Research On Interleaver Technology Based On IDMA

IDMA (Interleave-Division Multiple Access) is a multiple access scheme based on CDMA(code-division multiple-access), in which users are distinguished by different chip-level interleaving methods instead of by different signatures as in a conventional CDMA scheme. The IDMA inherits many advantages from CDMA. It has been a very competitive scheme for future mobile communications because of the better performance in reducing the MAI and a low-cost interference cancellation technique in multipath channels which improve the throughput of the system.Comparing with the traditional DS-CDMA, the IDMA scheme adopts different interleavers to distinguish users. A very low-cost iterative detection algorithm is derived in the receiver of IDMA scheme, in which MAI is weaken by repeating the process of interleaving and de-interleaving. Therefore the design of interleaver is one of key technologies of the IDMA scheme. User-specific interleaver can be generated randomly and independently in theory, but it is impracticable because the memory and bandwidth requirements are exorbitant for systems. The receiver in the IDMA scheme with orthogonal interleavers can eliminate the MAI perfectly, but it is impossible to find a set of orthogonal interleavers which number is larger than the spreading length. So we have to look for a method to design a set of weaken correlation interleavers.There are five chapters in the paper. Firstly, it introduces the background of the IDMA scheme, and gives its fundamental principle, iterative detection algorithm, key technologies and advantages. Then it analyzes how to design a good interleaver in Turbo code and IDMA scheme, and reviews some classical design methods of interleaver. In order to solve the problem of random interleaver requires too much memory and system bandwidth, it gives a novel way of IDMA interleaver design: symmetry interleaver. Traditional ways of IDMA interleaver design only pay attention to how to reduce the correlation among interleavers, but never solve the correlation of sequence after and before the same interleaver. So it designs a new interleaver: three-dimensional interleaver. It successful solves the problem of relatively high order self-interleave correlation and brought a better anti-fading and anti-burst error effect. The simulation results show that the two new interleavers can achieve the same performance with much less resource consumption comparing with random interleaver in the IDMA system.