非理想信道估计下OFDM系统按比例自适应的子载波分配算法

Proportional subcarrier allocation algorithm for OFDM system with imperfect channel estimation

在满足用户带宽接入需求约束下,针对时分双工OFDM下行链路系统最大化系统加权和速率问题,提出按比例自适应子载波分配算法。在最大信噪比(SNR)子载波分配策略基础上,引入用户权重,提出按比例自适应子载波分配策略,据此给出用户带宽接入概率表达式,通过求解具有约束条件的非线性最优化问题,得到满足用户带宽接入需求的用户权重。仿真结果表明:所提算法可自适应地根据用户带宽需求因子和平均SNR给出对应用户权重,并据此按比例地为用户分配所需带宽;随着用户平均SNR的增大,信道估计误差方差减小,当平均SNR达到17.5 d B时,几乎可以达到与理想信道估计下子载波分配算法相同的性能。

This paper proposes a proportional subcarrier allocation algorithm in a response to OFDMTDD system downlink-an effort to maximize weighted sum rate while meeting bandwidth access demands.This study consists of applying Max-SNR subcarrier allocation strategy to introduce the user weights and thereby producing proportional subcarrier allocation strategy;achieving the expression of probability of bandwidth access of users based on the proposed strategy,and finally realizing the user weights meeting bandwidth access demands by solving nonlinear optimization problem with constrains.Simulation results shows that proposed algorithm is capable of adaptively providing corresponding user weights according to user＇ s bandwidth demand coefficient and average SNR and allocating the required bandwidth for users based on the previously achieved weight;decreasing the variance of channel estimation error depending on the increased average SNR;and working with almost the same performance as SA-PCE （subcarrier allocation under ideal channel estimation） algorithm,as results when the average SNR is 17.5 dB.