CDMA网络常见干扰的分析与排查

随着无线通信技术的迅速发展和无线设备的广泛使用,无线设备对CDMA通信网络的干扰会不断增多,而排除CDMA系统的干扰已成为我们无线优化中的重点和难点问题之一,也是提升和体现CDMA系统网络质量的重要保障。本文介绍了CDMA系统4类常见干扰的分析及排查方法。     

基于无线数传与CDMA的远程测控网络

文中提出了微功率无线数传网络与CDMA网络相结合,组成远程测控网络。该网络以无线数传网络连接测控终端,通过无线中继单元将测控数据传输到CDMA网络;以CDMA网络作为测控数据远程传输媒介,通过Internet与数据中心相连。该网络兼具无线数传与CDMA网络的优点,通信稳定可靠,安装及运行成本低廉,已经在油井远程测控系统中被应用。     

MISO CDMA transmission with simplified receiver for wirelesscommunication handsets

The next-generation wireless personal and mobile communication systems are expected to accommodate not only high-quality voice services, but also a broad range of other multirate services. Of the various multiaccess techniques, wide-band code-division multiple access (CDMA) has been regarded as an important part of the third-generation wireless communication systems because of its high frequency utilization efficiency and suitability for handling multimedia and multirate services. In this paper, we consider a system with a simplified receiver structure for direct-sequence CDMA (DS/CDMA) wireless communication handsets, in which improved performance is demonstrated when compared to a conventional DS/CDMA system with a RAKE receiver at the mobile station. We arrive at this system by finding the optimal solution to a general multiple-input single-output (MISO) DS/CDMA smart antenna system. We find that this solution reduces to a pre-RAKE with space transmit diversity system under the assumption that a simple one-finger matched filter is used at the receiver. This system combines the advantages of pre-RAKE diversity and transmit antenna diversity. It is shown that significant system performance and capacity improvements are possible. The numerical results also reveal that this system is not too sensitive to channel estimation errors     

CDMA无线网络工程规划分析

本文主要介绍了CDMA无线网络的关键技术和工程规划流程.首先说明了CDMA无线网络在通信系统中的重要地位,接着从传播模型的校正、链路预算、容量和干扰分析等方面阐述CDMA网络的关键性问题,最后,详细介绍了CDMA无线网络工程规划的流程,并且,通过仿真得出了符合要求的覆盖效果.     

基于无线移动网络的远程数据采集系统的设计

针对远程遥测遥控系统的需求,设计实现了通用分组无线系统(General Package Radio System,GPRS)无线数据传输终端,并构建了远程数据采集与控制系统。本文详细介绍了该无线数据传输终端的设计过程及该终端在码分多址(Code Division Multiple Access,CDMA)1X/GPRS无线移动通信网络设计方案中的应用,该无线传输终端稍做改动就可应用于车辆监控、无线抄表等远程遥测遥控系统中。     

基于 CDMA 网络监测系统的研究

将CDMA2000作为无线频谱移动监测系统中数据传输的通道,为无线频谱移动监测系统提供实时的数据,它使得无线频谱移动监测系统更为方便和快捷地对系统内的各种资源进行管理     

Transporting CDMA signals over an analog optical link

We have investigated transmitting wireless code division multiple-access (CDMA) signals from a remote antenna to a centralized base station over an analog optical link. We present specifications for transmission of standard (IS.95) CDMA signals and demonstrate that unisolated uncooled lasers can meet these requirements. Tests were conducted using both a 1.3-μm Fabry-Perot laser and a 1.55-μm distributed-feedback laser (DFB)     

W-CDMA无线多媒体通信系统设计考虑

为了研究和开发第三代移动通信系统,进行Ｗ－ＣＤＭＡ 无线多媒体通信系统和技术的研究十分必要。针对我们个人通信与扩频实验室正在研究开发国家８６３ 高技术通信主题Ｗ－ＣＤＭＡ无线多媒体通信技术的实验系统,我们提出了Ｗ－ＣＤＭＡ无线多媒体通信系统的系统结构,系统信道配置和功能安排,Ｗ－ＣＤＭＡ通信方式,分析了信号调制解调的性能,提出信号功率控制方法。     

CDMA cellular engineering issues

The frequency reuse efficiency for the proposed code division multiple access (CDMA) cellular system is analytically derived, and it is shown that the cell capacity of a fully loaded multiple cell system is about 75% of what would be available for a single cell system. In addition, an engineering issue in transitioning from analog advanced mobile phone system (AMPS) to CDMA system is discussed. Calculating excessive interference power due to a CDMA channel, it is shown that when a CDMA channel is introduced in a cell, there should be at least one ring of buffer cells, in which the analog channels falling into the CDMA band are not reused     

3G无线视频监控系统的设计与实现

随着3G技术的日益成熟和嵌入式技术的飞速发展,数字化视频监控系统将逐步替代传统的模拟视频监控系统,同时随着人们生活质量的提高和活动范围的不断扩大对无线视频监控系统的需求越来越迫切,所以利用3G网络进行实时视频传输必将成为一种趋势。该系统在Linux操作系统下,搭建了一个基于ARM9的视频图像采集环境,并通过CDMA2000网络完成了视频图像的传输接收,实现了远程视频监控的功能。     

CDMA的特点及其应用领域

本文以Qualcomm公司的CDMA系统为例,介绍了CDMA系统的方案、特点及其无线接入、功率控制和软切换等主要技术,最后简要介绍了CDMA技术在个人通信系统中的应用前景。     

CDMA蜂窝网中的无线定位技术

近些年来,无线定位服务已经戚为CDMA系统中的一种非常重要的业务。本文将讨论CDMA蜂窝网中的无线定位问题，主要舟绍CDMA网络中的无线定位技术，并根据它们各自的特点对这些技术进行比较。     

Fast simulation of DS/CDMA with and without coding in multipathfading channels

Code-division multiple access (CDMA) has found widespread applications in various applications such as advanced wireless technologies and digital cellular communications. We consider the error-rate performance of asynchronous direct-sequence CDMA in a wireless radio communications environment that is characterized by Rayleigh multipath fading channels. Because of the system complexity, the performance of CDMA systems in such an environment is difficult to assess analytically. Monte Carlo simulations can offer an alternative performance evaluation tool. Unfortunately, in practice, such an alternative is often limited by an excessive computational burden. Importance sampling is a variance reduction technique which can significantly reduce the computational cost required by Monte Carlo simulations. This paper describes the basic principles behind this powerful technique. In particular, it illustrates its use as a computationally efficient and accurate tool for computer-aided design and analysis of uncoded as well as coded CDMA in wireless communications     

Using RF filtering to reduce competitor-induced interference

This paper examines the success of RF filtering on mitigating interference that occurs between two wireless multiple-access systems operating within the same geographic area. Such interference is referred to as "competitor-induced interference" and can significantly degrade system capacity and performance. Three dual-system scenarios are considered: a dual code-division multiple-access (CDMA) (IS-95) system, a CDMA mobile in an FM (AMPS) cell, and an FM mobile in a CDMA cell     

基于混合GPS/TDOA的CDMA网络无线定位研究

介绍了CDMA网络的无线定位技术,分析了不同技术的适用性和优缺点,提出了一种混合GPS TDOA定位方法。该方法将GPS和TDOA测量值相结合,弥补了独立的GPS和基于网络定位方法的不足,为CDMA网络无线定位提供高精度的解决方案。     

Performance analysis of MC‐CDMA by employing the MMSE‐PIC scheme in wireless communications

From the past decade, the multicarrier code division multiple access (MC‐CDMA) transmission schemes have placed major role in wireless communications. It is providing a secured wireless communication to the users with guaranteed performance. In many situations, the performance of the MC‐CDMA is restricted due to the interference caused by multiple access interference (MAI), which also influences the frameworks of CDMA. To overcome this issue, we concentrated on developing the efficient technique for data transmission with interference cancellation for downlink MC‐CDMA. In the proposed method, the interference cancellation procedure is done by using the regeneration and subtraction of MAI from the signal. The simulation results are evaluated using the MC‐CDMA system with different decision functions. Results proved that the proposed system is efficient in reducing the MAI along with an improved bit error rate (BER).     

Orthogonal complementary codes for interference-free CDMA technologies

This article addresses the issues of next-generation CDMA technologies for B3G wireless communications. To engineer a CDMA system whose performance will no longer be interference-limited, many challenging issues should be tackled, such as novel CDMA code sets, efficient spreading and carrier modulation schemes, and signaling format for high-speed burst traffic. This article reviews our ongoing research on next-generation CDMA technologies. In particular, we propose a new CDMA code design methodology, real environment adapted linearization (REAL), which can generate CDMA code sets with inherent immunity against multipath interference and multiple access interference for both uplink and downlink transmissions. It is also shown that interference-free CDMA can only be implemented with the help of orthogonal complementary codes. The article goes further to reveal that cell-wise capacity for such interference-free CDMA is equal to the number of element codes assigned to each user, making OFDM a natural choice to implement interference-free CDMA. Several other issues of OCC-CDMA, such as its system implementation and performance, are also addressed in this article.     

A System Level Energy Model and Energy-Quality Evaluation for Integrated Transceiver Front-Ends

As CMOS technology scales down, digital supply voltage and digital power consumption goes down. However, the supply voltage and power consumption of the RF front-end and analog sections do not scale in a similar fashion. In fact, in many state-of-the-art communication transceivers, RF and analog sections can consume more energy compared to the digital part. In this paper, first, a system level energy model for all the components in the RF and analog front-end is presented. Next, the RF and analog front-end energy consumption and communication quality of three representative systems are analyzed: a single user point-to-point wireless data communication system, a multi-user code division multiple access (CDMA)-based system and a receive-only video distribution system. For the single user system, the effect of occupied signal bandwidth, peak-to-average ratio (PAR), symbol rate, constellation size, and pulse-shaping filter roll-off factor is analyzed; for the CDMA-based multi-user system, the effect of the number of users in the cell and multiple access interference (MAI) along with the PAR and filter roll-off factor is studied; for the receive-only system, the effect of 1/f noise for direct-conversion receiver and the effect of IF frequency for low-IF architecture on the RF front-end power consumption is analyzed. For a given communication quality specification, it is shown that the energy consumption of a wireless communication front-end can be scaled down by adjusting parameters such as the pulse shaping filter roll-off factor, constellation size, symbol rate, number of users in the cell, and signal center frequency     

某电信运营商CDMA无线网络安全评估探讨

针对目前CDMA无线网络中存在大量运行风险的情况,通过建立无线网络安全评估指标体系,对某电信运营商的CDMA无线网络现状进行分析,指出网络出现的问题和隐患,从而评估无线网络的安全性,并最终提出了降低网络安全风险的措施和方法。     

从调制方式看4G

讨论了多载波技术(MCM)与CDMA技术相结合的多载波码分多址(MC-CDMA)技术的原理及其应用的优缺点,认为该技术将在下一代无线通信系统中发挥重要的作用.