Intersegment handover performance in integrated terrestrial satellite systems

To achieve a global cellular network, integration among segments offering different coverage (indoor, outdoor and global) must be pursued. Of course, the possibility to hold the call switching among different segments must be guaranteed. Hence, efficient algorithms to perform intersegment handover (ISHO) must be implemented. The paper aims at analysing some ISHO procedures developed in the frame of some European projects and other proposed in the literature, in a scenario with satellite and terrestrial segments interworking to achieve a worldwide cellular coverage. Performance evaluation will be carried out for different system configurations utilizing a dynamic satellite constellation simulator in the time domain. The impact of the distance user‐gateway on performance will be addressed. For each procedure, the execution delay and its complementary cumulative distribution have been evaluated for different constellation geometries at different distances from the gateway. Copyright © 2002 John Wiley & Sons, Ltd.     

Internetwork handover performance analysis in a GSM-satelliteintegrated mobile communication system

This paper evaluates the internetwork handover performance in a GSM and satellite integrated mobile communication system. The performance evaluation is based on an analytical model developed for internetwork handover. The handover performance parameters considered are the handover position, unnecessary handover probability, and call-dropping probability. Handover initiation is based on the signal level and distance measurement. The results are compared with those of the GSM handover performance. The analysis shows that the performance achieved in internetwork handover can be similar to those of the GSM handover with the considered handover initiation scheme     

Interbeam handover in LEO satellite systems

This paper evaluates the performance of interbeam handover in LEO satellite systems. The evaluation is based on an analytical model that is specific for interbeam handover. There are three performance parameters concerned: handover probability, forced termination probability and time availability. From the results it can be seen that the interbeam handover probability depends strongly on the roll-off characteristics of the beam pattern. Forced termination and time availability depend on the quality of the received signal and the selected criterion. A comparison between the use of signal level and position as handover criteria is presented. © 1998 John Wiley & Sons, Ltd.     

WLAN中基于MIPv6的移动VoIP切换性能仿真分析

移动IP是一个在Internet上基于网络层提供移动性支持功能的要求较高的VoIP业务,切换延迟将直接影响到话音质量,严重时甚至会中断正在进行的会话.文章借助ns2网络模拟器仿真分析了WLAN中基于MIPv6的移动VoIP切换性能.结果表明,MIPv6及其扩展协议的切换性能优劣顺序依次为:F-HMIPv6、FMIPv6、HMIPv6、MIPv6.尤其是F-HMIPv6协议,无论端到端延迟还是切换延迟,都得到了最大的改善.所得结论能为网络切换性能的进一步优化提供重要依据.     

CDMA系统中切换性能的界限和变动范围

该文提出了CDMA系统中切换性能的3个界限的数学表达式,以及建立在界限基础上的硬切换性能差异、软切换性能差异和软切换增益的变动范围的表达式,并通过这些公式对切换的性能空间做了划分和限定。作为上述分析的数学基础,该文推导了硬切换和软切换中断概率的表达式。最后,通过对WCDMA(FDD)系统的仿真,证明了切换的界限、变动范围和中断概率的公式的正确性,并且指出,使用它们刻划实际切换算法的性能将比Viterbi的估计更为准确和恰当。     

On the performance analysis of dynamic channel allocation with FIFO handover queuing in LEO-MSS

The exact analysis of dynamic channel allocation (DCA) with first-in/first-out (FIFO) queuing of handover (QH) requests is highly complex, due to the dynamic nature of channel allocation to different cells. This letter presents an approximate but accurate analytical method to evaluate the performance of DCA in conjunction with FIFO-QH in low earth orbit mobile satellite systems. The accuracy of the proposed analysis has been verified by means of computer simulation.     

一种LTE系统中的基站内切换实现方案

为了实现LTE(长期演进)系统中的基站内切换,文章从控制面和用户面信令流程的角度出发,提出了一种LTE系统中的基站内切换设计方案。通过基站内各模块的协同工作,可有效实现包含数据转发的基站内切换流程,确保切换过程中不丢包,实现平滑切换。将该方案应用于实际的测试中,进行了基站内切换的组网测试,并给出了实际的切换测试结果。     

HFC系统的业务量模型及分析

在HFC系统结构中，终端用户可以通过网络请求不同的业务服务，对于用户的网络接口单元（NIU），同轴电缆是其共用的传输介质。因此同轴电缆的业务传送能力，对于确定系统的规模，保证阻塞性能达到一个令人满意的水平，都是至关重要的。利用分析和仿真两种方法对同轴电缆的业务传送能力进行了研究。     

Simulation of handover conditions for cellular radio systems

A computer model has been used to study the effects of handover in a cellular radio system. Three parameters are used to represent the radio propagation conditions including fading, which can give rise to multiple handovers on a single crossing of the cell boundary. Means for reducing unnecessary handovers are discussed.     

Enhancing the performance of secured handover protocols in UMTS-WiMAX interworking

Interworking UMTS and WiMAX networks offers global roaming and cost effective broadband wireless Internet access. Designing efficient Intra and Inter WiMAX handovers in the interworking architecture is a challenging problem. Handovers must be instantaneous and secure at the same time. We attempt to solve this problem by designing Intra and Inter WiMAX handover protocols which are capable of operating in the UMTS-WiMAX interworking architecture and perform mutual pre-authentication between the mobile station and the target network prior to handover. Due to the pre-authentication procedure, our proposed handover protocols outperform standard handover protocols by dispatching fewer handover signaling messages, experiencing less handover delay and preserving computation resources of critical nodes in the interworking architecture. Furthermore, our proposed handover protocols meet essential security requirements and defend against common attacks affecting handover protocols.     

Intersegment handover between terrestrial and satellite segments:analysis and performance evaluation through simulation

In future generation communication systems, integration among different segments (terrestrial indoor, terrestrial outdoor and satellite) will be necessary if aiming at providing real global and contiguous coverage without interruption. To achieve integrated or interworking systems efficient algorithms to perform intersegment handover (ISHO) must be implemented. In this way, the switching among different segments can occur without dropping of the call. The paper aims at analyzing some ISHO procedures developed in the frame of some European projects and at evaluating their performance for different system configurations utilizing a dynamic constellation simulator in the time domain. On the basis of the above procedures, aiming at optimizing resources, a new procedure is proposed and analyzed. For each procedure the execution delay and its range of variation have been evaluated for different constellation geometry. Finally, a performance comparison among the various procedures is shown     

Modeling of the handover dwell time in cellular mobilecommunications systems

Handover request queueing has been extensively analyzed as a handover protection scheme for future cellular networks. In this frame, however, while channel holding time distribution and cell boundary crossing rate have been modeled, the distribution of the allowed queue waiting time-i.e., the handover dwell time-has remained an open question from the modeling standpoint. In this frame, this paper proposes a model of the handover dwell time in circular cells' coverage. The agreement between modeling and simulation results is very satisfactory. A fitting of an asymptotic behavior of the handover dwell-time distribution with a truncated Gaussian function is also provided, measuring the fitting goodness in various test cases. The practical insights the model can provide are also outlined in the paper     

Optimum size of soft handover zone in power-controlled UMTSdownlink systems

Soft handover has two opposing effects on UMTS downlink systems, and there is a trade-off between them. The optimum size of the soft handover zone, is analysed in a power-controlled UMTS downlink system. The sensitivity of this optimum size to different system parameters, such as downlink orthogonal factor, path loss exponent, shadowing fading variable, is also analysed     

Traffic grooming in mesh WDM optical networks - performance analysis

Traffic grooming is an important task in interworking between the wavelength-division multiplexing (WDM) optical network that supplies "pipes" at the wavelength granularity, and the attached client networks that usually require connections of subwavelength granularity. The focus of this paper is to conduct performance analysis of grooming dynamic client traffic in WDM optical networks with a mesh topology. This paper first briefly introduces the traffic grooming problem in WDM optical networks and the issues related to performance analysis. It then develops two link blocking models, an exact model based on the stochastic knapsack problem and an approximation model based on an approximate continuous time Markov chain (CTMC). The end-to-end performance analysis is conducted using the reduced load approximation. The result obtained from analysis is shown to be accurate compared with the numerical result obtained from simulation.     

Traffic model and performance analysis for cellular mobile radio telephone systems with prioritized and nonprioritized handoff procedures

A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.     

Dynamic segmentation of cellular networks for improved handover performance

One of the most important initial steps, inherent in the planning procedure of cellular networks, is their segmentation in operational parts that is performed at different levels corresponding to the hierarchy and topology of the network. The major goal of this procedure is the efficient deployment of the system and management of the distributed segmented parts while minimizing the signaling overhead in the network. As we show here, it can take place even during the operational phase of the network when certain shortcomings appear. In this work, we present an approach based on graph theory for the segmentation of cellular networks at the Base Station Controller (BSC) level that achieves a significant increase in the performance of the network. In particular, with the proposed method, both the handover attempts when a mobile station is moving to a cell belonging to a different BSC as well as the corresponding handover failure rate are decreased significantly, allowing for a continuous network upgrade. Copyright © 2007 John Wiley & Sons, Ltd.     

Improving TCP performance for vertical handover in heterogeneous wireless networks

The incorporation of wireless local area networks (WLANs) into existing cellular networks as supplementary access technologies has become an issue of great interest. However, vertical handover (VHO), which allows users to roam between a WLAN and a cellular network, causes an abrupt change in certain link characteristics such as the round trip time and data rate. Owing to such changes, reordering problem and premature timeout occur and trigger unnecessarily fast retransmission during VHO, causing throughput degradation. Thus, we propose a new transmission control protocol (TCP) mechanism, which resolves the reordering problem by suppressing unnecessary retransmission caused by spurious duplicate acknowledgments (dupacks) incurred because of the reordering problem, and prevents premature timeout by employing an adaptive retransmission timer. We analytically investigate the throughput of our proposed TCP scheme. The numerical and simulation results show that our proposed TCP performs better in terms of throughput than other schemes appearing in the literature. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of UAV wireless network coverage and handover performance

For the characteristics of unmanned aerial vehicle (UAV),such as high mobility,adjustable height,and high probability of line-of-sight channels,which introduced multiple challenges to the design and deployment of current and future wireless network,and the networking performance of UAV was the focus and difficult issues in the industry,the network coverage and handoff performance of heterogeneous UAV wireless network was analyzed,which provided insights into UAV wireless networking.Specifically,considering the outdated channel state information introduced by the UAV’s mobility,analytical expressions of handover probability,handover error probability,and coverage probability for heterogeneous UAV wireless network were derived by utilizing the tools from stochastic geometry.In addition,the impacts of the UAV’s mobility,height,as well as the density of terrestrial base stations on the aforementioned performance metrics were investigated.It shows that the outdated channel state information caused handover error,which increases first and then decreases with the increase of UAV’s moving speed and density of base stations.Meanwhile,the impact of UAV’s flight height on coverage probability is more significant than that of moving speed.