Combined handover algorithm for dynamic satellite constellations

A combined handover algorithm is proposed for a dynamic mobile satellite system. Handover decisions are based on user terminal (UT) position and signal strength measurement. The handover performances considered are handover position and call termination probability     

一种基于场强差的GSM网络移动台定位法

提出了一种在GSM无线蜂窝网络中利用服务BS（基站）和MS（移动台）测量的场强差值对MS进行定位的方法。通过计算机的仿真结果表明，该方法能够较好地克服多径和不规则地形带来的场强起伏，达到较高的定位精度。通过提出的的算法，可以克服传统的利用GSM蜂窝网络对移动台定位的局限性，从而使利用GSM蜂窝网络对移动台位置定位的实现更简单。     

Validation of an improved location-based handover algorithm using GSM measurement data

When a mobile station moves, the path loss and shadow fading contribute to the large-scale variation in the received signal strength. The variation of signal strength caused by shadow fadings is a random process, and handover decision mechanisms based on measurements of signal strength induce the "ping-pong effect." This paper proposes an improved handover algorithm, based on the estimates of location and velocity of the mobile station, to suppress the ping-pong effect in cellular systems. A practical approach based on GSM measurement data is used to estimate the location and velocity of mobile station to identify the correlation among shadowing components. The impact of location errors on handover performance was examined, and the proposed handover algorithm was applied to a real GSM system in urban Taipei city. The results indicate that the number of unnecessary handover can be reduced 18-26 percent by the proposed approach compared to the conventional method, while the signal outage probability remains similar. Besides, the computational complexity of the proposed algorithm is low, and the algorithm does not use a database or lookup table.     

Vertical Handover Analysis Using Modified MADM Method in LTE

Ubiquitous Communication is being a trend in this era. It is possible anywhere anytime with the sustenance and by the agreement of different service providers of Mobile technology. A mobile node which is attached to its base station relinquishes its connection while continuous mobility causes a fluctuation of signal strength. To overcome this issue, heterogeneous networks provision is obligatory. Normally Base stations serve several mobile nodes. Whenever a base station cannot handle a mobile terminal, it will assign its node to nearby available base station for service. The process of assignment of mobile nodes to another base station is termed as Heterogeneous handover. This type of Handover is needed for seamless integration of networks. LTE has proved promising outcomes in providing successful handover, Since it uses eNodeB infrastructure. In this work, Received signal strength is taken as main measure and analysed. Received Power acts as the building block for making possible handover across heterogeneous Radio Access Technologies. Proposed method suggests a vertical handover based on various signal measures. Enhanced Weighted Sum Method is incorporated for Handover decision making. Several criteria also utilized.

     

同小区内基于纠缠度计算的量子移动通信越区切换算法

量子通信具有绝对安全、保密的优势,将量子通信与传统移动通信二者的优点相结合,构造安全、保密、灵活、高效的量子移动通信系统是未来移动通信的发展方向,关于量子移动通信越区切换的研究目前尚未展开。为了解决量子移动通信系统的越区切换问题,提出了基于纠缠度计算的量子越区切换算法。根据用户位置的变化情况,首先定义了量子移动终端与量子基站天线之间的纠缠度,然后分析了影响该纠缠度的各种因素,最后对移动用户在各扇区之间的切换进行了深入分析和计算。研究结果表明,本文所提出的基于纠缠度计算的量子越区切换算法具有很好的可操作性和可实现性。本文对于构建未来量子移动通信系统及其标准的制定有着重要的技术支撑作用。     

A scalable network-based mobility management framework in heterogeneous IP-based networks

This paper proposes a mobility management scheme to provide a mobile node with high-quality handovers among heterogeneous wireless access networks. The proposed scheme employs a signaling architecture to support fast and reliable delivery of control messages by separating a control plane from a data transport plane in the core network. The proposed scheme is based on the network-based mobility management framework which requires the minimum modifications on terminal devices. With interaction between Layers 2 and 3, the proposed scheme accelerates the handover control procedures. It also enables a mobile subscriber to select a target network for a vertical handover with consideration of not only wireless signal strength but also user preference and quality-of-service status. The proposed scheme addresses the well-known problems of the Mobile IP-based approaches, triangular routing and bottleneck at the home agent, since it establishes a data tunnel for a mobile node along the shortest path between two different access networks. The simulation and experimental results indicate that our scheme provisions more efficient performance than the existing approaches in terms of handover latency, data packet loss, data delivery latency and load balancing.     

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.     

An efficient approach for DVB-H handover in DVB-H/UMTS hybrid networks

Handover in Digital Video Broadcasting for Handhelds （DVB-H） aims to provide continuous mobile broadcasting services when a user is traveling through cell boundaries. A good handover control can improve the power efficiency and gain much better reception quality. This letter provides a novel approach for DVB-H handover based on DVB-H/Universal Mobile Telecommunications System （UMTS） hybrid network, which moves the main handover function from the terminals to the networks, so that it reduces the operation complexity of the terminals and increases the power saving. When the terminal can not receive the DVB-H signal in the transmission shadow areas or because of some other reasons, the UMTS networks may offer the same service to users to make the service continuous. As the UMTS networks have the topology of the DVB-H networks, by communicating with the terminals, the UMTS networks can help the terminals to predict the handover, and avoid unnecessary handover.     

A general analysis of signal strength handover algorithms withcochannel interference

In this paper, the problem of computing cochannel interference statistics in signal strength measurements in mobile radio systems is presented. In a cellular environment with cross-correlated log-normal shadowings, extensions of Wilkinson's method and Schwartz and Yeh's (1982) method are proposed for evaluating the statistics of differences between signal strengths that a mobile terminal measures on the links to any pair of base stations in the presence of cochannel interferers. The derived statistics are then used in the performance analysis of relative signal strength handover algorithms. Results provided by the two methods are compared with simulation results, in order to assess their accuracy, and computational issues are addressed. From numerical results, it is also seen that handover algorithm performance has a noticeable dependence on both cross correlation among shadow fadings and the interference level. Finally, it is seen that previous approaches to derive cochannel interference statistics in the presence of log-normal shadowing can be obtained as particular cases     

移动定位的基本原理及技术研究

移动定位是指通过移动终端和移动网络的配合来确定用户的实际位置信息，并通过相关的短信及语音信号来完成一系列位置信息服务。获取移动定位信息的定位方法及技术已经成为当前的研究热点。本详细介绍移动定位的基本原理，并对移动定位的相关技术进行深入的研究与探讨。     

Research on dynamic handover decision algorithm based on fuzzy logic control in mobile FSO networks

Because of multiple advantages such as high bandwidth, high security, and flexible networking, the free space optical communication (FSO) has attracted more and more attention. However, the narrow beam of laser and the constrained access degree of optical node limit the development of mobile FSO networks, especially in the aspect of handover. In this paper, we propose a fuzzy logic control-based handover decision (FLC-HD) algorithm to ensure real-time and reliable communication. First, according to the predictive position and the motion information of mobile nodes obtained by the error correction extend Kalman filter algorithm, we obtain the received signal strength and the relative motion angles at next transmission. Second, we put forward the concept of threshold to ensure the completion of handover operations before the current link breaking. Third, the fuzzy logic control method is designed to select the optimal access point (AP) with three critical parameters, i.e., the received signal strength, the relative motion angles, and the access degrees of nodes. Simulation results show that the FLC-HD algorithm can improve the handover efficiency and relieve the ping-pong effect in mobile FSO networks.

     

A smart handover prediction system based on curve fitting model for Fast Mobile IPv6 in wireless networks

Seamless handover process is essential in order to provide efficient communication between mobile nodes in wireless local area networks. Despite the importance of a signal strength prediction model to provide seamless handovers, it is not embedded in standard mobility management protocols. In this article, we propose a smart handover prediction system based on curve fitting model to perform the handover (CHP) algorithm. The received signal strength indicator parameter, from scanning phase, is considered as an input to the CHP in order to provide a prediction technique for a mobile node to estimate the received signal strength value for the access points in the neighborhood and to select the best candidate access point from them in an intelligent way. We implemented the proposed approach and compared it with standard protocols and linear regression‐based handover prediction approach. Simulation results in complex wireless environments show that our CHP approach performs the best by predicting the received signal strength value with up to 800 ms in advance from real obtained value via scanning phase. Moreover, our CHP approach is the best in terms of layer 2 and overall handover latency, in comparison with standard protocols and linear regression approach, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

基于国家电波观测站网信号的短波机动用户位置认知方法

短波通信中频率选择是提高通信质量的必要手段,但短波机动用户却难以获取选频链路计算需要的位置信息. 文中设计了一种随时可利用多站信号进行机动终端位置认知的方法. 逆向应用时差定位原理,通过机动终端接收到的三个站点信号的两两信号时延差与虚路径差成正比,形成两条双曲线,交点就是机动用户的位置. 算法的关键是利用国家电波观测站网常态化发射的探测信号,同时设计了基于网格化预测时差与实测时差之间误差的位置概率函数,将定位问题转化为概率选择问题. 仿真分析和实测数据都验证了算法的可行性. 最后讨论了几种算法的改进策略,有望尽快实现工程应用.     

A multicell model of handover initiation in mobile cellularnetworks

A model is provided for the analysis of handover initiation algorithms in cellular systems, which are based on the averages of signal strength measurements and hysteresis. An extension of Vijayan's and Holtzman's (1993) model is achieved, which accounts for: (1) the effects of the angular direction when a mobile terminal moves from a current to a target base station; (2) the presence of more than two base stations; and (3) the effects of cross correlation of shadow fadings affecting the links between the mobile terminal and the various base stations. The level crossing theory of Gaussian processes is used to derive the algorithm performance. The results obtained from the model are in good agreement with those obtained from simulations. It is seen that the model tends to underestimate the algorithm performance, thus yielding a lower performance bound and guaranteeing an intrinsic design margin. It is also seen that, for a typical trajectory of the mobile terminal from the current base station, the number of handovers might be noticeably increased due to the presence of disturbant stations. Moreover, when cross correlation among shadow fadings is also accounted for, significant variations are observed in both the number of handovers and handover delay. As a final result, tradeoff curves are derived and presented for the most general case     

基于网络编码的无线物联网多中继协作切换机制

 本文针对网状结构的无线物联网中的多跳切换场景,提出了一种基于网络编码的多中继协作切换机制MRH.MRH机制中采用了基于势能场的路由探测算法,通过中继协作的方式,将移动终端同时注册到多个漫游域上.配合网络编码,MRH机制使移动终端建立了到多个无线物联网接入点之间的灵活、可靠的切换连接,实现了在多个无线物联网间的平滑切换.     

A New Empirical Formula for Handover Rate in Microcellular Systems

In this paper, we propose a new empirical formula for handover rate as a function of base stations separation, standard deviation of shadow fading, path loss exponent, averaging distance, and correlation distance. The handover initiation algorithm is based on averaged signal strength measurements using relative signal strength with hysteresis margin approach. We generate the data through computer simulations for the average number of handovers referred to as handover rate, for the practical range of path loss exponent and standard deviation of shadow fading. The proposed formula provides for a practical design tool to optimize the handover initiation performance under varied propagation environments.     

A forward fast media independent handover control scheme for Proxy Mobile IPv6 (FFMIH-PMIPv6) over heterogeneous wireless mobile network

Proxy Mobile IPv6 (PMIPv6) is a networked-based handover protocol for the IP layer, i.e., the layer 3 mobility management protocol. In this work, we integrate fast handover and IEEE 802.21 Media Independent Handover (MIH) Services with PMIPv6 to improve the handover performance over the heterogeneous wireless network environment. Since it may have multiple candidate destination networks to which a Mobile Node can select for handover, it needs to consider not only the signal strength but also the corresponding networking situation for the proper selection of the next network. To reduce the packet loss situation, the multicast mechanism is adopted to forward packets to these candidate destination networks during the handover processing period. In this work, a Forward Fast Media Independent Handover Control Scheme for Proxy Mobile IPv6 (FFMIH-PMIPv6) is proposed based on the aforementioned concerns. Through the simulations for performance analysis, it shows that the proposed FFMIH-PMIPv6 can have better handover performance in terms of handover latency, packet loss rate and throughput.     

异构无线网络环境下的切换触发时间选择算法

对移动用户在异构网络环境下的切换触发时间选择问题进行了研究。首先对移动终端触发切换的时间选择问题进行了理论分析,找到了最佳切换触发时间所应满足的条件。然后在切换耗时估计和接收信号强度预测的基础上,提出了一种预测最佳切换触发时间的算法。仿真结果表明,本算法能够有效降低用户的分组丢失概率和切换失败概率。     

Mobility management incorporating fuzzy logic for heterogeneous aIP environment

The next generation in mobility management will enable different mobile networks to interoperate with each other to ensure terminal and personal mobility and global portability of network services. However, in order to ensure global mobility, the deployment and integration of both satellite and terrestrial components are necessary. This article is focused on issues related to mobility management in a future mobile communications system, in a scenario where a multisegment access network is integrated into an IP core network by exploiting the principles of Mobile IP. In particular, attention is given to the requirements for location, address, and handover management. In a heterogeneous environment, the need to perform handover between access networks imposes particular constraints on the type of information available to the terminal and network. In this case, consideration will need to be given to parameters other than radio characteristics, such as achievable quality of service and user preference. This article proposes a new approach to handover management by applying the fuzzy logic concept to a heterogeneous environment. The article concludes with a presentation of mobility management signaling protocols     

A Traveling Distance Prediction Based Method to Minimize Unnecessary Handovers from Cellular Networks to WLANs

We propose a handover decision method based on the prediction of traveling distance within an IEEE 802.11 wireless local area network (WLAN) cell. The method uses two thresholds which are calculated by the mobile terminal (MT) as it enters the WLAN cell. The predicted traveling distance is compared against these thresholds to make a handover decision in order to minimize the probability of handover failures or unnecessary handovers from a cellular network to a WLAN. Our analysis shows that the proposed method successfully keeps the number of failed or unnecessary handovers low.