共查询到18条相似文献,搜索用时 203 毫秒
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通过对有效发射功率、接收机灵敏度、各种衰落余量等影响无线信号传播的关键问题的分析,最终得出EV-DO链路预算结果、前反向覆盖差异性以及EV—DO与cdma2000 1X系统前反向覆盖的比较。 相似文献
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CDMA系统是一个白干扰系统,其容量受多种环境和客观因素以及要求的系统服务质量的影响.具有一定的不确定性,是一种动态软容量。CDMA系统的容量,尤其是前向链路容量分析是一个复杂的过程。文章针对中国联通cdma2000 1X系统的实际情况.在儿理论上细致地分析95终端和1X终端共存环境下的cdma2000 1X系统前、反向链路容量的基础上, 相似文献
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作为当今3大主流3G标准之一的cdma2000以其技术的成熟性和经济性在国际市场竞争中处于优势地位。相对于其对应的2G标准,cdma2000引入了许多新技术,尤其是其在前向链路的发射部分采用了准正交函数(QOF)和独特的映射结构,提高了系统的性能和容量。本文仅分析cdma2000单栽波系统,先引入了准正交函数,再介绍其产生的过程,最后对cdma20001X系统前向链路的几种映射结构作详细的分析。 相似文献
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EV-DO作为一种基于CDMA的高速数据传输技术,前向采用时分复用方式,反向采用与cdma2000 1x相同的码分多址方式。因为EV-DO的前向采用的是时分复用方式,所以基站的容量主要取决于系统的反向链路情况。EV-DO特有的反向链路媒体介入控制算法机制可以参与调整基站反向链路,以优化小区的反向链路情况。 相似文献
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cdma2000 1x EV-DV系统为了获得更好的系统性能,在前向链路应用前向链路信道质量指示符(Channel Qual-ty Indicator,CQI)来得到前向链路的信道质量。文章提出了两种CQI的预测方法,一种是根据过去CQI数值,然后采用数值方法来得到CQI的非线性数值逼进模型参数,然后,再应用这个模型对CQI进行外推预测;另一种CQI预测算法是基于对过去的CQI值进行归一化最小均方(N-LMS)预测。对两种CQI预测算法和传统的CQI处理方法分别进行了分析和仿真,从链路级证明了算法的有效性。 相似文献
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一、影响1x EV-DO反向容量的因素 CDMA2000 1x EV-DO前向链路以时分为主,在前向链路设计中采用了先进的多用户调度技术、HARQ技术(结合递增冗余和提前中止技术)与速率控制技术等多种优化技术,有效改善了系统容量.而反向链路是以码分为主,系统容量主要受终端发射功率、基站码道数、用户分布和邻区干扰等因素影响.此外,1x EV-DO反向开销信道(反向导频信道、DRC信道和ACK信道)也需要占用终端的部分功率资源和系统码资源,从而导致系统反向容量的下降. 相似文献
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cdma2000中的新技术 总被引:1,自引:0,他引:1
1引言第三代(3G)移动通信系统的研究和开发正在世界范围内进行得如火如荼。在提交到国际电信联盟(ITU)的各种地面移动通信无线传输技术(RTT)的候选方案中,北美提出的cdma2000和欧洲提出的WCDMA凭借各自的优势分别成为第三代移动通信系统采用的主流技术。cdma2000由cdmaOne(其技术核心是IS-95标准)发展而来,它采用了众多的新技术(如前向发射分集、快速前向功率控制、反向链路相干解调、Turbo编码等),因而系统容量和性能相对于cdmaOne系统有较大提高,日益成为第三代移动通信领域的研究热点。cdma2000的目标是进一步提高… 相似文献
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This article first reviews the channel structure and spreading code assignment for the physical layer and transport channel multiplexing along with a sophisticated rate-matching scheme that accommodates composite transport channels with various levels of quality of service (QoS) on one physical channel. Then, the key technologies of wideband ds-cdma (w-cdma) wireless access are presented and the results of experiments pertaining to these technologies are evaluated. Flexible system deployment is possible by employing inter-cell asynchronous operation with a three-step fast cell search method. The signal-to-interference power ratio (sir) measurement based fast transmit power control (tpc) guarantees the minimum transmit power according to the channel load and the changes in the link conditions due to fading. Furthermore, various diversity technologies are described such as pilot symbol-assisted (psa) coherent Rake combining, antenna diversity, site diversity (soft/softer handover), and transmit diversity in the forward link that are effective in decreasing the required transmit power, which results in increases system capacity. This article also presents link-capacity enhancing techniques such as using an interference canceller (IC) and adaptive antenna array diversity (AMD) receiver/transmitter. Experimental results are presented for an actual multipath fading channel that indicate the potential of the IC and aaad transceiver to decrease the mobile transmit power in the reverse link and interference from high rate users with high transmit power in the forward link. 相似文献
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cdma2000 1x技术及其发展 总被引:2,自引:0,他引:2
文章以cdma20001x为中心,介绍了CDMA标准的发展、与cdma20001x的相关技术、从cdmaOne向cdma20001x演进策略及cdma20001x的发展趋势。 相似文献
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Transmit diversity in 3G CDMA systems 总被引:8,自引:0,他引:8
Derryberry R.T. Gray S.D. Ionescu D.M. Mandyam G. Raghothaman B. 《Communications Magazine, IEEE》2002,40(4):68-75
Transmit diversity (TD) is one of the key contributing technologies to defining the ITU endorsed 3G systems W-CDMA and cdma2000. Spatial diversity is introduced into the signal by transmitting through multiple antennas. The antennas are spaced far enough apart that the signals emanating from them can be assumed to undergo independent fading. In addition to diversity gain, antenna gain can also be incorporated through channel state feedback. This leads to the categorization of TD methods into open loop and closed loop methods. Several methods of transmit diversity in the forward link have been either under consideration or adopted for the various 3G standards. This article describes the concept of transmit diversity and explains the features of selected TD techniques 相似文献
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1x EV-DO是cdma2000 1x系统的演进,在cdma2000 1x的基础上能够提供高速移动数据传输业务.本文简要介绍了1x EV-DO的技术特点和前向链路的时隙结构,并对前向链路在不同传输速率条件下所能达到的覆盖范围进行了估算,结合估算结果对1x EV-DO系统进行实例分析,分析结果说明1x EV-DO系统很难提供3G标准所规定的静止环境2048kbit/s的无线接入速率,只有当用户数有限且传输信道质量优良的条件下,才有可能提供大约600kbit/s的最高无线接入速率. 相似文献
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Kishore S. Greenstein L.J. Poor H.V. Schwartz S.C. 《Wireless Communications, IEEE Transactions on》2006,5(2):417-426
This paper examines the uplink user capacity in a two-tier code division multiple access (CDMA) system with hotspot microcells when user terminal power is limited and the wireless channel is finitely-dispersive. A finitely-dispersive channel causes variable fading of the signal power at the output of the RAKE receiver. First, a two-cell system composed. of one macrocell and one embedded microcell is studied and analytical methods are developed to estimate the user capacity as a function of a dimensionless parameter that depends on the transmit power constraint and cell radius. Next, novel analytical methods are developed to study the effect of variable fading, both with and without transmit power constraints. Finally, the analytical methods are extended to estimate uplink user capacity for multicell CDMA systems, composed of multiple macrocells and multiple embedded microcells. In all cases, the analysis-based estimates are compared with and confirmed by simulation results. 相似文献
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Expressions for the average channel capacity of a multiuser diversity system combined with transmit diversity at each link are presented under the assumption of independent Rayleigh fading. The analysis results exactly agree with the simulation results and definitely show the impact of transmit diversity on multiuser diversity. 相似文献