Many wireless sensor network applications require real-time communications and real-time applications necessitate packets to reach destination on time. However, time requirement of packets vary according to the priority of packets and applications may send packets with different priorities. Therefore packet differentiation is essential for meeting the deadline requirements. We want to support real-time communications by using a routing algorithm which supports packet scheduling and gives precedence to urgent packets. The routing algorithm also utilizes transmit power adjustment in order to meet the deadline of urgent packets and save energy by reducing transmit power when possible. We have experimented on our Mica2 sensor network testbed to observe the effects of transmit power on range and end-to-end delay. Increasing transmit power increases the range and link quality, and reduces the number of hops to reach the destination. Therefore adjusting transmit power has a great effect on delivery time and can reduce the end-to-end delay. Our Routing Protocol with Power Adjustment(RPPA) uses different levels of transmit power for packets with different priorities. The protocol sends urgent packets with maximum power to minimize end-to-end delay and lower priority packets with reduced power to balance the load on nodes and save energy. Initial simulation results show that routing protocol adjusts the delivery time of a packet according to the deadline and the energy spent per packet is reduced when compared to routing protocols using fixed transmit power. Currently, we concentrated on the effects of rate and interference, and extending the routing protocol to increase the throughput and balance the load on different nodes.

DATE: 7 April, 2008, Monday@ 16:40
PLACE: EA 409