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码分多址数字蜂窝移动通信技术讲座──第七讲CDMA蜂窝移动通信系统的发展趋势朱云龙,吴彦群前6讲已将CDMA的基本概念,CDMA用于蜂窝移动通信的优越性、关键技术和组网设计等作了简要的介绍,本讲将简单地介绍CDMA的发展过程、现状、存在问题和发展趋势... 相似文献
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简要介绍了码分多址(CDMA)数字蜂窝移动通信技术的优点和我国蜂窝移动通信的现状;针对我国蜂窝移动通信扩容的难点,提出可采用900MHz CDMA数字蜂窝移动通信兼容系统进行扩容。 相似文献
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数字移动通信体制的新动向—扩频码分多址(SS/CDMA) 总被引:3,自引:0,他引:3
本文主要讨论数字移动通信中扩频码分多址技术,介绍了国外关于CDMA数字移动通信研究的动态,阐明了CDMA体制的优越之处,分析了CDMA的关键技术,并就我国数字移动通信体制提出建议。 相似文献
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本文对GSM和CDMA两种数字标准的发展过程做了简单介绍,并从系统特性、频谱效率、语音清晰度三个方面对GAM和CDMA两种数字移动通信技术做了比较。探讨了这两种技术的发展趋势。 相似文献
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一、CDMA系统结构 CDMA数字蜂窝移动通信系统的结构如图1所示: CDMA 数字蜂窝移动通信系统主要由交换子系统和基站子系统两大部分组成。连接两大子系统的接口(也就是连接BSC和MSC的接口)称之为A接口,A接口是CDMA数字蜂窝移动通信系统中一个非常重要的接口。在我国规定A接口必须是一个开放的接口,它必须遵从我国相关规范的要求。只有在A接口标准化之后,不同厂商的交换子系统才可以和其它厂商的基站子系统相连接。交换子系统主要由移动交换机MSC、鉴权中心AUC、短消息中心MC、归属位置寄存器HLR… 相似文献
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码分多址(CDMA)蜂窝移动通信(2)吴家滨(广东省移动通信局)5CDMA数字蜂窝移动通信系统的容量在FDMA或TDMA蜂窝移动通信系统中,容量的计算是根据C/I的要求,求出频率重复使用次数K,再根据总的能使用的带宽B;和每个信道或等效信道的带宽Be... 相似文献
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文章通过对TDMA 和CDMA 在HFC 同轴电缆网络环境中的通信容量的比较、分析,得到了与数字移动通信系统中不同的结论,在同轴电缆网络中TDMA 具有比CDMA 更大的容量 相似文献
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本文首先介绍CDMA、TDMA和FDMA这三种移动通信多址方式的差异,并介绍目前在数字蜂窝移动通信中,使用直接序列扩谱(DS-SS)CDMA的基本原理,在上述基础上简单介绍目前市场推出的窄带CDMA蜂窝移动电话系统,并探讨其容量、分析功率控制对容量的关系,最后,介绍CDMA蜂窝移动电话的自然属性,它对增加容量,提高通信服务质量等方面的一些好处。 相似文献
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Xiangbin Yu Xiaomin Chen Guangguo Bi 《International Journal of Communication Systems》2011,24(3):295-309
By introducing a full‐rate space–time coding (STC) scheme, a synchronous CDMA (code division multiple access) system with full‐rate STC is given, and the corresponding uplink performance is investigated in Rayleigh fading channel with imperfect estimation. Considering that existing STC‐CDMA system has high decoding complexity, low‐complexity multiuser receiver schemes are developed for perfect and imperfect estimations, respectively. The schemes can make full use of the complex orthogonality of STC to reduce the high decoding complexity of the existing scheme, and have linear decoding complexity compared with the existing scheme with exponential decoding complexity. Moreover, the proposed schemes can achieve almost the same performance as the existing scheme. Compared with full‐diversity STC‐CDMA, the given full‐rate STC‐CDMA can achieve full data rate, low complexity, and partial diversity, and form efficient spatial interleaving. Thus, the concatenation of channel coding can effectively compensate for the performance loss due to partial diversity. Simulation results show that the full‐rate STC‐CDMA has lower bit error rate (BER) than full‐diversity STC‐CDMA systems under the same system throughput and concatenation of channel code. Moreover, the system BER with imperfect estimation are worse than that with perfect estimation due to the estimation error, which implies that the developed multiuser receiver schemes are valid and reasonable. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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This paper presents an advanced architecture for residue number system (RNS)-based code-division multiple-access (CDMA) system for high-rate data transmission by combining RNS representation, phase shift keying/quadrature amplitude modulation (PSK/QAM) and orthogonal modulation. The residues obtained from a fixed number of bits are again divided into spread code index and data symbol for modulation. The modulated data symbol is spread using the indexed orthogonal codes and transmitted through a communication channel. The proposed system uses a lower number of orthogonal codes than conventional RNS-based CDMA and the performance is comparable. The computational complexity of the proposed system is compared against alternative schemes such as M-ary CDMA and conventional RNS-based CDMA. The modified system is simulated extensively for different channel conditions and the results are discussed. 相似文献
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容量的需求是推动CDMA数字蜂窝移动通信开发的主要动力。系统的容量受许多因素的影响,本文针对IS-95CDMA系统在采用了功率控制、话音激活和扇区划分技术的情况下,对系统的容量进行了分析,同时也分析了功率控制精度对容量的影响。 相似文献
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C. Valadon R. Tafazolli B. G. Evans 《International Journal of Satellite Communications and Networking》1998,16(1):59-76
In this paper the performance of multilevel trellis-coded modulations (MTCMs) for satellite mobile multimedia systems using synchronous CDMA is investigated. A model for the multiple-access interference arising from the non-orthogonality of the spreading waveforms is developed for different modulation and spreading schemes and transmission over the mobile satellite channel. Using this model, the performance of MTCMs for synchronous CDMA is analysed and compared with the Ungerboeck and Schegel–Costello trellis-coded modulation (TCM) designs. The impact on the transmission of synchronization errors between the different users is presented and the power control requirements are derived. © 1998 John Wiley & Sons, Ltd. 相似文献
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广义映射混沌扩频序列及其特性分析 总被引:9,自引:0,他引:9
该文从扩频通信对扩频码序列的要求出发,提出采用广义映射产生混沌数字序列的思路。通过对广义映射混沌数字序列相关性和平衡性的分析,给出一种改进的广义映射混沌数字序列生成方法。计算机模拟分析表明,使用该文方法生成的混沌序列具有良好的平衡性和保密性,更适合在码分多址通信中应用。 相似文献
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Described is a decorrelating filter that separates signals in a multiuser environment by relying on the relative delays to be sufficiently distinct. The input signal is fractionally sampled to allow for the differentiation of the user delays. Both zero-forcing and minimum mean-square-error versions of this filter are derived and probability of error expressions are given. The algorithm successfully separates unknown digital signals by using the known received pulse shapes and the symbol rate. A delay-division multiple-access (DDMA) scheme based on this signal decorrelator is proposed that will allow signals to be transmitted without spreading the signal spectrum. It is shown that in a noisy environment the signal-to-noise ratio penalty for DDMA can be severe yet the bandwidth advantage is very pronounced compared to spread-spectrum systems and is similar to other bandwidth efficient schemes. The performance of a code-division multiple-access (CDMA) system using this signal decorrelator is also given. The decorrelator can be used as a blind multiuser detector or as a preprocessor to enhance the performance of a CDMA system 相似文献
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给出了多载波CDMA系统构架。目前提出有3种方案,分别是:频域扩频(MC CDMA)、时域扩频(MC DSCDMA)和多音CDMA(MT CDMA)。以MC CDMA,MC DS CDMA为例,对两种模型在AWGN和Rayleigh信道的性能进行了仿真。仿真数据表明:多载波频率分集CDMA系统(MC CDMA)在无线宽带数据传输中性能大大优于时域扩频CDMA系统,具有良好的应用前景。 相似文献
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The objective of this paper is to evaluate the bit-error-rate performance of various adaptive structures in combating multi-user interference in an asynchronous code division multiple access (CDMA) system. In particular, two adaptive schemes, known as the N-tap filter and D-tap cyclical shifted bank filter, are considered. The least mean square (LMS) and predictive LMS (PLMS) algorithms are employed for the adaptation of tap weights. An analytical expression is developed for the numerical evaluation of the bit error probability. In addition, the bit error rate performances of the adaptive schemes are compared with those of the matched filter receiver. Results attest to the pratical usefulness of the LMS-based adaptive suppression schemes in combating multi-user interference in an asynchronous CDMA system. 相似文献