多用户自适应OFDM系统的比特分配算法

In this paper ,we study adaptive subchannel an bit allocation algorithms in multiuser OFDM system. The algorithm include two major type: minimization of the overall transmit power under the data rate constraint and maximization of the data rate under the power constraint, the two problems are referred as the margin adaptive(MA, the former) and rate adaptive(RA, the later). First, we study the optimal subchannel and bit allocation algorithms, which are nonlinear. it needs much of computation to solve them. In the text, we convert the optimal subchannel and bit allocation algorithms into liner ones and solve them by integer programming to make the problem simpler. However, because the number of constraints and variables increases, the complexity of the linear algorithms donˇt decrease. Due to this fact, we proposed a suboptimal approach which separately performs subcarrier allocation and bit loading. The approach needs much less computation than the original optimal approach. Simulation results indicated that the proposed suboptimal method can outperform existing techniques.