1. Analysis of BR preamble selection strategies in 5-step BR procedure IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C80216m-10_1249r1 Date Submitted: 2010-9-13 Source: Shao-Cheng Wang, Xiangying Yang shaocheng.wang@intel.com Intel * http://standards.ieee.org/faqs/affiliationFAQ.html Venue: IEEE Session#69, St. Petersburg, Russia. Re: IEEE 802.16-10/0045, “IEEE 802.16 Working Group Sponsor Ballot”, on P802.16m/D8 Base Contribution: This is base contribution. Purpose: To be discussed and adopted by TGm for 802.16m SB. 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 802.1 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. Introduction In D8 draft, for 5-step BR procedure, how the AMS selects the BR preamble among 24 BR preamble indices is undefined. In this analysis, we compare two strategies: 1) all- random strategy 2) semi-random strategy. We show that there is significant saving in collision probability by using the semi-random strategy compared to the all-random strategy. Therefore, we propose to add “should select randomly” language to clarify the undefined selection procedure but leave room for any optimization to implementation.

3. Random strategy All AMS randomly select from 24 preambles Collision probability: (similar to the “birthday problem”)

4. Semi-random optimization strategy For initial selections, AMS selects randomly If the previous BR is successful, AMS will re-use the same selection for following trial (within some timeout etc)

5. P-collision comparison There is significant saving in collision probability by using the semi- random strategy compared to the all-random strategy Note: the more MS use semi-random, the more savings in collision probability if some MS use semi-random and some MS use real random selection, there is no negative impact on any one

6. Conclusion In general, AMS selects BR preamble randomly among 24 BR preamble indices. But we show that there is significant saving in collision probability by using the semi-random strategy compared to the all-random strategy. Therefore, we propose to add “should select randomly” language to clarify the undefined selection procedure but leave room for any optimization to implementation. In the regular 5-step random access BR procedure, an AMS shall send a BR preamble sequence only. The AMS should select the BR preamble randomly among 24 BR preamble indices.