Random On-Off Accumulative Transmission for Asynchronous Wireless Sensor Networks

In this paper, a random on-off accumulative transmission (R-OOAT) scheme is proposed to achieve collision-tolerant (CT) media access control (MAC) for asynchronous wireless sensor networks. Unlike conventional MAC schemes that discard packages with collisions at receivers, the CT-MAC extracts the salient information from the colliding signals by using the R-OOAT scheme in the physical layer. Nodes employing the R-OOAT deliver information to a base station through asynchronous on-off transmission of multiple identical sub-symbols at random positions. The R-OOAT improves the deterministic OOAT (D-OOAT) proposed in [1], where sub-symbols are transmitted at deterministic positions. Compared to the D-OOAT, the R-OOAT scheme achieves a smaller collision probability and supports more simultaneous users, while it inherits all the advantages of the D-OOAT. Design guidelines of the R-OOAT system are presented for given parameters, such as the probability of collisions and the maximum number of supported users. It is demonstrated by simulation results that the new CT-MAC with R-OOAT scheme can operate at the presence of severe signal collision.