Logistic扩频序列在MC-CDMA系统中的性能分析

Performance Analysis of Logistic Spread Frequency Sequence in MC-CDMA System

文章通过对Logistic映射产生的混沌序列的特性进行定量分析,证明了Logistic映射序列在MC-CDMA系统中能够实现扩频通信的适应性;随后在分析影响MC-CDMA系统信噪比及误码率主要因素的基础上,在MC-CDMA下行链路基于BPSK调制方式,选择m序列、Gold序列、Logistic映射混沌序列分别作为扩频序列进行了实验仿真,揭示了系统误码率随序列长度、用户数、子载波数、信噪比的变化关系。在用户数和序列长度一定的情况下,信噪比在8dB之前,使用三种序列系统的误码率几乎相同,在信噪比为12dB之后Logistic序列误码性能明显优于其它两序列。而在序列长度和系统信噪比一定的情况下,在8个用户之前采用不同扩频序列系统误码率区分不明显,而在8个用户之后,随着用户数的增多,Logistic序列与其它两序列的误码率区分更加清楚。

This paper proved Logistic map is adaptability for spread frequency sequence in MC-CD- MA systems, through analyzing the key points of chaotic spread frequency sequence; then, the author analyzes main factors of affecting the signal-to-noise （SNR） and the bit error rate in MC-CDMA system, chooses downlink, and uses BPSK modulate; meanwhile, the experiments have been done with logistic sequence, m sequence and Gold sequence to show how the sequence length, the user number, the number of subcarrier, and the signal-to-noise influence the bit error rate in MC-CDMA system. Hypothesis user number and sequence length invariable, when SNR no more than 8dB the experiment get the nearly same bit error rate, when after 12dB the Logistic sequence＇s performance obviously to surpass other two sequences . Hypothesis the sequence length and SNR invariable, only more than 8 users the discrimination between logistic sequence and another two sequences is more distinctive.