Adaptive Subcarrier Allocation and Bit Loading for Multiuser OFDM Systems

This paper proposes a new algorithm of adaptive subcarrier allocation and bit loading for simultaneous voice and data transmission in multiuser OFDM systems. The algorithm dynamically assigns the number of subcarriers and bits/per symbol on each subcarrier for each user in a single cell. To cope with the stringent delay requirement of voice service, the subcarriers with low channel gains are assigned for voice transmission with a small number of bits per symbol to achieve the required bit error rate and transmission rate. With the remaining subcarriers, that generally have higher channel gains, and the transmission power, the throughput of data transmission is maximized by loading as many bits as possible on each subcarrier to achieve the required transmission rate and quality. Theoretical analysis and simulations on the proposed algorithm show that better performances are achieved compared to previously reported schemes.