简单空时编码发射机分集自适应OFDM系统

将自适应调制技术和空间分集技术有机地结合起来 ,提出了一种与简单空时编码发射机分集相结合的恒定比特率自适应正交频分复用 (OFDM)方案。该算法根据两径发射机的平均信噪比在各子载波上自适应地选择不同的调制模式 ,并保持恒定比特率。仿真结果表明 :在多径瑞利衰落信道下 ,该方案可以显著地改善 OFDM的性能。在无信道编码和误比特率为 10 - 5条件下 ,对于平均带宽效率为1bit/ (s.Hz)的双天线发射分集接收的自适应 OFDM系统与传统 OFDM系统相比可以获得约 35 d B的自适应分集增益。

Adaptive OFDM system with simple space-time coding transmit diversity

An adaptive orthogonal frequency division multiplexing (OFDM) scheme is described with a simple space time coded transmit diversity for frequency selected fading channel by combining adaptive modulation with spacial diversity. The different modulation types can be adaptively selected in all subcarriers using the average SNR of a two branch transmit diversity channel with a constant bit rate transmission adaptation algorithm. Simulation of the bit errors of an adaptive OFDM system with two branch transmit diversity shows that the OFDM performance in a multipath fading channel can be significantly improved using simple space time coded two branch transmit diversity. For 1 bit/s/Hz average bandwidth efficiency, the uncoded adaptive OFDM scheme with two transmitters and two receivers yields about 35 dB gains for a BER of 10 -5 compared to the conventional OFDM system.