A concatenated coded multiplexing scheme for multiuser OFDM downlink

The allocation of available resources in an OFDM multiaccess system is usually done by allotting a fixed set of subcarriers to each user. Adaptive allocation has been suggested to improve performance and provide increased granularity in terms of minimum number of subcarriers available to each user. But it has several drawbacks associated with the need for robust channel estimates and computational loading algorithms at the transmitter. In this paper, we investigate an approach which spreads the data of all the users over the complete set of subcarriers by appropriate combination of coding, multiplexing and interleaving. We analyze the performance of such a system and demonstrate the potential for substantial coding, interleaving and diversity gains relative to fixed subcarrier allocation, but with lower computational and signaling cost than adaptive schemes. We also present simulations for a suboptimal decoding scheme when the setup is applied to multiuser scenarios.