Soft Incremental Redundancy for Distributed Turbo Product Codes

In this paper, we propose a distributed turbo product code (DTPC) with soft information relaying over cooperative network using block extended bose Chaudhuri Hochquenghem (EBCH) codes as component codes. The source broadcasts extended EBCH coded frames to the destination and to a preassigned relay. After soft-decoding the received sequences and obtaining the log-likelihood ratio (LLR) values, the relay constructs a product code by arranging the decoded bit sequences in rows and re-encoding them along the columns using a novel soft block encoding technique to obtain soft parity bits with different reliabilities that can be used as soft incremental redundancy (IR) for source´s data which is forwarded to the destination. A modified turbo product decoder to cope with the data received over different channels and thus having different reliabilities is used at the destination. We compared the simulation results in additive white Gaussian noise (AWGN) channel using network scenarios with our previous work for decode and forward (DF) DTPC and with non-cooperative case. Results show 0.5 dB gain improvement over the non-cooperative turbo product codes (TPC) at bit error rate (BER) 10^-4. In addition, the BER performance is less affected by the decoding errors at the relay.