码分多址系统的抗干扰分析

对于800MHz频段CDMA系统的基站和直放站杂散辐射对GSM900的干扰限制已由信产部[2002]65号文作了明确的规定。那么,GSM900对CDMA的干扰以及所有时分多址系统对3G宽带CDMA系统的干扰影响有多大呢?文章以码分多址系统的抗干扰机理为基础,试图分析当多系统共(站)址时,这些干扰对码分多址系统容量的影响。     

基于子空间盲多用户检测算法的设计和仿真

随着数字移动通信技术的飞速发展,以码分多址(CDMA)为核心的第三代移动通信(3G)技术已经走入人们的日常生活。CDMA系统具有容量大、软容量、抗多径衰落强等优点,但多址干扰(MAI)的存在却严重的影响了系统的性能和容量,因此如何消除和抑制这种干扰就成了CDMA技术研究的热门话题之一,第三代移动通信系统已经将多用户检测技术(MUD)作为克服多址干扰的有效方法之一。文中主要研究了直接序列扩频码分多址(DS-CDMA)系统中的盲多用户检测算法,深入的研究了基于卡尔曼滤波的盲多用户检测算法,通过在卡尔曼滤波算法上引入子空间提高了原有卡尔曼滤波算法的效率。     

CDMA移动通信中的功率控制技术

移动通信的多址通信方式码分多址(CDMA)是一个自干扰系统,它对发射信号的功率控制在解决远近效应问题和增加系统容量方面是非常重要的。本文介绍了CDMA的系统模型和功率控制技术。     

CDMA直放站对GSM网络的干扰分析及解决方案

移动通信直放站是一种实现无线覆盖的技术手段.针对码分多址(CDMA)系统直放站对全球移动通信系统(GSM)网络的干扰问题,从频率关系和发射/接收特性对干扰来源进行了深入分析,阐述了3种主要干扰即杂散干扰、阻塞干扰和互调干扰产生的原因.根据隔离准则,从理论上计算出了抗干扰的隔离距离,并提出了实际工程中的相应解决方案.     

智能天线和联合检测

第三代移动通信系统采用宽带码分多址(CDMA)技术为主流技术.智能天线(SA)是移动通信系统中抗多径衰落的关键技术,联合检测(JD)是CDMA通信系统中抗多址干扰的关键技术,智能天线和联合检测技术相结合已成为当前宽带CDMA移动通信应用研究热点之一.本文基于数字通信时空域自适应滤波器的观点讨论单小区单载波CDMA系统基站接收所应用的智能天线和联合检测技术,给出了结合智能天线和联合检测的时空域滤波器结构.我国大唐电信和德国西门子联合开发的TD-SCDMA试验系统已经研发成功,本文在最后结合这一实例,阐述了智能天线和联合检测技术在目前国内TD-SCDMA系统开发中的应用.     

第三代移动通信系统中的多用户检测技术

多址干扰(MAI)是影响码分多址(CDMA)系统容量的主要因素。相对于传统的检测技术而言,多用户检测(MUD)技术可有效消除MAI的影响,提高系统容量。文章主要分析MUD技术在第三代移动通信系统(3G)中应用的必要性,介绍MUD技术的发展状况、基本思路和MUD接收机结构,并对其研究前景进行展望。     

多用户检测技术的应用与发展

第三代移动通信系统采用码分多址(CDMA)方式,由于CDMA系统是一个自干扰系统,存在多址干扰及远近效应,因而限制了系统的容量和性能。多用户检测技术能从根本上消除多址干扰,提高系统的性能。本文主要介绍了多用户检测的思想,分类和性能指标,还提出了多用户检测技术的新发展和几个具体系统中的应用。     

多用户检测技术的应用与发展

第三代移动通信系统采用码分多址(CDMA)方式。由于CDMA系统是一个自干扰系统,存在多址干扰及远近效应,因而限制了系统的容量和性能。多用户检测技术能从根本上消除多址干扰,提高系统的性能。本文主要介绍了多用户检测的思想、分类和性能指标,还提出了多用户检测技术的新发展和在几个具体系统中的应用。     

TD-SCDMA网络干扰浅析

时分同步码分多址系统（TD-SCDMA）采用了多项核心技术来解决网络中的干扰问题,但出于网络系统和无线环境的复杂性,干扰的出现很难避免。TD-SCDMA系统与全球移动通信系统（GSM）和码分多址系统（CDMA）的干扰模型有所差异,有着时分双工（TDD）系统特有的干扰存在方式,分析TD-SCDMA无线网络的干扰因素,需要在了解该网络特点的基础上,根据不同的干扰特征考虑不同的干扰存在方式,依据由内到外、频率相近的原则进行,从硬件故障到网络设计的不同角度进行干扰的定位和解决。     

CDMA／SDMA系统性能分析

空分多址接入技术（SDMA）可以通过信号不同的空间传播路径来区分用户，从而提高了蜂窝移动通信系统容量．而此技术又可以和其他多址方式相互兼容，比如频分多址，时分多址，码分多址．CDMA／SDMA系统就是码分多址和空分多址两种接入技术相结合的系统．该系统可通过时空编码实现的．文中分析此种系统的性能，并与多用户环境下的CDMA系统进行了比较．     

800MHz CDMA系统对900MHz GSM系统的干扰分析

800MHz CDMA系统对900MHz GSM系统的干扰问题是目前移动通信工程中的热点难题之一，是摆在工程技术人员面前迫切需要解决的工作。本文将分别对产生干扰的原因、机制以及解决方法进行阐述。     

Known and novel diversity approaches as a powerful means to enhancethe performance of cellular mobile radio systems

The main requirements to be met by third generation mobile radio systems are high cellular spectrum efficiency and high flexibility. The authors focus on high cellular spectrum efficiency, which is difficult to achieve due to the time variance and frequency selectivity of the mobile radio channel and due to interference. It is known that the degrading effects of these adverse characteristics of the mobile radio channel and of interference can be mitigated by diversity. The way how diversity influences cellular spectrum efficiency is derived in general. As a reference point, the types of diversity used in GSM are analyzed. In GSM, the potential for diversity enhancement inherent in code-division multiple-access (CDMA) is not exploited. A joint detection code-division multiple-access (JD-CDMA) system concept aimed at third generation mobile radio systems has been proposed which introduces a CDMA feature into systems based on time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA) like GSM and also advanced TDMA (ATDMA). The gains achievable by different types of diversity in GSM as well as in the JD-CDMA system concept are investigated. It is shown that considerable gains can be achieved by different types of antenna diversity and by exploiting the additional diversity potential of CDMA. Therefore, third generation standards should be flexible in order to allow the use of as many types of diversity as possible to enhance the cellular spectrum efficiency     

室内单个UWB设备对GSM系统的干扰分析

根据FCC频谱模板,分析了室内单个UWB设备工作时的发射信号对GSM通信系统(包括GSM900和DCS1800)的电磁干扰;仿真了UWB设备和GSM移动台间距离对GSMMS接收信噪比的影响。其中UWB干扰信号对GSM900的干扰在信噪比冗余度内。而对DCS1800的干扰远大于GSM900,当二者距离小于25cm时,降到9dB以下,通信质量严重下降,链路会因此中断。     

CDMA直放站对GSM网络的干扰分析及解决方案

针对CDMA系统直放站对GSM网络的干扰问题，从频率的关系和发射／接收特性两方面进行了深入分析，在理论上计算出了抗干扰的隔离距离，并提出了实际工程中的相应解决方案。     

利用宽带CDMA技术增加蜂窝系统容量研究

介绍了宽带CDMA技术的特点,分析了CDMA与GSM系统重叠覆盖时的蜂窝系统容量,用宽带CDMA系统与GSM系统进行顺带共享,可以大大提高整个系统的容量。     

WCDMA Downlink Coverage Reduction Due to Adjacent Channel Interference

This paper determines the coverage reduction of the Wideband CDMA (WCDMA) downlink in the case of interference, due to adjacent narrowband system. The coverage reduction has been evaluated in terms of blocking area around the interfering base station. The analysis takes into account different interference mechanisms and their individual effects to the coverage. The interference mechanisms which have been considered here are the out-of-band emissions of the base station transmitter, the adjacent channel interference due to non-ideal sideband filtering, the intermodulation and the crossmodulation. The coverage effects in realistic network environment have been computed by using accurate ray-tracing propagation models designed for the path loss calculation in the urban environment. In the numerical examples, the effect of GSM interference has been demonstrated, but the method can be utilized with other narrowband systems as well. The results can be utilized in radio system design, radio network planning (RNP) and the frequency allocation of the WCDMA systems.     

移动通信中干扰问题的分析

干扰是蜂窝结构移动通信中要考虑的核心问题 ,对移动通信中的同频干扰 ,邻频干扰及互调干扰作了简要分析 ,提出了一些解决方案 ,并对现代移动通信的发展进行了展望 :移动网络最终将宽带化、智能化、个人化 ,CDMA和GSM也将最终实现无缝沟通     

RADIO AND NETWORK COMPARISONS FOR MSBN AND GSM SYSTEMS IN A GEOSTATIONARY SATELLITE ENVIRONMENT

One of the most frequently debated issues in satellite communications concerns the comparison between time division multiple access (TDMA) and code division multiple access (CDMA) systems. Although, in our view, a general answer to this problem cannot be found, this paper presents comparisons of two systems utilizing the above-mentioned access techniques, both from a radio and a network point of view. In particular, the mobile satellite business network (MSBN), (a CDMA system currently being developed by the European Space Agency (ESA) for general satellite applications) and the full integrated extension to satellite systems of the global system for mobile communication (GSM) (the well-known frequency division multiplex (FDM)/TDMA pan-European mobile cellular system) are compared by taking, as the reference payload, the L-band land mobile (LLM) satellite (a spot-beam geostationary satellite whose launch should take place at the end of 1997). Reasonable assumptions take into account the fact that, on one hand, the MSBN system is not completely defined and, on the other, the GSM is applied in a context different from the one specified by the European Telecommunication Standard Institute (ETSI). Performance comparisons are carried out in terms of flexibility and number of available channels for the same quality requirements, emitted power levels, propagation environment and interference levels coming from adjacent satellites. It is concluded that MSBN is more flexible than GSM and that, as regards capacity, an advantage of GSM over MSBN is present in the transportable mobile case, whereas, in the vehicular mobile case, MSBN shows an advantage over GSM. © 1996 by John Wiley & Sons, Ltd.     

Implications of mobile cellular CDMA

The results of four extensive field tests of code division multiple access (CDMA) cellular technology performed between November 1991 and September 1992 are presented. These tests include: validation system field tests conducted in San Diego, California, operating over five cell sites, comprising a total of eight sectors, and involving up to 70 mobile units, plus simulated other user and other base station interference; tests in Munster, Germany, the configuration of which consisted of two cell sites and two mobiles plus 20 simulated other users operating in the 1700-MHz band; tests in Geneva, Switzerland, the same as in Munster, but operated in the 800-900-MHz band, with cells located at GSM base station sites; and a field test conducted in Washington, DC, operating on two-sectored cell sites involving seven mobile units, plus simulated other user and other base station interference     

Evolution Strategies for Mobile Telephony Employing Multiple Coexisting Technologies

In many countries, the analogue Advanced MobilePhone System (AMPS) is progressively being replaced bydigital technologies, with the intention of maximizingcapacity and service quality. This paper considers strategies for the evolution of mobiletelephony services, employing several coexistingmultiple access technologies, such as Code DivisionMultiple Access (CDMA) and Global System for Mobile(GSM), in recovering the spectrum previously used byanalogue technologies such as AMPS. We propose partialspectral overlay and interference control strategies forCDMA systems overlaying AMPS and GSM systems, to provide smooth transition paths for introducingthe CDMA technology, and we show that these overlaystrategies lead to significant increases in overallnetwork capacity.