多模移动终端的移动IP功能设计与实现

当前主流移动IP系统的移动台(MN)端均通过优先级策略选定当前代理,即以代理管理为中心实现移动IP协议。这些方案既难以提高多模移动终端所需要的跨媒体垂直切换能力,也不利于移动IP协议本身在Windows平台下的实现。给出了Windows平台下一种以链路管理为中心的移动IP客户端的设计与实现方案。     

移动终端基带芯片架构概论

文章分析了移动终端基带芯片的基本功能模块及其基本实现方法,并按照由简到繁的顺序,逐次讨论了传统的移动终端、智能终端以及多模终端的基带芯片架构,指出了移动终端基带芯片架构的发展方向和面临的主要问题。     

异构多模终端的接入选择功能架构

不同类型无线网络的融合是宽带无线通信发展的必然趋势。在异构融合网络环境中,无论何种无线网络都能够提供无所不在的最优服务。具有挑战性的问题就是异构多模终端的管理系统和接入选择功能架构的设计。一种异构多模终端管理架构通过与各协议层的有效交互,可以适应多种接入标准与技术的要求,实现多模异构终端的无缝接入和移动。接入选择是核心研究问题之一,接入选择功能架构主要包含3个模块：接入适配、移动管理、用户偏好。     

异构无线网络的自适应垂直切换判决算法

在未来的异构环境中,网络间的垂直切换将对QoS保证产生重要影响。针对移动终端在异构网络间切换不理想的问题,提出了一种自适应的垂直切换判决算法。采用基于用户多应用的代价函数对接入网络进行评估与选择,综合考虑移动终端当前的电池电量,判断当前业务是否需要进行网络切换,使移动终端能自适应地进行切换判决。仿真结果表明,该算法可以有效地延长移动终端的工作时间,减少乒乓效应,提高系统的切换性能,改善业务的QoS。     

一种基于业务切换的垂直切换判决算法

在下一代异构无线网络环境中,为满足在异构无线网络架构下采用不同切换方式的垂直切换请求,我们提出一种基于业务切换的垂直切换判决算法,并设计了一种基于业务切换的代价函数。通过数学分析和在UMTS,WLAN融合的网络环境下对该方案的切换失败率的仿真分析,证明了该方案在支持终端的移动性、保障用户业务请求满意度以及缓解网络负载压力上相比传统基于代价函数的垂直切换判决算法更具优势。     

支持移动多媒体的安全中间件

安全以其复杂性和高计算性成为移动通信和移动Internet、特别是移动电子商务发展的瓶颈。根据中间件屏蔽复杂性的特性,设计了一种支持移动多媒体通信的安全中间件模型。该模型主要实现2大安全性服务:基于3GPP标准建议实现移动终端和移动网络的安全通信,在此基础上基于WAP2.0标准实现移动终端与Internet等第3方服务提供商之间的安全通信。主要描述和分析了这个安全中间件模型,并在此基础上提出了一种实现移动终端到移动终端的端到端通信安全的方法。     

基于业务感知的WLAN-UMTS跨层切换优化方案

下一代的异构无线网络环境是移动无线接入和异构分布的网络,近年来由于智能多模终端的发展以及多种无线接入网络并存的网络环境,使得无缝的垂直网络切换成为人们关注的热点。文章在分析当前WLAN-UMTS(无线局域网-通用移动通信系统)切换方案不足之处的基础上提出了改进和创新,主要将802.21 MIH(介质独立切换)运用到切换的过程中,在应用层加入业务感知模块,使得终端可以根据业务的类型选择网络,最后基于NIST(美国国家标准和技术协会)使用NS2对新的切换方案进行了仿真。     

异构网络中基于角度移动模型的垂直切换率分析

异构网络中终端的移动特性是无线资源分配的一个重要因素,本文给出了一种终端的角度移动模型,分析了该模型下终端移动的方向角特点。根据终端移动的方向角特点,推导了用户在固定的时间间隔T内运动方向不变时的切换率闭合公式,并将时间间隔T趋于零时的切换率的理论极限值作为一个特例,从切换率的理论极限值可以明显看出,切换率与用户分布密度、用户移动速度以及小区半径之间的关系,通过切换率的计算说明了在一定条件下,小区内用户数是动态平衡的。然后进一步推导了异构网络中垂直切换率的闭合公式,并仿真证明了理论分析的正确性。仿真结果表明,在终端移动方向改变频繁、终端移动速率很低或者小区半径足够小时,可以利用切换率的理论极限值来近似实际切换率,这样可以有效降低理论计算切换率的复杂度。     

中间件及其在移动服务网中的应用

主要介绍中间件的种类、分布式体系结构、技术特点、工作机理及其应用。描述了中间件在优化移动服务网体系结构等方面的作用，重点阐述了移动服务网中几个子系统，如何采用中间件合理实现三层体系架构，探讨了采用中间件技术实现移动服务网扩展性的方式。     

异构无线网络终端接入选择功能架构的研究

在异构无线网络环境中,为了实现多模移动终端总是无缝连接到最适合应用需求的接入网络,本文首先提出一种异构终端管理系统,接着设计了接入选择功能架构,赋予终端选择接入网络的功能,并详细描述了3个核心部件(网络接口适配、用户偏好和移动性管理模块)的功能,最后论述了接入选择功能的执行和实现过程。     

An IPv6‐based mobility framework for urban vehicular networks

This paper proposes an IPv6‐based mobility framework for urban vehicular networks. In this framework, the architecture for urban vehicular networks is presented, and based on this architecture, the IPv6 address structure for urban vehicular networks is proposed. In this framework, a vehicle is always identified by its home address and does not need to be configured with a care‐of address. Based on this architecture, the pre‐handover algorithm is presented. In this algorithm, the third‐layer (L3) mobility handover is performed before the second‐layer (L2) one. When a vehicle finishes the L3 handover but does not perform the L2 handover, the corresponding access router or border router reserves the messages destined for the vehicle. After the vehicle completes the L2 handover, the access router or border router transmits the reserved messages to the vehicle. The performance of this framework is evaluated, and the results show that this framework reduces the handover cost and delay and lowers the packet loss. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of Handover Performance in LTE Femtocells Network

Handover management is one of the main factors representing the effectiveness of every wireless network technology. Due to the special characteristics of a femtocell, unnecessary handover occurs more frequently. This issue has attracted interest in developing a new handover algorithm in femtocell network. The standard handover algorithm relies on Reference Signal Received Power or Reference Signal Received Quality (RSRQ) level. However, this technique causes an unnecessary handover and reduces the user throughput. Mobility prediction is one of a popular technique to be implemented in handover algorithm. This paper analyzes the handover performance in femtocell network by using two types of handover algorithm which are standard A2-A4-RSRQ handover algorithm and proposed prediction handover algorithm. The analysis is performed in terms of the number of handover, the number of unnecessary handover, and the user throughput. The root cause of user throughput degradation is also analyzed. The results show that the prediction handover algorithm provides better performance than the A2-A4-RSRQ handover algorithm in terms of the number of handover and user throughput.     

基于重叠网络的移动IPv6快速切换

基本的移动IPv6切换延迟太大，不能满足实时业务的要求。本文提出了一种基于重叠网络的移动IPv6快速切换算法，这种算法通过在两个不同的IPv6子网间设置重叠网络来实现IP层的无缝(零延迟)切换。文中给出了算法实现的网络结构及其切换过程，并且对其性能进行了分析。算法实现了移动IPv6快速切换，在大部分情况下都可以达到最佳性能。     

Fuzzy Logic Based Self-Adaptive Handover Algorithm for Mobile WiMAX

It is well known that WiMAX is a broadband technology that is capable of delivering triple play (voice, data, and video) services. However, mobility in WiMAX system is still a main issue when the mobile station (MS) moves across the base station (BS) coverage and be handed over between BSs. Among the challenging issues in mobile WiMAX handover are unnecessary handover, handover failure and handover delay, which may affect real-time applications. The conventional handover decision algorithm in mobile WiMAX is based on a single criterion, which usually uses the received signal strength indicator (RSSI) as an indicator, with the other fixed handover parameters such as handover threshold and handover margin. In this paper, a fuzzy logic based self-adaptive handover (FuzSAHO) algorithm is introduced. The proposed algorithm is derived from the self-adaptive handover parameters to overcome the mobile WiMAX ping-pong handover and handover delay issues. Hence, the proposed FuzSAHO is initiated to check whether a handover is necessary or not which depends on its fuzzy logic stage. The proposed FuzSAHO algorithm will first self-adapt the handover parameters based on a set of multiple criteria, which includes the RSSI and MS velocity. Then the handover decision will be executed according to the handover parameter values. Simulation results show that the proposed FuzSAHO algorithm reduces the number of ping-pong handover and its delay. When compared with RSSI based handover algorithm and mobility improved handover (MIHO) algorithm, respectively, FuzSAHO reduces the number of handovers by 12.5 and 7.5 %, respectively, when the MS velocity is <17 m/s. In term of handover delay, the proposed FuzSAHO algorithm shows an improvement of 27.8 and 8 % as compared to both conventional and MIHO algorithms, respectively. Thus, the proposed multi-criteria with fuzzy logic based self-adaptive handover algorithm called FuzSAHO, outperforms both conventional and MIHO handover algorithms.     

基于速度触发的提前切换算法在LTE-R中的应用研究

随着高铁的快速发展,铁路移动通信系统对切换时延、切换成功率等要求更为苛刻。该文针对铁路长期演进(LTE-R)系统提出基于速度触发的提前切换算法,通过提前进行信令交互、设置切换预承载点切换的方式抑制过早或过迟切换所带来的通信中断、掉话等问题。通过信令流程图进行理论分析,并对长期演进(LTE)各结构类型数据计算可知,该算法均可缩短切换时延,其中TDD帧结构类型2时效果最为显著。最后通过仿真对比得到提前切换算法相比传统切换算法有着更高且更稳定的切换成功率,验证算法的有效性,为LTE-R在未来铁路专网的应用提供技术支持。     

A middleware architecture supporting seamless and secure multimedia services across an intertechnology radio access network - seamless content delivery in the future mobile internet

This article presents a middleware architecture to support multimedia services across intertechnology radio access networks in a secure and seamless manner. The proposed architecture uses the media-independent handover framework, where the handover decision function is based on triggering/collecting statistics from the physical, network, and application layers so that an ongoing multimedia session (video) can be transferred seamlessly and securely (using context transfer) across intertechnology radio access networks. Simulation results show that when a vertical handover is based on the proposed MIH framework (including the context transfer of AAA information), handover latency is reduced by 38 percent during WiFi to UMTS handover and 20 percent during UMTS to WiFi handover compared to a non-MIH-based handover scheme.     

A preset threshold based cross-tier handover algorithm for uplink co-channel interference mitigation in two-tier femtocell networks

This paper considers the co-channel interference mitigation problem and proposes a preset threshold based cross-tier handover algorithm for uplink co-channel interference mitigation in two-tier femtocell networks. The proposed cross-tier handover algorithm introduces a preset threshold cross-tier handover policy, which takes into account both the time-to-stay (TTS) of a macrocell user equipment (MUE)/femtocell user equipment (FUE) in a femtocell/the macrocell, and the received signal to interference plus noise ratio (SINR) at a femtocell access point (FAP)/the macrocell base station (MBS) in making a cross-tier handover decision for an MUE/FUE. A cross-tier handover decision is made by comparing the TTS of an MUE/FUE in a femtocells/the macrocell and the SINR at a FAP/the MBS with a preset TTS threshold and different SINR thresholds. The objective of the preset threshold based cross-tier handover algorithm is to increase the received SINR at the MBS/FAPs and thus improve the network performance. The performance of the proposed cross-tier handover algorithm with the minimum power transmission and the optimal power transmission is analyzed, respectively. Numerical results show that the proposed preset threshold based cross-tier handover algorithm can significantly improve the network performance in terms of the outage probability, user sum rate, and network capacity.     

多网络共存下基于贝叶斯的垂直切换算法

针对目前的垂直切换技术普遍不能满足多网络下的切换问题,提出了一种改进的基于贝叶斯决策的垂直切换算法。首先根据接入终端网络的信号强度、网络负载、误码率和网络阻塞率以及用户业务对网络的实际需求偏好建立多条件相关的切换概率分布,计算出先验切换概率;然后通过贝叶斯决策算法计算出后验概率来进行判决比较,从而选取最优的接入网络。仿真结果表明,该算法不仅能有效地实现不同接入技术之间的垂直切换,从而减少不必要的切换,提高了切换成功的概率,而且还能在维持各网络平均负载达到30%~40%时减轻通信热点的阻塞情况,为用户提供更优的服务质量。     

移动卫星网络中基于最小费用的切换算法

对于移动卫星网络,合理的星地链路切换方案需要在保证最小切换时延的同时,能够最优地使用网络资源。该文通过引入业务的中断概率和费用模型,给出了切换过程中重路由的最优触发条件,提出一种基于最小费用的切换(SMCH)算法。该算法可在保证切换业务通信的连续性和时延等指标不被破坏的基础上,通过适当的触发重路由来降低切换费用。仿真表明该算法在保证切换业务的QoS,降低切换费用以及适应性、灵活性等方面都优于同类切换算法。     

Handover with resource pre-allocation in the OFDMA systems

This article proposed a new handover algorithm for beyond the third generation (B3G) systems with an orthogonal frequency division multiple access (OFDMA) downlink. In the proposed algorithm, handover mobile termination (MT) chooses a subchannel set in the candidate cells by a subchannel booking rule, based on the terminal speed and the subchannel's channel state information (CSI). Moreover, the handover decision is made after analyzing if at least one candidate cell can reserve the subchannel set for the handover user. Simulation results show that the algorithm reduces the number of handovers and guarantees the quality of service (QoS) for the handover users. It yields better system performance in the OFDMA systems.