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

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ Non-Persistent CSMA Mechanism ] Date Submitted: [Nov. 2006 ] Source: [Pei Liu, Liang Li ] Company: [Hisilicom Technology Co. Ltd, Vinno Technologies Inc. ]

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

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  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: [ IEEE 802.15.4c ] 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 performance of CSMA/CA is mainly evaluated by the system throughput. • At present, 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. 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. Pei Liu, Hisilicon

  5. Obtainthe 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 The Non-persistent CSMA/CA Algorithm Procedure of np-CSMA/CA Channel model （CAP） 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. Pei Liu, Hisilicon

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

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

  10. 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. Pei Liu, Hisilicon

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