k Betty Zhao etc., Huawei Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Acknowledgement Scheme for 4k Fragmentation Date Submitted: Sep. 16, 2011 Source: Betty Zhao, Bin Zhen, Zhihao Xing, Yanping Jiang, Yongjun Liu, Yong Xu, Houcheng Tang Company: Huawei Technologies Co., Ltd. Voice: , Re: [ TG4k Call for Proposals] Abstract: An acknowledgement scheme for 4k fragmentation Purpose: Response to TG4k Call for Proposals Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P Slide 1 Sep 2011

Betty Zhao etc., Huawei k Why fragment Necessity and benefits of fragmentation in 4k have been well-stated in doc and Lower data rate (i.e. longer air time ), plus dramatically changing channel environment, make reliable transmissions more difficult. MAC frame fragmentation can: - Reduce air time of each PPDU - Less vulnerable to changing channel conditions - Less vulnerable to interference, better coexistence performance in the shared spectrum Sep 2011 Slide 2

Betty Zhao etc., Huawei k Comparison of 3 ACK schemes Figures are from doc Sep 2011 Slide 3

Betty Zhao etc., Huawei k Comparison of 3 ACK schemes Progressive acknowledgement - Strength: reliable, may survive in bad environment, support immediate retransmission - Shortage: time-consuming, bandwidth-consuming Aggregated acknowledgement - Strength: easy to implement (general method), time-saving - Shortage: vulnerable to interference and channel conditions, may result in heavy retransmissions Hybrid acknowledgement - Strength: balance between efficiency and reliability, adaptive to environment - Shortage: need more configuration and processing Sep 2011 Slide 4

Betty Zhao etc., Huawei k Problems in Hybrid and Aggregated Acknowledgement What 4k has Star topology (> 1000) Sharing spectrum Sep 2011 Slide 5 Increased back-off time  for fragments transmission  for acknowledgement transmission with info of received fragments Channel Sensing / Back-off time FP 1 FP 2 FP 3 Channel Sensing / Back-off time EACK Channel Sensing / Back-off time FP 4 FP 5 FP 6 End-point Collector

Betty Zhao etc., Huawei k Problems in Hybrid and Aggregated Acknowledgement What 4k has Dramatically changing environments Sep 2011 Slide 6 Increased possibility of channel condition going bad during fragments transmission. End-point Collector Channel condition Lose FP 4 to 7 due to channel condition went bad FP1FP2FP3FP4FP5FP6FP7

Betty Zhao etc., Huawei k Proposed Solution A group of fragments are received correctly. - Collector sends 15.4 ACK to acknowledge that all the fragments are received correctly. Sep 2011 Slide 7 FP 1 FP 2 FP 3 ACK Channel Sensing FP 4 FP 5 FP 6 End-point Collector FP 7 FP 8 FP 9 FP 10 A group of fragments All the fragments are received correctly. Channel Sensing

Betty Zhao etc., Huawei k Proposed Solution A group of fragments are received, but there are failed fragments. - Collector sends a sequence of NACK frames, and prepares EACK (including security filtering) at the same time. - Collector sends EACK at the end of the NACK sequence whenever it’s ready. - After EACK received, end-point starts to transmit next group of fragments. Sep 2011 Slide 8 FP 1 FP 2 FP 3 NA CK Channel Sensing FP 4 FP 5 FP 2 End-point Collector NA CK EACK FP 6 FP 7 FP 8 FP 9 A group of fragments NACK sequence Contain info of failed fragments There’re failed fragments in the received group. Channel Sensing

Betty Zhao etc., Huawei k Proposed Solution A group of fragments are received, but the channel condition was not good enough. - Collector measures RSSI/LQI of each received fragment. After reception completed, if the values are under certain threshold, - Collector sends a sequence of NACK frames, and prepares EACK with channel-switching info at the same time. - Collector sends EACK at the end of the NACK sequence whenever it’s ready. - After EACK received, end-point starts to transmit next group of fragments on the new channel according to EACK. Sep 2011 Slide 9

k Betty Zhao etc., Huawei Sep 2011 FP 1 FP 2 FP 3 NA CK Channel Sensing FP 4 FP 5 FP 6 End-point Collector NA CK EACK FP 7 FP 8 FP 9 FP 10 A group of fragments NACK sequence Contain the new channel number Channel condition is not good according to RSSI/LQI values. Measure RSSI/LQI Channel 1 Channel 2 Channel Sensing Collector and end-point switch channel together. Slide 10 Questions in this case: If channel condition goes bad quickly, NACK sequence and EACK may not be received. Should EACK be broadcast to inform other end-points the channel- switching, or any other methods to do that?

Betty Zhao etc., Huawei k EACK frame format Sep 2011 Slide 11 Channel Switching IE Fragment IEOther IEs

Betty Zhao etc., Huawei k Benefits Guarantee contention-free access of EACK -> Increase fragments transmission efficiency Switch channel in time when channel condition goes bad -> Increase transmission reliability in the dramatically changing environment and sharing spectrum. No new MAC frames added except NACK Compatible with existing MAC mechanism Furthermore, - number of fragments of next group - data rate of next fragment group - other parameters … may be adjusted as needed during fragments transmission. Sep 2011 Slide 12

Betty Zhao etc., Huawei k Summary EACK carries status of received fragments, channel-switching info and other parameters as needed. Use NACK sequence to guarantee EACK received within certain time Adjust transmission parameters (e.g. channel) when necessary Fit for Aggregated acknowledgement and Hybrid acknowledgement For further discussion: How to inform other end-points efficiently when channel is switched Subfields of fragment frame and EACK Numbering method of each fragment Sep 2011 Slide 13

Betty Zhao etc., Huawei k Thank you! Sep 2011 Slide 14 Questions?