先进的CDMA数字接收机

该文分析了Rake接收机存在的带内干扰和多址接入干扰等问题,提出了带横向滤波器和连续干扰补偿器的数字接收机,从而较好地解决了带内干扰、多址接入干扰等问题。     

一种CDMA接收机在单频点阻塞干扰环境中的性能分析

本文考虑同步码分多址通信系统在单频点阻塞干扰环境中,一种抗多址干扰单用户检测接收机(I.Acax等人1994年提出)的误码率特性.结果表明,这种接收机(A-T接收机)在系统用户数很大时仍具有良好的抗单频点阻塞干扰性能。     

一种CDMA接收机在单频点阻塞干扰环境中的性能分析

本文考虑同步码分多址通信系统在单频点阻塞干扰环境中，一种抗多址干扰单用户检测接收机的误码率特性。结果表明，这种接收机在系统用户数很大时仍具有良好的抗单频点阻塞干扰性能。     

宽带CDMA数字中频接收机

本文建立了宽带CDMA的阻塞模型,在此基础上,提出一种数字中接收机的实现方案,并对主要电路的性能要求作了分析,给出了关键器件设计与实现的方法。     

测量接收机

介绍了测量接收机的原理及对测量结果会产生明显影响的主要参数。     

多速率CDMA系统自适应接收机

随着移动通信的发展，多速率数据通信业务越来越多。第三代移动通信系统能够支持可变服务质量的不同数据速率业务。因此，多速率接收机的研究也越来越引起重视。多速率系统中，当干扰信号具有不同速率参数时，不同用户的周期平稳性不同，单速率自适应FIR接收机的性能会严重下降。提出了一种适合于多速率多址干扰下的自适应滤波器组接收机，仿真结果表明，自适应滤波器组接收机能够更有效地消除多种模式的多址干扰，比单速率接收机具有更好的性能。     

短波干线通信接收机的阻塞现象

一、概述近年来,短波频段使用的日趋拥挤,发射功率的日益增高,使接收机往往不得不处在与信号频率相距极近的强干扰条件下进行工作.这些干扰频率虽处在接收机通频带之外,但因前几级电子管受强干扰作用而处于非线性状态下工作,往往会引起信号阻塞、交叉调制等附加干扰.短波干线通信的距离极长,加上短波传播中经常有的衰落现象等,这就确定了短波干线通信接收机必须是高灵敏度的,显然,这种高灵敏度接收机是更容易     

CDMA移动台GPS接收机测试系统

本文阐述了CDMA移动台GPS接收机测试系统相对位置定位和绝对位置定位的精确度进行校准,能够完成移动台GPS接收机灵敏度的认定工作。     

STBC MIMO CDMA系统CMVDR接收机研究

提出了STBC MIMO CDMA系统中一种新的基于多用户ML估计的带制约的最小方差无失真响应(CMVDR)接收机，能有效抑制多址干扰(MAD和符号间干扰(ISI)。给出了多用户、多径的STBC MIMO CDMA系统信道模型及ML参数估计，并给出了分部加权和整体加权两种CMVDR接收机，本接收机也适用于SIMO CDMA系统。进行了系统模拟，并对分部加权和整体加权两种CMVDR接收机的性能以及自适应CMMSE接收机的性能进行了比较分析。     

CDMA移动台接收机的研究与实现

研究了CDMA系统中移动台接收机的主要技术，设计并实现了CDMA系统中移动台的捕获跟踪、RAKE接收和频率校正等模块。     

VLSI Implementation of the Multistage Detector for Next Generation Wideband CDMA Receivers

The multistage detection algorithm has been proposed as an effective interference cancellation scheme for next generation Wideband Code Division Multiple Access (W-CDMA) base stations. In this paper, we propose a real-time VLSI implementation of this detection algorithm in the uplink system, where we have achieved both high performance in interference cancellation and computational efficiency. When interference cancellation converges, the difference of the detection vectors between two consecutive stages is mostly zero. Under the assumption of BPSK modulation, the differences between the bit estimates from consecutive stages are 0 and ±2. Bypassing the zero terms saves computations. Multiplication by ±2 can be easily implemented in hardware as arithmetic shifts. However, the convergence of the algorithm is dependent on the number of users, the interference and the signal to noise ratio and hence, the detection has a variable execution time. By using just two stages of the differencing detector, we achieve predictable execution time with performance equivalent to at least eight stages of the regular multistage detector. A VLSI implementation of the differencing multistage detector is built to demonstrate the computational savings and the real-time performance potential. The detector, handling up to eight users with 12-bit fixed point precision, was fabricated using a 1.2 m CMOS technology and can process 190 Kbps/user for 8 users.     

Design of Turbo-MUD Receivers for Overloaded CDMA Systems by Density Evolution Technique

This paper deals with a turbo multiuser detector suitable for applications in overloaded coded DS-CDMA systems. The turbo-MUD receiver is based on the use of a linear MMSE detector in the first iteration and a parallel interference cancellation scheme in the successive ones. The inputs of the interference cancellator are both the detector outputs and the soft information from a bank of turbo decoders. The performance of the proposed receiver has been derived by means of computer simulations and applications of the density evolution theory: in particular, this technique permits to properly evaluate the number of MMSE iterations, simplifying the overall receiver design.     

Blind Multiuser Receivers for ISI CDMA Channels Using the ε-Approximation Algorithms

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒｅｉｓｃｕｒｒｅｎｔｌｙａｓｉｇｎｉｆｉｃａｎｔｉｎｔｅｒｅｓｔｉｎｔｈｅｄｅｓｉｇｎｏｆｈｉｇｈ ｒａｔｅｗｉｒｅｌｅｓｓＣｏｄｅＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅＡｃｃｅｓｓ (ＣＤＭＡ)ｎｅｔｗｏｒｋｓ[1 ,9～1 0 ] .ＩｎｔｈｉｓＣＤＭＡｓｙｓｔｅｍ ,ｅａｃｈｕｓｅｒｉｓａｓｓｉｇｎｅｄａｕｎｉｑｕｅｓｉｇｎａｔｕｒｅｗａｖｅｆｏｒｍｔｈａｔｉｓｕｓｅｄｔｏｍｏｄｕｌａｔｅｉｔｓｔｒａｎｓｍｉｔｔｅｄｓｙｍｂｏｌｓ.Ｉｔｉｓ,ｈｏｗｅｖｅｒ,ｎｏｔｐｏｓｓｉｂｌｅｔ…     

EMI认证测量中FFT接收机测量时间的注意事项

引言 2010年6月,CISPR 16-1-1第3版第1修正案[1]规定,基于FFT的测量接收机(下简称FFT接收机)可用于电磁干扰认证测量,希望将扫描时间降低几个数量级,且不会降低测量准确度.FFT接收机在测量期间,通过在多个频率上并行计算,测量比分辨率带宽大得多的多个频谱段,如图1所示.与此相反,传统EMI接收机用给定的测量时间,在分辨率带宽内测量信号,因此对于整个频率范围需要较长的扫描时间.     

Performance of Nonlinear Receivers in Asynchronous Spectral-Phase-Encoding Optical CDMA Systems

Because of limits on the speed of the photodetector, a nonlinear thresholder is needed at the receiver of a spectral-phase-encoding optical code-division multiple-access system to discriminate between the correctly decoded short pulse and the low-intensity interference. The two most common nonlinear receivers based on second harmonic generation and self-phase modulation effects are analyzed in this paper. Mathematical models are provided, and analytical results are obtained to estimate the receivers' performances. Numerical simulations are carried out for both receivers with different system parameters. Both m-sequences and random binary codes are examined for spreading. The results provide a profile of how these nonlinear receivers perform with various system settings. It is found that, when an m-sequence is used as the spreading code, the encoded signal does not obey Gaussian statistics, and the system performs better than an equivalent system using a random code.     

Performance Analyses of OFDM–CDMA Receivers in Multipath Fading Channels

Orthogonal frequency-division multiplexing (OFDM) is a promising scheme for multicarrier (MC) transmission. The combination of OFDM and code-division multiple access (CDMA) which is referred to as OFDM–CDMA, has recently attracted much research interest in wireless communications. In this paper, we evaluate the downlink performance for two forms of adaptive OFDM–CDMA receivers in multipath fading channels: 1) MC–CDMA and 2) MC–direct sequence (DS)–CDMA. We propose theoretical minimum mean square errors (MMSEs) for MC–CDMA and MC–DS–CDMA to compare the performances in different situations. Moreover, one drawback of OFDM schemes is the rate reduction due to the cyclic prefix (CP) overhead, which significantly affects the channel utilization in MC–DS–CDMA systems. We propose adaptive receiver structures with both subcarrier- and code-interval equalizations to improve the performance of MC–DS–CDMA systems with shorter or no CP. Simulation results demonstrate the effectiveness of the proposed receivers and the correctness of the theoretical derivations.      

测量和分析CDMA导频污染的利器--中兴ZXPOS CNA1软件

介绍了利用中兴通讯自主开发的无线网络规划优化系列软件NetScope中的分析软件ZXPOS CNA1来测试和分析CDMA网络优化中的导频污染问题，并通过实际案例归纳总结出解决导频污染的常用方案。     

利用频域检索的单音干扰消除算法

在正交频分复用（OFDM,Orthogonal Frequency Division Multiplexing）系统中,当每次处理的OFDM符号较少时,OFDM数据子载波上的调制符号将严重影响单音干扰的参数估计。针对这个问题,本文提出一种利用频域检索的单音干扰消除算法。该算法首先利用离散傅里叶变换（DFT,Discrete Fourier Transform）粗估计单音干扰频点,然后通过检索干扰频点附近子载波的调制符号,消除其对单音干扰频域主瓣的影响,提高干扰参数估计精度,从而实现精确的单音干扰重构与消除。仿真结果表明,新算法可以有效地提高单音干扰参数估计精度,并可以降低OFDM系统误码率。      

基于FFT滑动平均极大似然法的正弦信号频率估计

该文基于正弦信号采样序列的FFT频谱,利用谱图上多条显著谱线与峰值谱线实部之间的关系,推导建立了一用于信号频率估计的滑动平均模型,基于此模型得出的极大似然频率估计器结合传统的Quinn方法后得到一种新的基于FFT谱滑动平均极大似然估计算法。仿真实验表明该算法精确有效,估计性能优于Rife,Quinn法,十分接近CRLB下限,计算量不大且信噪比门限要求可降至-9dB左右。