Cooperative Network Coding with Soft Information Relaying in Two-way Relay Cchannels

Manuscript received May 1, 2009; revised July 1, 2009; accepted July 3, 2009. Abstract—Network coding in wireless network can improve network throughput by exploiting the broadcast nature of the wireless network. Taking into consideration the error prone nature of wireless networks, we investigate the design of network coding implemented in physical layer, and propose a cooperative network coding scheme with soft information forwarding (SIR), which combines soft network coding and distributed turbo coding scheme in two-way relay channels (TWRC) in this paper. In order to mitigate the error propagation effect due to the imperfect decoding at the relay, soft network coding is deployed in the proposed scheme, where soft-input soft-output (SISO) encoder and decoder for recursive systematic convolutional (RSC) codes are implemented. Moreover, the soft information of both systematic bits and redundancy parity bits are forwarded at the relay by using higher-order constellations to achieve diversity gain. Aided by distance spectrum of turbo codes, concept of uniform interleaver, and Gaussian approximation of soft decoding information, union bound on the error performance of our scheme is analyzed. Both the analysis and simulation confirm that the proposed scheme achieves significant gain over conventional network coding in quasi-static fading channels.