基于目标运动估计的越区切换优化策略

地空数据通信系统的越区切换不仅要尽可能地减少切换次数,还要保持地面通信路由优化,以提高地空通信保障的可靠性。通过采用基于加速度的运动估计预测目标位置,并融合最短路径算法确定越区切换站点,在保证地空数据通信质量的同时提高了越区切换的效率,满足空中目标自由机动情况下的跨区域无缝通信要求。     

第三代移动通信系统的切换问题

软切换是CDMA系统中引入一个新概念,除了技术实现上的改善外,还给通信话音质量、系统容量等方面带来了突破。越区切换是第三代移动通信系统的研究热点。该文综述了各种切换的定义、分类、切换的过程,WCDMA和cdma2000中切换。最后提出有待解决的问题。     

载人航天通信网

<正> 载人航天通信网可以为载人航天系统的指标、控制、跟踪、遥信、遥测、遥控提供优质,可靠不间断的服务,是以保障天地通信为特点立体化通信网。它由超短波通信系统,短波通信系统,卫星通信系统,微波通信系统,移动通信系统,光纤通信系统、话音交换系统、数据交换传输系统,图像采集编辑交换传输系统,时间统一系统及通信网监测管理系统组成。     

基于GSM-R铁路无线通信系统的越区切换探析

基于铁路在移动闭塞区间条件下GSM-R无线通信系统对越区切换的可靠性,采用计算机仿真的方法得到GSM-R通信系统在通信故障情况下越区切换成功概率。并结合相应理论指导对铁路无线通信系统GSM-R中的越区切换事件进行了建模和分析,并使用仿真工具分析了GSM-R越区切换的可靠性。     

GSM-R网络越区切换的优化

GSM-R网络是铁路专用的移动通信系统,为CTCS-3级列车控制系统提供了数据传输的基础平台。在高速环境下,GSM-R网络越区切换会对通信造成短暂的中断,从而影响CTCS-3级列控系统的业务通信质量。本文重点研究GSMR网络越区切换的优化,提高系统的可靠性和有效性。文章从高速环境下的越区切换的性能入手,为了进一步提高GSMR承载CTCS-3级列控系统的通信质量,在传统切换算法的基础上,提出以马尔可夫模型为重点的越区切换模型,并分析越区切换成功率。     

GSM—R网络越区切换性能研究

GSM—R（GSM for Railway）是以GSM（全球移动通信系统）为平台,集列车公务通信和区间通信为一体的铁路专用移动通信系统,已经成为我国铁路通信技术的发展方向。越区切换是GSM—R系统的关键技术之一,由于列车速度的提升导致多普勒效应更严重、切换位置更靠后、越区切换更频繁,最终GSM—R的安全性和可靠性会严重降低,因此对越区切换的研究具有非常重要的意义。本文分析了GSM—R网络越区切换掉话的原因并提出了优化方案。     

机载超短波话音通信中实时等增益合并算法

针对机载超短波话音通信系统中通信话音丢失的问题,将等增益合并技术应用到机载超短波话音通信系统中,并结合实时时延估计技术和buffer缓冲时延补偿技术,提出一种实时等增益合并算法.仿真结果表明,该算法根据不同信道间信息的互补来增强接收效果,改善机载话音通信系统中通信话音丢失的问题,有助于提升机载超短波话音通信的稳定性和可靠性.     

城市轨道交通数字集群通信系统越区切换方案设计

数字集群通信系统为城市轨道交通运营企业提供行车指挥调度、控制信息传输等服务,是调度人员与列车司机之间唯一的专用无线通信手段,越区切换性能直接影响到运营效率和行车安全。文章以城市轨道交通为系统应用场景,基于无线通信理论和网络技术,结合数字集群通信系统的基本特点,通过深入分析越区切换过程及其影响因素,对城市轨道交通数字集群通信系统越区切换方案进行设计,并结合广州市轨道交通数字集群通信系统的建设和维护进行测试验证。     

数字无线通信技术在森林防火中的应用

森林防火数字无线通信包括超短波通信网、短波通信网、卫星通信系统和应急通信保障车等几个方面;在日常预防及扑火应急通信中超短波通信网的作用是最为重要的,同时超短波通信网为用户实现了专用链路资源,为扑火应急通信提供了数据远程传输的手段;超短波通信基站的建设依托于林场资源及地理环境等条件,所以在基站的基础设施建设方面也提出了很多挑战。重点介绍数字超短波通信网的建设和火场应急情况下的结合便携通信设备、卫星设备和应急通信保障车的无线语音、数据和视频的传输方案及应用。     

基于预留信道和强占优先相结合的接入策略

报道了一种用于话音／数据综合的蜂窝移动通信系统中的基于预留切换信道和强占优先策略相结合的业务接入方案。在本方案中为具有越区切换请求的话音呼叫提供了预留切换信道和强占数据业务的优先权相结合的接入策略。同时为了提高系统总的承载话音的业务量,也为新近产生的话音呼叫提供了一定的强占数据业务的优先权。结果表明：我们的方案可以为移动用户提供更好的服务质量。     

Design and implementation of a layer-II fast handoff protocol in emergency communication system

Immobility,limited bandwidth and poor support to real-time service are common shortcomings in traditional emergency communication system.Moreover,the data transmission speed is highly limited in high-speed services by the long handoff delay and fixed handoff trigger threshold when the mobile terminals moving between network nodes.In order to overcome these shortcomings,a new emergency communication system with multifrequency hierarchical clustering structure was designed.A new layer-II fast handoff protocol was designed for such network structure to deal with handoff issue in real-time services.In this handoff protocol,the handoff trigger threshold is self-adaption based on the moving velocity of mobile terminals.     

TD-SCDMA集群通信系统基于移动速度的切换策略研究

TD-SCDMA数字集群系统是集群通信系统的一个发展方向。首先介绍集群通信系统的单呼和组呼,分析这两种不同通信方式切换的特点;然后对TD-SCDMA系统的传统切换进行介绍,给出TD-SCDMA集群系统基于移动台移动速度的自适应切换算法;最后对切换性能进行简单分析。     

Characterization of soft handoff in CDMA systems

Many analytical approaches have been proposed for handoff analysis based on hard handoff in mobile communication systems. In code-division multiple-access (CDMA) systems with soft handoff, mobile stations (MSs) within a soft handoff region (SR) use multiple radio channels and receive their signals from multiple base stations (BSs) simultaneously. Therefore, the SRs should be considered for handoff analysis in CDMA systems. An analytical model for soft handoff in CDMA systems is developed by introducing an overlap region between adjacent cells and the handoff call attempt rate and the channel holding times are derived. Applying these results to a nonprioritized CDMA system, the effects of soft handoff and the mean cell residual time are investigated and compared with hard handoff     

下一代移动通信网络中的切换管理研究

本文概述了下一代移动通信网络中的切换管理研究框架结构,对切换管理研究涉及的领域加以介绍,并为下一代移动通信网络的切换管理系统性研究指引了方向.     

基于RSS准则的CDMA软切换越区研究

硬切换技术中移动台在接收新基站信号之前中断与原基站的通信,通信中断的概率非常大。而软切换技术需要先建立与新基站之间的通信,等接收到原基站信号低于门限值时再切断与原基站的通信,故具有很高的可靠性。采用接收到的信号强度准则对软切换建立仿真模型,对两个小区之间的软切换进行了仿真,仿真结果表明,软切换的可靠性高于硬切换,采用软切换技术降低了系统的掉话率,提高了通信质量。然而,软切换也将使系统的复杂度和信道开销有所增加。     

Artificial bee colony–based spectrum handoff algorithm in wireless cognitive radio networks

In this work, we proposed a new artificial bee colony–based spectrum handoff algorithm for wireless cognitive radio systems. In our wireless cognitive radio system, primary users, secondary users, and related base stations exist in the same communication environment. For our artificial bee colony–based algorithm, secondary users that always struggle to discover an idle channel have a leading role. While honey bees work hard to find the best‐quality nectar source for foraging, secondary users try to find idle channels for making communication. In this way, secondary users are organized for different missions such as sensing and handoff similar to honey bees to minimize spectrum handoff delay by working together. In the spectrum handoff stage, some secondary users must sense the spectrum so that the interrupted secondary user may perform the spectrum handoff process. In our developed spectrum handoff algorithm, the spectrum availability characteristic is observed on the basis of the missions of the bees in the artificial bee colony algorithm with the aim of minimizing the spectrum handoff delay and maximizing probability of finding an idle channel. With the help of the algorithm that is developed using the artificial bee colony, spectrum handoff delay of secondary users is considerably decreased for different number of users without reducing probability of finding an available channel.     

Joint mobility tracking and handoff in cellular networks via sequential Monte Carlo filtering

We consider the application of sequential Monte Carlo (SMC) methodology to the problem of joint mobility tracking and handoff detection in cellular wireless communication networks. Both mobility tracking and handoff detection are based on the measurements of pilot signal strengths from certain base stations. The dynamics of the system under consideration are described by a nonlinear state-space model. Mobility tracking involves an online estimation of the location and velocity of the mobile, whereas handoff detection involves an online prediction of the pilot signal strength at some future time instants. The optimal solutions to both problems are prohibitively complex due to the nonlinear nature of the system. The SMC methods are therefore employed to track the probabilistic dynamics of the system and to make the corresponding estimates and predictions. Both hard handoff and soft handoff are considered and three novel locally optimal (LO) handoff schemes are developed based on different criteria. It is seen that under the SMC framework, optimal mobility tracking and handoff detection can be implemented naturally in a joint fashion, and significant improvement is achieved over existing methods, in terms of both the tracking accuracy and the trade-off between service quality and resource utilization during handoff.     

移动IPv6及其切换

对未来移动网络首选的移动Ipv6的工作原理作了详尽的介绍,在此基础上,对移动IPv6的各种切换方案作了深入的探讨,进而引入了类比于3G移动通信系统切换的思想,最后提出了移动IPv6切换的下一步研究方向。     

Soft handoff algorithms for CDMA cellular networks

This paper discusses the design of soft handoff algorithms for cellular communication systems. The handoff process is modeled as a hybrid system and handoff design is cast as an optimization problem based on such a model. Performance is evaluated in terms of call quality, average number of active base stations, average number of active set updates, and average amount of interference. A soft handoff algorithm, which achieves a tradeoff between these performance criteria, is obtained using principles of dynamic programming. One key feature of the algorithm is that it incorporates the effects of mobility and shadow fading in the handoff decision. Different diversity combining schemes are considered including selective combining, equal gain combining (EGC), and various optimized combining (OC) methods in the soft handoff mode. For EGC and OC, Wilkinson's and Schwartz and Yeh's methods are used to compute the statistics for the power sum of the signals. Simulation results indicate that the performance of the handoff algorithm is a function of the different combining schemes and of the different methods used to compute the statistics of the power sum. Moreover, it is observed that interference cancellation is important in order for the algorithm to be viable for cellular systems which experience interference due to using nonorthogonal multiple access.     

多载波蜂窝移动通信系统中的多业务切换算法

提出一种用于多载波蜂窝移动通信系统的子信道合并切换算法。采用多维Markov链对子信道合并切换算法进行系统建模分析,得到了呼叫阻塞率、切换阻塞率等关键系统性能参数的解析结果。与切换保护信道算法相比,子信道合并切换算法在对其他类型呼叫性能影响很小的前提下,改善了对带宽要求较高的业务的切换性能。该算法还可以与其他资源预留切换算法相结合,改善其性能。