Distributed Irregular Codes Relying on Decode-and-Forward Relays as Code Components

A near-capacity distributed coding scheme is conceived by incorporating multiple relay nodes (RNs) for constructing a virtual irregular convolutional code (IRCC). We first compute the relay channel's capacity and then design IRCCs for the source and relay nodes. Extrinsic information transfer (EXIT) charts are utilized to design the codes for approaching the achievable capacity of the relay channels. Additionally, we improve the transmit power efficiency of the overall system by invoking both power allocation and relay selection. We found that even a low-complexity repetition code or a unit-memory convolutional code is capable of forming a near-capacity virtual IRCC. The performance of the proposed distributed IRCC (DIRCC) scheme is shown to be perfectly consistent with that predicted from the EXIT chart. More specifically, the DIRCC scheme is capable of operating within 0.68 dB from the corresponding lower bound of the relay channel capacity, despite the fact that each RN is exposed to realistic decoding errors due to communicating over imperfect source-relay channels.