Grouped Interleave-Division Multiple Access

Recently, a new multiple access scheme called interleave-division multiple access (IDMA) has attracted much attention, in which interleaves are used as the only means for user separation. It has been shown that the IDMA can achieve near single user performance in multi-user environment with very low receiver complexity. In this paper, active users are arranged into several groups to form a new scheme called grouped-IDMA, where each group of users is characterized by an orthogonal code. By employing group-specific orthogonal spreading code for group separation, grouped-IDMA inherits the advantages of IDMA and orthogonal CDMA. Our analysis and simulation results show that the new scheme outperforms IDMA when user number is relatively large, and the multiple access interference (MAI) can be reduced in a more efficient way. In addition, the group size, an important parameter to the proposed scheme, is also discussed in order to achieve optimal performance.