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。     

一种新颖的CDMA功率控制组合方案

提出了一种新颖的组合CDMA功率控制方案。它由基于反向信道预测的功率补偿算法和常规闭环功率控制组合而成。计算机仿真结果表明,所提出的组合功率控制方案能够很好地补偿信道的快速衰落。     

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系统中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。仿真经结果表明，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。     

基于单个自适应神经元的CDMA反向功率控制算法

CDMA(码分多址)是现代移动通信中的一项重要技术。文章从分析CDMA移动通信的“远近效应”问题着手，提出了一种基于单个自适应神经元(Adaptive Neuron)的反向闭环功率控制算法。该方法能够平滑信道衰落的影响，使基站接收到的小区中所有用户的信号功率基本相等，从而克服反向链路功率控制的“远近效应”并增加系统容量。与传统的固定步长功率控制方法进行仿真比较的结果显示，这种算法具有更快的响应时间，更小的超调量和跟踪误差。     

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。     

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。     

无线传感器网络中支持并行传输的信道与功率联合优化博弈算法

针对无线传感器网络中干扰日益增大引起网络容量下降、能耗增加的问题,该文建立了信道分配与功率控制联合优化博弈模型。在该模型中链路将既能保持自身成功传输又不影响其它链路传输的信道作为可选信道,以实现链路的并行传输。继而基于该模型设计了一种支持并行传输的信道分配与功率控制联合优化博弈算法(JCPGC)。该算法利用最佳响应策略对模型求解,并通过超模博弈等理论证明了JCPGC能够收敛到纳什均衡。此外,该算法充分考虑信道分配和功率控制之间独立又相互影响的关系提高了网络容量。仿真实验结果表明,JCPGC具有大容量、低干扰和低能耗的特性。     

OFDM系统频率选择性信道功率分配方案

自适应分配技术根据子信道的瞬时估计值动态地分配传输比特数和发送功率,可以优化正交频分复用（OFDM,Orthogonal Frequency Division Multiplex）系统的整体性能。这里讨论了基于容量优化的自适应比特分配算法,基于误比特率优化的最佳功率分配算法和次佳功率分配算法。仿真结果表明,对不同信道环境下三种算法的特点和性能进行了分析和比较。仿真结果表明,自适应分配技术可以优化系统的容量和误比特率。     

无线传感器网络基于容量和传输能耗的功率与信道联合博弈算法

针对无线传感器网络(WSNs)日益增大的干扰导致网络容量下降的问题,同时考虑到网络能量有限性,该文综合网络容量和链路传输能耗,构建了高容量低传输能耗的功率控制与信道分配联合博弈模型,并通过理论分析证明该模型存在最优功率和最优信道。继而采用最佳响应策略,在该博弈模型基础上提出了一种功率控制与信道分配联合优化算法(PCOA),理论证明其能收敛到纳什均衡状态,且具有较小的信息复杂度。最后,仿真结果表明,PCOA算法能够达到降低网络干扰和链路能耗,增大网络容量的目的。     

Erlang Capacity of a Voice/Data Cellular CDMA Uplink System Using Prioritized Admission Control and Adaptive Power Control

A CDMA uplink system that carries both voice and data traffic is investigated. The reservation-based admission control scheme is used to prioritize voice mobiles, and the truncated channel inversion power control scheme is used by data mobiles to improve system capacity. The performance of the system is measured by the Erlang capacity. Two methods of determining the Erlang capacity are presented. The first method decouples the analysis of blocking and outage performance, thus simplifying numerical search. The second method takes into account the impact of mobile traffic fluctuations on interference statistics, and thus yields more accurate results. Numerical results are provided that show significant differences between the two methods. Finally, the Erlang capacities of the system are compared for different power control schemes.     

Performance study for a microcell hot spot embedded in CDMAmacrocell systems

The code-division multiple-access (CDMA) system can provide more capacity than other systems, and the hierarchical layer of cells is required for system design. However, the problem is whether the same radio frequency (RF) channels used in a CDMA overlayed/underlayed macrocell and microcell structure also obtain a high capacity as in the homogeneous structure. We investigate the interference of uplink and downlink from both the microcell and macrocell under a hierarchical structure. A downlink power control scheme and two power control methods for the uplink are also considered. Performance measures such as blocking probability, C/I, capacity, and service hole area are also obtained by computer simulation. Besides, some extra efforts for a microcell are also noted, such as more power need to be transmitted by a microcell base station (BS) if the same RF channels are used in the hierarchical structure. The capacities of macrocell and microcell in the overlaying/underlaying structure are limited by the uplink and downlink, respectively. With downlink power control, the microcellular capacity can be increased. However, the combination of downlink power control for the microcell and C/I uplink power control for the macrocell causes the overall system capacity to significantly increase     

Performance Evaluation of Admission Control and Adaptive Modulation in OFDMA WiMax Systems

In this paper, we study the performance of multi-cell OFDMA WiMAX systems, in both downlink and uplink. We calculate analytically the number of collisions when the number of users in each cell is known. We then calculate the QoS indicators (e.g., blocking rates, download time and bit error rates) taking into account the physical layer conditions (modulation, propagation and MIMO), the MAC layer techniques (HARQ and radio resource management algorithms) and the traffic characteristics, in a cross-layer approach. We finally evaluate the impact of using adaptive modulation and coding on the overall performance of the system. This analysis allows us to calculate the Erlang capacity of a WiMAX system. Our numerical applications then show how to choose the best admission control and modulation schemes that extend the Erlang capacity region.      

WCDMA系统中功率控制的研究

功率控制是新一代无线通信网络的关键技术之一.在WCDMA系统中,如何有效地进行功率控制,在保证用户要求的QoS前提下,最大程度降低发射功率,减少系统干扰从而增加系统容量,是WCDMA技术中的重点.文中详细阐述了WCDMA系统中功率控制的原理、算法及存在的问题和相关研究方向,针对WCDMA系统内环功率控制、外环功率控制、上行功率控制、下行功率控制等进行了分析,提出了一种简单实用的外环功率控制算法.     

WCDMA手机上网节电方法探究

通过对WCDMA功控算法的深入研究,提出降低手机上网功耗的方法,并在现网中验证,利用MR内部测量数据对手机发射功率变化情况进行评估。从实验效果来看这些方法可有效降低手机的功耗、减轻系统上行负荷,达到改善用户体验、提升系统容量的目的。     

一种TD-SCDMA系统容量的仿真模型

TD-SCDMA采用智能天线、上行同步、联合检测、动态信道分配等技术使系统容量大大提高,系统投资成本也低于其他3G标准,因此研究容量仿真算法对TD-SCDMA系统的实用化具有现实意义.文章在介绍静态仿真概念、仿真场景、仿真方法的基础上,利用智能天线系统下的干扰计算方法,给出了一种理想功率控制下的TD-SCDMA系统容量仿真算法,并描述了仿真场景模型构架.     

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。     

Erlang capacity of OC-CDMA with imperfect power control

The authors investigate the Erlang capacity for reverse link in cellular mobile networks using an overlapped carrier CDMA (OC-CDMA) which is defined as a variation of FD (frequency division)/DS-CDMA where overlapping between adjacent carriers is permitted. Numerical results demonstrate that up to 49.6% of the Erlang capacity increase is achievable in certain circumstances with the conventional power control scheme. Finally, a sophisticated power control scheme is proposed, which takes into account the number of active users in adjacent carriers to achieve a higher Erlang capacity gain     

Proportional-fairness resource allocation for uplink OFDM-based cognitive radio systems

This paper has proposed a proportional-fairness resource allocation algorithm, including both subcarrier assignment algorithm and power allocation algorithm, for uplink orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. First, to get a better performance in the proposed system model, the influence factor (a,b,c) was introduced to realize the assignment of the subcarriers. Second, the transmit power of the secondary users (SUs) was allocated to the corresponding subcarriers in order to maximize the uplink capacity of the SUs subject to both power and interference constraints. With the appropriate influence factor in the subcarrier assignment, the loss of transmitted data rate arising from the fairness was minimized. Simulation results showed that the proposed algorithm can achieve a perfect fairness among the SUs while maximizing the system capacity simultaneously, and is of a low computation complexity.     

Multiservice capacity and interference statistics of the uplink of high altitude platforms (HAPs) for asynchronous and synchronous WCDMA system

In this work, the capacity and the interference statistics of the uplink of high-altitude platforms (HAPs) for asynchronous and synchronous WCDMA system assuming finite transmission power and imperfect power control are studied. Propagation loss used to calculate the received signal power is due to the distance, shadowing, and wall insertion loss. The uplink capacity for 3- and 3.75-G services is given for different cell radius assuming outdoor and indoor voice users only, data users only and a combination of the two services. For 37 macrocells HAP, the total uplink capacity is 3,034 outdoor voice users or 444 outdoor data users. When one or more than one user is an indoor user, the uplink capacity is 2,923 voice users or 444 data users when the walls entry loss is 10?dB. It is shown that the effect of the adjacent channels interference is very small.