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Enhancement to 802.15.4-2006 with Adaptive Frequency Diversity

This document proposes enhancements to the IEEE 802.15.4-2006 MAC Layer with Adaptive Frequency Diversity for reliability and deterministic aware applications.

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Enhancement to 802.15.4-2006 with Adaptive Frequency Diversity

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Enhancement to 802.15.4-2006 with Adaptive Frequency Diversity] Date Submitted: [03 July, 2008] Source: [Qin Wang / Peng Zeng], Company [University of Science & Technology Beijing/ Shenyang Institute of Automation-Chinese Academy of Sciences /] Address [ 30 Xueyuan Road, Beijing 100083, China] Phone: [+8610-62334781], FAX: [+8610-82372028 ], E-Mail: [ wangqin@ies.ustb.edu.cn] Re: [IEEE P802.15.4e Call For proposal] Abstract: [This document proposes an enhancement to IEEE 802.15.4-2006 MAC Layer with Adaptive Frequency Diversity for the Reliability and Deterministic Aware Applications] Purpose: [This document is a response to Item a) better support the industrial markets in IEEE P802.15.SG4e Call for Application on 14 November, 2007] 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. IEEE 802.15-08-0505-00-004e

  2. Enhancement to 802.15.4-2006 with Adaptive Frequency Diversity Qin Wang1) , Peng Zeng2) 1)University of Science & Technology Beijing 2) Shenyang Institute of Automation-Chinese Academy of Sciences 03 July 2008 wangqin@ies.ustb.edu.cn IEEE 802.15-08-0505-00-004e

  3. Components. • Mesh+Star topology • Extended superframe • CSMA/TDMA+FDMA during active period • TDMA+FH/AFD during scheduled period • Two-stage allocation IEEE 802.15-08-0505-00-004e

  4. TDMA+FH in the Inter cluster period and manger period scheduled period CH1 CH2 CH3 CH4 CH5 CH6 CH7 Intra-cluster Sleeping Collect data from SNs Inter cluster & Manager period sleeping TDMA+ FDMA+AFD * retry * retry R2=>R1 *=>R1 R1=>R3 R3 =>R1 R2 =>R1 R1=>R2 The Inter cluster period and manager period are scheduled by the system manager. IEEE 802.15-08-0505-00-004e

  5. E-Superframe MAC • Note: Difference between AFD with Frequency Hopping (FH) • FH: Change communication channel according to a scheduled frequency hopping pattern, regardless how the real channel condition is. • AFD: Change communication channel according to the real channel condition. In another word, bad channel condition, which can be measured with packet drop rate or resend time, triggers the operation of changing channel. IEEE 802.15-08-0505-00-004e

  6. Successful transmission rate over time (7 hours) IEEE 802.15-08-0505-00-004e

  7. Successful transmission rate over time (3 days) IEEE 802.15-08-0505-00-004e

  8. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) Measurement Denote the interval of channel blocked in number of slot as ICB Probability of ICB=1,2,3,4,5 vs. Packet loss rate in 0-30% IEEE 802.15-08-0505-00-004e

  9. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) Measurement Denote the interval of channel blocked in number of slot as ICB Probability of ICB=1,2,3,4,5, >5 vs. Packet loss rate IEEE 802.15-08-0505-00-004e

  10. a b TDMA+FDMA+AFD in the Intra-cluster periods (cont.) Analysis: • considering two kinds of slot assignment: • a: two continuous transmission opportunities • b: two discontinuous transmission opportunities • define: • A: transmission failure in the first opportunity; • B: transmission failure in the second opportunity; • For a certain link on a fix channel , if a and b all fail, • P(a) = P(B|A)= P(AB)/P(A) • P(b) = (P(A)+P(B))/2 • In a similar way, for a, b • Define: • C: transmitting fail in the first channel, • D: transmitting fail in the second channel • For a certain link, if a and b all fail, • P(a) = P(CD)/P(C) • P(b) = (P(C)+P(D))/2 • conclusion • If P(a)<P(b), • for a fixed channel, retransmitting immediately will bring high link reliability than retrying later. • For a fixed link, changing channel when channel failed brings high reliability than fixed channel changing. IEEE 802.15-08-0505-00-004e

  11. TDMA+FDMA+AFD in the Intr-cluster periods Scheduled period of a E-superframe Scheduled period of a E-superframe CH Intra Cluster_1 inter cluster & manager period Intra Cluster_1 inter cluster & manager period sleeping 1 Intra Cluster_2 inter cluster & manager period sleeping Intra Cluster_2 inter cluster & manager period 2 Intra Cluster_3 inter cluster & manager period sleeping Intra Cluster_3 inter cluster & manager period 3 Intra Cluster_4 inter cluster & manager period sleeping Intra Cluster_4 inter cluster & manager period 4 sleeping Intra Cluster_5 inter cluster & manager period Intra Cluster_5 inter cluster & manager period 5 Intra Cluster_6 inter cluster & manager period sleeping Intra Cluster_6 inter cluster & manager period 6 Intra Cluster_7 inter cluster & manager period sleeping Intra Cluster_7 inter cluster & manager period 7 Intra Cluster_8 inter cluster & manager period sleeping Intra Cluster_8 inter cluster & manager period 1 • Channel allocation: (1) choose a channel from {ch1..ch8} as CH_i; (2) choose a channel from {ch9..ch16} as CH_j, while init or re-init. • Criteria: (1) haven’t been chosen by neighbors; (2) with best SNR for communication • The channel used in the contention period could be different with CH_i and CH_j IEEE 802.15-08-0505-00-004e

  12. REQ REQ Rx Rx ACK ACK Rx Rx Rx Rx Rx Rx ACK ACK ACK ACK ACK ACK Tx Tx Tx Rx Rx Rx Tx Tx Tx Rx Rx Rx Rx Rx Tx Tx Rx Rx Content retry 2 TDMA+FDMA+AFD in the Intra-cluster periods (cont.) Communication intra cluster-i. Each slot have m minislot, m can be sent by system manager. In each minislot, a node can send a message and receive an ACK. With REQ, cluster head announce which communication is successful. Inter-cluster Retry period Inter-cluster Retry period CAP 1 2 Ri Rx Rx Rx Rx ACK ACK ACK ACK N1 Tx Tx N2 Tx Tx N3 Tx N4 Tx Tx Rx N5 Tx Tx Contention period channel Invited retry 1st channel 2nd channel 1 IEEE 802.15-08-0505-00-004e

  13. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) Algorithm • A slot is divided into m mini-slots, m is set by system manager. A mini-slot is used to finish a communication. Thus, there are m communication opportunities in a slot. • The communication rules are as follows: • 1) Employ ch_i to communicate in the first mini-slot • 2) if the first communication fails, employ ch_i to retry • 3) Form the third mini-slot to the mth mini-slot, employ ch_i to retry, or retry in a defined alternative channel according to configuration. • If the communication failed in the m mini-slots, the device will sleep until the first intra-cluster retry slot. While waking up, the device changes to the defined alternative channel, and listens to the broadcast from the cluster-head. The broadcast from cluster-head has the status of the communications on each link, success or fail. For the link on which communication failed, a timeslot is assigned in the broadcast message. • For the devices who didn’t receive ACK, if cluster-head has received the data but the device lost ACK, the device will know the its package has been received successfully, thus, will not retry again. Otherwise, the device transmits packets in the assigned time slot. • After the device retry, it changes back to the former channel. • If the device retry failed, it can retry during the next CAP. • If the packet loss rate of a link is too high during a period, cluster head will notice the device to change to a new channel in the manager period. IEEE 802.15-08-0505-00-004e

  14. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) IEEE 802.15-08-0505-00-004e

  15. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) With immediate retry, but without channel diversity. Five cluster, about 70 nodes in a cluster. <15% packet loss rate. IEEE 802.15-08-0505-00-004e

  16. TDMA+FDMA+AFD in the Intra-cluster periods (cont.) With immediate retry, but with channel diversity. Five cluster, about 70 nodes in a cluster. <15% packet loss rate. IEEE 802.15-08-0505-00-004e

  17. Summary • Besides packet loss rate, the interval of channel blocked in number of slot is very important metrics for increasing reliability of communication • Immediate retry in MAC layer is a efficient way to increase reliability. • Frequency diversity is a effective way to increase reliability, while it is secondary to immediate retry . IEEE 802.15-08-0505-00-004e

  18. Conclusion from 0503 & 0504 • Mesh+Star topology • Extended superframe • CSMA/TDMA+FDMA during active period • TDMA+FH/AFD during scheduled period • Two-stage allocation • AFD: immediate-retry, backup-channel IEEE 802.15-08-0505-00-004e

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