A Simple Complexity Reduction Strategy for Interleave Division Multiple Access

Interleave Division Multiple Access (IDMA) is a multiple access scheme similar to CDMA and it relies on an iterative ("turbo") multiuser detection and decoding technique. IDMA applies a very low rate code which is typically realized by a convolutional code followed by a simple repetition code. We propose to limit the decoding of the convolutional code at the receiver aiming at complexity reduction. Although the transmitted bits cannot be recovered without decoding the convolutional code, decoding only the repetition code already gives some improvements of soft information to the next ("turbo") iteration. We show that such a simple scheme can be of advantage of IDMA against CDMA to achieve significant complexity reduction with graceful performance degradation. We also provide analyses to answer when it makes sense to apply the simple strategy.