A novel multiuser subcarrier and bit joint allocation algorithm for OFDM system

It has been suggested that multiuser orthogonal frequency division multiplexing (OFDM) systems employ adaptive subcarrier allocation as well as adaptive bit allocation. The Subcarrier and Bit Joint Allocation (SBJA) algorithm is proposed under the TDD mode of operation. Our objective is to maximize the overall data rate while simultaneously satisfying the requirements on each user´s quality of service (QoS), the total transmit power. The proposed algorithm has two steps by considering the user who just arrives and users in service respectively. Through introduction of ´service load´, different kinds of traffic have the same standard to compare. Simulation results show that SBJA algorithm can reduce outage percentage and increase the capacity of the system effectively over the fixed subcarrier and bit allocation. Moreover, the complexity of system realization in the SBJA algorithm is much less than that of rate adaptive (RA) optimization, while the spectral efficiency of SBJA can be close to that of the RA optimization.