Optimal Detection of IDMA Signals

In this paper the system model of an uncoded and fully synchronised interleave division multiple access (IDMA) scheme is transformed into an equivalent matrix model. This new model allows for additional alternative insights into the principles of IDMA and it is shown that the arising matrices are highly structured and very sparse. Furthermore the optimal detector for IDMA is derived and compared to the standard iterative decoder. The authors use exit charts and an empirical rank analysis to highlight that systems without an alternating signature mask always have a low rank and that parallel interference cancellation then fails.