多用户OFDM系统的最优功率分配

Optimum power allocation of OFDM system with multi-User

本文从时域、频域、时频域三方面综合考虑多用户OFDM的功率分配方式,推出了各种情况下的最优功率分配方式。最后得出最优功率分配具有统一的water-filling形式,只是不同的分配方式,其Lagrange因子的取值不同。对多用户OFDM系统,其最大容量与子载波数目无关,每个子载波具有相同的平均功率分配。而对于每个用户而言,其平均功率分配方式与其经历的信道特性相关,当具有相同的信道特性时,每个用户分配的平均功率也相同。本文还提出了一种关于Lagrange因子的简单的迭代算法。同时根据上面分析的情况,提出了几种简单实用的功率分配算法。理论结果表明在多用户情况下,频域等功率分配算法接近于最优。

Three optimum power allocation equations of OFDM system with multi-user are derived in time domain, frequency domain and time-frequency domain. Conclusions are drawn through theory analysis that each subcarrier has the same fading statistics characters for multi-user system. Then maximum capacity achieved by optimum power allocation is irrelevant to the number of subcarriers. Finally, several simple power allocation algorithms are proposed which can achieve similar performance to optimum algorithm in frequency domain.