Cyclically Shifted Multiple Interleavers
Katsutoshi Kusume, Gerhard Bauch · 2006
We propose a simple strategy to generate multi- ple interleavers. As suggested in literature, using user-distinct interleavers is an effective means to separate multiple users, if applied in addition to user-specific spreading codes in code division multiple access (CDMA). In this paper we particularly focus on interleave division multiple access (IDMA), which has a close relation to CDMA, but users are separated only by user- distinct interleavers. Hence, multiple interleavers are essential system components for IDMA. Despite its importance, usually interleavers for such systems are randomly chosen and there are only few papers on the generation of multiple interleavers. We show that the conventional multiple interleavers proposed for CDMA are not sufficient for the user separation in IDMA. Moreover, in order to minimize memory requirements and signaling overheads to store and exchange interleavers, a simple interleaver construction rule is desirable in practical systems. Therefore, we propose to derive multiple interleavers from a single interleaver, common for all users, with only a few user- distinct cyclic shifts. Although this simple design is empirical and no optimality is claimed, simulation results show sufficiently good performance. We also proposed a simple procedure to exchange the information of interleavers.