基于功率控制CDMA容量优化的应用

为了克服CDMA系统的远近效应和边缘效应,解决CDMA网络容量受限的问题,采用了功率控制技术,对前向链路减小基站发射功率,对反向链路调整移动台发射功率,降低系统内的干扰水平,满足用户QoS要求,有效提高CDMA系统容量。理论阐述了功率控制技术与CDMA系统容量的关系,从系统载扰比分析入手验证了功率控制对CDMA系统容量的影响,得到了基于功率控制技术两种容量优化方法即远近控制和C/I控制。实际案例仿真结果表明,通过优化功率控制参数的方法能够有效地提升CDMA系统的容量,促使CDMA网络软容量达到最佳,为CDMA网络优化人员提供可以借鉴的思路和方法。     

CDMA移动通信中外环功率控制研究

CDMA是一个干扰受限系统,反向链路功率控制对于克服“远近效应”和增加系统容量是非常重要的。本文从减小用户发射功率及误帧率FER波动的目标出发,提出了一种外环功率控制的算法。仿真结果表明,采用该算法的系统具有可行性,有着良好的抗干扰能力。     

CDMA蜂窝通信系统的容量问题

CDMA系统是干扰受限系统,其容量取决于系统内用户的相互干扰,为了不影响通话质量而使得系统容量最大化,功率控制是有效措施之一,更是系统容量最大化的基础.本文从不同角度讨论了CDMA系统的容量问题,以及功率控制对系统容量的影响.仿真表明,CDMA系统容量在无衰落和有衰落环境下差异较大,有效的功率控制技术不但能够大大降低系统干扰,还能很好地提高系统容量.     

τ指数距离驱动功率控制在CDMA中研究

简要阐述了CDMA通信系统的特点和功率控制的作用,提出了τ指数距离驱动功率控制算法.该算法根据用户距基站距离的不同,收发信号采用不同的功率,从而使小区内所有用户享有均匀服务.在其基础上对CDMA蜂窝通信系统的下行链路进行理论的分析,结果表明:采用τ指数功率控制的系统比没有采用功率控制的系统,其容量至少提高三倍.     

DS/CDMA系统中同信道干扰取消技术

在码分多址系统中,多址干扰和远近效应是影响系统性能、限制系统容量的主要因素。为了抑制多址干扰和远近效应对DS/CDMA系统的影响,可以采取各种数字滤波技术。本文介绍了DS/CDMA系统中目前所采用的时域和空间域数字滤波技术,然后对这两种数字滤波技术提出了自己的一些看法。     

异构网络中基于用户划分的资源分配与功率控制方案

部署异构网络是提高移动通信系统容量至关重要的举措。然而宏基站的高发射功率会使得微蜂窝边缘用户受到严重的干扰;同时,微蜂窝周围的宏蜂窝用户由于靠近微基站将同样受到其所造成的干扰,因此这些用户应该受到保护。通过研究异构网络下行传输中的资源分配与功率控制策略,提出了一种基于用户划分的资源分配与功率控制方案。首先根据用户的信干噪比对用户进行分类,同时为受干扰严重的边缘用户划分保护频带。此外,通过动态地调整每个基站在保护频带上的传输功率,在不过度牺牲系统性能情况下减轻边缘用户的干扰。仿真结果表明,与传统方案相比,该方案能够有效抑制宏蜂窝和微蜂窝边缘用户的干扰并提高整个系统的吞吐量。     

超密集网中基于分簇的功率优化控制方案

超密集网(UDN)的组建可增加热点地区的系统容量,但由于网络中存在严重区间干扰,限制了UDN的部署。为此,提出一种基于小区分簇的功率优化控制方案。通过预先设定的系统平均干扰阈值进行分簇,将系统中干扰较大的小区分到一个簇中,当簇中的小区对其他小区用户的干扰低于设定的阈值时,将此小区从这个簇中去除。该方案的功率控制由控制器根据簇内基站所占的权重值为各个基站分配相应的功率值,从而达到控制目的。仿真结果表明,该方案能够有效抑制网络中的干扰,提高系统吞吐量。     

CDMA系统中一种基于代价函数的联合功率控制算法

功率控制技术是CDMA系统中克服远-近效应、降低多址干扰、增大系统容量的一项关键技术。首先比较了传统功率控制和联合功率控制算法,然后提出了一种基于联合系数的功率控制算法,该算法结合了功率控制技术和MM SE多用户检测技术。仿真结果表明,采用提出的功率控制算法,在系统内发射总功率一定的条件下,可以使各用户获得更高的信干比服务质量,系统容量也具有进一步提高的潜力。     

CDMA系统中的联合功率控制技术

功率控制和多用户检测是CDMA系统中克服远近效应、抑制多址干扰(MAI)的关键技术.将两者结合起来的联合功率控制技术具有很大的优越性,并有极大的研究潜力.重点综述了联合功率控制与线性多用户检测技术以及联合功率控制与非线性多用户检测技术的研究进展,并对今后的研究方向进行了概括性的描述.     

基于ABS的干扰协调方案研究

异构网通过运用不同功率的基站同频部署,扩大了网络覆盖率及系统容量。但同时这种多层结构也带来了小区间干扰问题。ABS是一种时域上的小区间干扰协调技术,解决了下行传输中高功率宏基站和低功率小基站共享频域资源时的干扰问题,但该技术的缺点是降低了宏基站的用户容量。文中研究了一种从频域、时域、功率三个维度联合进行干扰协调的新型ABS解决方案。仿真结果证明该方案可以显著增加宏基站用户的吞吐量,同时不对小基站产生过多干扰。     

Identifying the capacity gains of multihop cellular networks

Claims for the advantages of applying multihop relay in CDMA cellular networks have been widely accepted in the literature. However, such claims have yet to be closely examined. In this paper, capacity increase in CDMA cellular networks through multihop relay is quantified. As CDMA networks are interference-limited, interference has to be analyzed to estimate the system capacity. Toward this end, we derive formulas to calculate interference experienced in multihop CDMA cellular networks by both base stations and mobile terminals. The formulas are generic and applicable whether or not power control is exercised between mobile terminals. The capacity of multihop CDMA cellular network is compared to that of single hop CDMA cellular network to verify the claimed advantage. We demonstrate that a 23% capacity increase is achieved when relaying with power control. We also extend the work to illustrate the effect of call distribution on the capacity of the cell and its neighbors – both in the single and multiple hop cases. Furthermore, we ascertain that call distribution inside a cell hardly affects the capacity of adjacent cells when using multihop relay. This specific advantage overcomes the inherent capacity degradation caused by near border calls, which is the biggest burden on the capacity of single hop CDMA cellular networks. To the best of our knowledge, this effort is the first of its kind in this area.     

GAME based dynamic resource scheduling in QoS aware radio access networks

Radio resource management and QoS are finally inseparable in wideband CDMA networks. In this paper, we propose a novel wireless resource scheduler, called GAME-C, that integrates our genetic algorithm for mobiles equilibrium (GAME) with the standard CDMA transmitter closed loop power control (CLPC). GAME assigns optimally both transmitting power and bit rate to every mobile station. Optimal allocation is in the sense that every user gets only enough resources necessary for meeting or exceeding its QoS requirements while minimizing interference to other users. Having done that, we gain further benefits as well. In addition to QoS provisioning, lower transmitting power extends a mobile station battery life. Moreover, the base station coverage efficiency is improved by decreasing the probability of blocking new connections or dropping current ones. In short, GAME-C expands the number of QoS-satisfied mobile stations in a cell. Various simulations show improvements achieved over the established (CLPC) basic scheme.     

基于协作中继的多点广播码分多址信息系统设计

为了提高多群多点广播中继网络系统的性能,提出一种改进的协作中继多点广播码分多址(CDMA)系统设计。该方案利用协作中继辅助的分布式波束形成 实现单天线基站多播,获得了较好的空间分集增益。在该系统中,多个基站利用多个中继节点向多个目的地的各个小组传播消息;利用CDMA技术来减少中继节点以及目的地节点的多址干扰(MAI)障碍,同时每个中继节点作为线性预编码波束合成器,可以在合适的代码空间重塑基站信号;对线性波束形成矩阵进行优化,使得中继节点的功率最小化,从而满足QoS在信号干扰噪声比方面的要求。系统性能仿真对比实验的结果表明,提出的改进方案明显优于传统的正交复用方案(FDMA / TDMA)。     

Power control in CDMA networks based on soft computing methods

Power control is a fundamental procedure for CDMA mobile radio communication systems. In multiservice CDMA systems, power control should be used to minimise the transmission power of each connection, in order to limit the multiple access interference, while obtaining the desirable SIR levels. This paper starts from a transmitted-power allocation algorithm (TPAA) that considers a set of uplink transmissions, which should be supported by the system. In the sequel, the TPAA algorithm is used for training an Elman neural network, which, due to its internal characteristics, is applicable in the time critical context of power control. Simulations and numerical results are analysed for obtaining a solid basis for employing our scheme in the power control of CDMA systems.     

基于漏泄电缆的井下CDMA无线覆盖技术

针对采用天线作为CDMA无线通信系统覆盖设备时存在信号绕射及穿透能力较差,在弯曲度及高低起伏大的巷道无法保证无线信号的覆盖距离及信号质量,无法随意增大矿用CDMA基站发射功率来满足无线覆盖要求的问题,提出了一种利用漏泄电缆进行井下CDMA无线信号覆盖的解决方案。该方案中,井下CDMA基站输出的射频信号通过二功分器连接到漏泄电缆,可实现巷道的无线信号覆盖。实际应用表明,采用该方案信号覆盖稳定,通信效果良好。     

基于CDMA技术的无线监控系统的研究与应用

利用CDMA技术,可以完成控制中心对移动终端设备的无线监控,从而实现监控系统的高质量性,高效率性以及高抗干扰性。本文给出了一种基于CDMA技术的无线监控系统方案,主要介绍了这种无线监控系统在警犬机器人中的应用,其中重点讨论了该应用系统的硬件组成以及软件的设计与功能实现。     

Multiphase transfer of control signal for adaptive power control in CDMA systems

Capacity improvment in cellular networks is highly dependent on the effectiveness of power control. A power control procedure is needed to compensate for the fluctuation of a mobile's transmitting power received at a base station and to increase the capacity of the mobile communication system via decreasing intra- and inter-cellular interference. Here we consider fuzzy set theory based delayed adaptive step-size closed loop power control scheme(s). In this scheme transmitters adjust their power step sizes according to the received multiphased power control signals (delayed commands) from base stations. Code division multiple access (CDMA) system standards (cdmaOne, CDMA2000 and ETSI UMTS/UTRAN) limit the number of bits to two for the length of the control command in time slots. Hence, the number of commands is limited to four per time slot (in practise to two: up and down fixed amount, the rest are zero and unused values) when a sign and magnitude binary word format is used. In the developed algorithm, the number of commands is enlarged to 16 per two sequential time slots (four bits) without an increase in the standardized control bit rate by transmitting control commands in two sequential phases (time slots). First two bits of the command are transmitted in the current time slot and a receiver stores them and waits for the next time slot, which includes the last two bits of the control signal. The receiver interprets control command after receiving all 4 bits. Therefore, the control frequency is decreased (delayed control) to half of the original but respectively the dynamic scale is increased to 4 times larger (in practise 7 times: 7 values up and 7 down, 1 value for zero and 1 unused) for the sign and magnitude binary coding. A single transmitter's control results with the developed controller in a frequency selective fading channel in a CDMA network with interfering nodes and Gaussian noise are compared to the predefined step size power control scheme, which is a de facto standard the power control in cellular networks.     

基于软件无线电技术的智能天线在CDMA系统中的应用

讨论了基于软件无线电技术的智能天线在CDMA系统中的实现结构，并给出了一个实用的可应用于CDMA系统的基于软件无线电思想设计的智能天线硬件实现平台。