Packet Combining Over Rayleigh Channels using Signal-to-Noise Ratio Information and Detection by the Maximum A-Posteriori Criterion

We present and analyze a packet combining strategy for wireless networks with slow Rayleigh fading. The scheme is based on adding the current signal-to-noise ratio (SNR) as an overhead to the packet and packet combining using the maximum a posteriori (MAP) criterion. We consider single and multiple wireless hops, and we perform comparisons against the optimum case, the maximum ratio combiner (MRC). For the single wireless hop, we show that the error probability curve is very close to the optimum. In addition, we study the effect of selection and an alternative based on averaging over the channel statistics that has poorer error performance, but needs less processing and overhead. In multiple wireless hops, some nodes act as relays and the error probability increases. However, combining several branches, each with two hops, allows for diversity order equal to the number of branches. We demonstrate the performance of the proposed strategy by computer simulations. The fusing packet scheme that is presented in this paper is adequate for sensor networks