An Efficient Multi-channel Management Protocol for Wireless Body Area Networks

1. An Efficient Multi-channel Management Protocol for Wireless Body Area Networks Wangjong Lee*, Seung Hyong Rhee*, Youjin Kim** and Hyungsoo Lee** * Kwangwoon University, Korea, ** Electronics and Telecommunications Research Institute, Korea International Conference on Information Networking (ICOIN), 2009 Computer Systems Lab Group Meeting Presented by: Zakhia Abichar April 15, 2010

2. Application: Nike+ Receiving device options • 2 nodes: sensor & receiving device • Sensor inserted into shoes • Sensor measures distance • Transmits in wireless to on-body device; upload to computer • Track progress; train on a program Wireless-enabled iPodCost: $19 (sensor-only) Wireless-enabled iPodCost: $29 (sensor +wireless receiver) Sensor Sensor insertion Nike SportbandCost: $78 (sensor +Sportband) Track progress

3. HRM: HeartRate Monitor Pacer Sensor Application: Adidas miCoach • System: miCoach pacer (cost: $139) • 3-nodes system: • Sensor measure the speed • HRM measure the heart rate • Pacer gathers the information via wireless • Pacer gives audio feedback: speed up, slow down • Based on HRM & training goal • Wireless standard used ANT+ • Also available: miCoach ZONE • HRM + sport-like device (Cost: $69) • Monitor hear-rate while exercising

4. Wireless Body Area Networks • They are also called WBAN • Can be considered a successor of WPAN (Wireless Personal Area Network) • WBAN have a range of 3 meters (9.8 ft) • Medical or non-medical according to use • In 2.4 GHz ISM band and 400 MHz band of MICS • ISM: Industrial Scientific Medical, used for Wi-Fi • MICS: Medical Implanted Communication Service

5. Technical Topic • We need a protocol to reduce the interference in the MICS band • Interference between MICS systems • or between MICS and primary systems • There is a an LBT (Listen-Before-Talk) protocol defined • LBT isn’t good for non-collision and emergency traffic • This paper proposes an efficient way of multi-channel management • The channel is reserved • Channel aggregation makes a single wide channel and satisfies various traffic types

6. Outline • Preliminary material • Proposed scheme • Simulation results

7. 401 402 403 404 405 406 MHz METAIDS MICS Preliminaries • IEEE working to make WBAN standards through Task Group 802.15.6 • ITU-R issued Recommendation SA.1346 for MICS devices ITU-R: InternationalTelecom. Union - Radiocommunication METAIDS: Meteorological Aids SA.1346: • MICS devices should limit to -16 dBm in a bandwidth of 300 kHz to prevent interference with METAIDS • Channel spacing of 25 kHz with channel aggregation up to 300 kHz • Also, there is LBT specs • MICS use low power, concluded there’s no interference with METAIDS

8. Distributed and Beacon-Enabled MAC Protocol • This is the proposed scheme • MICS band consists of 10 channels with 300 kHz bandwidth • 1 channel is the control channel. The other 9 are data • The control and data channels are not fixed • Outbody device allocates the channels to inbody devices through the control channel • Outbody device continuously sends a beacon frame on the control channel

9. Channel Assignment • Outbody device initiates communication with inbody devices • It also senses the channels to set up a control channel • MICS devices are secondary users; transmit/received when METAIDS devices are silent • They should coexist with other MICS; using LBT protocol • Outbody device selects one channel as the control channel after sensing • It also assigns a channel number to each channel except the control channel

10. Channel Assignment • On control channel, a beacon superframe consists of 9 beacon slots • Each beacon slot maps to a data channel • A beacon in the 1st slot means the 1st channel is reserved • No beacon in the nth means the nth channel is not reserved • Inbody devices listen to control channel to know what channel to use • Inbody devices then send a data packet to the outbody device on the reserved channel

11. Supporting Sleep State • Inbody devices have 2 modes: wake mode & sleep mode • There is a duty cycle: wake/sleep • At wake up, inbody device listens to control channel • If there is a channel allocated for it, it talks to outbody device • During this time, a beacon is sent on the control to indicate the data channel is busy • At end of communication, inbody device sleeps. Outbody device stops the beacon for the sleeping device • If there was no data channel for it at wake up, inbody device sleeps

12. Channel Aggregation • MICS frequency band has narrow channels • This limits traffic types that need high bandwidth • Outbody device can allocate aggregated data channels • by transmitting the same beacon in adjacent beacon slots • the channels are combined in a single wideband channel • This scheme prevents a waste of resource by using channel guards • It also reduces transmission failure caused by narrow channel

13. Single MAC for 2 PHYs • Two PHYs for WBAN: ISM (2.4 GHz) and MICS (400 MHz) • Use ISM for outbody communication and MICS for inbody communication • Like MICS, ISM band is divided into non-overlapping channels • the same proposed scheme can be used • WBAN device has two PHY layers and one MAC layer

14. Simulation Results • Simulation with ns-2, CMU wireless extension and MAC modules developed by Intel (refs.) • Topology: 2 inbody devices communicating with 1 outbody device

15. Throughput of Proposed Scheme and LBT • In proposed scheme, control channel is overhead • In LBT, sensing before transmission is overhead • sensing time is varied in simulation Listening Time = 0.05 ms Listening Time = 0.1 ms

16. Throughput with Channel Aggregation • First case is one aggregate channel of 900 kHz • Second case is 3 separate channels of 300 kHz each • Aggregation increases the throughput Channel: 1 x 900 kHz Channel: 3 x 300 kHz