate and transmission opportunity

13. Slide 13 Synchronous HARQ Option 1A DownlinkUplink In the example above, for a TDD ratio of 5:3, persistent scheduling can only be initiated in subframes 0-3. In sub-frame 4, persistent scheduling is prohibited, so dynamic scheduling or semi-persistent scheduling must be used. To simplify operation, we could impose a restriction that persistent scheduling (synchronous HARQ) can only be used when the frame structure allows the time between retransmissions to be 5 msec. In other cases, dynamic scheduling or semi-persistent scheduling must be used.

14. Slide 14 Open Issues Comparing persistent scheduling (synchronous HARQ) to semi-persistent scheduling, there are two open issues: - In synchronous HARQ, we need to predefine the first HARQ transmission or define a start of packet indication. - In synchronous HARQ, holes in the time-frequency space are created due to HARQ early termination. We need to define an efficient mechanism to fill these holes. For example, some mobile stations are assigned fixed resources for synchronous HARQ, while other mobile stations are assigned dynamic resource for synchronous HARQ (resource adaptive synchronous HARQ).

15. Slide 15 Proposed Text Insert the following text into the Medium Access Control Sub-Layer (i.e. Chapter 10 in IEEE 80216m-08_003r1.pdf): ------------------------------- Text Start --------------------------------------------------- 10.1 Timing of Acknowledgement Information For each TDD ratio, for each subframe, the timing relationship between the reception of the packet and the transmission of acknowledgement information shall be pre-defined in the standard with a minimum value of 3 subframes (i.e. if the traffic occurs in sub-frame N, then acknowledgement information shall be transmitted no earlier than sub-frame N+4).. 10.2 Synchronous HARQ For synchronous HARQ, the period of the allocation shall be an integer number of radio frames.