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Body Area Sensor Network

Semester Project. Body Area Sensor Network. Medium Access Control (MAC). Michel Estermann Supervisor: Clemens Lombriser. Medium Access Control Tasks. Provide reliable peer-to-peer communication in a multi-node network Control & allocate access to the medium

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Body Area Sensor Network

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  1. Semester Project Body Area Sensor Network Medium Access Control (MAC) Michel Estermann Supervisor: Clemens Lombriser

  2. Medium Access Control Tasks • Provide reliable peer-to-peer communication in a multi-node network • Control & allocate access to the medium • Provide and encapsulate functionality to higher layers: • Accept data to send • Return received data

  3. Requirements • Low overall power consumption • Short active listen time • Reduced idle listening • Low message overhead • No blocking through busy waiting • Simplicity

  4. Communication Test

  5. Communication Test

  6. Communication Test

  7. Conclusion • Small number of neighbours (~5-10) • Only 0dBm output power useful • Master is not useful • Limited carrier sensing • Need of a broadcast address & channel • Destination address in control messages required • Timer clock drift: around7•10-6

  8. BASN-MAC Key Concepts • Based on S-MAC (T-MAC) • Listen/sleep low duty-cycle • Interrupt driven (Timer of mC) • CSMA with RTS/CTS messages • Virtual clusters with same schedule • Dedicated channel for data transmission • No interruption during data transmission

  9. Low Duty-Cycle Schedule

  10. Initialization & Synchronization

  11. Schedule Correction Node 1 Node 2 diff = (next listen – delay) – (schedule entry – cur)

  12. Schedule Correction

  13. Communication

  14. Theoretical Datarate • Assumptions: • No collision, carrier idle, no packet loss, no waiting • Power up: 3ms • Avg. carrier sensing time: 5ms • Change to TX – send message –change to RX: 2ms • Listen time 100ms, periode 400ms • Max. data payload 24 Bytes • Max. number of frames 255 powerUp + 2*send + 2*receive + 3*CS = 26ms Data Transmission: (24 +5 Bytes *255) / 256kbps + 69ms =~300ms Datarate: 6120 bytes / 400ms = ~15 kB/s

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