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: [Versatile MAC for Body Area Network ] Date Submitted: [4 May, 2009] Source: [J.S Yoon, Gahng S. Ahn, Myung J Lee, Seong-soon Joo] Company [CUNY, ETRI] Address [140th St. and Convent Ave, New York, NY, USA ] Voice:[+1-212-650-7180], FAX: [], E-Mail:[jsyoon@ee.ccny.cuny.edu, gahn@ccny.cuny.edu, lee@ccny.cuny.edu , ssjoo@etri.re.kr] Re: [Versatile MAC for BAN proposal responding to TG6 Call for Proposals (15-08-0811-03-0006-tg6- call-proposals) ] Abstract: [This document describes a Versatile MAC that is being proposed to the TG6 group ] Purpose: [Discussion in 802.15.6 Task Group ] 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. <J.S.Yoon>, <CUNY>

2. Versatile MAC for Body Area Networks June S Yoon, Gahng S Ahn, Myung J Lee, Seong S. Joo CUNY, ETRI <J.S.Yoon>, <CUNY>

3. Outline • Motivation • Challenges • BAN MAC • Overview • Details of each period • AD, CAP, Beacon, DTS, ETS, CAP Extension • Energy saving • Prioritization • Performance • Summary <J.S.Yoon>, <CUNY>

4. Motivation To design a simple MAC protocol to support various QoS for Body Area Networks <J.S.Yoon>, <CUNY>

5. Design Challenges • QoS Assurance • High reliability and guaranteed latency requirement for real time data, especially vital data Need deterministic structure • Flexibility • Support various types (periodic, non-periodic, medical, entertainment…) of traffic, data rate and PHYs  Instantly adaptable to application’s requirements • Energy efficiency • Less energy consumption especially for implanted device Need efficient active/inactive scheduling <J.S.Yoon>, <CUNY>

6. Proposed BAN MAC Features • Versatile MAC • Best breed of Contention based and TDMA • Supports various (burst, periodic, continuous) types of traffic • Straightway reservation (Ad-CAP-Beacon) • Fast reservation and prompt adaption • Latency reduction for delay sensitive real time data • Emergency data transmit slot • Highly adaptable to abrupt emergency data • Support high QoS and reliability • Priority supported • Low energy consumption <J.S.Yoon>, <CUNY>

7. Versatile MAC Overviews <J.S.Yoon>, <CUNY>

8. BSF (BAN Superframe) • Ad (Advertisement) • Synch, interval, address • CAP • Reservation, Non-periodic data • Beacon • Synch, reservation status announcement • DTP (Data Transmit Period) • DTS (Data Transmit Slot) • Periodic data transmit by reservation • ETS (Emergency Data Transmit Slot) • Periodic data & Emergency data <J.S.Yoon>, <CUNY>

9. Details of each period <J.S.Yoon>, <CUNY>

10. Advertisement • The beginning of BSF (BAN Superframe) followed by contention access period • Ban Coordinator (BC) broadcasts it at the beginning of BSF and contains basic information such as • Synchronization • BC (Ban Coordinator) address • Ad Interval, length of periods • A newly joined node adjusts its clock, gets information on BC and BSF <J.S.Yoon>, <CUNY>

11. CAP • Contention access period • Backoff and carrier sense to avoid collision • Prioritized back-off and carrier sense to serve higher priority first • Data Transmission • Command frames for DTS reservation exchanged • Non-periodic data including alarm and periodic data failed to reserve DTS can be sent • BC collects all the DTS requests and allocate them according to their priorities and slot availability • Allocate first available slot based on the priority order to prevent DTS shortage • Lower priority slots may be preempted by higher priority data <J.S.Yoon>, <CUNY>

12. Beacon • BC Broadcasts beacon before DTP • Notifies sync, interval, length, DTS reservation status • All the nodes that reserved DTS should listen beacon every AI to check reservation status changes • Sequential Ad-CAP-Beacon enables straightway slot reservation and prompt accommodation to changes <J.S.Yoon>, <CUNY>

13. Comparison: Reservation delay (From data generation to slot assign confirm by beacon) Assume slot size and AI, BI are same (BO=6, SO=3, 128 slots) & reservation is done right away if data is generated during CAP • Proposed approach • Min: 1 slot (7.68ms) • Data generation at the end of CAP • Max: 129 slots (0.991s) • Data generation at the beginning of beacon • Beacon (1)+ AI (128) • 15.4 based approach • Min: 120 slots (0.922s) • Data generation at the end of CAP • CFP & Inactive(119) + Beacon(1) • Max: 248 slots (1.905s) • Data generation at the beginning of CFP • CFP & Inactive(119) + BI(128) + Beacon(1) Difference = 119 slot, 0.91s <J.S.Yoon>, <CUNY>

14. Data Transmit Period • TDMA Period for the latency-critical continuous and periodic data • DTS (Data Transmit Slot) • Nodes transmit data at the slot assigned by BC • ETS (Emergency Data Transmit slot) • Contention access period • If any, emergency data is transmitted at this slot • A node assigned to this slot performs carrier sense first so as to prevent collision with emergency alarm • Enables urgent transmission for abrupt Emergency alarm <J.S.Yoon>, <CUNY>

15. Comparison: Alarm delay (From alarm generation to transmit) Assume slot size and AI, BI(15.4) are same (BO=6, SO=3, 128 slots) and All CFP and DTP are occupied • Alarm delay decreases as the number of ETS slot increases, however, at the expense of increased delay (carrier sense time) of the ETS slot owners. <J.S.Yoon>, <CUNY>

16. Options • ECAP (CAP Extension) • The duration between the ends of DTP and AI • If power is not a concern for BC, it can stay awake and maintain CAP • All kinds of data can be transmitted including retransmission • Batch ACK • Ack at the last active slot for all data transmission in DTP • Delayed ACK • Ack for multiple-slot transmission from a same source <J.S.Yoon>, <CUNY>

17. Prioritization <J.S.Yoon>, <CUNY>

18. BAN Data Prioritization • Prioritization based on QoS (latency) requirement • Priority 0: Emergency reaction alarm • Emergency vital signs, Battery depletion, ... • Priority 1: Medical Continuous data • Latency critical data • E.g. EEG/ECG/EMG • Priority 2: Medical Routine data • Reliability critical but lesser latency requirement • E.g. Temperature, blood pressure • Priority 3 : Non-medical Continuous data • Video, audio • Priority 4 : Others • Priority classes are dictated by the applications <J.S.Yoon>, <CUNY>

19. Prioritized Transmit in DTP • Priority based allocation • Higher priority data served first in case of contention among different priority traffics • Emergency data transmission in ETS • Owner of the slot performs carrier sense before transmission • Alarms perform short random backoff and carrier sensewinner takes the slot, loser try again at the next ETS or CAP • T(Backoff+Carrier sense+TxAlarm) < T(Carrier senseOwner) <J.S.Yoon>, <CUNY>

20. Prioritized Transmit in CAP • Higher priority data access channel first •  Prioritized back-off • Prioritized Back-off exponent = Min. Back-off exponent-1 • Constant • Raises the probability that emergency alarm takes less back-off duration than others. • Prioritized carrier sense • Prioritized Carrier sense duration = Carrier sense duration x0.5 • Situation that normal and prioritized back-off starts at the same time with same duration, emergency alarm can captures channel first. <J.S.Yoon>, <CUNY>

21. Energy Saving • Coordinator • Goes into inactive If no activity is scheduled after CAP or DTP • Sensor (continuous data) • Once DTS reservation is done, the node stay inactive period except for beacon and its reserved transmit time • Sensor (routine data) • Wakeup only for report and transmit during CAP or CAP Extension whichever available first • Sensor (Alarm) • Wakeup only for report and transmit during CAP, CAP Extension or ETS whichever available first <J.S.Yoon>, <CUNY>

22. Summary of BAN MAC <J.S.Yoon>, <CUNY>

23. Summary • Versatile MAC • CAP: Contention period • DTP: TDMA period, Enables high QoS • Straightway reservation • Fast reservation, adaptation • Latency reduction • Emergency data transmit slot • Highly adaptable to abrupt emergency data • Support high QoS and reliability • Priority supported <J.S.Yoon>, <CUNY>