Submission Title: [channel dependent initial backoff of CSMA] Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [channel dependent initial backoff of CSMA] Date Submitted: [November, 2005] Source: [Bin Zhen, Huan-Bang Li, Ryuji Kohno, Company: National Institute of Information and Communications Technology ] Contact: Bin Zhen Voice:+81 46 847 5445, E-Mail: zhen.bin@nict.go.jp] Abstract: [ Channel dependent multiple channel access method of 802.15.4a to improve throughput and save power consumption] Purpose: [Opportunistic channel access] Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15. TG4a

Channel dependent initial backoff of CSMA Bin Zhen, Huan-Bang Li, and Ryuji Kohno National Institute of Information and Communications Technology (NiCT) TG4a

Motivations Time varying wireless channel Different users experience peaks in their channel quality at different times Dense distribution of sensor nodes Multi-user diversity to maximize system capacity P. Knopp and P.A. Humblet, “Information capacity and power control in single-use multiuser communications,” ICC, 1995 Not only solve collision, but also transmit when user has favorable channel condition maximize system throughput minimize energy consumption TG4a

Contention in 15.4a Burst traffic An event is sensed and reported by more than one sensors Coordinator broadcasts pending data to more than one nodes. All of them contend the channel All traffic can only occur during active period. 15.4a targets simple UWB sensor which is of limited power and computing resource Limited candidate random set and simple algorithm Channel quality dependent multiple access Add a new random dimension Give node in favorable channel more transmission probabilities TG4a

Channel quality information Channel quality evaluation parameters IEEE 802.15.4 has defined Link Quality Indicator Received energy, SNR, or a combination of them BER, RSSI, noise measurements, interference margin Channel quality sources Beacon from coordinator Coordinator broadcast beacon periodically for device to evaluate channel quality Data exchange between nodes TG4a

Channel dependent initial backoff Initial backoff of CSMA is used to reduce collision in beacon-enabled network Total randomly from 0 to 2BE-1 Map channel state to initial backoff of CSMA initial backoff = channel dependent part + random part Initial backoff τ=f(γ) τmax τ1 Poor channel γ1 Channel state TG4a

Suggested parameters The default value of macMinBE is 3 when BLE is not set. Channel dependent initial CSMA Channel dependent backoff: [0~3] Random backoff: [0~4] TG4a

Performance Total 20 nodes with BERs from 0.1% to 1%. Random initial backoff Average BER= 0.59% Channel dependent initial backoff average BER= 0.35% Total 20 nodes with BERs from 0.1% to 1%. Randomly, 4 of them become active in a round TG4a

Conclusions Channel dependent carrier sense initial backoff Channel state evaluation before carrier sensing Channel dependent backoff + random backoff Fully backward compactable with 15.4 MAC Nodes in unfavorable channel wait for channel to become good Time sensitive traffics are in GTS Benefits High throughput and low power consumption Ride on the peak of channel TG4a