CDMA蜂窝网中功率控制对系统容量的影响

ＣＤＭＡ蜂窝网中存在远近效应，必须引入功率控制。功率控制对系统容量有极大的关系。本针着重功率控制精度以系统容量的影响，提出功率控制的高斯误差颁假设，并得到系统容量随功率控制变化的规律及可参考的计算方法。     

分数阶功控时的Ad Hoc网络传输容量

Ad Hoc网络是干扰受限系统,为了获得较高的网络传输容量,需要引入合适的功率控制策略,降低网络中的干扰。分数阶功率控制是一种新型的功率控制策略,是对信道反转功率控制的改进。这里推导分数阶功率控制时的中断概率和传输容量的n阶近似表达式,研究了n阶近似表达式的准确度,讨论了分数阶功率控制相对于信道反转功率控制对网络性能的改进。通过研究表明,适当的选择合适的分数阶功率控制系数可以使得中断概率最小,传输容量最大。     

WCDMA基站的载波和功率容量限制控制方案实现

为降低运营商和设备制造商的网络无线扩容成本．缩短网络扩容建设的时间,文章提出了一种WCDMA基站的载波和功率容量限制控制方案,从WCDMA基站容量限制控制的网络结构入手,依次举例介绍了射频模块容量控制的两个维度——基站载波容量资源限制控制和基站功率容量资源限制控制。     

CDMA移动通信系统的功率控制研究

较系统地介绍了ＣＤＭＡ移动通信系统功率控制的概念和原理，分析了功率控制前后的链路的容量。同时还介绍就理想的精确功率控制和实际的（非理想、非精确）功率控制两种情况推导出反向链路的爱尔兰容量。     

CDMA卫星通信系统功率控制研究

文章从卫星通信系统的功率控制原理入手,提出了一种适合CDMA卫星通信系统的功率控制方法;给出了精准的功率控制时的系统容量,通过推导给出的中断概率公式和例举的CDMA卫星通信系统实际数据,将功率控制误差对于系统容量的影响进行了仿真.仿真结果表明,当标准方差不断增大,系统的中断概率增大,系统容量随之显著减小;而采用精准的功率控制技术,可以有效改善系统性能.     

家庭基站系统中的联合信道与功率控制算法

摘 要：本文提出了一种联合信道分配与功率控制算法,通过优化目标将家庭网络的信道分配和功率控制结合,限定干扰范围,采用凸优化和次梯度方法,求解出功率的闭合式,优化了家庭网络的容量。算法又将家庭网络容量与宏网络容量联系,使宏网络容量得到了提升。仿真结果表明,与单纯的功率控制算法相比,本文算法提高了系统容量。     

一种CDMA系统反向功率控制的算法

本文简要介绍了基于ＩＳ－９５的ＣＤＭＡ系统反向信道功率控制的原理及其算法实现，从理论上分析了理想的精确功率控制和非精确功率控制对反向信道爱尔兰容量的影响，并对反向闭环功控算法和外环功率控制算法进行了仿真，得到爱尔兰容量最大的仿真算法。     

基于Matlab的CDMA系统功率控制算法研究

对CDMA系统功率进行控制的最根本目的是增加系统容量.以及CDMA系统的干扰及功率与系统容量之间关系,以及移动通信信道(特别是快衰落)对功率控制产生的负面影响,利用Matlab对CDMA系统功率控制算法进行了性能上的仿真.仿真得到慢衰落和快衰落的模拟环境,CDMA系统容量受限于用户问的相互干扰,由反向链路上固定步长功率控制分配算法条件下接收信号的功率的统计图可知,仿真结果与理论分析高度吻合.固定步长功率控制方法的系统稳定性差,且有很大过调量和稳定时间.因此可通过:提高功率测量速度、提高控制量的精调程度两种方法提高控制精度.     

CDMA前向功率控制算法

本文通过对Ｗ．Ｃ．Ｙ．Ｌｅｅ教授前向线路功率控制模型修正，提出前向线路功率控制模型中的优化问题。介绍了最大容量前向功率控制算法及其数学模型，并给出了前向线路最大容量发功率的边界条件，提出了一种简单的最大容量功控方案。     

CDMA系统中的自适应反向闭环功率控制

在码分多址(CDMA)移动通信系统中,反向链路功率控制对克服远近效应和增加系统容量是非常重要的。本文提出了一种基于改进的神经网络(MNN)的自适应闭环功率控制算法,该方法平滑了移动信道衰落的影响,使基站接收到的小区中所有用户的信号功率相等。仿真结果表明,由于神经网络能够较好地识别反向链路的时变特性,MNN功率控制方法比传统的固定步长功率控制方法取得了更好的控制性能和系统容量。     

TD-SCDMA系统容量分析

中国提出的第三代移动通信系统（ＴＤ－ＳＣＤＭＡ），采用了智能天线技术，大大提高了系统容量。本文在基于非理想功率控制和非理想波束的情况下，对ＴＤ－ＳＣＤＭＡ系统的容量进行理论分析。     

Power imbalance effects on packet CDMA

This paper presents an analysis of packet code-division multiple-access (CDMA) with single user receivers and power level variations. The power level variations are due to imperfect power control. The teletraffic is modeled as an M/G/∞ queueing system. Average error rates and outage probabilities that a user sees are evaluated for a single cell CDMA system. The effects of power level variations are investigated using a combination of an approximation and an upper bound, and the loss in traffic capacity is evaluated. Numerical results for CDMA systems with different processing gains and coding gains are presented. It is shown that imperfect power control reduces significantly the CDMA teletraffic capacity, and much has to be gained by improving the power control schemes. The methods and results of this work could be used for quantifying the required accuracy of power control in CDMA and for evaluation of the capacity loss due to power control errors     

A Capacity Analysis Method for Uplinks in DS/CDMA Cellular Systems with Imperfect SIR-Based Power Control and Multipath Fading

The letter proposes a method to analyze the system capacity of uplinks with imperfect SIR-based power control in direct sequence/code division multiple access (DS/CDMA) cellular systems with the multipath fading. It considers the received signal-to-interference ratio (SIR) as a random variable due to imperfect SIR-based power control. Based on assumptions regarding the average received SIR, a set of linear equations for the average received power on each uplink is derived. An outage-based system capacity can be then obtained according to the feasibility of the average received power vector and the average bit error rate. Finally, by applying central limit theorem, a closed-form solution for system capacity is approximately derived. Results show that numerical results of the closed-form solution have a good match with simulation results, which supports the validity of the proposed capacity analysis method.     

Capacity, throughput, and delay analysis of a cellular DS CDMAsystem with imperfect power control and imperfect sectorization

An analytical model is developed to evaluate the performance of a cellular slotted DS CDMA system in terms of user capacity, throughput, and delay for the reverse link, i.e., from mobile to base station, considering interference from both home cell and adjacent cells. The user capacity is studied for voice communications and the throughput and delay are investigated for data communications. The effect of both imperfect power control and imperfect sectorization on the performance is investigated. It is shown that the system is rather sensitive to small power control errors and that voice activity monitoring and sectorization are good methods to improve the performance of cellular DS CDMA systems     

Forward‐link analysis of a two‐tier CDMA system with imperfect power control

Power control is an effective technique to reduce cochannel interference and increase capacity for cellular radio systems. The purpose of forward‐link power control in a CDMA system is to reduce the amount of interference in neighbouring cells by reducing the total amount of power transmitted. In an underlaying two‐tier system, microcell's capacity is limited by the forward link due to the interference from macrocell's basestation. Therefore, forward‐link power control is required to enhance system capacity and reduce outage probability. In this paper, we study the effect of imperfect forward‐link power control due to the limitation of power transmitted by basestation. Performance measures including capacity, outage probability and service hole area are analysed. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance analysis of CDMA with imperfect power control

The standard correlation receiver for code-division multiple access (CDMA) systems is susceptible to the near-far problem. Power control techniques attempt to overcome near-far effects by varying transmitted power levels to ensure that all signals are received with equal power levels. Since these algorithms cannot perfectly compensate for power fluctuations in a mobile communications channel, the capacity of the system is reduced for a given bit-error rate (BER). This paper examines the performance of a CDMA system using imperfect power control by extending analytical techniques that account for multiple access interference. Single cell capacity is compared with systems employing perfect power control     

功率控制对S-CDMA-HFC系统上行信道Erlang容量的影响

同步ＣＤＭＡ（Ｓ－ＣＤＭＡ）解决了双向ＨＦＣ系统的上行信道噪声和容量问题,基于Ｓ－ＣＤＭＡ的ＨＦＣ是新一代ＨＦＣ系统。从系统实现的角度来看,非理想功率控制会明显降低系统业务容量。本文简单介绍了Ｓ－ＣＤＭＡ－ＨＦＣ系统模型和上行信道概况,分析了非理想功率控制对Ｓ－ＣＤＭＡ－ＨＦＣ系统上行信道Ｅｒｌａｎｇ容量的影响,并给出了数值结果与结论。     

CDMA cellular systems performance with fading, shadowing, andimperfect power control

This paper addresses capacity estimation for cellular code-division multiple-access (CDMA) systems, assuming the IS-95 standard as a reference. Extending a previous analytical method (Viterbi et al., 1994), we obtain a sequence of bounds on capacity, and then we introduce an accurate approximation to reduce computation complexity. The analysis accounts for interference internal and external to the reference cell, fading, shadowing, and imperfect power control. Outage probability is expressed in terms of the characteristic functions (cf's) of the interference and imperfect power control random variables (RV's). The interference contributions are computed on the basis of a Poisson distribution for the number of users in a lognormally shadowed channel. Results are provided for different channel conditions and are validated against Monte Carlo simulations. A comparison against previously published CDMA capacity estimates is carried out, aimed at clarifying some controversial issues. It is also confirmed that large system capacity is achievable under tight power control     

Uplink capacity optimization by power allocation for multimedia CDMA networks with imperfect power control

A closed-form capacity quasi-optimal power allocation scheme is presented for the uplink of multimedia code-division multiple-access (CDMA) systems with randomized received signal-to-interference ratio (SIR) resulted from the errors of power control. The optimality in capacity comes from that this scheme provides class-dependent SIR margins subject to the constraint of differentiated outage requirements. The statistics of signal under imperfect power control is modeled as lognormal random variable. The objective of capacity maximization is formulated as the minimization of total average received powers since the capacity of a CDMA system is interference limited. Under this model, we first derive the necessary conditions that a capacity-optimal power allocation should satisfy. By using conservative bounds, we provide a closed-form approximate solution to this optimization problem. This approximate solution provides nearly the same admissible region for multimedia traffic under imperfect power control as the accurate solution (the optimal one) does. The closed-form quasi-optimal power allocation scheme proposed in this paper is just based on this approximate solution. By numerical example we verify our analysis and show that great capacity gain (e.g., 92% as a maximum in the example) can be achieved by our scheme over its counterpart.