GRP-based interleaver for IDMA systems over frequency selective channel

An interleave-division multiple-access (IDMA) system supports the presence of multiple users in a cell by resorting to a different interleaver per user. Therefore the choice of the interleaver critically impinges on system performance. A new interleaver structure is proposed for the so-called STBC-OFDM-IDMA [space-time block coding (STBC), orthogonal frequency division multiplexing (OFDM) and IDMA] architecture, combining the viable features of the STBC, the OFDM and the IDMA techniques. This interleaver is based on the new idea of adopting permutation control keys generated using two cryptography elliptic curves in which the degree of randomness of the interleaved sequence is scalable by using several rounds and a different subkey in each round. In addition to offering a certain degree of data security, it is shows through simulation results that the resulting architecture incorporating the proposed interleaver yields a viable bit error rate performance.