A review of bit-error-rate performance of interleavers in IDMA systems

The centrality of interleavers in interleave-division multiple-access (IDMA) cannot be over-emphasised, the interleaver being the only means of isolating signals for different users of the multiple-access system. This work gives a critical review of bit-error-rate (BER) performance of interleavers and IDMA systems. Existing literature shows that there are disagreements among results published by different authors on BER performance of interleavers and IDMA systems. For example, some published works showed that different kinds of interleavers have similar BER performance; in contrast, other published works indicated wide variation in BER performance of interleavers. Similarly, results by some authors showed that IDMA systems have poor performance in multi-user environments, exhibiting high error floor for as little as two users. In contrast, other authors indicated that IDMA systems perform well, close to Shannon limit. In the light of this prevailing situation, it is difficult to say if IDMA system truly gives better BER performance than code-division multiple-access (CDMA) as commonly believed. This paper examines the true position of IDMA with respect to its BER performance relative to CDMA.