Improving Network Coded Cooperation by Soft Information

Bit-wise XOR network coding has been shown to perform well in cooperative wireless transmission because of its simple coding operation and overall robustness increase due to combining of several messages. Our aim is to develop a cooperation protocol that uses basic and easy to implement operations but still combines the messages well and achieves good performance. For this purpose, we modify the conventional network-coded cooperation protocol to work with soft information. We analyze the performance by first deriving a closed form Bit Error Rate (BER) approximation and then verify its correctness by simulation. Both, analytic and simulation, results show that the BER approximation is accurate and that the new protocol gains about 5 dB in an indoor scenario with movement. We conclude that soft information should be used whenever possible, and that it works especially well in the proposed combining scheme with network coding.