DS-CDMA系统中功率控制技术的发展与分析

讨论了DS-CDMA系统的功率控制技术，介绍了功率控制的不同分类标准，UTRA标准中功率控制技术的主要内容，功率控制是DS-CDMA系统中的核心技术，它能够有效抑制远近效应，提高系统容量，而且可以降低移动台总的发射功率，延长电池寿命。     

社会科学与管理科学

Y2000-62074-1126 0007204无线电资源管理=Session S29:radio rGSOHECe manage-ment[会,英]//1999 IEEE International Conference onCommunications,Vol.2 of 3.—1126～1166(H)本部分8篇论文的内容有:基于 IS-95的 CDMA系统的正向功率分配,多媒体 DS-CDMA 系统反向线路的最佳功率分配,非均匀通信量多单元 DS/CDMA系统的功率分配最佳化,宽带蜂窝通信网中动态信道分配,蜂窝网络中信道分配的最佳算法,TDD/FDD-CDMA 混合蜂窝网络频率选择策略,无线/移动网络的多速率资源控制方法,干扰和通信负载对干扰自适应动态信道分配的 TDMA/FDMA 系统性能的影响。     

CDMA系统智能天线盲自适应波束形成

给出了基于最大化信号对干扰和噪声的功率比(MSINR)准则的盲自适应波束形成在线递推算法,旨在提高DS-CDMA系统中智能天线的性能.将MSINR准则转化为一种新的等价的无约束准则函数,通过最大化此准则函数来在线估计最优波束形成向量.算法直接利用了DS-CDMA系统解扩前和解扩后的观测信号,无须训练序列.通过在线迭代估计,降低了计算波束权值的复杂度.不同通信环境中的仿真结果表明,该算法具有较高的估计精度和很好的抗多址干扰能力.     

下一代DS-CDMA网络中的资源管理

直接序列码分多址接入(DS-CDMA)已成为下一代无线蜂窝网络中提供高速多媒体业务的主要接入技术。TD-SCDMA蜂窝网络与时分多址(TDMA)/频分多址(FDMA)网络有很大差别,前者独有的特征可用于提高系统容量。文中描述了DS-CDMA蜂窝网络中的资源管理,指出在资源管理机制设计中面临的主要挑战,讨论了资源管理的关键问题,包括拥塞控制、速率和功率控制、蜂窝规划和呼叫接入控制。     

DS-CDMA系统中结合多用户检测的功率控制研究

功率控制和多用户检测是CDMA移动通信中克服远近效应,抑制多址干扰(MAI)的两项关键技术。该文提出了一种在DS-CDMA系统中综合考虑功率控制和多用户检测的方案。该方案能更加有效地消除干扰信号,同时在满足信干比(SIR)要求时,所有用户发射总功率最小,收敛速度最快。     

对5G小蜂窝系统功率控制方法的探讨

5G小蜂窝系统可以提高传统通信系统的吞吐量,降低功率的损耗,实现绿色通信.基于此,本文简要分析了5G小蜂窝系统的特点与发展,并分别从高普效功率控制方法、高能效功率控制方法以及高普效、低能耗功率控制方法等方面,分析了5G小蜂窝系统功率控制方法,为相关工作人员提供技术参考.     

DS-CDMA系统中反向链路的外环功率控制

CDMA系统为了获得满意的性能,要求严格的功率控制。在DS-CDMA系统中,反向链路上的闭环功率控制由内环和外环组成。内环通过一系列的功率升降命令,使所接收的信噪比尽可能的接近目标信噪比;外环动态地调整目标信噪比,使用户的误帧率性能尽可能的接近所要求的性能。文章通过建立外环功率控制的仿真模型,研究了外环功率控制对系统性能的影响,分析了在外环功控下发射功率的分布规律。     

自适应RBF神经网络在CDMA移动通信上行链路功率控制中的应用研究

提出了一种自适应RBF神经网络功率控制方案。详细研究了该网络在DS-CDMA通信中，进行上行链路闭环功率控制(基于信扰比(SIR))的应用理论，给出了该网络参数的计算方法。最后用计算机仿真法模拟出该控制器的运行性能。结果表明基于SIR的自适应RBF神经网络功率控制器能自适应地调整移动台的发射功率，使基站接收信号的信扰比始终非常接近于一个常数，且有比定步长功率控制更小的SIR跟踪误差，从而可以降低接收信号的中断概率、提高信道容量。     

异步DS-CDMA系统扩频序列分析

在无法获得稳定的全网同步特殊情况下,异步DS-CDMA系统是一种维持通信网络畅通的有效途径。该文首先分析了异步DS-CDMA多用户系统下多用户干扰（MAI）产生机理以及对系统性能带来的影响,在仿真环境下建立了异步DS-CDMA多用户系统模型,然后对三种扩频序列的相关特性进行仿真分析。比较分析了不同接入时延误差和不同失步用户数两种情况下,系统使用不同扩频序列时在AWGN信道下的误码率特性。分析表明,混沌序列是更加满足异步DS-CDMA系统的扩频序列,论文结果对可靠通信系统研究具有参考价值。     

WCDMA系统中的单小区线性功率控制

功率控制是WCDMA移动通信系统中提高系统容量和保证链路通信质量的关键技术.介绍了WCDMA系统中功率控制的原理,阐述了单小区中的线性功率分配算法,并对原来的功率分配算法进行了改进.     

Constrained power control

High system capacities can be achieved by controlling the transmitter power in multiuser radio systems. Power control with no constraint on the maximum power level has been studied extensively in earlier work [1–18]. Transmitter power is at a premium in radio systems such as cellular systems and PCS. There is a limit on the maximum transmitter power especially at the terminals (e.g. mobile units and handsets) since the power comes from a battery. In this paper we study power control that maximizes the minimum carrier to interference ratio (CIR), with a constraint on the maximum power. The optimal power vector solution lies on the boundary of the constrained power vector set and achieves a balance in the CIR's. Results indicate that the constraints do not induce any stability problems. A distributed scheme with favourable convergence properties and close to optimum performance is presented. Simulation results show that the algorithm tries to maximize the number of terminals served with CIR greater than or equal to the target CIR, while conserving power.     

基于干扰矩阵的高密WLAN场景下集中式功率控制

针对高密无线局域网( WLAN)场景中系统干扰严重导致吞吐量降低的问题,提出了一种集中式动态发射功率控制算法( CDTPC)。接入控制器( AC)依据接入点( AP)定时上报的信道扫描报告和邻居报告建立干扰矩阵,通过分析干扰矩阵确定干扰源AP集和覆盖漏洞AP集,并对干扰源AP和覆盖漏洞AP进行动态功率控制,在保障覆盖的情况下减小WLAN系统内干扰、提高网络整体吞吐量。仿真表明：在高密WLAN场景中,使用CDTPC算法进行功率控制前后各AP吞吐对量均有所提高,系统整体吞吐量提高了41.5%。     

Robust$H_infty$Power Control for CDMA Cellular Communication Systems

Power control is an important factor for direct-sequence code division multiple access (DS-CDMA) cellular radio systems to achieve higher communication link quality and better system capacity. In order to track the desired signal-to-interference-plus-noise ratio (SINR) under round-trip delay, multiple access interference (MAI), channel fading, and noise, a time delay-based state-space model is developed for representing the tracking error dynamics and a state feedback controller is introduced for SINR tracking control. Then the power tracking problem can be regarded as a control problem. In this paper, a robust$H_infty$power tracking control design is proposed to achieve a robust optimal SINR tracking from the minimization of the worst-case effect point of view. This robust optimal power tracking design problem can be transformed to solving the eigenvalue problem (EVP) under some linear matrix inequality (LMI) constraints. The LMI Matlab toolbox can be used to efficiently solve the EVP via convex optimization to achieve a robust optimal SINR tracking design. Under the proposed distributed framework, the information of channel gain is not needed.     

Power control strategies for multichannel cognitive wireless networks with Opportunistic Interference Cancellation

In this letter, an Opportunistic Interference Cancellation （OIC） is first introduced as a rate control strategy for secondary user in cognitive wireless networks. Based on the OIC rate control method, an optimal power control strategy for multichannel cognitive wireless networks is proposed. The algorithm aims to maximize the total transmit rate of cognitive user through appropriately controlling the transmit power of each subchannel under the constraint that the interference temperature at the primary receiver is below a certain threshold. Three suboptimal power control methods, namely Equal Power Transmission （EPT）, Equal Rate Transmission （ERT） and Equal Interference Transmission （EIT）, are also proposed. The performances of the proposed power control methods are compared through numerical simulations.     

Signal and interference statistics of a CDMA system with feedbackpower control

Power control is essential in the use of direct-sequence code-division multiple-access (CDMA) techniques over fading radio channels. The paper investigates a feedback power control approach that allows power commands to be updated at a higher rate than the rate of multipath fading. The signal and interference statistics as received at the base stations after power control are obtained for a simulated CDMA system which includes multiple base stations with diversity receivers and a large number of power-controlled users continuously moving at various speeds. The authors show that often-used analyses based on perfect average power control lead to optimistic capacity results (by about 25%) because interference is underestimated by as much as 1 dB     

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     

Improving cell edge throughput for LTE using combined uplink power control

Uplink power control is used in 3GPP Long Term Evolution (LTE) systems to maximize the power of the desired received signals while limiting the interference. This paper analyzes two power control mechanisms, Fractional Power Control (FPC) and Interference Based Power Control (IBPC). A way of combining them is proposed in order to find an efficient algorithm to control the transmitted Power Spectral Density (PSD) in order to compensate poor channel conditions and thus to obtain better performance in terms of cell edge throughput.     

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.     

基于状态机控制的飞机供电系统仿真

飞机供电系统是整个飞机系统的重要部分,负责向机上的所有负载提供可靠的电能。电源控制单元能够针对飞机的故障采取相应的保护措施,保证飞机的安全飞行。传统的飞机供电系统仿真采用逻辑器件完成电源控制作用,这种方法对供电系统多重故障的处理过于复杂。基于Ansoft/Simplorer软件,本文提出了一种基于状态机控制的飞机供电系统仿真新方法。通过状态变量和状态转换条件的设置,实现电源控制单元功能,完成飞机供电系统仿真。结果表明,状态机控制方法能够准确快捷地实现飞机供电系统的仿真。     

舵机加载系统的最优控制

分析了舵机加载系统的结构原理,建立其简化模型,并研究了最优控制在舵机加载系统中的应用.舵机加载系统中加载设备和舵机系统间存在强烈的耦合,针对舵机运动对加载系统跟踪性能的影响,应用前馈控制对舵机运动扰动进行补偿.为进一步提高系统性能,引入最优控制.根据舵机加载系统的特点,比较研究了3种不同的最优控制方法.常用的是工程近似最优控制方法,为进一步消除稳态误差,可以引入积分控制.与上述方法不同,对加载系统进行最优控制时,采用积分策略增广系统状态方程,并引入期望衰减度定义性能指标构造系统的最优控制.仿真结果表明,在文中所构造的最优控制和前馈控制的复合控制下,加载系统具有相对最佳的跟踪性能.