1. Submission Title: [Non-persistent CSMA Mechanism]
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Non-persistent CSMA Mechanism]
Date Submitted: [Nov ]
Source: [Pei Liu, Liang Li ] Company: [Hisilicom Technology Co. Ltd, Vinno Technologies Inc. ]
Address: [Nan Tian Bld., No.10 Xinxi. Rd Shang-Di Information Industry Base, Hai-Dain District, Beijing,China ]
Voice:[ ],
Re: [ IEEE c ]
Abstract: [Description the upgraded MAC issues on Chinese WPAN Standard Draft]
Purpose: [To encourage discussion.]
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
Submission
Pei Liu, Hisilicon

2. The CSMA/CA Operation Procedure in IEEE 802.15.4-2006 MAC
The CSMA/CA algorithm is used within CAP in IEEE MAC, which may operate in either of two topologies: the star topology or the peer-to-peer topology.
The performance of CSMA/CA is mainly evaluated by the system throughput.
At present, the throughput is derived from CSMA/CA mechanism of IEEE Standard
Submission
Pei Liu, Hisilicon

3. Drawbacks of Current MAC Protocol
The CSMA/CA mechanism in WPAN is quite different from IEEE802.11:
The virtual carrier-sense mechanism, and the RTS（request-to-send ）/CTS（clear-to-send) are not employed in WPAN, because of the low data rate, short packets, and high ratio of packet header and control packets to payload data for a single node, compared to
Only the slotted CSMA/CA is employed in , but in WPAN, slotted and unslotted CSMA/CA may be employed, depending on the network modes.
Therefore, a large error may result from calculation of success CCA probability and throughput. Furthermore, the computational complexity of success CCA probability and throughput are quite high.
Submission
Pei Liu, Hisilicon

4. The Basis of Non-persistent CSMA/CA
The CSMA/CA algorithm in WPAN is similar to non-persistent CSMA. It’s feasible to apply np-CSMA for analyzing the WPAN CSMA/CA processing and confirming the throughput on WPAN.
The throughput is defined as the proportion of time to successfully transmit payload bits in the investigated cycle, the period between two successful packet transmissions.
Submission
Pei Liu, Hisilicon

5. The Non-persistent CSMA/CA Algorithm
Obtain the parameters: collision transmission time, success transmission time, idle time after success and collision, and the CCA time
Calculate the average collision times
in a cycle
Calculate the throughput
Procedure of np-CSMA/CA
Channel model
（CAP）
Submission
Pei Liu, Hisilicon

6. The Non-persistent CSMA/CA Algorithm
Steps:
Build up the Markov model for accessing channel. Calculate the possibility of accessing the channel (such as the ratio of successful CCA, the possibility of first CCA in back off period), and ones of two consecutive successful CCA.
Acquire the average idle time in communications, and average collision times between successful communications in consideration of timeout.
Calculate the throughput based on the CAP model and parameters.
Submission
Pei Liu, Hisilicon

7. The Non-persistent CSMA/CA Algorithm
The model of np-CSMA/CA
calculate the throughput
calculate the cycle
confirm the time parameters
calculate average collision times in a cycle
Submission
Pei Liu, Hisilicon

8. The Non-persistent CSMA/CA Algorithm
slotted
CSMA/CA
BE=mac
MinBE
NB=0,CW=2
Battery life
extension？
Locate backoff period boundary
Delay for random
(0~2BE -1) unit backoff periods
Perform CCA
Channel idle？
CW=2,NB=NB+1
BE=min(BE+1,
aMaxBE )
NB>
macMaxCSMABackoffs?
failure
CW=CW-1
CW=0?
success Y N
BE=min（2,mac
MinBE)
(step1)
(step5）
(step4)
(step3)
(step2)
Slotted CSMA/CA algorithm
Submission
Pei Liu, Hisilicon

9. The Non-persistent CSMA/CA Algorithm
Unslotted CSMA/CA algorithm
Submission
Pei Liu, Hisilicon

10. Simulation Results of the Throughput Within CAP under CSMA Method
Supposed:
One co-ordinator and end devices with a star topology
The number of devices is known, and
The throughput is defined as
Where Tp is the time to successfully transmit payload bits in the investigated cycle, Tv is the period between two successful packet transmissions, shown as the CAP channel model.
Other conditions strictly pursue the std CSMA/CA in
Submission
Pei Liu, Hisilicon

11. Simulation Results of the Throughput Within CAP under CSMA Method
The details of the simulation conditions:
Other parameters use the default values defined for 2.4GHz frequency channels such as 3, 5 and 4 for macMinBE, aMaxBE and macMaxCSMABackoff, respectively.
packet payload
55 or 115 bytes
overhead
15 bytes
ACK length
11 bytes
Channel bit rate
250 kbps
Backoff unit
10 bytes
CCA time
4 bytes
Submission
Pei Liu, Hisilicon

12. Simulation Results of the Throughput Within CAP under CSMA Method
Submission
Pei Liu, Hisilicon

13. The Features of Non-persistent CSMA/CA
Large reduction of the complexity of CAP analysis
Much accuracy CCA assessing with low complexity, based on the new channel model
Much accuracy evaluation of throughput in consideration of timeout.
Submission
Pei Liu, Hisilicon