Analysis of Internet Protocol Based Multicast on Duty-Cycled Wireless Sensor Networks

Many Internet protocol -based multicast protocols for Wireless Sensor Networks (WSNs) rely on the routing tree obtained through the Routing Protocol for Low power and lossy networks, to reach subscribers of a multicast group. WSNs often activate radio duty cycling (RDC) to save energy. Our purpose is to examine the effect of the link layer (LL) transmission mode, on the performance of those multicast protocols in function of RDC and multicast protocol parameters. First, the average packet delay in function of the LL transmission mode and the radio channel check rate (CCR), is investigated for restricted topologies through mathematical modeling and simulation. Both show that LL broadcast produces equal or less delay for reaching its interested children in the first hop compared with LL unicast. However, LL broadcast suffers from higher delays, inversely proportional to the CCR, for subsequent hops. LL unicast's delay per hop increases linearly with the number of interested children. Second, the simulation model is used to study the effect of using a mix of LL unicast and broadcast for different CCRs in randomly generated topologies. Average delay, energy consumption and packet delivery ratio are determined in function of hop distance. The average delay can be optimized by using a mixed mode, in which a threshold determines from how many interested children onwards a LL broadcast should be used. The results indicate which optimal threshold, in function of the CCR, should be chosen to optimize delay and energy consumption.