1. Submission Title: [channel dependent initial backoff of CSMA]
Project: IEEE P 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: ,
Abstract: [ Channel dependent multiple channel access method of a to improve throughput and save power consumption]
Purpose: [Opportunistic channel access]
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.
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2. Channel dependent initial backoff of CSMA
Bin Zhen, Huan-Bang Li, and Ryuji Kohno National Institute of Information and Communications Technology (NiCT)
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3. 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
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4. 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
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5. Channel quality information
Channel quality evaluation parameters
IEEE 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
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6. 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
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7. 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]
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8. 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
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9. 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
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