不同功率控制条件下的WCDMA下行软切换增益分析

在WCDMA无线网络中，由于新业务的非对称性，下行链路更有可能成为系统容量的瓶颈。本文对不同功率控制条件下的下行软切换增益做了较为深入的研究，为无线网络规划提供了一定的依据。     

WCDMA无线网络规划分析

首先概述了WCDMA无线网络规划的范围及一般步骤和流程;然后详细论述了功率控制、业务类型、上/下行链路、切换方式等方面WCDMA无线网络规划与GSM规划的区别;接着重点讨论了WCDMA无线网络规划中系统容量、负载因子、干扰容限、小区覆盖半径等参数的确定;最后指出了在规划WCDMA无线网络时综合考虑覆盖、容量和质量的重要性。     

软切换对WCDMA下行链路容量的影响

介绍了WCDMA系统中软切换模型，并在此基础上深入分析了下行容量影响因素，和软切换在下行链路容量的影响，推导出下行容量计算公式，为进一步研究和仿真WCDMA下行容量提供理论基础。     

关键技术在网络规划中的应用

全面论述了进行WCDMA无线网络规划的关键技术。首先详细介绍了前向功率规划技术及其主要考虑的几个方面；接着介绍了功控规划及进行功控规划所要注意的问题。容量规划技术及提高基站站点下行链路容量的5种方法；最后介绍了软切换技术。     

WCDM系统容量与覆盖关系研究

文章对WCDMA系统的容量与覆盖的关系进行了深入的探讨，从WCDMA系统的上、下行容景与覆盖两方面进行了详细分析。同时，结合实验网的测试数据，对影响WCDMA系统上、下行链路容量的主要因素进行了讨论，提出了一些改善WCDMA系统上、下行链路容量与覆盖的方法。     

WCDMA中的关键技术在网络规划中的应用

全面论述了进行WCDMA无线网络规划的关键技术。首先详细介绍了前向功率规划技术及其主要考虑的几个方面;接着介绍了功控规划及进行功控规划所要注意的问题,容量规划技术及提高基站站点下行链路容量的5种方法;最后介绍了软切换技术。     

WCDMA中的关键技术在网络规划中的应用

全面论述了进行WCDMA无线网络规划的关键技术。首先详细介绍了前向功率规划技术及其主要考虑的几个方面;接着介绍了功控规划及进行功控规划要注意的问题,容量规划技术及提高基站站点下行链路容量的5种方法;最后介绍了软切换技术。     

CDMA上行链路功率控制函数对系统容量的影响

根据对ＣＤＭＡ蜂窝系统上行链路干扰模型的分析，导出了行链路功率控制函数与系统容量之间的关系式，计算机模拟结果表明，与其它几个常用的功率函数相比，由本提出了使下行链路系统容量最大的最佳功率控制函数不使上行链路系统量最大，而且还比下行时的系统容量大１．４倍左右。     

TD-SCDMA无线网络的预规划

文章介绍了TD-SCDMA无线网络初步规划的必要性，重点讨论了TDSCDMA无线网络初步规划中的链路预算以及容量设计，并得到一个预规划的结果，为TDSCDMA无线网络的详细规划提供了一定的参考依据。     

WCDMA无线网络规划中的链路预算

链路预算是WCDMA无线网络规划的重要内容.本文主要论述了在WCDMA无线网络规划中的上下行链路预算的基本原理和处理过程,在其中引入一种新的预算方法--上下行链路的迭代处理预算,并通过这一方法来解决容量与覆盖规划的平衡问题.     

WCDMA上下行链路不平衡问题研究

探讨了WCDMA无线网络中普遍存在的上下行链路不平衡问题的判定方法,通过对基础数据、性能数据、参数数据、MR数据、路测数据的综合关联分析,得出了造成上下行链路不平衡的各种原因,最终给出网络优化工作中解决该问题的分析流程。     

基于输出信号过采样的RoF下行链路辨识

在分析ROF(Radio over Fiber)系统的组成与下行传输模型的基础上,提出了一种对ROF系统下行链路模型的辨识算法.ROF下行链路由非线性无记忆的光纤链路和一个时变的线性多径无线信道组成,通过对ROF系统输出的失真信号进行过采用,从而辨识出无线信道的传输函数,重构ROF系统的中间信号,最后由系统的输入信号和重构的中间信号估计出ROF系统非线性链路的模型参数.通过仿真分析表明,该算法对ROF系统下行链路模型辨识的有效性.     

一种适用于B3G移动通信系统下行共享信道的调度算法

本文针对后三代(B3G)移动通信系统中的宽带无线信道特性和流媒体业务特征,分析了可用于高速下行共享信道的各种传统分组调度算法,提出面向流媒体业务能够提高系统吞吐量的基于优先级公平调度(Priority-Based Fairness Scheduling,PBFS)算法.该算法根据各移动用户收发信道质量和业务传输的QoS要求动态调整各用户的业务传输优先级,确定下行共享信道的调度方案.并给出该算法的简化形式S-PBFS.仿真结果表明,与传统调度算法相比,S-PBFS算法在数据包传输时延受限的条件下具有无线信道利用率高、实现复杂度低等特点.     

A buffer management algorithm for improving up/down transmission congestion protocol fairness in IEEE 802.11 wireless local area networks

The fair allocation of the resources is an important issue in wireless local area network (WLAN) because all wireless nodes compete for the same wireless radio channel. When uplink and downlink transmission congestion protocol (TCP) flows coexist in WLAN, the network service is biased toward the uplink TCP flows, and the downlink TCP flows tend to starve. In this article, we investigate the special up/down TCP unfairness problem and point out that the direct cause is the uplink acknowledgement (ACK) packets occupy most buffer space of access point. We thus propose a buffer management algorithm to ensure the fairness among uplink and downlink TCP flows. In order to limit the greedy behavior of ACK packets, the proposed algorithm adjusts the maximum size of buffer allocated for the ACK packets. Analysis and simulation results show that the proposed solution not only provides the fairness but also achieves 10–20% lower queue delay and higher network goodput than the other solutions. Copyright © 2012 John Wiley & Sons, Ltd.     

Transmit beam-tracking algorithm in FDD CDMA cellular wireless system

A beam-tracking algorithm for downlink transmit beamforming in an FDD CDMA cellular wireless system is investigated. The method takes advantage of the power-controlled system and searches for the beamformer direction corresponding to the minimum transmit power. There is no complex computation needed; thus it simplifies the downlink transmit beamforming system.     

TD-SCDMA系统中基于上行参数的下行波束赋形算法

在TD－SCDMA系统中，我们在基站发送端进行波束赋形来提高下行链路的性能。以最优准则－最大信干噪比特征分解算法为例，我们分析基于上行参数进行下行赋形的基本原理，模拟了不同环境下赋形算法的性能，并与全向情况进行比较，得出了相应的结论。     

Delay analysis for sleep-based power saving mechanisms with downlink and uplink traffic

In wireless networks, sleep-based power saving mechanisms can reduce the energy consumption at the expense of additional packet delay. This paper proposes a queueing model to analyze the packet queueing delay. Compared with the existing models which consider downlink traffic only, both downlink and uplink traffic are considered in the analysis.     

MC V-BLAST系统的MIMO信道盲估计

本文研究多载波垂直分层空时(MC V-BLAST)系统的下行频率选择性衰落多输入多输出(MIMO)无线信道估计问题.本文首先为MC V-BLAST系统提出了一种新颖的移不变性编码方法.利用上述移不变性性质,本文进一步提出了相应的下行频率选择性衰落MIMO无线信道的盲估计方法.仿真结果表明了本文移不变性编码方法的有效性和信道盲估计方法的性能.     

Bandwidth utilization efficiency enhancement for OFDM‐based WSN

Normally IEEE 802.16 (WiMAX) is used for mainly downlink traffic applications. However in the upper tier of 2‐tier (WiMAX‐WiFi) wireless sensor network, the uplink bandwidth faces bottlenecks for high throughput. In this paper, a solution has been proposed for this limitation of uplink bandwidth allocation through the use of queuing theoretic performance modeling. A Markov‐modulated Poisson process traffic model has been formed for orthogonal frequency division multiple access‐based transmission along with discrete time Markov chain system model for queuing. A downlink traffic pattern has been defined for wireless sensor network nodes. Analytical methods are used to estimate the performance parameters like throughput, delay, and probability of packet drop for resource allocation. An algorithm is formulated to find out minimum resource requirement for downlink and to transfer rest of the resources to uplink bandwidth allocation, for throughput enhancement. Uplink frame utilization is determined through another discrete time Markov chain model for adaptive triggering between the proposed maximum and the normal downlink to uplink ratio operations, for efficient distribution of bandwidth resources. Algorithm and simulation results prove outstanding improvement in the uplink throughput around 50%, without degrading the downlink throughput.     

A MIMO-OFDM prototype for next-generation wireless WANs

Coupled with a robust and efficient OFDM air interface, MIMO technologies lead to a very compelling high-speed data downlink solution for future wireless systems. This article presents Nortel Networks' MIMO-OFDM concept prototype and measured performance results. This prototype has been developed in the framework of a Nortel Networks system concept for 3G evolution systems and next-generation wide area wireless networks. The prototype is based on a shared access MIMO-OFDM physical layer in the downlink, supporting adaptive modulation and coding, with peak rates up to 37 Mb/s. The uplink is based on an enhanced UMTS WCDMA physical layer. Performance for the high-speed downlink has been measured under various emulated fading conditions. The measured performance illustrates the robustness of OFDM in frequency-selective channels and high-speed mobility channels, supporting speeds as high as 200 km/h. The prototype can also be used for over-the-air assessment of the technology.