In this paper several turbo receivers for Interleave-Division Multiple-Access (IDMA) systems will be discussed. The multiple access system model is presented first. The optimal, Maximum A Posteriori (MAP) algorithm, is then presented. It will be shown that the use of a precoding technique at the emitter side is applicable to IDMA systems. Several low complexity Multi-User Detector (MUD), based on the Gaussian approximation, will be next discussed. It will be shown that the MUD with Probabilistic Data Association (PDA) algorithm provides faster convergence of the turbo receiver. The discussed turbo receivers will be evaluated by means of Bit Error Rate (BER) simulations and EXtrinsic Information Transfer (EXIT) charts.

This paper is focused on the design of a set of orthogonal linear periodic time varying (LPTV) filters and proposes to apply this result to spread spectrum multiuser transmissions. The construction method of such an orthogonal set is presented, emphasizing that only an invertible LPTV filter is required, since the full set is then deduced from this kernel element. Based on this theoretical result, a spread spectrum multiuser transmission is proposed. In order to appreciate the performance of the proposed system, simulations are performed and results are compared to a classical DS-CDMA system.