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Performance Evaluation of IEEE 802.15.4 MAC for Low Rate Low Power Wireless networks

Performance Evaluation of IEEE 802.15.4 MAC for Low Rate Low Power Wireless networks. Gang Lu Bhaskar Krishnamachari Cauligi S. Raghavendra Department of Electrical Engineering-Systems http://ceng.usc.edu/~anrg/. Outline. Overview of IEEE 802.15.4 TM /ZigBee TM Physical Layer MAC Layer

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Performance Evaluation of IEEE 802.15.4 MAC for Low Rate Low Power Wireless networks

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  1. Performance Evaluation of IEEE 802.15.4 MACfor Low Rate Low Power Wireless networks Gang Lu Bhaskar Krishnamachari Cauligi S. Raghavendra Department of Electrical Engineering-Systems http://ceng.usc.edu/~anrg/

  2. Outline • Overview of IEEE 802.15.4TM/ZigBeeTM • Physical Layer • MAC Layer • Super frame Structure • CSMA and polling • GTS in CFP • Synchronization • Simulation

  3. Introduction to LR-WPAN • Low-Rate Low-Power Wireless Networks • Wireless sensor networks • Industrial Control and Monitoring • Environmental and Health Monitoring • Home Automation, Entertainment and Toys • Security, Location and Asset Tracking • Emergency and Disaster Response • IEEE 802.15.4 • A new MAC for LR-WPAN • IEEE 802.11: an “overkill technology” • Bluetooth: high data rate for multimedia applications, small size network, high power consumption

  4. Features of IEEE 802.15.4 • 16 channels in the 2450 MHz band, 10 channels in the 915 MHz band, and 1 channel in the 868 MHz band • Over-the-air data rates of 250 kb/s, 40 kb/s, and 20 kb/s • Star or peer-to-peer operation • Allocated 16 bit short or 64 bit extended addresses • Allocation of guaranteed time slots (GTSs) • Carrier sense multiple access with collision avoidance (CSMA-CA) channel access • Fully acknowledged protocol for transfer reliability • Low power consumption • Energy detection (ED) • Link quality indication (LQI)

  5. Network Topologies IEEE 802.11 only describes the MAC and PHY layer. Upper layers are designed by ZigBee which has not be released. From ``Home Networking with IEEE 802.15.4: A Developing Standard for Low-Rate Wireless Personal Area Networks", Ed Callaway, Paul Gorday and Lance Hester, IEEE Communications Magazine Aug. 2002

  6. PHY: Channel Structure From ``Home Networking with IEEE 802.15.4: A Developing Standard for Low-Rate Wireless Personal Area Networks", Ed Callaway, Paul Gorday and Lance Hester, IEEE Communications Magazine Aug. 2002

  7. PHY Features • Both PHYs are based on DSSS • 2.4GHz PHY provides 250kbps • 868/915 MHz PHY provides 20kbps and 40kbps respectively • Sensitivity: -85dBm for 2.4GHz and -92dBm for 868/915MHz • Range: 10-20m Power feature of CC2420 From ``Home Networking with IEEE 802.15.4: A Developing Standard for Low-Rate Wireless Personal Area Networks", Ed Callaway, Paul Gorday and Lance Hester, IEEE Communications Magazine Aug. 2002

  8. MAC: Super frame • Beacon Mode: • PAN coordinator broadcasts a beacon which tells the superframe structure • CAP: Contention Access Period • CFP: Contention Free Period • GTS: Guaranteed Time Slot • Turn off radio in inactive period to save energy • Beaconless mode • Just CSMA-CA

  9. Collision Access Period • Transaction • either the coordinator needs to indicate in its beacon when messages are pending for devices • or the devices themselves need to poll the coordinator to determine whether they have any messages pending. • CSMA-CA • Power consumption during the backoff period • IEEE 802.15.4 provides a “Battery Life Extension” (BLE) mode which limited the backoff exponent to 0-2. • Reduced the idle listening period

  10. GTS in CFP • A device can request dedicated bandwidth to achieve low latency • Used only for communication between PAN coordinator and devices • PAN coordinator maintain and assign the GTS slots used by devices • A device enables its radio at a time prior to the start of the GTS and transmit during GTS without CSMA-CA

  11. Synchronization • PAN coordinator transmits beacon frames periodically to announce the superframe structure • A device need to know the superframe before any data transmission • Synchronization methods: • Tracking • Enable its radio periodically to receive the beacon • Non-tracking • Enable its radio when necessary and search for the next beacon

  12. Simulation • Only evaluate the beacon mode on star topology • Radio parameters in table 1 • 7X7 grid with 49 node • 4m distance between adjacent node • CBR traffic with 50% randomization

  13. CSMA-CA

  14. Duty Cycle-Energy

  15. GTS in CFP

  16. Synchronization Tracking Non-tracking • Tracking: Enable radio periodically to receive the beacon • Non-tracking: Enable radio when necessary and search for the next beacon

  17. Synchronization Crossover curve Analysis & Simulation result

  18. Conclusion • An overview of IEEE 802.15.4 • Evaluation of MAC • CSMA-CA in CAP • Energy Latency Tradeoff of Duty Cycle • Energy Latency Tradeoff of GTS in CFP • Tradeoff between tracking and non-tracking synchronization • Plan to make NS-2 model available online

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