Interleave Division Multiple Access (IDMA)

In this chapter, we start with a comparison on non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA). We show that the performance difference between NOMA and OMA is marginal assuming perfect channel state information (CSI), capacity-achieving coding, and centralized control. The real challenges arise from channels without such idealistic assumptions. We will then discuss an interleave division multiple access (IDMA) scheme that provides an efficient NOMA solution in non-idealistic channel considerations. We will outline the following attractive features of IDMA: •IDMA facilitates a low-cost iterative technique for multi-user detection (MUD) . •IDMA with proper power control can achieve near-capacity multi-user sum-rate. •IDMA with decentralized power control can offer significantly higher throughput than conventional ALOHA in random-access environments. •IDMA together with data-aided channel estimation (DACE) can fully exploit the advantages of massive multiple-input multiple-output (MIMO) systems. Finally, we will briefly compare several proposals for LTE fifth-generation (5G) cellular systems. We will show that they share with IDMA the principle of reducing short cycles in their graphic representations so as to facilitate iterative detection. Some of the software used in this chapter are available in the following site: http://www.ee.cityu.edu.hk/7Eliping/Research/Simulationpackage/.