Adaptive Sub-Carrier and Bit Allocation Algorithms for Multi-User OFDM Wireless Systems

Multi-user orthogonal frequency division multiplexing (OFDM) with adaptive sub-carrier and bit allocation are considered in this paper. Assuming having the knowledge of the instantaneous users´ channel gains, three typical dynamic sub-carrier and bit allocation algorithms are analyzed and compared. All the algorithms´ goal are to minimize the total transmit power with the user data rate constraint. Here, an improvement method is proposed for Zhang algorithm. Finally, performance comparisons between adaptive schemes and static ones are given. The results prove that adaptive algorithms´ performances are greatly better than that of the traditional fixed sub-carrier allocation method.