Geographic routing with limited information in sensor networks

Geographic routing with greedy relaying strategies have been widely studied as a routing scheme in sensor networks. These schemes assume that the nodes have perfect information about the location of the destination. We consider three scenarios: (i) where nodes have location errors (imprecise GPS), (ii) where only coarse geographic information about the destination is available, such as the quadrant or half-plane in which the destination is located, and (iii) where only a small fraction of the nodes have routing information. In this paper, we show that even with such imprecise or limited destination-location information, the routing delays are /spl Theta/(1/M(n)). We further show that routing delays of this magnitude can be obtained even if only a small fraction of the nodes have any location information, and other nodes simply forward the packet to a randomly chosen neighbor, and we validate our analysis with simulation. Finally, we consider the throughput-capacity of networks with progressive routing strategies that take packets closer to the destination in every step, but not necessarily along a straight-line. Such a routing strategy could potentially lead to spatial "hot spots" in the network where many data flows intersect at a spatial region (a node or group of nodes), due to "sub-optimal" routes with increased path-lengths. In this paper, we show that the effect of hot spots due to progressive routing does not reduce the network throughput-capacity in an order sense. In other words, the throughput-capacity with progressive routing is order-wise the same as the maximum achievable throughput-capacity.