BICM-ID for relay system allowing intra-link errors and a similarity constellation to ARQ schemes
Meng Cheng, Ade Irawan, Khoirul Anwar, Tad Matsumoto · Institutional Repositories DataBase (IRDB) · 2012
In this paper, we propose an accumulator-assisted (ACC) relay system with bit-interleaved coded modulation using iterative decoding (BICM-ID) technique and apply the network topology to an Automatic Repeat Request (ARQ) scheme. Our code design is based on the analysis of the extrinsic information transfer (EXIT) chart. The ACC enables the convergence tunnel of the EXIT curves opening until almost the (1, 1) point of the mutual information, which avoids the error floor. The most advantageous point of the proposed technique is that even though errors may happen in the intra-link (source-relay), they can be corrected at the destination by exploiting the correlation knowledge between the source and the relay nodes. This technique siginificantly reduces the complexity of the relay where the source bits are simply extracted, even though errors may occur due to the imperfect channel. The error rate of the intra-link can beestimated at the destination node by using the a-posteriori Log likelihood Ratios (LLRs) of the two decoders. Then, it can be further utilised in the iterative processing. Since the relay location directly inuences the quality of the intra-link, we change the relay locations, and provide the analysis of the performances corresponding to different relay locations. The theoretical background of this technique is the Slepian-Wolf/Shannon theorem for correlated source coding. The simulation results show that the bit-error-rate (BER) performances of the proposed system are very close to theoretical limits supported by the Slepian-Wolf/Shannon theorem. In this paper, it is also shown that if the intra-link is error free, the topology of the relay network is equivalent to an ARQ scheme that exploits Shannon's random coding theorem by utilising an interleaver in the framework of ARQ. Based on this observation, results of simulations conducted to evaluatethe throughput of an ARQ scheme are presented.