Hop-constrained energy-aware routing in wireless sensor networks

Efficient use of the limited energy available with sensor nodes is an important consideration for routing protocols. In an attempt to improve the lifetime of a sensor network using energy-aware routing, existing protocols might route a packet along a longer path - thus increasing its latency. Many applications of sensor networks, e.g., surveillance and security, require that the maximum latency in routing a packet be bounded. We consider the problem of energy-aware routing with a bound on the maximum number of hops any packet can traverse to reach a base station. We formulate a linear program (LP) to minimize the maximum energy spent by any node in the network subject to a limit on the number of hops any packet may traverse. A solution to the LP yields routing information in terms of the number of packets to be forwarded along each edge; however, non-integral values of the flow variables might require splitting a packet across multiple routes. As packet splitting incurs additional overhead in tracking various fragments, it is desirable to have integral routing information. We, therefore, propose a rounding algorithm based on the minimum cost flow problem and prove that the energy spent by a node in the resulting integral solution is at most a constant more than the optimal LP solution