An efficient handoff management scheme for mobile wireless ATMnetworks

A new handoff management scheme for wireless ATM networks is proposed. In this scheme, all cells are connected to their neighboring cells by permanent virtual circuits (PVCs) and to the access switch (AS) by switched virtual circuits (SVCs) which are only for new calls. Some carefully chosen cells, called rerouting cells, are also connected to the AS by PVCs. In summary, if a mobile roams to an ordinary neighboring cell, its traffic path is simply elongated by a PVC connecting the old and new cells. If a mobile roams to a rerouting cell, its traffic path is rerouted to a PVC between the AS and rerouting cell. By using PVC's for handoff calls, we can guarantee fast and seamless handoff. At the same time, our scheme improves the path efficiency by limiting the maximum number of hops that a path can be extended. Also, allowing path rerouting at a suitable time means the network resources are more efficiently utilized     

An adaptive resource reservation for vehicular mobile networks

This paper presents the time‐based bandwidth reservation (TBR) algorithm, suitable for handoff management in cellular systems. TBR is based on real‐time measurements of mobile stations (position, velocity and acceleration). The scheme consists in sending reservation requests to the neighboring cells based on an extrapolation of the user's motion. The originality of our approach lies in dynamically adjusting the amount of time for which bandwidth has to be allocated and reserved in a cell. In addition, we propose an optimal channel requests arrangement (CRA) algorithm in order to improve the performance of TBR in terms of resource utilization. Finally, we propose VTBR, an adapted and extended version of TBR for better support of vehicular network specificities where service degradation or forced call termination may occur owing to frequent handoffs. Detailed simulation results for TBR and VTBR schemes and a comparison with the guard channel scheme are presented. The results show that TBR and VTBR can efficiently improve the flow dropping probability. Copyright © 2008 John Wiley & Sons, Ltd.     

An adaptive low-overhead resource discovery protocol for mobile ad-hoc networks

In this paper we propose a Distributed Hash Table (DHT)-based peer-to-peer resource discovery protocol designed for large-scale Mobile Ad-hoc NETwork (MANET). The proposed Mobile Resource Discovery Protocol (MRDP) uses a distributed dynamic clustering algorithm to adaptively and rapidly group nodes in a MANET for resource discovery purpose, and utilizes DHTs to efficiently cache resource information in a peer-to-peer manner. We provide a probabilistic lower bound on the performance of the MRDP. We also present simulation results under different scenarios to show that MRDP has low message overheads and its performance is highly insensitive to the size of the MANET. These characteristics make MRDP suitable for large-scale MANETs.     

An adaptive handoff strategy for cognitive radio networks

Spectrum handoff plays an important role in spectrum management as it is the process of seamlessly shifting the on-going transmission of a secondary user (SU) to a free channel without degrading the quality of service. In this paper, we develop an adaptive handoff algorithm that allows an SU to detect the arrival of a primary user (via sensing) and adapt to a reactive or a proactive handoff strategy accordingly. The adaptive handoff scheme first allows an SU to decide whether to stay and wait on current channel or to perform handoff. Then, in case of handoff, an SU intelligently shifts between proactive or reactive handoff modes based on primary use (PU) arrival rate. Further, a PU prioritized Markov approach is presented in order to model the interactions between PUs and SUs for smooth channel access. Numerical results show that the proposed handoff scheme minimizes the blocking probability, number of handoffs, handoff delay and data delivery time while maintaining channel utilization and system throughput at maximal level compared to simple reactive and proactive schemes.     

Group vertical handoff management in heterogeneous networks

Traditional vertical handover schemes postulate that vertical handovers (VHOs) of users come on an individual basis. This enables users to know previously the decision already made by other users, and then the choice will be accordingly made. However, in case of group mobility, almost all VHO decisions of all users, in a given group (e.g., passengers on board a bus or a train equipped with smart phones or laptops), will be made at the same time. This concept is called group vertical handover (GVHO). When all VHO decisions of a large number of users are made at the same time, the system performance may degrade and network congestion may occur. In this paper, we propose two fully decentralized algorithms for network access selection, and that is based on the concept of congestion game to resolve the problem of network congestion in group mobility scenarios. Two learning algorithms, dubbed Sastry Algorithm and Q‐Learning Algorithm, are envisioned. Each one of these algorithms helps mobile users in a group to reach the nash equilibrium in a stochastic environment. The nash equilibrium represents a fair and efficient solution according to which each mobile user is connected to a single network and has no intention to change his decision to improve his throughput. This shall help resolve the problem of network congestion caused by GVHO. Simulation results validate the proposed algorithms and show their efficiency in achieving convergence, even at a slower pace. To achieve fast convergence, we also propose a heuristic method inspired from simulated annealing and incorporated in a hybrid learning algorithm to speed up convergence time and maintain efficient solutions. The simulation results also show the adaptability of our hybrid algorithm with decreasing step size‐simulated annealing (DSS‐SA) for high mobility group scenario. Copyright © 2015 John Wiley & Sons, Ltd.     

Efficient mobility management for vertical handoff between WWAN and WLAN

As we move toward next-generation all-IP wireless networks, we are facing the integration of heterogeneous networks, such as WWAN and WLAN, where vertical handoff is required. In vertical handoff between WWAN and WLAN, mobile hosts should be able to move freely across different networks while satisfying QoS requirements for a variety of applications. In order to achieve seamless handoff and maintain continuity of connection, we propose a novel mobility. management system that integrates a connection manager to detect network condition changes in a timely and accurate manner, and a virtual connectivity manager that uses an end-to-end principle to maintain a connection without additional network infrastructure support. A prototype system was built to test the effectiveness of the proposed system. Experiments show that seamless roaming between WLAN and WWAN can be achieved, and much better performance can be obtained than with the traditional scheme.     

An adaptive location management scheme for mobile broadband cellular systems

This paper presents an adaptive location management strategy that considers both location updating and paging by evaluating realistic mobility patterns. It proposes the design of an adaptive macro-location area based on multi-registration adapted to the terminals’ trajectory to reduce location updates. The solution includes an estimation of residence probabilities in the areas of the multi-registered list. This facilitates the design of a sequential paging scheme that reduces the average paging cost. Results show the capability of the solution to adapt to mobility patterns and traffic conditions in the network to minimize the overall location cost. Furthermore, the multi-registration approach and the reduced complexity in both network infrastructure and mobile terminals make the solution suitable for new packet-based broadband cellular systems.     

一种新的无线异构网络的自适应垂直切换算法

针对当前无线异构网络融合技术中的垂直切换机制,提出了一种以平均接收信号强度为评价指标,并由此指标判断可能的运动趋势的自适应垂直切换算法。仿真结果表明:相比于传统的固定门限的平均接收信号强度垂直切换算法,提出的方法能较好地预测并提前触发该发生的切换,改善切换性能。     

一种基于资源管理的视频服务器自适应QoS控制中间件

介绍了一种基于资源管理的视频服务器自适应QoS控制中间件,提出了“软”资源预留机制,提高了服务器资源管理的可靠性和准确性。在此基础上,提出了主动QoS调整机制。实验表明该中间件可以有效地确保系统QoS。     

An efficient vertical handoff scheme for microcellular and macrocellular interworking

The next generation wireless network environments increasingly become integrated to support anywhere, anytime connectivity for various applications like multimedia, full‐motion video and high data rates with appropriate quality of service (QoS). With these emerging needs, interworking of microcellular and macrocellular networks has been accompanied by service providers. However, these networks have different technologies, which make efficient vertical handoff a challenging issue. In this study, an efficient vertical handoff scheme (EVHS) for interworking between microcellular and macrocellular networks is proposed and analyzed. The handoff decision criteria of the proposed scheme include crucial features like user mobility, network conditions, pricing issues, and user preferences in addition to the received signal strength (RSS). EVHS ensures the selection of the most appropriate network in terms of cost and acceptable QoS according to users' preferences. The results show that EVHS scheme outperforms other proposed schemes in the literature in terms of incompletion probabilities, grade of service (GoS) and cost without causing degradation in system utilization. Besides, although EVHS scheme is mainly intended for user satisfaction, the results show that it does not cause a significant degradation in the revenue of the service provider. Copyright © 2009 John Wiley & Sons, Ltd.     

An efficient radio resource management strategy for adaptive OFDM cellular systems

This paper presents an efficient Radio Resource Management （RRM） strategy for adaptive Orthogonal Frequency Division Multiplexing （OFDM） cellular systems. In the proposed strategy, only those users who have the same distance from their base stations can reuse a same subcarrier. This can guarantee the received Carrier-to-Interference ratio （C/I） of each subcarrier to be acceptable as required by system planning. Then by employing different modulation scheme on each subcarrier according to its received C/I, system spectral efficiency can be gracefully increased. Analytical and simulation results show that the spectral efficiency is improved by 40% without sacrificing the Bit Error Rate （BER） performance and call blocking probability and system capacity of the proposed strategy is better than conventional systems.     

一种基于紧耦合网络结构的终端垂直切换系统

随着移动终端无线数据业务的迅速发展,在异构无线网络间提供无缝连接和高速的多媒体服务将成为下一代无线网络[1]（4G网络）的重要特性。提出了一套基于紧密耦合网络结构的终端垂直切换系统。该系统利用核心网络的PCF切换机制,有效解决了IP移动问题。被设计成客户端的一个软件接口,易于在现实世界中快速实施。     

Adding network-layer intelligence to mobile receivers for solving spurious TCP timeout during vertical handoff

With the help of mobile IP/IPv6 and soft handoff, ongoing TCP sessions can remain active and handoff packet loss can be avoided. However, TCP still faces several performance degradation issues due to the disparities in bandwidth and propagation delay between different access networks. Particularly, during vertical handoffs, some undesirable phenomena may erroneously trigger TCP congestion-control actions and thus degrade TCP performance. In this article we tackle the spurious timeout problem frequently associated with handovers from fast to slow links. We propose three network-layer schemes: fast ACK, slow ACK, and ACK delaying. These schemes require only minor modifications to the network layer of mobile receivers and no change to the TCP protocol and the TCP sender. The simulation results show that these schemes can effectively improve TCP performance during soft vertical handoffs     

基于IPv6的快速切换改进方案

在移动IP网络中,当前的移动性管理方案由于其基本协议的切换时延较大、丢包率较高而不能适应实时业务和移动通信的要求,所以需要改善移动性管理策略的切换性能,尽量实现无缝切换和零丢包率。提出了一种基于移动IPv6的快速切换的改进方案,采用一种新的地址分配方式使得移动节点能够在移动至新的网络后迅速获取新的转交地址,有效地减少了切换所产生的时延和丢包率,具有较好的切换性能。     

异构无线网络资源管理与切换控制技术

随着通信技术的发展,新型业务逐渐增多,传统的通信网络无法满足各种业务之间巨大的性能需求差异,未来的通信网络逐渐向异构网络进行发展。针对异构网络中资源调配与垂直切换的问题,利用虚拟网络技术与资源虚拟化技术设计了异构网络中的无线资源管理方法,并设计了子网间垂直切换算法。该算法利用层次分析法与熵权法得到各网络参数的综合权值,加权得到各网络的效用值并依此选择最优网络。通过搭建系统平台验证了设计的异构无线网络的有效性,为后续异构无线网络的研究提供了参考。     

LTE-A移动台自适应切换无线资源管理测量带宽的方法

考虑到LTE-A系统对于移动台无线资源管理( RRM )测量的要求,急需一种能同时考虑测量精度和能量消耗的RRM测量方案。为了满足上述需求,提出了一种新的测量带宽选择方法,即自适应切换测量带宽方法。该方法使得移动台可以根据信道质量自行在窄带和宽带测量之间进行切换。仿真结果显示提出的方法能够达到足够的测量精度,同时还考虑了移动台的能量消耗。     

未来移动通信网的无线资源管理

自从数字移动通信网以前所未有的穿透力进入移动通信市场以来,人们对无线个人通信（ｗｉｒｅｌｅｓｓ ｐｅｒ—ｓｏｎａｌ ｃｏｍｍｕｎｉｃａｔｉｏｎｓ）的要求与日俱增。这也正是目前无线通信成为工业界主要焦点的源动力之一。随即,互联网的盛行促进了无线用户对高速数据传输的需求,据预测,无线高速多媒体的时代已不遥远。由此,我们可以在展望无线网发展的巨大潜力的同时,也意识到高用户量、高数据传输量和多种业务并存给未来无线网络带来的潜在挑战。解决这一问题不仅需要一流的设备,而且需要一流的无线资源管理技术。 目前国际…     

Improving TCP performance with fast adaptive congestion control during soft vertical handoff

Recently, the research on the interworking between 3G cellular networks and WLANs is actively being constructed. To integrate these two technologies, there are many issues such as the network architecture, mobility management, and security which should be solved. During vertical handoff, some undesirable phenomena may mistakenly trigger TCP congestion control operations and thus degrade TCP performance. In this paper, we propose an approach that can quickly estimate available bandwidth when a mobile node (MN) handoff occurs. A sender updates the adaptive slow-start threshold (ssthresh) and congestion window size (cwnd) to improve TCP performance during soft vertical handoff in hybrid mobile networks. Our scheme requires only minor modifications of the transport layer of the end hosts. Simulation results show that our scheme effectively improves the TCP performance.     

一种适用于GEO卫星移动通信系统流业务的无线资源管理方法

提出了一种适用于GEO卫星移动通信系统流业务的无线资源管理方法,保障在共享信道上传输的流业务的速率和延时需求.该方法由3个功能实体组成：1）接纳控制/信道分配实体,用于接受或拒绝新的资源请求;2）分组调度实体,负责为每个连接提供所需的传输服务,满足传输速率要求;3）质量控制实体,监测目前系统为当前服务提供的QoS是否与签约QoS一致.在NS2仿真平台建立了相应的系统模型,进行了动态仿真.     

An adaptive resource sharing strategy for TDMA

A satellite-based TDMA network consisting of four stations within different rain climatic zones has been operated in the 20/30 GHz frequency range using a recently developed flexible TDMA system allowing for FEC code rate and transmission bit rate variation. In this paper a strategy is presented to counteract overall link degradations due to atmospheric attenuation by dynamic allocation of resources. A spare time slot within the TDMA frame as a ‘common resource’ for bit rate and code rate switching offers up to 12 dB gain, whereas up-link power control, as it is implemented in this configuration, can cope with fades of 8 dB at maximum. For an experimental network configuration the expected long-term performance in terms of system availability is estimated for a viable version of the resource sharing strategy. Thereby, a model to calculate the probability of concurrent attenuation at the individual earth-station sites (‘satellite based diversity’) has been applied and the resulting probability to exhaust the resources is considered as a function of the degrading correlation between attenuations. Simulations with measured data via a ‘channel simulator’ and satellite measurements during the summer months of 1994 with the adaptive TDMA system are planned to test the functionality of the fade countermeasure strategy. Long-term propagation measurements on large-scale site diversity are required to verify predictions on the effective utilization of common resources.