Integrated cost-based MAC and routing techniques for hop count forwarding in wireless sensor networks

This paper presents integrated MAC/routing solutions for wireless sensor networks. At the MAC layer, every node accesses the channel according to its own cost by means of properly defined cost-dependent access probabilities. Costs are used to capture the suitability of a node to act as the relay and may depend on several factors such as residual energies, link conditions, queue state, etc. Our cost-aware MAC discriminates nodes right in the channel access phase by therefore assisting the forwarding decisions to be made at the routing level. In fact, nodes with high costs are ruled out from channel contention and are not considered when making routing decisions. This provides the routing layer with better relay candidates and, at the same time, decreases the number of in-range devices contending for the channel, thereby reducing interference. The proposed MAC scheme is coupled with routing over hop count (HC) coordinates. To this end, we introduce a set of rules designed to perform HC routing by exploiting first and second order neighborhood information. These are then integrated with our MAC scheme according to a cross-layer approach and their effectiveness is demonstrated by means of analysis and simulation.