3G UMTS网络的无线链路增强技术--HSDPA/HSUPA

HSDPA和HSUPA是3GPP协议规范中定义的UMTS网络无线链路增强技术，分别在Release 5和Release 6中引入。文章在介绍HSDPA和HSUPA采用的关键技术的基础上，对两种无线链路增强技术进行了简要的比较分析。     

地铁场景5G无线链路预算与优化方案研究

从地铁场景5G无线链路预算模型入手,以现网实际情况为基础,结合理论分析和现场实测数据,对链路预算模型多个参数取值进行校正,得出更加逼近实际情况的参数取值;根据新的链路预算参数,提出符合地铁场景5G无线网络设计方案的优化设计方法,并给出实验验证结果;同时结合业界工程能力和技术发展情况,提出了方案精细化设计思路,在同等覆盖标准的情况下实现地铁项目投资及运营成本的明显下降。     

基于3G网络的新型无线监控系统

以3G网络为平台,设计开发了一种新型的无线监控系统.本系统由两大部分组成:终端影像监控设备和后台计算机监控中心.两部分之间通过3G网络进行实时数据传输.本文主要研究了视频数据编码技术和无线信号射频收发技术,设计了一种新型的适用于本系统的编码原则和射频收发技术方案.     

基于3G网络的远程无线监控系统设计

针对远程无线监控系统的应用需求和移动通信的发展,提出一种基于2G/2.5G/3G网络的远程无线监控系统,设计了系统的总体方案,介绍了系统的组成结构和工作原理,着重阐述了系统的硬件和软件设计。该系统拓展了移动通信网络的应用范围,提高了远程监控系统的灵活性和稳定性,具有广泛的应用前景。     

无线信道特性对3G系统的影响

与2G系统相比，3G全部使用2GHz频段，采用CDMA技术的空中接口规范，占用更宽的带宽，传输信电速率更高。因此，3G面临的无线环境也与2G系统有较大的差别，并对3G系统的组网与优化带来影响。清华大学王京老师在本期“专家答疑”栏目解答了有关问题。     

3G系统网络优化

1概述随着3G技术的出现,运营商们也在研究相应的3G网络配置策略,以满足现在和将来不同层次的业务需求。同时,对于网络基础结构的建设投资来说,运营商的商业计划也都必须支持这些策略。因此,对于3G网络,最重要的是要找到切实可行的容量和覆盖范围之间的平衡关系,提供具有竞争力的业务。23G无线接入特点在由熟悉的2G网络向3G网络转换时,无线网络为了满足真正的多业务,使其设计规划迎来了许多新的挑战:(1)高度完善的空中接口,在承载和复用大量话音业务方面,以及特别是从低速到高速,最大可达2Mb/s的范围内固定和可变速率的数据业务方面具有高…     

后3G移动通信无线接入网络的发展趋势

本文研究了移动通信网中各种无线接入系统标准和异种网络构架，分析了不同无线接入网的控制方式和拓扑结构，探讨了适合后3G移动通信系统发展的无线接入网构架。     

B3G移动网络的演进

文章从B3G的定义出发，介绍了移动通信和宽带无线接入两大领域中的宽带无线技术，最后探讨了B3G网络的演进路线。     

第三代移动通信系统的链路预算分析

链路预算是网络规划与设计中必不可少的一步,通过链路预算能够指导规划区内小区半径的设置、确定所需基站数目和站址的分布。详细分析第三代移动通信系统的链路预算问题,并与第二代移动通信链路预算进行比较,分析第三代移动通信系统网络规划与设计中的难点和关键,并给出第三代移动通信系统链路预算方法、步骤以及关键设置参数。     

Analysis of link lifetime in wireless mobile networks

Link lifetime (LL) analysis is crucially important in designing and evaluating wireless mobile network protocols. Although a considerable amount of research has been conducted on this issue, the current paper studies several aspects of link lifetime for the first time, e.g. a closed form expression for the probability distribution of the residual link lifetime (RLL) for the constant velocity mobility model is obtained, which facilitates marginal studies on the behavior of link lifetime. As a case, using a tail analysis of LL and RLL distributions, we analytically prove that they are heavy-tailed. Using this outcome, a self-similar behavior in the traffic pattern of a sample delay tolerant network is justified analytically. To extend the model, the effect of stationary nodes, the effect of buffer zone, and the effect of link establishment policies between different node categories on the link lifetime are investigated. Extensive simulation experiments are performed to validate the obtained analytical results and derivations precisely. Moreover, simulation results confirm that the analytic results can also be used for two well known mobility models (random waypoint and random direction) with a negligible error.     

无线Mesh网络中基于链路负载估算的拥塞控制策略

针对无线Mesh网络的网络特性,提出了一种基于链路负载估算的拥塞控制策略LLECC。LLECC算法计算有效链路带宽和链路负载估算确定RED算法中的调整因子,通过调整因子调整RED算法中的参数从而实现动态的对无线网络拥塞控制。详细讨论了LLECC算法的实现过程和相关参数的计算方法,通过仿真分析验证了该算法对无线Mesh网络性能的提高。     

CCI-based link quality estimation mechanism for wireless sensor networks under non-perceived packet loss

This paper proposes a chip correlation indicator (CCI)-based link quality estimation mechanism for wireless sensor networks under non-perceived packet loss. On the basis of analyzing all related factors, it can be concluded that signal-to-noise rate (SNR) is the main factor causing the non-perceived packet loss. In this paper, the relationship model between CCI and non-perceived packet loss rate (NPLR) is established from related models such as SNR versus packet success rate (PSR), CCI versus SNR and CCI-NPLR. Due to the large fluctuating range of the raw CCI, Kalman filter is introduced to do de-noising of the raw CCI. The cubic model and the least squares method are employed to fit the relationship between CCI and SNR. In the experiments, many groups of comparison have been conducted and the results show that the proposed mechanism can achieve more accurate measurement of the non-perceived packet loss than existing approaches. Moreover, it has the advantage of decreasing extra energy consumption caused by sending large number of probe packets.     

Statistical estimation of link availability and its impact on routing in wireless ad hoc networks

In this paper, an analytical framework is developed and validated via simulation for statistical estimation of the evolution of the separation between a pair of mobile nodes in an ad hoc network. Simulation results demonstrate that path selection based on minimization of the product of the link statistic significantly outperforms minimum‐hop and fixed threshold‐based ‘path‐stability’ schemes. A hierarchical mobility model integrating the dynamic effects of velocity, group movement and geographic scope is used to generalize the results. Another significant result is the performance enhancements hold in large networks irregardless of the assumptions used for statistical estimation. The effect of merging many independent groups appears to restore independent mobility. Finally, results show that at the highest mobility levels, 90% of the longest surviving paths fail within 60 s. None of the strategies approach this optimal value. This important result suggests that optimal predictive mechanisms alone are insufficient to ensure scalable routing in ad hoc networks. Copyright © 2004 John Wiley & Sons, Ltd.     

3G无线网络规划中的关键问题

随着人们对无线数据需求的不断增长,尤其是Internet的发展,第三代移动通信系统(3G)也开始步入商用化进程。第三代系统(3G)基于码分多址(CDMA)的接入方式。与第二代系统相比,第三代系统引入了大量的各种比特率和多样化的业务,它最大可支持的数据速率达到2Mb/s。正因为它提供的多种比特率和多样化的业务使得在3G网络规划中对不同业务的预测和对它建模变得特别困难。另外由于第三代系统和第二代系统在无线接入方式的不同,使得在3G网络规划中要考虑更多、更复杂的问题,例如导频污染、软切换增益、容量和覆盖的迭代预测等等。本文结合3G系统…     

无线频谱资源分配在5G网络中的进展分析

随着现代网络技术的高速发展,现代移动通信的触角已经开始逐步延伸到5G时代,无线频谱也相应的得到了更深层次的应用和发展,尤其是在资源分配方面.由于频谱资源分配受多种因素的影响,因此在实际运用过程中必须对其做进一步的研究.对此,本文将系统的分析和探讨无线频谱资源分配在5G网络中的发展.     

Efficient resource allocation for China's 3G/4G wireless networks

The all-IP DiffServ model is expected to be the most promising architecture for QoS provisioning in China's next-generation wireless networks, due to its scalability, convenience for mobility support, and capability of interworking heterogeneous radio access networks. This article focuses on efficient resource allocation in a wireless DiffServ architecture. Resource utilization efficiency is particularly important for China's wireless networks as the mobile user density in China is and will continue to be much higher than that in other countries. More specifically, we propose a novel buffer sharing scheme to provide assured service for real-time layer-coded multimedia traffic, which can guarantee the specific packet loss requirement of each layer with UDP as the transport layer protocol. An adaptive optimal buffer configuration can be applied to achieve maximum resource utilization over the time-varying channel. Assured service is also provided to TCP data traffic for guaranteed throughput, where the cross-layer coupling between the TCP layer and link layer is exploited to efficiently utilize the wireless resources.     

3G无线接入网的两种传输技术

根据3G技术无线接入网的技术要求,对无线接入网的两种传输技术--多业务传输平台(MSTP)和异步传输模式(ATM)进行了比较,同时考虑到实际组网需适应3G网络的业务特点和传输网的未来发展,结合国内外ATM和MSTP实际应用状况,可以认为MSTP作为3G无线接入网的过渡技术,其成本较低,是目前传送网的最佳解决方案.     

Analysis and enhancements of HELLO based link failure detection in wireless mesh networks

Link failure in wireless mesh networks (WMNs) is a common even, and it is the main reason for packet losses and network unreliability. Link failures must be detected quickly in order to maintain high packet delivery ratio and mitigate their bad impacts on the network performance. Link layer failure feedback approach and HELLO based link failure detection approach are the two approaches for link failures detection in WMNs. In this paper, we will investigate HELLO based link failure detection approach. We will start by mathematically analyzing this approach which is implemented in routing protocols that catch two routes. After that, we will prove that the packet delivery ratio can be increased by 1.5 by implementing two paths instead of one. In addition to that, we will propose a novel framework that dynamically assigns the values of HELLO based link failure detection approach parameters based on the communications types and the QoS requirements. Finally, we will propose a novel protocol to enhance HELLO based link failure detection approach.