DS-CDMA系统多波形优化的多址干扰抑制方法

摘要

针对异步直扩-码分多址(DS-CDMA)系统多址干扰引起误码率性能降低的问题,提出了DS-CDMA系统多波形优化的多址干扰抑制方法.首先,从常规波形中选取所有q(q≥3)种波形组合,通过q种波形能量谱的平均分别计算每种组合的等效波形能量谱;然后,引入能量谱平坦度量化计算每种组合的等效波形能量谱平坦度;最后,优化选取平坦度大的波形组合,并循环使用这些优化波形组合与扩频序列进行扩频信号的构造,同时,CDMA用户在发射端使用构造的扩频信号扩频并在接收端使用同样的扩频信号进行解扩.仿真结果表明:与双波形方法相比,多波形优化方法能够有效抑制用户间的多址干扰,使多址干扰下的CDMA用户误码率性能提升2 dB.%A method to suppress multi-address interference (MAI) with multiple waveform optimization for DS-CDMA systems is presented to focus on the problem of bit error rate (BER) performance reduction for MAI.All q(q≥3) waveform combinations (WC) are selected from the conventional waveforms.The equivalent waveform energy spectrum of each WC is calculated through averaging the energy spectrum of the q kinds of waveforms.Then,the energy spectrum flatness is introduced to calculate the flatness of these equivalent waveform energy spectrums.The WC with a larger flatness is selected and is circularly used with spread-spectrum sequence to obtain the spread-spectrum signal.CDMA users use the spread-spectrum signal to spread spectrum at transmitting terminals and to despread-spectrum at receiving terminals simultaneously.Simulation results and a comparison with the double chip waveform method show that the MAI among CDMA users is effectively suppressed,and the value of MAI parameter is further reduced by the multiple waveform optimization method while the BER performance improves by 2 dB.