Implementation of Cooperative Diversity using Message Passing in Wireless Sensor Networks

Cooperative diversity can be achieved by a relay node (R) assisting in a transmission between a source (S) and a destination (D). However, in general, the proposed cooperation schemes ignore the quality of the S-R channel in the decoding process. This paper introduces a novel and robust scheme for cooperative diversity that accounts for the quality of the S-R channel. In our scheme, the relaying node provides parity checks for the estimated source symbols, which are used to assist in the decoding of the source message using message passing. Performance measures, such as bit error rate, are then not limited by the S-R channel quality and improve with increasing signal-to-noise ratio on the S-D and R-D channels. No feedback signals are required, with only simple computations at the relay. Simulations show that, as with earlier proposals, our scheme achieves full diversity order in the case of a good S-R channel.