用于CDMA的四相混沌扩频序列

本文由混沌映射产生用于直扩码分多址（ＤＳ／ＣＤＭＡ）系统的四相扩频序列，证明了周期为Ｎ的此类扩频序列的四种广义奇相关均服从均方值为Ｎ的瑞利分布。混沌四相序列的相关峰值较混沌二相序列有显著的下降，多址性能与传统四相扩频序列相同。     

二相与四相无限折叠混沌扩频序列的相关特性分析

本文利用无限折叠迭代混沌映射产生二相与四相混沌扩频序列。分析了序列轨迹点具有的分布律与相关特性,模拟结果表明它们分别能获得比同等长度的二相与四相Logistic序列、四相Chebyshev序列、m序列、Gold序列更好的自相关与互相关性能,有利于解决CDMA移动通信中对相关性要求很严格的抗多址（多径）干扰、多用户检测等关键问题。     

用于混沌扩频保密通信的不等长四相扩频序列

本文重点研究不等长四相混沌扩频序列的广义奇互相关性质。理论分析和仿真实验表明,不等长与等长的四相混沌扩频序列在许多方面具有相似的性质,所获结果为不等长四相混沌扩顺序列在保密通信等方面的应用提供了理论基础。     

基于混沌和CNN交错反馈产生扩频序列的性能分析

提出了一种基于细胞神经网络和混沌交错反馈产生扩频序列的设计方法,用计算机仿真对该混沌扩频序列的平衡特性、游程特性、位移特性、相关特性和线性复杂度等伪随机特性进行了系统的分析,并分析了该序列的奇/偶相关特性.结果表明,该混沌扩频序列具有理想的伪随机特性,可以作为扩频通信中的扩频码,同时系统的交错加强了通信的保密性.     

一种适合多载波码分多址系统的扩频序列

多载波码分多址（MC-CDMA）技术结合了正交频分复用（OFDM）技术和码分多址（CDMA）技术的优点,具有数据传输速率高、频谱利用率高、抗干扰能力强和系统容量大的优点,是现阶段备受瞩目的一种无线通信方式。由于该通信系统中的码分多址技术结合了多载波调制技术,所以要求该系统中使用的扩频序列在兼具良好的自相关、互相关特性的同时,还要有较低的峰均比,这对扩频序列的设计提出了较高的要求。为了满足上述要求,设计了一种以Golay码为基础码,以m序列对Golay码进行加扰的扩频序列,该扩频序列具有良好的自相关、互相关特性,且峰均比较低。通过对比仿真验证,证明了本文中设计的扩频序列具有良好的特性,适用于MC-CDMA系统。     

混沌扩频序列在多用户DS-CDMA系统中的应用

分析了混沌伪随机序列的自相关和互相关特性,采用Logistic序列作为扩频序列应用到多用户DS-CDMA系统中.分析了不同用户数下多用户干扰对系统BER的影响,并与M序列扩频系统进行了比较.计算机仿真表明,混沌伪随机序列具有优良的自相关和互相关特性,和传统的M序列相比,采用混沌扩频序列,可以大大降低系统的多用户干扰,使得系统的BER性能有大幅改善.     

混沌扩频序列产生器

本文给出了基于一类混沌映射的扩频序列产生方法,运用混沌的遍历理论分析了周期趋于无穷时混沌扩频序列的性能,并对实际性能作了计算机模拟。结果显示,混沌扩频序列具有良好的平衡特性、相关特性和理想的线性复杂度,且数量极多,是直接序列扩频通信的优选序列。     

Logistic映射混沌扩频序列的奇/偶相关特性分析

本文简要分析了Logistic映射混沌扩频序列的奇/偶相关特性以及序列的有限长度效应对奇/偶相关特性的影响;提出了一种EOE Logistic映射混沌扩频序列的构造方法.理论分析表明,EOE Logistic映射有限长度扩频序列的奇/偶相关特性较原序列有所改善.计算机仿真结果验证了理论分析的正确性.     

非线性扩频序列的Hamming相关特性

本文讨论了两类非线性扩频序列（Ｎｏ序列和Ｋａｓａｍｉ序列）的Ｈａｍｍｉｎｇ相关特性,求出了这两类扩频序列的Ｈａｍｍｉｎｇ相关函数值,就Ｈａｍｍｉｎｇ相关特性而言,这两类序列不具有最佳相关性能。     

混沌扩频序列在多用户DS-CDMA系统中的应用

分析了混沌伪随机序列的自相关和互相关特性,采用Logistic序列作为扩频序列应用到多用户DS—CDMA系统中。分析了不同用户数下多用户干扰对系统BER的影响,并与M序列扩频系统进行了比较。计算机仿真表明,混沌伪随机序列具有优良的自相关和互相关特性,和传统的M序列相比,采用混沌扩频序列,可以大大降低系统的多用户干扰,使得系统的BER性能有大幅改善。     

基于四相正交序列的ZCZ序列构建方法

提出了一种新的构建四相ZCZ序列的方法，并且构建的四相ZCZ序列具有较宽的零相关区。提出的方法对于构建N相ZCZ序列也是有效的。     

Quadriphase sequences for spread- spectrum multiple-access communication

This paper studies constructions for quadriphase sequences that are suitable for use as signature sequences in quadriphase spread-spectrum multiple-access communications. Quadriphase sequences are closely related to biphase (i.e., binary) sequences, and many of the properties of the former can be expressed in terms of properties of the latter. Methods of construction are presented which obtain sets of quadriphase sequences from sets of biphase sequences. Methods of construction of quadriphase sequences are provided based upon the properties of the multiplicative characters of the finite field GF(q)whereq equiv 1 mod 4. These methods use codewords from low-rate Reed-Solomon codes, which are mapped onto the fourth roots of unity.2q + 2sequences of periodq - 1are constructed, for which the maximum magnitudes of the periodic cross correlation and the periodic out-of-phase autocorrelation are bounded by3 sqrt{q} + 5.     

Binary and quadriphase sequences with optimal autocorrelation properties: a survey

Time-discrete signals with good autocorrelation properties are used in various applications in communications engineering. From an implementation point of view, usually sequences with a small phase alphabet and a maximal energy efficiency, i.e., a uniform envelope, are most favorable. For this reason, known methods as well as several new construction techniques of binary and quadriphase sequences with optimal or best known autocorrelation properties are discussed in this correspondence. In many cases, the achievable correlation properties can be improved significantly if a single zero element per sequence is accepted. These "almost" binary and "almost" quadriphase sequences are considered as well. The optimality criteria used include the maximum absolute sidelobe and the merit factor of the periodic and the odd-periodic autocorrelation function, respectively. For sequence lengths of up to 44 in the binary case and up to 32 in the quadriphase case, the best known parameters obtained by computer search are compared with the constructed results.     

Error probabilities for generalized quadriphase DS/SSMAcommunication systems with random signature sequences

Methods to determine the average error probabilities in quadriphase direct-sequence spread spectrum multiple-access (DS/SSMA) communication systems are proposed. The systems being considered employ random signature sequences and arbitrary chip waveforms that are time-limited to one chip interval. The methods range from an algorithm that determines upper and lower bounds with arbitrary accuracy, to simple formulas that provide accurate estimates efficiently. Each method will find applications in different areas. Numerical examples are provided to illustrate each of the methods     

四相zcz序列的交织构造

为了弥补四相正交序列周期短的缺陷,将最佳四相正交序列应用于零相关区(ZCZ,Zero Correlation Zone)序列中,提出一种用交织法构建四相ZCZ序列的方法。首先选择合适的移位序列,经交织变换生成具有更长周期的ZCZ序列,再用正交矩阵将该序列进行扩展而得到新的序列集,实现了最佳四相正交序列和正交矩阵的结合。该方法构造的序列具有更大的周期和较大的容量,从而可以更好地在实际工程中加以利用。     

灵巧干扰对Taylor四相码信号的干扰效果分析

介绍了Taylor四相码的产生和性能,针对其带外频谱衰减快、辐射频谱宽度窄而难于干扰的特点,结合噪声干扰和欺骗干扰的特性对Taylor四相码进行灵巧干扰.通过Matlab仿真验证了灵巧干扰的有效性,并给出了干扰模型与仿真结果.     

Mismatched filtering of periodic quadriphase and 8-phase sequences

Quadriphase and 8-phase sequences with good autocorrelation properties are required in higher order digital modulation schemes, e.g., for channel estimation or synchronization. Since such sequences with perfect periodic autocorrelation function exist only for a few lengths, mismatched filtering is discussed. Mismatched filtering entirely suppresses all sidelobes of the correlation function at the expense of a slightly reduced signal-to-noise ratio (SNR). We present new construction methods for quadriphase and 8-phase sequences which exist for many lengths and exhibit significantly lower SNR losses than any other known sequences.     

一种高安全性的复合混沌序列的性能研究

基于Logistic型混沌序列及Chebyshev型混沌序列构造出一种新的复合型混沌序列。对该复合型混沌序列的初值敏感性和复杂度等混沌性质以及平衡性、相关性等扩频性能进行了仿真研究。仿真结果表明,该复合型混沌序列有着更强的初值敏感性和更高的复杂度;除此之外,该复合型混沌序列在平衡性、自相关、互相关方面性能不仅优于原混沌序列,而且与应用在GPS系统中的P码相比,在相关性性能方面也有优势。本文提出一种序列优选方式,通过该优选方法选出的复合型混沌序列数目比Logistic型和Chebyshev型混沌序列的优选序列数分别多出31%和67%。该复合型混沌序列是一种安全性高,扩频性能优良,生成简单,序列数目众的扩频码片。     

Design of pseudonoise sequences with good odd and even correlationproperties for DS/CDMA

Proposes and investigates a method for designing pseudonoise (PN) sequences having both good odd and even correlation properties, which are important for acquisition and demodulation in spread spectrum (SS) communications. Odd correlation properties of PN sequences should be designed as well as their even or periodic correlation properties so that the cochannel interference can be reduced as small as possible. Polyphase PN sequences with such good correlation properties can be derived from biphase PN sequences with a good aperiodic correlation property under a certain condition. Absolute values of odd and even correlation functions of these sequences are equal at each shift. The authors evaluated their peak correlations properties and bit error rate performance. Numerical evaluations show that the derived polyphase sequences have lower peaks of correlations and lower bit error rate than their original sequences. Furthermore, the authors defined the generalized odd correlation function for polyphase SS systems, and derived a way to improve the generalized odd correlation properties