OFDM系统的自适应调制技术

Adaptive Modulation for OFDM

首先介绍了OFDM系统中的自适应调制技术,然后在chow自适应调制算法的基础上提出一种改进的OFDM自适应比特分配算法,该算法适用于严重频率选择性衰落、信噪比较低的情况.仿真结果表明,在相同频带利用率情况下,使用自适应调制技术的OFDM系统与传统的使用固定比特分配的OFDM系统相比,误比特性能有了显著提高;改进的自适应调制算法性能与原算法相近,但实现简单、性能稳定,适合在宽带无线通信系统中运用.

In this paper,at first the adaptive modulation technique of OFDM is described,then on the basis of chow' s adaptive modulation algorithm,an improved adaptive bit allocation algorithm in OFDM is presented. The improved algorithm is more suitable for the heavy frequency-selective fading channel at poor signal to noise ratio.The simulation results both show that the system outperforms the traditional OFDMsystem in BER performance under the same bandwidth efficiency,and the improved algorithm which is more simple and stable maintains the same performance compared with the original algorithm.Because of that it is suitable for application in broadband wireless communication system.