Joint network-channel coding with Repeat Accumulate codes for wireless relay networks

This paper presents two different repetition based joint network-channel coding schemes for a three-terminal communication system where two-users want to exchange information via a relay. The transmission is divided into three slots in time where the first and second slots are allocated to the RA (Repeat Accumulate) encoded data of the users. In the first scheme we propose, the relay decodes the received signals and transmits a bit-wise XOR-ed packet using RA coding in the third slot. In the second scheme, the relay demodulates the received signals without decoding and estimates the RA code symbols of each user, then transmits the XOR-ed symbol packet. Unlike the schemes in the literature, the introduced decoding algorithms do not require the relay to decode entire codeword without errors and remove the need for channel feedback without sacrificing the diversity order. The maximum-likelihood decision rule for transmission without channel coding is also derived.