Performance Evaluation of IEEE 802. 15 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/ April 9, 2004

Outline Overview of IEEE 802.15.4TM/ZigBeeTM Physical Layer MAC Layer Super frame Structure CSMA and polling GTS in CFP Synchronization Simulation April 9, 2004

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 April 9, 2004

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) April 9, 2004

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 April 9, 2004

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 April 9, 2004

PHY Features Rx 19.7mA Tx Power feature of CC2420 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 Rx 19.7mA Tx P=-25dBm 8.5mA P=-15dBm 9.9mA P=-10dBm 11mA P=-5dBm 14mA P=0dBm 17,4mA 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 April 9, 2004

MAC: Super frame Beacon Mode: Beaconless 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 April 9, 2004

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 April 9, 2004

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 April 9, 2004

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 April 9, 2004

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 April 9, 2004

CSMA-CA April 9, 2004

Duty Cycle-Energy April 9, 2004

GTS in CFP April 9, 2004

Synchronization Tracking Non-tracking Tracking: Enable radio periodically to receive the beacon Non-tracking: Enable radio when necessary and search for the next beacon April 9, 2004

Synchronization Crossover curve Analysis & Simulation result April 9, 2004

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 April 9, 2004