1. Bit selection and repetition IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: C80216m-08_1271 Date Submitted: 2008-10-30 Source: Soma Bandyopadhyay TATA Consultancy ServicesE-mail:Soma.bandyopadhyay@tcs.comSoma.bandyopadhyay@tcs.com Kiran Kuchi kkuchi@cewit.org.inkkuchi@cewit.org.in J Klutto Milleth klutto@cewit.org.inklutto@cewit.org.in CEWiT Venue: IEEE 802.16m-08/040 - Call for Comments and Contributions on Project 802.16m System Description Document (SDD) Base Contribution: This is the supported contribution for the comment uploaded as tgmsdd_Bandyopadhyay_Soma.cmtb. Purpose: To be discussed and adopted by TGm for the 802.16m SDD during the session #58 meeting in Dallas, USA 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.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. Background In 802.16, both synchronous and asynchronous mode of HARQ are supported. Downlink it supports asynchronous and uplink synchronous. It uses HARQ with soft combining (erroneously received packets are stored in buffer memory and later combined with the retransmitted packets). Set of coded bits transmitted in each retransmission can be varied provided they represent the same information bits, also the modulation scheme can be varied Based on the decision of synchronous and asynchronous mode of HARQ resource allocation parameter varies Important parameters are :  Allocation period  MCS

3. Motivation Who guides the resource-allocator to take the decision of synchronous and asynchronous HARQ  Drivers of synchronous and asynchronous HARQ Downlink supports asynchronous mode of HARQ  Adaptive and non-adaptive mode.  Variation of MCS /Constant MCS  Rate matching block works accordingly. Adaptive HARQ Mechanism: The intention of this proposal is to address the FFS of the section Adaptive HARQ of 11.13.2.3 of IEEE 802.16m- 08/003r5 SDD document

4. Proposal Downlink : Supports asynchronous mode of HARQ. Uplink : Supports synchronous mode of HARQ. Scheduler uses the traffic parameters of the incoming packet as determined by the admission control module. Incoming data packets are accumulated in the data-buffer, accumulation of certain amount of data, is termed as accumulated data length (al) (al < total buffer length). Based on its available bandwidth and link quality DL-transmitter determines the modulation and coding rate (MCS), and also determines the resources required to be mapped inside the physical layer. It determines the allocation period (AT), which is a function of buffer length, modulation and coding rate. AT (Allocation period) = f(al,MCS). AT gives the time duration while same resource allocation will be used by the physical layer. Data packet of fixed-size arrives at fixed time intervals does not require any variable MCS. Retransmission and HARQ ACK feedback time duration are also predictive and fixed in case of fixed size data packet, thus the non-adaptive HARQ becomes the best choice.Signaling overhead can be reduced by invoking A-synchronous HARQ as synchronous way in this case (considering as a special case of a-synchronous). It has been also assumed that link quality is not varying significantly in this case

5. Proposal

6. Proposal- Contd Data packets of variable size with variable data rate need the varying resource allocation every time for every new transmission and even for retransmission. So getting of HARQ-feedback and retransmission time will vary accordingly. Thus a-synchronous HARQ with adaptive HARQ i.e. having varying modulation and coding rate becomes the best choice in this case.

7. Proposal- Contd Non adaptive HARQ – Fixed packet size and predictive data Adaptive HARQ - Data packets of variable size with variable data rate need the varying resource allocation every time for every new transmission and even for retransmission. So getting of HARQ-feedback and retransmission time will vary accordingly. Thus a- synchronous HARQ with adaptive HARQ i.e. having varying modulation and coding rate becomes the best choice in this case.