DGRAM: A Delay Guaranteed Routing and MAC protocol for wireless sensor networks

This paper presents an integrated MAC and routing protocol called Delay Guaranteed Routing and MAC (DGRAM) for delay sensitive wireless sensor network (WSN) applications. DGRAM is a TDMA-based protocol designed to provide deterministic delay guarantee in an energy efficient manner. The design is based on slot reuse to reduce the latency of a node in accessing the medium, while ensuring contention free medium access. The transmission and reception cycles of nodes are carefully computed so that data is transported from the source towards the sink while the nodes could sleep at the other times to conserve energy. Thus, routes of data packets are integrated into DGRAM. We provide a detailed design of time slot assignment and delay analysis of the protocol. One major advantage of DGRAM over other TDMA protocols is that the slot assignment is done in a fully distributed manner making the DGRAM network self-configuring. We have simulated DGRAM using ns2 simulator and compared the results with those of SMAC for a similar network. Simulation results show that the delay experienced by data packets is always less than the analytical delay bound for which the protocol is designed. As per simulation results, the average energy consumption does not change as the event rate changes, and is less than that of SMAC. This characteristic of DGRAM provides flexibility in choosing various operating parameters without having to worry about energy efficiency.