IRA code design for IDMA-based multi-pair bidirectional relaying systems

In this paper, the design of Irregular Repeat Accumulate (IRA) Codes for Interleave-Division Multiple-Access (IDMA)-based multi-pair bidirectional relaying systems is presented. Bidirectional relaying allows to efficiently cope with the loss in spectral efficiency that is inherent to relaying systems due to the half-duplex constraint. However, as soon as multiple communication pairs use one common relay for communication, the question of medium access arises. Since orthogonal medium access schemes again introduce a rate loss to the system, nonorthogonal medium access based on IDMA is proposed. Further, in order to optimize the IDMA-based system regarding spectral efficiency, IRA codes are applied which allow for a highly flexible code design. This paper gives a description of the general code design process based on EXIT-analysis. Moreover, some design examples are given and the resulting systems are compared to conventionally coded IDMA systems based on convolutional codes.