Wireless sensor communication system based on direct-sum source coder

The authors propose a low delay and low complexity communication system for wireless sensor networks based on a so-called direct-sum source coder. The source encoder converts a continuous-amplitude signal into an n-tuple binary representation directly by a scalar quantisation. The authors derive the mean-square error distortion of the proposed scheme from which the power allocation strategy can be optimally designed for each of the quantisation bits. The authors also consider the performance of a conventional system where the Lloyd-Max source coder/decoder is employed. The simulation and analytical results show that the proposed system offers superior performance compared with the conventional system with low-system complexity and low delay. Furthermore, this investigation reveals that there is no performance gain obtained from the optimal power allocation over the equal gain allocation for low signal-to-noise ratio, when no channel state information is available at the transmitter side. Based on this observation, a well-structured form of power allocation for the whole SNR range is achieved.