可变增益CDMA和多码CDMA的原理和性能比较

阐述了下一代CDMA的设计中可变增益和多码两种多速率方案的原理,对可变扩展增益方案的不同扩展因子的性能,及这两种方案的“远近问题,信道估计MSE,信干比SINR的性能进行了介绍和比较。     

时隙多码CDMA和单码 CDMA多址接入技术研究

CDMA作为一种多址接入技术在无线网络中已广为应用.本文在多码CDMA和单码GDMA研究的基础上,构造了时隙多码CDMA和单码CDMA在无线分组数据网络中的随机多址接入模型,并且分析了两种系统的吞吐率特性和归一化时延特性.     

时隙多码CDMA和单码CDMA多址接入技术研究

ＣＤＭＡ作为一种多址接入技术在无线网络中已广为应用。本文在多码 ＣＤＭＡ和单码 ＣＤＭＡ研究的基础上, 构造了时隙多码ＣＤＭＡ和单码ＣＤＭＡ在无线分组数据网络中的随机多址接入模型,并且分析了两种系统 的吞吐率特性和归一化时延特性。     

一种新的光CDMA编码方案

本文以光正交码（OOC）为基础,提出了一种新的光CDMA编码方案。这种新的方案充分利用了已有的成熟的OOC编码技术,可以灵活方便地构造出光正交跳频以及光正交时间/频率组合码。这种新的地址码具有良好的自相关、互相关性能、较大的容量和良好的系统性能,还可以灵活地和现有的光天源器件相匹配。     

一种扩展戈莱码的编译码方法

在MIL-STD-188-141A协议中采用的是扩展戈莱(Golay)码。它是[23,12]戈莱(Golay)码演变而来的。提出了一种在[23,12]Golay生成矩阵的基础上得到扩展戈莱码生成矩阵的方法,并对扩展戈莱码的译码方法进行了讨论,最后用MATLAB对编译码算法进行了仿真。     

一种可以高速传输数据的MTCM正交序列多码CDMA系统

为了有效地实现用户高速数据的传输本文提出了一种ＭＴＣＭ正交序列多码ＣＤＭＡ系统。这对此系统在ＡＷＧＮ信道的性能进行了计算，并和未编码系统的数值结果进行了分析和比较。     

一种新的RS码识别方法

现有的信道编码识别方法通常基于矩阵化简来进行识别,其容错性能较差。针对此问题,提出了一种新的RS码识别方法。首先建立了盲识别模型,利用矩阵秩函数识别RS码的二进制衍生码长,利用码根信息差熵函数识别本原多项式;在此基础上,利用码根统计完成生成多项式的识别。该方法避免了繁琐的矩阵化简方法,复杂度较低。实验结果表明,在较高误码率环境下,该识别方法能够利用较少数据完成对RS码的识别,且识别效果较好。     

一种基于二进制矩阵的CDMA长码状态快速算法

本文介绍了一种基于二进制矩阵迭代运算的确定当前时刻CDMA长码状态的快速算法 ,对其性能进行了仿真和分析 .与传统的MSRG结构或SSRG结构的CDMA长码状态算法的运算量相比较 ,新方法将巨大的运算量 (可能出现 2 42 - 1次的长码发生器运算 )降为不超过 4 2× 4 2次长码发生器运算和 4 2次 4 2× 4 2阶矩阵模 2相乘运算 ,极大的提高了确定当前时刻长码状态的速度 ,在基本不增加硬件复杂性的基础上 ,提高了确定当前时刻长码的实时性能     

一种新的多速率时频码MB-OFDM超宽带系统模型

该文提出了一种新的多用户超宽带系统模型,该模型基于MB-OFDM系统,各个用户的数据通过在时域和频域同时进行的一种编码(Time-Frequency Code,TFC)进行区分。同时给出了针对这种系统的一种自适应TFC分配算法,该算法在保证每个用户的最小传输速率请求的前提下,使传输功率最小化。理论分析和实验表明,该系统及其相应的TFC分配算法可以有效地增加多速率用户接入系统的能力,并且有效地节省发射功率,而这正是一个超宽带系统所需要的。     

一种适合多码传输的码序列产生方案

通过研究准同步条件下Gold序列的正交相关特性，针对解决多速率业务并行传输时多码需求的问题，提出了一种Gold码和Gold序列的分类方法。     

A new design method of CDMA spreading codes based on multi-rate unitary filter bank

It is well-known that the multi-valued CDMA spreading codes can be designed by means of a pair of mirror multi-rate filter banks based on some optimizing criterion. This paper indicates that there exists a theoretical bound in the performance of its circulating correlation property, which is given by an explicit expression. Based on this analysis, a criterion of maximizing entropy is proposed to design such codes. Computer simulation result suggests that the resulted codes outperform the conventional binary balanced Gold codes for an asynchronous CDMA system.     

Performance of a CDMA System with an Adaptive Receiver and a New Family of Complex Valued Spreading Sequences

This paper presents the results of a capacity evaluation for a direct-sequence (DS), code-division, multiple access (CDMA) system over both an additive white Gaussian noise (AWGN) channel and a Rayleigh fading channel. The system considered uses an adaptive receiver. The performance of sets of sequences from various binary and complex valued families is examined. The performance of the system is measured in terms of the total efficiency, and it is shown that the new sequence sets offer higher system capacity and lower signal-to-noise power spectral density ratios.     

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。     

Spreading‐code‐dependent bit error rate and capacity analysis for finite asynchronous CDMA systems

Most CDMA systems serve only finite number of active users. Therefore, using Gaussian approximation to evaluate its performance is inappropriate. In such finite CDMA systems, the selection of spreading codes is of great importance because its performance is very much spreading‐code‐dependent. In this paper, a new algorithm based on multiple variable Bernoulli process is introduced to evaluate bit error rate due to co‐channel interference and thus the capacity of a CDMA system. The algorithm can also be used for large‐sized CDMA systems. The results show that small Kasami and Gold‐like codes offer higher capacity than the others do. Copyright © 1999 John Wiley & Sons, Ltd.     

A Design of 2 L-Channel FIR Paraunitary Filter Banks with Complex Coefficients

1　ＩｎｔｒｏｄｕｃｔｉｏｎＭｕｌｔｉｒａｔｅｆｉｌｔｅｒｂａｎｋｓｈａｖｅｆｏｕｎｄｍａｎｙａｐｐｌｉｃａ ｔｉｏｎｓｉｎｄａｔａｃｏｍｐｒｅｓｓｉｏｎ ,ａｄａｐｔｉｖｅｆｉｌｔｅｒｉｎｇａｎｄｔｅｌｅｃｏｍｍｕｎｉｃａｔｉｏｎｓ[1～2 ] .Ａｎｄｍａｎｙｍｅｔｈｏｄｓｆｏｒｄｅｓｉｇｎｉｎｇｔｈｅｆｉｌｔｅｒｂａｎｋｓａｒｅｐｒｏｐｏｓｅｄ .Ｈｏｗｅｖｅｒ,ｔｈｅｓｅｆｉｌｔｅｒｂａｎｋｓａｒｅａｌｍｏｓｔｆｉｌｔｅｒｓｗｉｔｈｒｅａｌｃｏｅｆｆｉ ｃｉｅｎｔｓ.Ｉｎｔｈｅｃａｓｅｏｆｐｒｏｃｅｓｓ…     

异步码分多址通信中混沌扩频序列的选择

根据异步码分多址通信的特点,本文提出了扩频序列的优选准则,并给出了混沌序列的优选方法.计算结果表明,根据该方法优选的混沌序列伪随机特性得到了显著提高,与Gold序列相比较,更适于异步码分多址通信系统的应用.最后,对各种混沌码组的性能进行了比较.     

A Novel Space-time Spreading Transmit Diversity Scheme for Wireless CDMA System

1　Introduction　Thefundamentalchallenge,whichmakesreliablewirelesstransmissiondifficult,isthetime varyingmulti pathfading .Theoretically ,themosteffectivetechniqueformitigatingmulti pathfadinginawire lesschannelistransmitterpowercontrol.ButinCDMAsystems,powercontrolislimitedbythetransmitterdynamicrangeandthenear fareffect.Diversityisanefficientandpracticaltechniquetocombattime varyingmulti pathfading .Andanten nadiversityiswidelyappliedtoreducetheeffectofmulti pathfading .Theclassicalappro…     

A Multicarrier CDMA System for Joint Time-Frequency Diversity Using Divided Spreading Sequence

One of the principal disadvantages of multicarrier modulation technique is the sensitivity to the frequency offset introduced by Doppler shift. This frequency offset introduces inter-carrier interference (ICI) among the multiplicity of carriers in the multicarrier modulated signal. However, Doppler spread induced by temporal channel variations can provides another means for diversity. In this paper, we propose a modified multicarrier code division multiple access (CDMA) system to exploit Doppler diversity as well as multipath diversity. The key work of our framework is a canonical time-frequency-based decomposition of the mobile wireless channel into series of independent fading channel. The decomposition naturally leads to a time-frequency generalization of the Rake receiver that exploits both multipath and Doppler diversity.     

基于保护环的ATM多播树自愈机制

本文提出了一种采用预设计的方法生成可恢复ATM多播树的自愈机制,该机制考虑了多播树的任何单链路和单节点失效两种情况.多播树的所有链路都包含在不同的保护环中,点相邻的保护环通过不经过公共点的接通路径相连.节点检测到失效时,只需激活相应的保护环和接通路径即可.仿真结果验证了该机制的有效性和可靠性.