Fast timer-based maximum function computation over noisy multiple access channels

In wireless sensor networks (WSNs), to efficiently make the maximum value and the identity of corresponding sensor nodes available at the sink node is an important problem. In this paper, we develop a timer-based max function computation scheme over multiple access channels (TMCoMAC) in which timer scheme is combined with code division multiple access (CDMA) scheme to achieve fast max function computation with satisfying computation success probability. CDMA code is introduced to mitigate the influence of collision that limits the computation success probability of traditional timer-based computation schemes. An optimization problem to maximize the computation success probability is formulated and solved by using an iterative method. Numerical results are provided to show that our proposed algorithm can improve computation success probability with less delay overhead when CDMA sequence is sufficiently long. More specifically, our proposed scheme improves the computation success probability by about 16% - 24% compared to benchmark algorithm.