多载波时频联合分集码分多址系统及性能分析

On the performance of multicarrier time-frequency RAKE systems

多载波系统对频率偏移比较敏感,频偏会引起信道间干扰,进而使符号同步受到影响.这里提出了一种改进的多载波直接扩频序列码分多址(DS CDMA)系统,发射端通过对用户伪随机序列进行正交化处理使子载波信号在时域和频域的正交性达到最大化.接收端使用时频RAKE接收机,可以使系统具有频偏分集和时延分集的性能.仿真结果显示,采用时频RAKE接收的多载波直接扩频序列码分多址系统,误码率性能得到了显著提高.

Multicarrier systems are much more sensitive to frequency offset, which results in inter-carrier interference (ICI) and affects symbol synchronization. A modified multicarrier DS-CDMA (direct sequence code division multiple access) system is presented, in which the transmitter maximizes the orthogonality of subcarrier in time and frequency domain by dealing with the user's PN(pseudo noise) sequence in Walsh sequence. Moreover the combined performance of frequency diversity and time diversity can be gained by using time-frequency RAKE receiver. Simulation results show that the performance of BER (bit error rate) was improved largely in the multicarrier DS CDMA system with time-frequency RAKE receiving.