Cooperative and noncooperative ARQ protocols for microwave recharged sensor nodes

The generic autonomous platform for sensor systems, or GAP4S, is a maintenance-free wireless sensor network in which the sensor battery needs not be replaced. Power is delivered to the sensor via a microwave signal that is radiated by a base-station. The base-station also acts as the entry point to a wider communication network, e.g., the Internet. This paper describes three automatic repeat request (ARQ) protocols that may be used in GAP4S to yield reliable and fair data transmission from the sensor nodes to the base-station. Two of the protocols take advantage of cooperative communication, whereby neighboring sensor nodes help during the retransmission process. The presented analysis on the saturation throughput of the ARQ protocols helps quantify the gain achievable when cooperative communication is used in GAP4S in a variety of working conditions.