基于MIMO-OFDM系统的改进型空时频编码算法

An Improved Algorithm of Space-Time-Frequency(STF) Codes Based on A MIMO-OFDM System

在宽带无线通信中,与信道延迟扩展相比符号周期变得越来越小,此时发射信号要经历频率选择性衰落。通过结合空时编码与宽带正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术,提出了一种能够同时获得时间、空间和频率分集增益的分组正交空时频编码方法。该方法采用新的映射规则,降低了OFDM子载波之间的相关性。与已有的空时频编码方案相比,可获得更大的分集增益,改善了系统的误比特率性能,且并未导致系统的复杂度增加。

Sections 1 and 2 of the full paper explain our algorithm mentioned in the title, which we believe is better than existing ones and whose core consists of： （ 1 ） if the symbol period becomes shorter compared with delay expansion of the channel in the broadband wireless communication systems, the transmitted signals will lead to frequency selective fading; by combination of space-time codes with orthogonal frequency division multiplexing （ OFDM）, we propose an encoding method of orthogonal space-time-frequency block codes which can simultaneously obtain space, time and frequency diversity gains; （2） aiming at de-correlation of the subcarriers of OFDM, we apply a new mapping rule. Fig. 2 gives simulation results, which, compared with the test data of existing schemes of space-time-frequency （STF） codes, show preliminarily that our scheme can indeed maximize diversity gains and achieve optimal system bit error rate （BER） performance with a moderate decoding complexity.