Irregular Distributed Space-Time Code Design for Near-Capacity Cooperative Communications

This paper presents an Irregular Distributed SpaceTime (Ir-DST) coding scheme designed for near-capacity cooperative communications. A serial concatenated scheme comprising an IRregular Convolutional Code (IRCC), a recursive Unity-Rate Code (URC) and a Space-Time Block Code (STBC) was designed for the sake of approaching the corresponding source-to-relay link capacity, where the IRCC was optimized with the aid of Extrinsic Information Transfer (EXIT) charts which was used at the source node. At the relay node, another IRCC is concatenated serially with an identical STBC. The relay´s IRCC is re-optimized based on EXIT chart analysis for the sake of approaching the relay network´s capacity, before transmitting the relayed information. We will demonstrate that the topology of the Ir-DST system coincides with that of a Distributed Turbo Code (DTC). At the destination node, a novel three-stage iterative decoding scheme is constructed in order to achieve decoding convergence to an infinitesimally low Bit Error Ratio (BER). Finally, it is shown that our joint source-and-relay mode design based on EXIT chart analysis is capable of near-capacity cooperative communications.