doc.: IEEE Submission, Slide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Versatile MAC for Body Area Network Update for UWB PHY] 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:[ ], FAX: [], Re: [Versatile MAC for BAN proposal responding to TG6 Call for Proposals ( tg6- call-proposals) ] Abstract:[This document describes a Versatile MAC that is being proposed to the TG6 group ] Purpose:[Discussion in Task Group ] Notice:This document has been prepared to assist the IEEE P 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 P

doc.: IEEE Submission Versatile MAC for Body Area Networks June S Yoon, Gahng S Ahn, Myung J Lee, Seong S. Joo CUNY, ETRI, Slide 2

doc.: IEEE Submission Outline Motivation Challenges Versatile MAC Overview Functionalities of Each Period –AD, CAP, Beacon, DTP, Options –Energy saving –Prioritization –Summary Simulation Conclusion, Slide 3

doc.: IEEE Submission Motivation To design a simple MAC protocol to support various QoS for Body Area Networks, Slide 4

doc.: IEEE Submission MAC Design Challenges QoS Assurance –High reliability and guaranteed latency requirement for real time data, especially vital signs  Need deterministic structure  Special care for emergency reaction alarm 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, Slide 5

doc.: IEEE Submission Versatile MAC Overviews, Slide 6

doc.: IEEE Submission Versatile MAC Features Versatile –Best breed of Contention based and TDMA –Supports various (burst, periodic, continuous) types of traffic Straightway reservation –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 Simple, easy to implement, Slide 7

doc.: IEEE Submission BSF (BAN Superframe) Ad (Advertisement) –Synch, interval, address CAP –Reservation, Non-periodic data Beacon –Synch, length of slot, reservation status announcement DTP (Data Transmit Period) –DTS (Data Transmit Slot) Continuous, Periodic data –ETS (Emergency Data Transmit Slot) Emergency data & Periodic data, Slide 8

doc.: IEEE Submission Flexible BSF BSF flexibly adjusts its length in accordance with requirements of sensor nodes, Slide 9

doc.: IEEE Submission Functionalities of Each Period, Slide 10

doc.: IEEE Submission Advertisement The beginning of BSF (BAN Superframe) followed by contention access period Ban Coordinator (BC) broadcasts it at the beginning of BSF and it contains basic information such as –Synchronization –BC ID –Ad Interval, length of periods A newly joined node adjusts its clock, gets information on BC and BSF, Slide 11

doc.: IEEE Submission CAP Contention access period –Backoff and CCA to avoid collision –Prioritized back-off to serve higher priority first Data Transmission –Command frames exchange for DTS reservation –Non-periodic data including alarm and periodic data failed to reserve DTS can be sent BC collects all the DTS requests and sort them according to their priorities and slot availability –Allocate from the first available slot based on the priority order to prevent DTS shortage –Lower priority slots may be preempted by higher priority data, Slide 12

doc.: IEEE Submission 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 synchronize and to check reservation status changes Sequential ‘Ad-CAP-Beacon’ enables straightway slot reservation and prompt accommodation to changes, Slide 13

doc.: IEEE Submission Straightway Reservation & Transmission Why ? How? In a life critical situation, e.g. patient in ER, wounded soldier in battle field, urgent reporting after initial placement of sensors is as important as emergency alarm Placing ‘Ad  CAP  Beacon’ in a row enables urgent transmission, Slide 14

doc.: IEEE Submission Data Transmit Period TDMA Period for the latency-critical continuous and periodic data BC allocates DTS first and then ETS if no more DTS is available Since ETS is dedicated slot for Emergency data, the node assigned to ETS performs CCA before its transmission so as to avoid collision with Emergency data, Slide 15

doc.: IEEE Submission ETS for Emergency Alarm ETS ( Emergency Data Transmit slot) –Contention access period –Number of slot is configurable and evenly distributed throughout DTP period –If any, emergency data is transmitted at ETS while the node assigned to this slot performs CCA Emergency alarm can be sent in CAP, ETS, and CAP Extension whichever available first –Enables urgent transmission for abrupt Emergency alarm, Slide 16

doc.: IEEE Submission Options ECAP (CAP Extension) –The duration between the ends of DTP and next advertisement –If power is not a concern for BC, it can stay awake and extend 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, Slide 17

doc.: IEEE Submission Prioritization, Slide 18

doc.: IEEE Submission BAN Data Prioritization Prioritization based on QoS (latency) requirement –Priority 0: Emergency alarm (CAP, ETS, CAP Extension) Emergency vital signs, Battery depletion,... –Priority 1: Medical Continuous data (DTS) Latency critical data –E.g. EEG/ECG/EMG –Priority 2: Medical Routine data (DTS) Reliability critical but lesser latency requirement –E.g. Temperature, Blood pressure –Priority 3 : Non-medical Continuous data (DTS) Video, audio –Priority 4 : Non-medical, non-time sensitive (CAP) Priority classes are dictated by the applications, Slide 19

doc.: IEEE Submission Prioritized DTS Allocation For Priority classes 1, 2, and 3 Priority based allocation (1) –Higher priority data served first in case of contention among different priority traffics, Slide 20 Priority based allocation (2) –Higher priority data can preempt lower priority if no DTS is available –This change immediately becomes effective through straightway reservation

doc.: IEEE Submission Access Policy in CAP Perform random back-off first then CCA before access channel Back-off classes –Class 0: Priority 0 (Emergency alarm) –Class 1: Priority 1 and 2 (Medical) –Class 2: Priority greater than 2 (Non-Medical) Back-off unit range Back-off period: aUnitBackoffperiod x Back-off unit –The lower the priority the longer the back-off period, Slide 21

doc.: IEEE Submission Access Policy in ETS Alarm may share ETS with Priority 1~3 data Priority 1~3 data perform CCA first to avoid collision Alarm also performs CCA for the case of contending among multiple alarms, Slide 22 CCA Duration of slot owner (fixed) = unitCCAperiod x N Random CCA for alarm CCA Duration of alarm = [0, unitCCAperiod x (N-1)]

doc.: IEEE Submission Energy Saving Inherent advantage of TDMA architecture for power saving over non-TDMA structure. Coordinator –Goes into inactive If no activity is scheduled after CAP or DTP Sensor (continuous data) –Once DTS reservation is done, the node stays 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, Slide 23

doc.: IEEE Submission Summary of Versatile MAC Functionalities, Slide 24

doc.: IEEE Submission Simulation, Slide 25

doc.: IEEE Submission Simulation Scenario Simulation time: 5 min. Star topology –1 BAN Coordinator and variable number of child nodes Superframe size (BO=6, SO=3) –Slot size: 7.68ms –AI: 128 slot –CAP: 8 slot –Ad & Beacon: 1 slot each Channel capacity –250Kbps for comparison with IEEE –2Mbps for A/V application Channel model: CM3, 2.4Ghz –Body surface to body surface IEEE : BO=6, SO=3, Slide 26

doc.: IEEE Submission Comparison: Reservation delay (From data generation to slot assignment confirm by beacon) Concatenate ‘Ad-CAP-Beacon’ enables reservation fast All nodes contend for reservation –Data generation time is uniformly distributed If remaining CAP time is not enough because of contention, wait & retry at the next CAP –Longer delay than one node case, Slide Difference: 0.914

doc.: IEEE Submission Comparison: Emergency Alarm delay (From alarm generation to arrival at coordinator), Slide 28 Simulation time: 5 min Packet size: 18byte Number of node - Periodic data node: 15 - Alarm node: 1,2,3,4,5,7,10 Alarm arrival rate -1pkt/10sec (Poisson) Number of ETS:1,3,7

doc.: IEEE Submission Back-off Delay Simulation time: 5min Min. Backoff Exponent=3 Max. Backoff Exponent=5 unitBackoffperiod = 320us Number of node –1 to 25 / class, Slide 29

doc.: IEEE Submission Throughput Simulation time: 5 min Channel capacity: 2Mbps Number of node: 10 –EEG (5), audio, video Body temp, Heart beat, and Coordinator Data rate –Body temp: 16bps –Hear beat: 128bps –EEG: 3.2kbps –Audio: 30kbps –Video: 1Mbps Header: 104bit (13byte), Slide 30

doc.: IEEE Submission Conclusion 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 Simple, easy to implement –A little modification to IEEE , Slide 31

doc.: IEEE Submission Channel Access Policy with UWB PHY, Slide 32

doc.: IEEE Submission Challenges With ISM band, we could use 1)CCA after prioritized back-off in CAP 2)Random CCA in ETS, Slide 33 But CCA is not feasible with UWB

doc.: IEEE Submission Access Policy in CAP CCA or Carrier sense is not feasible with UWB PHY Aloha type of access is the only possible solution (e.g.IEEE a) –Aloha (Non-Beacon mode) –Slotted Aloha (Beacon mode) Slotted Aloha is better than Aloha but still high probability of collision We propose “Slotted Aloha with Prioritized Back-off”, Slide 34

doc.: IEEE Submission Simulation: 60 sec Inter-arrival time: 1pkt/sec (Poisson) Packet size: 16byte, Slide 35 BO=6, SO=3 CAP size = 8 slot 1 to 5 node per each class

doc.: IEEE Submission Channel Access in ETS (1) Problem: –CCA in ETS is not feasible. –Buffered alarms try to access channel at the same time as soon as ETS begins. –Slotted Aloha with Prioritized Backoff is not enough because random backoff may too long to deal with contentions in a short data slot. Solution: –ETS Preoccupancy using two way handshaking Nodes transmit ETS allocation request with back-off BNC replies a node whose request arrived first Only the replied node transmit emergency alarm Others retry at next ETS or CAP, Slide 36

doc.: IEEE Submission Channel Access in ETS (2) ETS is divided into N mini backoff slots, an ETS reply slot, and an Emergency alarm slot –Each node select random backoff unit between [0, N). –At the selected mini slot, the node sends ETS request frame. Mini slot > ETS request –After the end of backoff slots, BNC send ETS reply to the winning node whose request arrived first. Mini slot > ETS reply –After receiving the ETS reply, the winning node sends an emergency alarm. Mini slot < Emergency Alarm, Slide 37 Random Backoff ETS request Mini Slot ETS reply Backoff Window Emergency Alarm ETS