Joint decoding and data fusion in wireless sensor networks using turbo codes

We consider the problem of joint decoding and data-fusion in data gathering sensor networks modeled by the Chief Executive Officer (CEO) problem. Correlation between sensorspsila data is known at the fusion center and is employed to update extrinsic information received from soft-in soft-out (SISO) decoders. It is shown in the literature that this scheme has a lower bit error rate compared with the schemes that separately decode data received from each sensor and then estimate the value of the source. Previous works consider correlated Gaussian sources and apply a single SISO decoder. We consider the binary CEO problem, where all sensors observe the same binary source corrupted by independent binary noises, and apply turbo codes to encode and transmit them to the fusion center. We show how extrinsic information is passed between SISO decoders and the vertical-decoding unit that updates extrinsic information using channel correlations. We illustrate the performance of the joint decoder for different correlations and rates. Simulation results show promising improvements compared with the separate decoding scheme. We also compare the bit error rates achieved by turbo codes with the ones achieved by convolutional codes and discuss the results.