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: [Improved Low Energy Mechanism based on 4e MAC_WSNIRI] Date Submitted: [9 November, 2011] Source: [Yang Yang1, Xiang Wang1, Heqing Huang1, Jie Shen1, Tao Xing1,2, Haitao Liu1] Company [Wuxi SensingNet Industrialization Research Institute1 , SIMIT2] 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 mechanism based on 4e MAC 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 Mechanism based on 4e MAC 09-Nov-2011

3. Outline • Characteristic of 4k network • What MAC Mechanism We Should Provide • Why Asynchronous • Low Energy Mode in 4e • Proposed Low Energy MAC for 4k • Summary

4. 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 • power consumption are the major design requirement

5. What MAC Mechanism We Should Provide • some analysis of synchronous network • higher transmission successful rate • but should consider power consumption lower limitation • need periodically listen for beacon or exchange frames for synchronization consider tradeoff between synchronization accuracy and power consumption • need prior time slot allocation processing • pre-allocation slots dynamic consideration • frames exchange to reserve slots more transmission consumption • design goal: minimize active time, minimize overhead • suggest to provide asynchronous mechanism in 4k when the network consumption is very strict

6. Why Asynchronous • asynchronous MAC • advantage: can reach very low power consumption • disadvantage: transmission may conflict • for characteristic of 4k network • maybe we have hidden terminal problem, near-far problem… but as the daily scheduled data transmission requirement is very low, the conflict probability will be very small, even though transmission failed, consumption of retransmission will not be very high • 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 the lowest active duty, transmission of end point will hard to be interrupted or make interference to other coexisting networks

7. Low Energy Mode in 4e (1) • Coordinated Sampled Listening (CSL) • receiver periodically performs channel sampling for radio traffic • sender transmits wakeup frame sequence prior to payload frame

8. Low Energy Mode in 4e (2) • 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

9. Low Energy Mode in 4e (3) • 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

10. Proposed Low Energy MAC for 4k (1) • based on non-beacon mechanism in 15.4 • end point • listen the channel periodically, other time keep sleeping • if has data to transmit, send frame by using CSMA/CA • without receiving Ack, retransmit the frame • collector • main powered, keep listening for the channel • if coordinator has unicast frame to send, after receiving frame from the corresponding end point, send the frame as Ack for the frame

11. Proposed Low Energy MAC for 4k (2) • when collector has high QoS lever frame or emergency frame need to send to endpoint, collector need to wakeup end point • end point • listen the channel periodically, for being available to be woke up by collector • collector • send wakeup sequence • {wakeup frame + interval of wakeup frames} • indicate the unicast/broadcast type of the next frame in wakeup frame

12. Proposed Low Energy MAC for 4k (3) • if the high QoS level data or emergency data is unicast • destination address of wakeup frame is the address of the corresponding end point • on receipt of wakeup frame, end point send data request frame • on receipt of data request frame, collector stop sending wakeup sequence, and send corresponding data frame immediately

13. Proposed Low Energy MAC for 4k (4) • if the high QoS level data or emergency data is broadcast or multicast • destination address of wakeup frame is the broadcast address, • on receipt of wakeup frame, end point send data request frame, then turn on RX at the designated time for receiving data from collector • on receipt of data request frames from all the corresponding end points, collector stop sending wakeup sequence, and send corresponding data frame at the designated time

14. Proposed Low Energy MAC for 4k (5) • 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

15. Summary • focus on the characteristic of 4k • analyze advantages and disadvantages of synchronous network and asynchronous network, suggest to provide asynchronous mechanism as 4k MAC consideration • analyze the low energy mode in 4e • for unicast normal data, keep the lowest end point active duration • supply improved wakeup mechanism, to support high QoS level frame or emergency frame communication • support star topology • give the message chart of proposed MAC • corresponding modification of MAC • welcome to be improved by merging with other proposals or further discussion

16. Thank you!