Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Non-persistent CSMAMechanism] Date Submitted: [Nov. 2006 ] 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:[86-10-82882552], E-Mail:[liupei@hisilicon.com, liangli@vinnotech.com] Re: [This document is an updated version of IEEE 802. 15-06-0463-01-004c] 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 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. 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 IEEE802.15.4-2006 MAC, which may operate in either of two topologies: the star topology or the peer-to-peer topology. • The network throughput is a important evaluation for the performance of CSMA/CA. • In IEEE802.15.4-2006, the throughput is derived from CSMA/CA mechanism of IEEE802.11 Standard 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 802.11. • Only the slotted CSMA/CA is employed in 802.11, 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 throughputarequite high. Pei Liu, Hisilicon

4. Definition of Networking Throughput • 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. Where Tpis thetime to successfully transmit payload bits in the investigated cycle, Tvis the period between two successful packet transmissions, shown as the CAP channel model. Pei Liu, Hisilicon

5. Promoting 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. Pei Liu, Hisilicon

6. Communication Model on one Channel Communication Model in one Channel • Acquire the average idle time in communications, and average collision times between successful communications in consideration of timeout. • CAP is an typical linear Markov process with periodic feature with the following reasons. In IEEE 802.15.4CSMA/CA procedure，a device should sense channel before transmitting data. As the channel is idle, device transmit data on this channel. Or, device may back off basing on the backoff algorithm and sense channel again. However, each device and each time of sensing channel are independent. Pei Liu, Hisilicon

7. confirm the time parameters calculate the throughput calculate average collision times in a cycle calculate the cycle calculate the throughput Calculation Throughput • 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. • Calculate the throughput based on the CAP model and parameters. Pei Liu, Hisilicon

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

9. Same Procedure for non-persistent CSMA/CA and the original CSMA/CA UnSlotted CSMA/CA Algorithm Pei Liu, Hisilicon

10. Same protocol, Primitives and Parameters for non-persistent CSMA/CA and Original CSMA/CA • The Non-persistent CSMA/CA is one proposed procedure instead of the original CSMA/CA in 15.4-2006 std. The same protocol is applied too. In other word, the proposed non-persistent CSMA/CA don’t change the protocol. • Therefore, all of primitives, parameters and conditions strictly pursue the ones in the CSMA/CA algorithm in IEEE802.15.4. • So it is compatible with 15.4-2006. Pei Liu, Hisilicon

11. Example of the Throughput simulation Within CAP • 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. Pei Liu, Hisilicon

12. Example of the Throughput simulation Within CAP The L is the number of payload slots within CAP Pei Liu, Hisilicon

13. The Features of Non-persistent CSMA/CA • Supplying a much simpler and more accurate analyzing method for CAP in WPAN than the current 15.4 CSMA/CA • it is compatible with original CSAM/CA in 15.4-2006 with • having the same procedure • having the same protocol. • having the same primitives, parameters and conditions Pei Liu, Hisilicon