非理想信道状态信息下的OFDM比特分配算法

提出一种在非理想信道状态信息条件下,以平均误比特率为目标的正交频分复用(OFDM)比特分配算法.该算法对子信道当前频率响应值进行估计,估计值经延时后反馈至发送端,并以此作为自适应比特分配的依据.仿真结果表明,当信道估计器的均方误差小于-15dB时,信道估计误差对自适应OFDM系统的性能影响不大.采用多个信道估计值来确定比特分配可以减小信道信息延时对系统性能的影响,有效提高系统性能.

Bit Allocation Algorithm for OFDM Systems with Imperfect Channel State Information

With imperfect channel state information(CSI),a bit allocation algorithm was proposed for orthogonal frequency division multiplexing(OFDM) systems.The algorithm aims at the constraint of the average bit error rate.The receiver transmits the channel estimates with delay to the transmitter.Adaptive bit allocation is based on the channel estimates.Simulation results show that channel estimation error is not a significant problem in adaptive OFDM systems as long as the mean square error(MSE) achieves-15dB.Performance loss is moderate when the MSE is less than-15dB.Worthwhile,the use of multiple estimates is shown to mitigate the effect of CSI delay and improve the performance.