共查询到20条相似文献,搜索用时 31 毫秒
1.
《Broadcasting, IEEE Transactions on》2009,55(4):796-801
2.
Aditya Yadav Maushumi Barooah Sandip Chakraborty Sukumar Nandi 《Wireless Personal Communications》2014,77(1):507-527
Ensuring quality of service (QoS) for the mobile users during vertical handover between IEEE 802.11 wireless local area networks (WLAN) and data network provided by Ultramodern Telecommunication Systems (UMTS) is one of the key requirements for seamless mobility and transfer of existing connections from one network to another. QoS fulfillment is a complex problem and requires participation of both the mobile users as well as the connection networks. The QoS assurance criteria for existing connections can be affected by fluctuations of data rates when a user moves from the high speed WLAN network to the low speed UMTS network, even in the presence of another WLAN network in its vicinity. This can happen if the alternate WLAN network is highly loaded. Therefore handover from a high speed network to a low speed network should be avoided, whenever possible. This paper proposes a QoS based handover procedure that prioritizes the existing connection over the new connections so that rate fluctuations due to handover can be avoided if there exist another WLAN network in the range of the mobile user. Whenever the possibility of handover is detected, a pre-handover bandwidth reservation technique is used to reserve bandwidth at the alternate WLAN networks to avoid QoS degradation. The proposed scheme is implemented in Qualnet network simulator and the performance is analyzed and compared with traditional handover techniques. 相似文献
3.
To enhance the communication performance at handover between multi-rate WLANs, we propose a new handover decision method that can be applied to our previously reported handover management scheme, which handled a handover by utilizing two WLAN interfaces (IFs) through cross-layer collaboration between layer 2 and layer 4. It should be noted that we here propose a new handover decision scheme for traversing between multi-rate WLANs, while our previous decision scheme works only in fixed-rate WLANs. In this paper, to treat a handover between multi-rate WLANs, we employ two kinds of information: (1) the most frequently used data rate (MFDR) for assessing the stable communication performance of a multi-rate WLAN, and (2) the frame retransmission ratio (FRR) for assessing its exact communication performance. The MFDR enables us to estimate the area where we should start handover. If the MFDRs of two interfaces are same in the area, the FRR allows us to compare the wireless condition on the two interfaces precisely to give an optimal handover point. Through simulation experiments, we show that our proposed scheme certainly estimates an appropriate handover point as a result of multi-path transmission (s), thereby providing handover successfully. That is, the proposed method can determine handover at an optimal point depending on the various distances between access points, the mobile node (MN) velocity, and the MN moving pattern. Moreover, our proposed scheme prevents the redundant network load caused by multi-path transmission as much as possible, thereby providing the ideal TCP communication performance. 相似文献
4.
Jongdae Park Hoyoung Ryu Soon Seok Lee Sueng Jae Bae Ju Yong Lee Mihui Kim Min Young Chung 《International Journal of Network Management》2013,23(3):155-171
In order to increase the capacity of wireless communication networks with minor changes and low cost, internetworking between cellular networks and wireless local area networks (WLANs) is considered as an attractive solution. In the internetworking of cellular networks and WLANs, a cost‐efficient vertical handover mechanism is required for seamless service provision. In this paper, we propose a cost‐efficient vertical handover mechanism for the packet‐based cellular networks and WLAN internetworking, where HMIPv6 and IEEE 802.21 are complementarily integrated to optimize the handover procedures. To design the mechanism, we introduce pre‐binding update and hierarchical packet forwarding concepts which can reduce handover signaling cost and delay. A mathematical model for handover rates and costs is proposed in order to analyze the proposed mechanism. In performance evaluation, we investigate how various factors affect handover rates and costs, and compare the proposed mechanism against the conventional mechanism. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
《Communications Magazine, IEEE》2006,44(2):73-84
To offer wireless data access services that are more efficient than GPRS or UMTS networks, public WLANs are in a predominant position to embrace the wireless broadband era. Reusing the existing mechanisms for user authentication, access control, billing, and roaming handling procedures in mobile territory to construct a complementary network, public WLAN (PWLAN) has drawn the attention of cellular operators such as Vodafone and T-Mobile. In this article we aim to investigate a practical end-to-end PWLAN architecture capable of using GPRS/UMTS SIM-based authentication for current mobile users and carrying out Web-based authentication for occasional users without SIM modules simultaneously. Additionally, we consider a confederation of various PWLAN service providers by a RADIUS-based roaming mechanism to leverage the existing resources of cellular operators. The proposed considerations and guidelines provide a baseline skeleton to build an extendable environment and successfully construct a flexible cellular/PWLAN hotspot in mobeeLAN service. 相似文献
6.
7.
WLAN-GPRS integration for next-generation mobile data networks 总被引:5,自引:0,他引:5
The ongoing wireless LAN standardization and R&D activities worldwide, which target bit rates higher than 100 Mb/s, combined with the successful deployment of WLANs in numerous hotspots justify the fact that WLAN technology will play a key role in wireless data transmission. Cellular network operators have recognized this fact, and strive to exploit WLAN technology and integrate this technology into their cellular data networks. For this reason, there is currently a strong need for interworking mechanisms between WLANs and cellular data networks. We focus on these interworking mechanisms, which effectively combine WLANs and cellular data networks into integrated wireless data environments capable of ubiquitous data services and very high data rates in hotspot locations. We discuss the general aspects of integrated WLANs and cellular data networks, and we examine the generic interworking architectures that have been proposed in the technical literature. In addition, we review the current standardization activities in the area of WLAN-cellular data network integration. Moreover, we propose and explain two different interworking architectures, which feature different coupling mechanisms. Finally, we compare the proposed interworking architectures, and discuss their advantages and drawbacks. 相似文献
8.
Song W.J. Jong-Moon Chung Daeyoung Lee Chaegwon Lim Sungho Choi Taesun Yeoum 《Communications Magazine, IEEE》2009,47(4):66-73
Recent mobile devices are integrated with multiple network interfaces. Users want their devices connected to the network anytime anywhere. It is highly feasible for a user to change connection to another network for users that leave the service area of its current serving network, where handover needs to be executed seamlessly such that ongoing service sessions are not interrupted. The handover operation not only requires switching the interfaces within a device but also involves seamless reconfiguration of the supporting networks. In this article, an improved IP-based vertical handover technology for mobile WiMAX [1, 2], 3GPP legacy systems (i.e., Global System for Mobile communications and Universal Mobile Telecommunications System) [3, 4], and 3G Long Term Evolution [5, 6] is presented, which is based on existing optimized handover techniques between mobile WiMAX and 3GPP accesses [7?9]. Formerly proposed 3GPP WiMAX optimized VHO solutions introduced new elements, such as the forward attachment function and access network discovery and selection function. The ANDSF supports the discovery of target access, and the FAF provides the functionality that authenticates the UE before the execution of VHO. However, the previous technique has limitations that result in data loss and abnormal disconnection to the source access [7?9]. This article provides a solution by introducing an additional network element called the data forwarding function (DFF) that eliminates the data loss during VHO execution. In addition, the DFF resolves the problem of abrupt disconnection to the source network. The simulation results show that the proposed VHO technique is effective in minimizing data loss during VHO execution between mobile WiMAX and 3GPP networks. As the proposed solution of this article is an IP based handover solution, it can be similarly applied to other communication networks. 相似文献
9.
In this paper, a channel preemption model for vertical handoff in a WLAN-embedded cellular network is presented. In a heterogeneous
networking environment, since many wireless LANs may be deployed within the coverage of a cellular network, horizontal handoffs
among neighboring WLANs and vertical handoffs between a WLAN and the cellular network could occur frequently. Performance
in terms of blocking probability of the cellular network can be seriously degraded if the channels are not appropriately allocated.
The novelty of this paper is right in that a newly initiated mobile node (MN) outside the WLAN coverage can preempt the channels
occupied by an MN inside the WLAN coverage when the cellular channels are completely used up. The channel preempted MN is
forced to switch its network access to a WLAN. This proposed channel preemption scheme can effectively reduce the blocking
probability while not disrupting any of the existing connections within WLANs. For the purpose of performance evaluation,
we build a three-dimension Markov chains to analyze the proposed channel preemption mechanism. We derive the equations of
move-in and move-out mobility rates based on the node speed and residence times, respectively. The network performance in
terms of the number of active WLAN users, the channel utilization and the channel blocking probability of a cellular network,
the preemption probability, and the preempted probability of an MN are calculated. From the analytical results, we observe
the performance improvements by varying the node speed and the ratio of WLAN coverage. 相似文献
10.
Pontes A.B. dos Passos Silva D. Jailton J. Rodrigues O. Lopes Dias K. 《Wireless Communications, IEEE》2008,15(5):86-95
Recently there has been much effort, in both academia and industry, to integrate a plethora of wireless technologies in order to provide ubiquitous broadband access to mobile users. Handover management is still one of the most challenging issues to be solved for seamless integration of wireless networks. This article addresses the integration of IEEE 802.11 WLANs and IEEE 802.16 WMANs, focusing mainly on the handover management aspects. First, we describe architectures, futuristic application scenarios such as the envisioned heterogeneous multihop wireless networks (HMWNs) and moving networks, as well as the related research issues. Second, we present IEEE 802.21, a new emerging standard aimed at providing a framework for media-independent handover (MIH) among heterogeneous networks. Finally, we discuss how the MIH framework can help handover management for the integrated network. 相似文献
11.
A new method to support UMTS/WLAN vertical handover using SCTP 总被引:6,自引:0,他引:6
This article proposes a new method to facilitate seamless vertical handover between wide area cellular data networks such as UMTS and WLANs using the stream control transmission protocol (SCTP). The multihoming capability and dynamic address configuration extension of SCTP are applied in UMTS/WLAN overlay architecture to decrease handover delay and improve throughput performance. Unlike techniques based on mobile IP or session initiation protocol, the SCTP-based vertical handover scheme does not require the addition of components such as home/foreign agents or a SIP server to existing networks. Therefore, the proposed scheme provides a network-independent solution preferred by service providers. Performance evaluations are presented to demonstrate the effectiveness of the proposed scheme. 相似文献
12.
QoS Handover Management in LEO/MEO Satellite Systems 总被引:4,自引:0,他引:4
Low Earth Orbit (LEO) satellite networks are foreseen to complement terrestrial networks in future global mobile networks.
Although space segment topology of a LEO network is characterized by periodic variations, connections of mobile stations (MSs)
to the satellite backbone network alter stochastically. As a result the quality of service delivered to users may degrade.
Different procedures have been proposed either as part of a resource allocation mechanism or as part of an end-to-end routing
protocol to manage transitions of MSs from one satellite to another (handover). All of these techniques are based on the prioritization
of requested handovers to ease network operation and therefore enhance provision of service. This paper proposes a new handover
procedure that exploits all geometric characteristics of a satellite-to-MS connection to provide an equable handover in systems
incorporating onboard processing satellites. Its performance is evaluated by simulations for a variety of satellite constellations
to prove its general applicability.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Bin Liu Nadia Boukhatem Philippe Martins Philippe Bertin 《Wireless Communications and Mobile Computing》2014,14(5):565-582
Next generation mobile networks will provide seamless mobility between existing cellular systems and other wireless access technologies. To realize a seamless vertical handover (inter‐radio access technology handover) among these different access technologies, a multi‐interfaced mobile station (i.e., multihomed) is a good approach to provide better handover performance in terms of packet loss rate and handover latency. In this article, we propose a novel layer 2 multihoming approach for inter‐radio access technology handover between Universal Mobile Telecommunications System (UMTS) and Worldwide Interoperability for Microwave Access (WiMAX) in both integrated and tight coupling architectures. This layer 2 multihoming approach has the ability of enabling either soft handover or make‐before‐break handover to adapt to mobility scenarios for the sake of a lossless and short latency handover procedure. Our simulation results show that, in case of handover from UMTS to WiMAX for transmission control protocol (TCP) traffics, the layer 2 multihoming approach can achieve a lossless and zero latency handover procedure by enabling soft handover. In case of handover from WiMAX to UMTS, because of the fact that the performance gain of soft handover is more affected by the differences of bandwidth and transmission delay between these wireless links, the make‐before‐break handover is preferred to achieve lossless and short latency handover procedure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
The complementary characteristics of wireless local area networks (WLANs) and wideband code division multiple access (CDMA)
cellular networks make it attractive to integrate these two technologies. How to utilize the overall radio resources optimally
in this heterogeneous integrated environment is a challenging issue. This paper proposes an optimal joint session admission
control scheme for multimedia traffic that maximizes overall network revenue with quality of service (QoS) constraints over
both WLANs and CDMA cellular networks. WLANs operate under IEEE 802.11e medium access control (MAC) protocol, which supports
QoS for multimedia traffic. A cross-layer optimization approach is used in CDMA networks taking into account both physical
layer linear minimum mean square error (LMMSE) receivers and network layer QoS requirements. Numerical examples illustrate
that the network revenue earned in the proposed joint admission control scheme is significantly more than that when the individual
networks are optimized independently. 相似文献
15.
随着WLAN技术的发展,WLAN在全社会得到了越来越广泛的应用,中小型WLAN的数量越来越多,它们的网络安全问题也变得越来越突出。文中详细探讨了在中小型WLAN中加强AP连接安全、加强WLAN网络准入身份认证、对WLAN网络安全风险进行控制和隔离、开展人工入侵检测、加强人员管理、加强网络安全制度建设等网络安全防范方法,通过综合运用各种网络安全技术及管理手段来保障中小型WLAN的安全,使其安全地为人们提供便捷的通信服务。 相似文献
16.
网络切换技术不仅可以保证用户的网络连接,同时能够以较强的信号传输网络数据。网络切换技术的性能对网络服务质量(quality of service, QoS)的影响至关重要。然而,现有的切换算法多数存在严重的乒乓效应,这不仅造成网络资源的严重浪费,还会损害用户的QoS。为此,提出了一种基于强化学习的异构网络垂直切换方案,主要从触发切换、网络选择及判决切换等方面进行优化。在触发切换时将垂直切换考虑成必要切换和择优切换,通过Q-Learning(QL)算法在选择网络时优化垂直切换;然后以QoS为条件,在判决切换时加入驻留定时器,从多角度减少用户切换次数,降低乒乓效应对异构网络垂直切换的影响。仿真结果表明,基于强化学习的异构网络垂直切换方法可以在保证QoS的条件下有效减少用户切换网络的次数,短时间内频繁切换的情况也有所改善,降低了乒乓效应的影响。 相似文献
17.
18.
A call admission control framework for voice over WLANs 总被引:1,自引:0,他引:1
In this article a call admission control framework is presented for voice over wireless local area networks (WLANs). The framework, called WLAN voice manager, manages admission control for voice over IP (VoIP) calls with WLANs as the access networks. WLAN voice manager interacts with WLAN medium access control (MAC) layer protocols, soft-switches (VoIP call agents), routers, and other network devices to perform end-to-end (ETE) quality of service (QoS) provisioning and control for VoIP calls originated from WLANs. By implementing the proposed WLAN voice manager in the WLAN access network, a two-level ETE VoIP QoS control mechanism can be achieved: level 1 QoS for voice traffic over WLAN medium access and level 2 QoS for ETE VoIP services in the networks with WLANs as the local access. The implementation challenges of this framework are discussed for both level 1 and level 2. Possible solutions to the implementation issues are proposed and other remaining open issues are also addressed. 相似文献
19.
The accessibility of available wireless access technologies with increasing demand for real time multimedia application becomes an essential part for mobile communication. Mobile users resourcefully utilize the heterogeneous environment for best quality of service (Qos) anywhere and anytime. Efficient handover optimization and intelligent mobility management is a key requirement for designing next generation wireless networks. Therefore, a novel IEEE 802.21 media independent handover (MIH) standard is adopted to provide an associated service for intelligent handover procedures. In addition, dynamic mobility management decision server (MDS) and IEEE 802.21a security extension for MIH services are also integrated in the proposed architectures to support fast, seamless and secure handover optimization in inter-domain mobility. Simulation results prove that the presented work resourcefully minimizes the packet loss, unnecessary handover probability and vertical handover delay by avoiding time consuming scanning process for target network discovery. The system thus achieves Qos guarantee by balancing the network load and throughput improvement for different applications with Proxy MIPv6 mobility management protocol. 相似文献
20.
Marc Emmelmann Sven Wiethoelter Andreas Koepsel Cornelia Kappler Adam Wolisz 《Wireless Personal Communications》2007,43(3):803-816
The challenge to provide seamless mobility in the near future emerges as a key topic in various standardization bodies. This
includes first of all the support of seamless handover between homogeneous networks. Distinct technologies—such as IEEE 802.11WLANs
(Wi-Fi) and IEEE 802.16 MANs WiMAX—have recently augmented such support to existing standards to enable seamless homogeneous
handover. Cellular networks, in contrast, already included this inherently from the start. Currently considerable effort goes
into coupling of different radio access technologies. Therefore, the second key topic in standardization is seamless heterogeneous
handovers. IEEE, IETF, as well as 3GPP consider different approaches toward architectures and protocols enabling seamless
mobility management. In this work, we discuss recent and on-going standardization activities within IEEE, IETF, and 3GPP toward
seamless homogeneous as well as heterogeneous mobility support. 相似文献