基于接收信号强度预测的自适应垂直切换算法

城市部署的超密集异构无线网络中车辆终端的运动状态和业务类型差异巨大,针对不同运动状态和业务类型的终端并发接入导致的频繁切换和拥塞问题,提出一种基于接收信号强度预测的自适应垂直切换算法。在切换触发阶段使用长短时记忆神经网络预测接收信号强度,在信道链路质量恶化之前提前触发切换,在网络选择阶段综合考虑网络参数以及终端在不同运动状态和业务类型下的接入偏好,并选出综合效益值最高的网络作为切换目标网络。仿真结果表明,该算法能更好地适应终端运动状态和业务类型的变化,能降低不必要的切换次数和网络拥塞度。

一个采用TCP Handoff技术的基于内容调度系统

针对传统的Web调度系统普遍存在可扩展性差、系统开销大等种种缺陷 ,我们研究了一种新的基于内容调度系统。该系统在Linux内核TCP/IP层实现 ,主要采用了TCPHandoff、报文捎带等技术。本文详细阐述了基于内容调度系统的设计原理和实现过程。实验表明 。

Web服务器集群中TCP Handoff技术及其实现

在传统的Web服务器集群系统中,前端分发器由于通过的数据量太大容易形成瓶颈,进而影响系统的整体性能。该文利用TCPHandoff技术,分散了通过前端分发器的绝大部分网络流量,解决了Web服务器集群中前端分发器的瓶颈问题。通过在Linux环境下的原型系统实现和实验数据分析,证明了该技术的有效性。

基于计算资源动态可用性的计算卸载切换策略

计算卸载和切换是提升车载边缘计算的计算性能和服务质量的关键问题。但由于车辆的移动性,可用计算资源的动态性变化将会导致卸载场景不断变化,进而导致任务完成时间增加。为此,提出基于计算资源动态可用性的计算卸载切换策略,包括在路径固定情况下上传目标服务节点的选择策略和基于动态可用计算资源的切换策略。实验结果表明,相对于现有研究,所提策略能够有效地缩短任务完成时间,提升计算卸载性能。

高通量卫星通信系统移动用户越区切换测试方法

高通量卫星通信系统使用的点波束和频率复用技术大幅提高系统容量的同时,带来了车载终端、机载终端、船载终端类用户在组网通信时需要进行移动切换的难题。为在室内环境下测试移动用户的越区切换策略,结合卫星信道特性,提出了一种测试环境构建方法,模拟了移动用户在多个波束覆盖的交叠区域跨越波束场景。测试结果表明,该方法能够有效构建越区切换场景,解决测试难题。

基于Netfilter的TCP Handoff实现研究

该文提出了在Linux内核利用Netfilter的支持来实现TCPHandoff的方法,详细描述了实现算法。测试结果表明,该方法是可行的,并且相对于目前国际上传统的实现方法有一定的优势。

Cognitive Radios： A Survey On Spectrum Sensing, Security and Spectrum Handoff

Pervasive wireless computing and communication have created an ever-increasing demand for more radio spectrum. Since, most of the spectrum is underutilized, it motivated the introduction of the concept of cognitive radios, a dynamic spectrum access enabling technology. The first stage of cognitive radio is to sense the environment and determine which parts of the spectrum are available. This is achieved through spectrum sensing. However, spectrum sensing poses the most fundamental challenge in cognitive radios. Moreover, cognitive radios suffer from many vulnerabilities and the security attacks can severely degrade the performance of cognitive radios. This paper surveys state-of-theart research on spectrum sensing and security threats in cognitive radios. Lastly, we also consider the analysis of issues related to spectrum handoffs in cognitive radios.

SPECTRUM HANDOFF IN COGNITIVE RADIO WITH FUZZY LOGIC CONTROL

The secondary usage of spectrum has been investigated in Cognitive Radio(CR) network to resolving the spectrum scarcity issue in wireless communication.When Primary Users(PU) who own the spectrum appear,spectrum handoff is needed to maintain the communications of Secondary Users.But the decision making of spectrum handoff is a challenge issue for CR network,because the input of decision making,which obtain through spectrum sensing,is heterogeneous and inexact.In this paper we will use fuzzy logic control theory to solve this issue and make use of new information for handoff operation:the probability of PU's occupancy at a certain channel.Our new algorithm can make more intelligent decision compared to simple traditional spectrum handoff decision making and reduce the probability of spectrum handoff,also the performance of SU's communication can be enhanced.

Vertical handoff algorithm in heterogeneous networks to maximize system benefit

A new vertical handoff decision algorithm is proposed to maximize the system benefit in heterogeneous wireless networks which comprise cellular networks and wireless local area networks （WLANs）. Firstly the block probability, the drop probability and the number of users in the heterogeneous networks are calculated in the channel-guard call admission method, and a function of the system benefit which is based on the new call arrival rate and the handoff call arrival rate is proposed. Then the optimal radius of WLAN is obtained by using simulation annealing （SA） method to maximize the benefit. All the nodes should handoff from cellular network to WLAN if they enter WLAN＇s scope and handoff from WLAN to cellular network if they leave the scope. Finally, the algorithm in different new call arrival rates and handoff call arrival rates is analyzed and results show that it can achieve good effects.

A Novel Handoff Algorithm for Hierarchical Cellular Networks

In this paper, we propose a novel speed and service-sensitive handoff algorithm and analytical model for hierarchical cellular networks.First, we use the Gauss-Markov mobility model to predict the speeds of mobile stations, and divide mobile stations into three classes based on the predicted speeds: fast, medium-speed, and slow.Then, according to the mobility classification,network conditions, and service types, mobile stations will be handoff to the proper target networks prior to the deterioration of the currently operating channel. We further develop an analytical model to evaluate the performance of such a hierarchical system with different speed classes and service types. Simulations and analytical results show that the proposed handoff algorithm can significantly improve the network performance in terms of the handoff failure probability, unnecessary handoff probability, and network throughput, comparing with the traditional algorithms.

An Improved Handoff Algorithm for Heterogeneous Wireless Networks

Heterogeneous Wireless Network is currently a major area of focus in communication engineering.But the important issue in recent communication is the approachability to the wireless networks while maintaining the quality of service.Today,all the wireless access networks are working in tandem to keep the users always connected to the internet cloud that matches the price affordability and performance goals.In order to achieve seamless connectivity,due consideration has to be given to handoff precision and a smaller number of handoffs.Several researchers have used heuristic approaches to solve this issue.In the present work,a hybrid intelligent algorithm has been suggested for vertical handoff decisions.This hybrid intelligent algorithm is based on dual optimization approach which uses“Particle Swarm Optimization(PSO)”and“Mobile Robustness Optimization(MRO)”techniques for improving the quality of services.This approach performs well even in the failure network conditions and gives the best results in terms of connectivity.The results at the last has been compared with the conventional techniques and it has been observed that the proposed methodology outperforms the existing one.

A QoS-aware vertical handoff algorithm based on predictive network information

In converged heterogeneous wireless networks, vertical handoff is an important issue in radio resource management and occurs when an end user switches from one network to another (e.g., from wireless local area network to wideband code division multiple access). Efficient vertical handoff should allocate network resources efficiently and maintain good quality of service (QoS) for the end users. The objective of this work is to determine conditions under which vertical handoff can be performed. The channel usage situation of each access network is formulated as a birth-death process with the objective of predicting the available bandwidth and the blocking probability. A reward function is used to capture the network bandwidth and the blocking probability is expressed as a cost function. An end user will access the certain network which maximizes the total function defined as the combination of the reward function and the cost function. Simulation results show that the proposed algorithm can significantly improve the network performance, including higher bandwidth for end users and lower new call blocking and handoff call blocking probability for networks.

An Optimized Vertical Handoff Algorithm Based on Markov Process in Vehicle Heterogeneous Network

In order to solve the problem the existing vertical handoff algorithms of vehicle heterogeneous wireless network do not consider the diversification of network's status, an optimized vertical handoff algorithm based on markov process is proposed and discussed in this paper. This algorithm takes into account that the status transformation of available network will affect the quality of service(Qo S) of vehicle terminal's communication service. Firstly, Markov process is used to predict the transformation of wireless network's status after the decision via transition probability. Then the weights of evaluating parameters will be determined by fuzzy logic method. Finally, by comparing the total incomes of each wireless network, including handoff decision incomes, handoff execution incomes and communication service incomes after handoff, the optimal network to handoff will be selected. Simulation results show that: the algorithm proposed, compared to the existing algorithm, is able to receive a higher level of load balancing and effectively improves the average blocking rate, packet loss rate and ping-pang effect.

SOFT HANDOFF ALGORITHM BASED ONSIGNAL LEVEL STRENGTH

The goal of this paper is to seek a good algorithm to decrease theunnecessary soft handoff probability in order to reduce the soft handoff dis-tance, i. e. , to reduce the time of additional channel occupied by mobile sta-tion for implementing the soft ha

Energy-Efficient Target Channel Sequence Design for Spectrum Handoffs in Cognitive Radio Networks

Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies,spectrum handoff can guarantee the transmission continuity of secondary users(SUs). In this paper,we address a new and more generalized spectrum handoff problem in cognitive radio networks(CRNs),by considering simultaneously energy efficiency,multiple spectrum handoffs and multiple channels. Furthermore,effects of the primary users'(PUs')arrival and service rate on the target channel sequence selection are also considered. In order to obtain the energy-efficient target channel sequence,we firstly analyze the energy consumption and the number of delivered bits per hertz in the spectrum handoff process,and formulate a ratio-type energy efficiency optimization problem,which can be transformed into a parametric problem by utilizing fractional programming. Then,we propose an algorithm combining dynamic programming with bisection(DPB)algorithm to solve the energy efficiency optimization problem. Our simulation results verify that the designed target channel sequence has better performance than the existing algorithms in terms of energy efficiency.

A Novel Probability-Based Handoff Strategy for Multimedia LEO Satellite Communications

A novel bandwidth allocation strategy and a connection admission control technique arc proposed to improve the utilization of network resource and provide the network with better quality of service （QoS） guarantees in multimedia low earth orbit （LEO） satellite networks. Our connection admission control scheme, we call the probability based dynamic channel reservation strategy （PDR）, dynamically reserves bandwidth for real-time services based on their handoff probability. And the reserved bandwidth for real-time handoff connection can also be used by new connections under a certain probability determined by the mobility characteristics and bandwidth usage of the system. Simulation results show that our scheme not only lowers the call dropping probability （CDP） for Class I real-time service but also maintains the call blocking probability （CBP） to certain degree. Consequently, the scheme can offer very low CDP for rcal-time connections while keeping resource utilization high.

Dynamic Handoff Priority Adjustment Based on Mobility-Awareness in Multimedia Cellular Networks

In multimedia cellular networks, when a Mobile Host requests multimedia services, it may experience hand-offs to several cells before the request is completely served. If a target cell cannot provide adequate bandwidth for a service request, instead of directly dropping the request, the MH is put into the handoff queue and hopefully the requested bandwidth can be satisfied by later released bandwidth. Obviously, it is important to properly assign priorities for queued handoff of MHs based on their inborn dynamics to avoid unnecessary dropping. In this paper, we present a dynamic handoff priority adjustment scheme which applied a handoff queuing scheme to dynamically adjust handoff priority based on receiving signal strength, service class, and mobility of Mobile Hosts. In addition, idle bandwidth reserved by inactive MHs is reallocated to urgent handoff MHs to reduce the call dropping probability. The goal of the proposed dynamic handoff priority adjustment scheme is to further reduce call dropping probability while still maintaining high bandwidth utilization and acceptable call blocking probability on multimedia cellular networks.

AN OPTIMIZED SCHEME FOR FAST HANDOFF IN IP-BASED CDMA WIRELESS COMMUNICATION NETWORKS

This paper proposed an optimized fast handoff scheme for real time applications in next generation IP based CDMA wireless networks. The idea is to utilize optimized IP multicasting handoff (based on PIM SM), which is triggered by CDMA layer 2 functionality. An IP based cellular network model with WCDMA FDD air interface and IP based packet traffic is adopted. No special network entities and signaling for handoff are added in our network model. The simulation results show that low delay and low packet lost rate can be obtained.

The Design of High Speed Soft Handoff on the CDMA Mobile Communication System

In this paper,a brief introduction to SCH of CDMA system is provided.Then the paper account for Soft Handoff of High Speed Packet Data and the method.On the base of above account,this paper give the flow of High Speed Packet Data's Soft Handoff.