Design and analysis of coded multiplexing for the multiuser OFDM downlink

The allocation of available resources/subcarriers is an important design aspect for next generation wireless OFDM multiuser systems. The approaches considered usually assign a subset of subcarriers to each user and do not consider the loss of coding and diversity gains when a user is allotted very few subcarriers. We investigate an approach which exploits the multiplexing diversity available in the system in the absence of channel state information at the transmitter. This is achieved by spreading the data of all users over the complete set of subcarriers by using an appropriate combination of coding, multiplexing and interleaving. The performance of such a system is analyzed and the potential for substantial coding, interleaving and diversity gains is demonstrated. This paper also outlines a new approach to evaluate performance bounds for concatenated codes with higher order modulation on a fading multipath channel, by simplifying the description of pairwise error events using an ideal modulator assumption. Simulations are presented for a suboptimal decoding scheme, which does not rely on information from other users