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: [Low Energy MAC Proposal for TG4k_WSNIRI] Date Submitted: [6 September, 2011] Source: [Yang Yang1, Xiang Wang1, Heqing Huang1, Jie Shen1, Tao Xing1,2, Haitao Liu1, Betty Zhao3] Company [Wuxi SensingNet Industrialization Research Institute1 , SIMIT2, Huawei3] Address [No.767, Jinzhong Rd, Shanghai, China] Voice:[+86-021-52188899-635], FAX: [+86-021-52182002] E- Mail:[youcyyang@gmail.com] Re: [Call for Proposals, DCN: 15-11-0147-02, 10 May, 2011] Abstract: [This document proposed low energy MAC mechanism to support implementation of 802.15.4k.] Purpose: [Proposal for consideration of inclusion into 802.15.4k.] 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.

2. Low Energy MAC Proposal for TG4k 12-Sep-2011

3. Outline • Overall goals and requirements • Characteristic of 4k network • Basic MAC Mechanism Discuss • Why Asynchronous • Low Energy Mode in 4e • Proposed Low Energy MAC for 4k • Further Consideration • Summary

4. Overall Goals and Requirements • addresses critical infrastructure monitoring applications • amendment to IEEE 802.15.4, the amendment supports: • operation in any of the regionally available licensed, license exempt, and special purpose frequency bands • simultaneous operation for at least 8 co-located orthogonal networks • application data rate of less than 40 kbits per second • propagation path loss of at least 120 dB • >1000 endpointspermains powered infrastructure • asymmetric application data flow • extreme difference in capabilities and performance between endpoint devices and coordinating devices (collectors) • coordinator may support all standardized modulations (MCS) and data rates • coordinator may be required to support antenna diversity or antenna beam steering • end point must be able to conserve energy • reliable operation in dramatically changing environments (no control over environment) • mechanisms that enable coexistence with other systems in the same band(s) • addresses critical infrastructure monitoring applications • amendment to IEEE 802.15.4, the amendment supports: • operation in any of the regionally available licensed, license exempt, and special purpose frequency bands • simultaneous operation for at least 8 co-located orthogonal networks • application data rate of less than 40 kbits per second • propagation path loss of at least 120 dB • >1000 endpoints per mains powered infrastructure • asymmetric application data flow • extreme difference in capabilities and performance between endpoint devices and coordinating devices (collectors) • coordinator may support all standardized modulations (MCS) and data rates • coordinator may be required to support antenna diversity or antenna beam steering • end point must be able to conserve energy • reliable operation in dramatically changing environments (no control over environment) • mechanisms that enable coexistence with other systems in the same band(s)

5. Characteristic of 4k network • 15-11-0359-04-004k-technical-guidance-document • point to multi-thousands of points communications • asymmetric link • more data from end-point to coordinator • for end point, don’t communicate directly with each other, need low energy operation necessary for multi-year battery life (>20 year) • for coordinator, mains powered • enable the collection of scheduled and event data • small, infrequent messages • tolerant of data latency • as data duration may be very long, channel condition may be varying during packet transmission

6. Basic MAC Mechanism Discuss • synchronous or asynchronous? • synchronous • advantages: higher transmission successful rate • disadvantages: have power consumption lower limit • need periodically listen for beacon or exchange frames for synchronization • need tradeoff between synchronization accuracy and power consumption • prefer asynchronous as the basic MAC consideration

7. Why Asynchronous • asynchronous MAC • advantage: can reach very low power consumption • disadvantage: transmission may conflict • for characteristic of 4k network • daily scheduled data transmission requirement is very low, so the conflict probability will be very small • end point can send event data immediately, latency of event data will be lower than TDMA • varying and lossy environment will make the network dynamic, in asynchronous network, end points join or leave will be very easily, with the lowest interruption to the existing communications, and don’t need to coordinate the slot distribution • keep low active duty, transmission of end point will hard to be interrupted or make interference to other coexisting networks

8. Low energy mode in 4e • Coordinated Sampled Listening (CSL) • receiver periodically performs channel sampling for radio traffic • sender transmits wakeup frame sequence prior to payload frame • Receiver Initiated Transmission (RIT) • receiver periodically broadcasts datareq frames and listen for a short amount of time for incoming transmissions every macRitPeriod • sender waits until receiving datareq frame from receiver then immediately transmit payload frame • wake-up mechanism shall be improved • in 4k applications, frame send by coordinator mainly should be broadcast frame, like configuration frame, RIT mode not support broadcast • if coordinator use CSL mode directly, each time coordinator want to send a frame, even it just want to wake up one end point, during the wake up duration, all nodes in network can’t communicate

9. Proposed Low Energy MAC for 4k (1) • based on non-beacon mechanism in 15.4 • coordinator main powered, keep listening for the channel • end point keep sleeping, if end point has data to transmit, send frame by using CSMA/CA, and waiting for Ack. Without receiving Ack, end point will retransmit the frame • if coordinator has unicast frame to send, after received frame from the corresponding end point, send the frame as Ack for the frame

10. Proposed Low Energy MAC for 4k (2) • end point listen for channel each macListenInterval, with the duration macListenDuration, for being available to be woke up by coordinator • although end point will be active periodically, different from TDMA mechanism, macListenInterval will not be limited by synchronization accuracy • if coordinator want to send a broadcast or multicast frame, send wakeup sequence, make an appointment about the frame transmission time • if coordinator want to send an unicast frame (QoS level > macQoSThreshold), send wakeup sequence until received Ack from the corresponding end point, then send frame

11. Proposed Low Energy MAC for 4k (3) • support topology: star topology • 4k applications need point to multi-thousand points communications, and end point don’t communicate directly with each other • star topology may be the best choice • can support dynamic network • end point join or leave the network will be easy

12. Further Consideration • corresponding modification of MAC • primitive modification • MAC frame format modification • add new MAC PIB attributes

13. Summary • focus on the characteristic and requirements of 4k, proposed a low energy MAC • analyze advantages and disadvantages of synchronous network and asynchronous network • analyze the low energy mode in 4e • for unicast normal data, keep the lowest end point active duration • supply improved wakeup mechanism, to support broadcast or high QoS level frame communication • support star topology • concluded further consideration points • welcome to be improved by merging with other proposals or further discussion

14. Thank you!