引入冗余的差分空时分组编码OFDM系统

Redundancy Introduced Differential Space-Time Block Coded OFDM System

鉴于引入冗余的差分空时分组编码(DSTBC:DifferentialSpaceTimeBlockCode)是在平坦瑞利衰落信道下得出的,且提供的速率有限。为了在频率选择性衰落信道中提供高速数据业务,提出了一种基于该码的OFDM(OrthogonalFrequencyDivisionMultiplexing)系统。发端首先进行DSTBC编码,然后进行OFDM调制,再通过两根发天线将信号发送出去;接收端使用一根天线,先进行OFDM解调,再使用Viterbi算法进行DSTBC译码。仿真结果表明,由于使用的新差分空时分组码可以提供编码增益,该系统的性能比传统的DSTBC编码OFDM系统要好,在信噪比(SNR:SignalNoiseRatio)较高时可以改善约1dB,比使用相干STBC(SpaceTimeBlockCode)的OFDM系统相差2dB。若在此DSTBC编码之前级联一个外码,可进一步改善系统性能。

Redundancy introduced DSTBC(Differential Space-Time Block Code) is given in flat rayleigh fading channels, and it can only provide a limited speed. To provide high speed data service in frequency selective fading channels, a new differential space-time block coded OFDM (Orthogonal Frequency Division Multiplexing)system based on the DSTBC scheme is provided. The transmitter first performs DSTBC, then OFDM modulation, and finally signals are transmitted from two antennas. The receiver first performs OFDM demodulation, then DSTBC decoding with Viterbi algorithm. The new DSTBC scheme provides a differential coding gain due to redundancy introduced in the differential encoding. Simulation results show that the new DSTBC coded OFDM system can provide a better performance than traditional DSTBC coded OFDM system, and can improve about 1dB for higher SNR, which is only 2dB worse than coherent space time block coded OFDM system. If an outer code is concatenated before the DSTBC encoder, the system performance can be further improved.