基站簇优化改善CDMA软切换因子方案探讨

在CDMA网络优化中,降低软切换因子问题尤为重要。通过软切换因子优化思路,介绍了射频优化和参数优化,结合实际网络,分析了基站簇优化改善CDMA软切换因子的方法。实验证实基站簇优化可以有效降低CDMA软切换因子。     

CDMA网络高软切换因子优化探讨

软切换是CDMA系统中独特的一种切换技术,可以保证切换过程中信息传输的连续性,降低了掉话的概率,提升了网络服务质量。但随着C网基站数量不断建设增加、网络结构的不断变化,产生了过多的软切换比例占用了大量的系统资源,从而降低了资源利用率。因此如何在保证网络质量的同时降低软切换因子成为当前网络优化工作的一个重点。     

关于动态软切换参数优化分析及实践

本文主要对CDMA网络中的动态软切换算法原理进行探讨分析,计算出相关动态软切换的启控点,并通过实例阐述了动态软切换开启能有效降低了软切换因子比例,提高资源利用率。     

CDMA跨载波硬切换触发机制分析

众所周知．软切换是CDMA的关键技术之一,也是区别于GSM网络的一大特点。软切换技术具有切换中断率低、可靠性高等优点,因此,CDMA网络中的硬切换往往会被人们所忽视。但是在CDMA网络中,还是不可避免地存在着硬切换。由于硬切换对通信质量有影响,并且切换成功率较难保证,因此在实际网络优化过程中,必须对硬切换进行良好的控制与优化．保证硬切换区域的通信质量。     

业务负载和软切换参数对CDMA系统软切换率的影响

本文分析了在有阴影衰落的传播环境下,CDMA系统的软切换率与网络的业务负载大小、软切换门限以及导频信道功率比例等参数的关系,并进行了仿真。     

CDMA的软切换与硬切换

文章简要介绍了移动通信中切换现象的成因，通过GSM系统与CDMA系统的对比，说明为什么CDMA系统能实现软切换，解释了软切换能提供比硬切换更佳用户感受的原因，详细介绍了CDMA系统软切换、更软切换、硬切换的流程，比较了其中异同点，最后提供了涉及第三方MSC硬切换的流程，使得读者对CDMA网络切换有更全面的了解。     

CDMA软切换特性及其对系统性能的影响

本文对CDMA软切换增益、T-ADD和T-DROP等参数对软切换比例的影响等软切换特性进行了分析,在此基础上,分析了软切换对系统容量、覆盖范围等性能的影响情况,提出了软切换比例的合理取值范围.     

CDMA2000网络的关键技术--软切换

CDMA网络切换的分类及其软切换的特点软切换作为CDMA2000系统的关键技术之一,与业务资源管理、功率控制、信道管理等共同构成RRM子系统,它不仅和CDMA系统的网络质量(通话质量、掉话性能等)有密切关系,与覆盖、容量、干扰也有着复杂的关系,因此正确地理解CDMA网络切换的概念,有助于网络规划与建设工作。切换的基本概念是:当MS靠近原来服务小区的边缘,将要进入另一个服务小区时,原基站与MS之间的链路将由新基站与MS之间的链路来取代的一个过程。在CDMA网络中,通话状态下的切换按照MS与网络之间连接建立释放的情况以及频率占用情…     

软切换参数对CDMA1X性能的影响及优化

分析并仿真得到了在CDMA1X系统中,不同业务负载情况下的软切换开销因子与静态和动态软切换门限,以及导频信道功率比例等参数的关系,并在此基础上提出了相应的网络优化措施。仿真采用蒙特卡罗"快照"法,并在进行传播损耗计算时加入了阴影衰落的影响。     

cdma2000网络的关键技术--软切换

介绍了CDMA网络中软切换的概念、特点、工作原理、重要的切换参数以及判决和切换流程,讨论了软切换参数对CDMA系统的影响。     

Congestion control policies for IP-based CDMA radio access networks

As CDMA-based cellular networks mature, the current point-to-point links used in connecting base stations to network controllers evolve to an IP-based radio access network (RAN) for reasons of lower cost due to statistical multiplexing gains, better scalability and reliability, and the projected growth in data applications. In this paper, we study the impact of congestion in a best-effort IP RAN on CDMA cellular voice networks. We propose and evaluate three congestion control mechanisms, admission control, diversity control, and router control, to maximize network capacity while maintaining good voice quality. We first propose two new enhancements to CDMA call admission control that consider a unified view of both IP RAN and air interface resources. Next, we introduce a novel technique called diversity control that exploits the soft-handoff feature of CDMA networks and drops selected frames belonging to multiple soft-handoff legs to gracefully degrade-voice quality during congestion. Finally, we study the impact of router control where an active queue management technique is used to reduce delay and minimize correlated losses. Using simulations of a large mobile network, we show that the three different control mechanisms can help gracefully manage 10-40 percent congestion overload in the IP RAN.     

Vertical handoff in integrated CDMA and WLAN systems

Future wireless networks are expected to consist of different types of wireless networks such as code division multiple access (CDMA) networks and public wireless local area networks (WLANs). The integrated network will require vertical handoffs between different networks. In this letter, we propose vertical hard- and soft-handoff algorithms and evaluate their performance in commercial wireless networks.     

A flexible dynamic traffic model for reverse link CDMA cellular networks

In this paper, we focus on the reverse link traffic analysis of a code-division multiple-access (CDMA) cellular network in dynamic environments. In this respect, we propose a new and flexible traffic model, which takes into account the interference-limitedness attribute of CDMA capacity as well as its soft-handoff feature. This new traffic model is developed according to an interference-based call admission control (ICAC) method and a geographical structure with three regions. The main advantage of this traffic model is in its flexibility when we consider different traffic conditions including time-varying status of traffic in the neighboring cells.     

Pilot interference cancellation technology for CDMA cellular networks

This paper considers the link-level and network-level performance of code division multiple access (CDMA) pilot interference cancellation (pilot IC) technology, a low-complexity advanced receiver technology being considered for use in commercial third generation (3G) CDMA cellular systems. The concept behind this technology is to estimate and cancel at the handset receiver the interference effects associated with CDMA downlink pilot signals broadcast from the base stations of the network. The canceling of interference at the receiver improves the signal-to-interference/noise ratio (SINR), which enables increased cell capacity or throughput. In this paper, we derive SINR expressions for evaluating the probability of error performance of both the RAKE and pilot IC handset receivers, under conventional random spreading code assumptions. The approach can easily and accurately model a wide variety of transmitter, channel, and receiver conditions, including the effects of channel estimation. We also utilize radio network simulations to illustrate and quantify the capacity gains available for 3G CDMA networks through the use of pilot IC handsets. Network simulations are also used to examine the reduced level of soft-handoff found to be possible in pilot IC-based networks and the increased flexibility available in setting pilot power levels. We further consider the impact of using stronger pilot signals for improving the demodulation performance of sensitive higher-order modulation constellations that are needed to support spectrally efficient high-rate data services.     

Chip-interleaved block-spread CDMA versus DS-CDMA for cellular downlink: a comparative study

A so-termed chip-interleaved block-spread (CIBS) code division multiple access (CDMA) system has been introduced for cellular applications in the presence of frequency selective multipath channels. In both uplink and downlink operation, CIBS-CDMA achieves multiuser-interference (MUI) free reception within each cell. This paper focuses on the cellular downlink configuration and compares CIBS-CDMA against the conventional direct-sequence (DS) CDMA system, which relies on a chip equalizer to restore code orthogonality and, subsequently, suppresses MUI by despreading. We provide a unifying framework for both systems and investigate their performance in the presence of intercell interference and soft-handoff operation. Extensive comparisons from load, performance, complexity, and flexibility perspectives illustrate the merits, along with the disadvantages, of CIBS-CDMA over DS-CDMA, and reveal its potential for future wireless systems.     

Forward-link soft-handoff in CDMA with multiple-antenna selection and fast joint power control

We consider forward-link soft-handoff with multiple antenna selection and fast joint power control at high data rates in a cellular code-division multiple-access network, where signals are directed to a mobile station (MS) from antennas located at the same or different base stations. The total power transmitted to any mobile is divided among the active antennas selected according to the momentary channel conditions so as to maximize the signal-interference ratio at each MS. Multiple-antenna selection is used to mitigate the effects of both short- and long-term fading, and achieve the best soft-handoff with respect to system capacity and complexity. To achieve capacity gains with soft-handoff, we derive optimum handoff thresholds corresponding to the optimum handoff region in different cell environments. Numerical results demonstrate that under high Doppler spread and large handoff-delay conditions, the proposed soft-handoff employing two transmit antennas and the optimum handoff threshold achieves a significant gain in microcell environments, but not in macrocell environments.     

Spatial Averages of Coverage Characteristics in Large CDMA Networks

The aim of the present paper is to show that stochastic geometry provides an efficient computational framework allowing one to predict geometrical characteristics of large CDMA networks such as coverage or soft-handoff level. The general idea consists in representing the location of antennas and/or mobile stations as realizations of stochastic point processes in the plane within a simple parametric class, which takes into account the irregularities of antenna/mobile patterns in a statistical way. This approach leads to new formulas and simulation schemes allowing one to compute/estimate the spatial averages of these local characteristics in function of the model parameters (density of antennas or mobiles, law of emission power, fading law etc.) and to perform various parametric optimizations.     

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。     

干扰消除技术在CDMA网络中的应用

CDMA网络中存在前反向的多址干扰,降低了前反向容量。为了减少多址干扰对前反向容量的影响,对多址干扰产生的原因和机理进行深入分析,详细介绍了多用户检测技术和干扰消除技术。通过对造成干扰的所有用户信号信息进行检测,根据多址干扰信号的结构特征进行干扰消除和信号恢复,从而改善各个信号的信噪比,提高CDMA系统的前反向容量。重点介绍了准线性干扰消除技术QLIC（Quasi-Linear Interference Cancellation）和反向干扰消除技术RLIC（Reverse Link Interference Cancellation）的基本原理,分别对QLIC技术和RLIC技术的容量增益进行了理论推导,并计算了QLIC和RLIC对CDMA网络容量提升的程度。QLIC和RLIC是现有CDMA网络容量提升的重要技术手段,能够为运营商进行技术升级和网络部署提供重要参考。     

一种新的分组无线网隐终端问题解决方案

在C-T/CDMA方式中，最主要的问题是发送端的每次数据发送是盲目的，因而冲突概率很高。本文把RTS/CTS短分组交换方式引入到C-T/CDMA方式中，提出一种基于RTS/CTS调度的多址方式，既解决了隐终端问题，又降低了冲突概率，从而提高了网络的性能。