Several problems are required to be fixed in order to apply geographical routing protocol Greedy Perimeter Stateless Routing (GPSR) in wireless sensor networks. First, GPSR is designed under the assumption of symmetric links (i.e., bidirectional reachability) which is not realistic for many practical sensor networks. Second, in sensor networks, packet destinations are often marked with locations instead of identifiers like IP address and therefore packets are routed to the home node which is

more »

... node geographically closest to the destined location. GPSR is not efficient in identifying the home node when the target location is outside the exterior perimeter of the sensor network. Third, due to the dynamic nature of sensor networks, maintaining data consistency, that is, data retrieved from the home node for a location should be consistent with the data sent to the same location, becomes a challenge when home nodes change. We propose On-demand GPSR (OD-GPSR), a data driven geographical routing protocol customized for sensor networks with solutions to the above three problems. Simulation results show that OD-GPSR performs well in terms of energy efficiency and packet delivery rate at the cost of a little bit more packet delivery delay.