Optimum multiuser OFDM systems with unequal subchannel assignment

This paper considers the design of multicarrier transceiver systems like OFDM/DMT supporting multiple users. The supported users may have differing quality of service (QoS) requirements, quantified by their respective bit rate and symbol error rate specifications. Different users on the system can be potentially assigned different number of subchannels, to reflect their service priorities. Our goal is to minimize the transmitted power given the QoS specifications for the different users, subject to the knowledge of colored interference at the receiver input of the OFDM system. In particular we find an optimum bit loading scheme that distributes the bit rate transmitted across the various subchannels belonging to the different users, and subject to this bit allocation, determine an optimum transceiver.