Fast Handoff Scheme Research Articles

A Fast Seamless Handoff Scheme between IEEE 802.11 and EPS Networks Using Optimized Proxy Mobile IPv6

A Fast Seamless Handoff Scheme between IEEE 802.11 and EPS Networks Using Optimized Proxy Mobile IPv6

An Adaptive Multimedia-Oriented Handoff Scheme for IEEE 802.11 WLANs

Previous studies have shown that the actual handoff schemes employed in the IEEE 802.11 Wireless LANs (WLANs) do not meet the strict delay constraints placed by many multimedia applications like Voice over IP. Both the active and the passive supported scan modes in the standard handoff procedure have important delay that affects the Quality of Service (QoS) required by the real-time communications over 802.11 networks. In addition, the problem is further compounded by the fact that limited coverage areas of Access Points (APs) occupied in 802.11 infrastructure WLANs create frequent handoffs. We propose a new optimized and fast handoff scheme that decrease both handoff latency and occurrence by performing a seamless prevent scan process and an effective next-AP selection. Through simulations and performance evaluation, we show the effectiveness of the new adaptive handoff that reduces the process latency and adds new context-based parameters. The Results illustrate a QoS delay-respect required by applications and an optimized AP-choice that eliminates handoff events that are not beneficial.

Fast Handoff among IEEE 802.11r Mobility Domains

This paper deals with secure fast handoff among access points (APs) of different IEEE 802.11r mobility domains. We leverage standard IEEE 802.11i mechanisms to let a station preauthenticate and establish a pairwise transient key with some target AP before- hand. Upon reassociation, the new AP aware of the preauthenticated station can thus com- plete handoff sooner than would otherwise be required. In order to resolve target APs timely, we introduce a location server that maintains network topology of an autonomous system covering multiple mobility domains. The location server assesses with which AP(s) the mobile station may reassociate next using its migration tendency. Accordingly the station is instructed to preauthenticate with fewer potential next APs than unnecessary. Performance discussions indicate that our proposal is effective in practice. Our approach is not only complementary to emerging IEEE 802.11r-based techniques but also useful to any network-layer fast handoff schemes for streamlined communication.

Secured Fast Handoff in 802.11-Based Wireless Mesh Networks for Pervasive Internet Access

Authentication issue has been mostly ignored to ensure fast handoff in 802.11 Wireless Mesh Network (WMN). With the proliferation of WMNs in recent years for practical deployment, secured fast handoff has drawn much attention to enforce authenticated access while reduce the extra delay caused by enabling authentication operations. In this paper, we present an overview on the state-of-the-art advance in this field and tackle the problem from a practical perspective based on experiments and analysis on our real-world testbed HAWK. We propose a novel fast handoff scheme Network-assisted Radio Signature to eliminate probing delay by taking advantage of the characteristic of the actual dynamic topology about mesh routers in WMN. Moreover, we apply an optimistic authentication mechanism Dual Re-authentication to counteract the authentication delay while providing the secured wireless access. In this manner, we have reduced the end-to-end handoff delay of WMN back again to a level below 50ms to achieve secured handoff and support time-sensitive applications. We describe detailed mechanisms, simulation, implementation and experimental results. To our best knowledge, we are the first to achieve such an optimal performance of secured fast handoff.

To Our Readers

In IEEE 802.11 networks, many access points (APs) are required to cover a large area due to the limited coverage range of APs, and frequent handoffs may occur while a station (STA) is moving in an area covered by several APs. However, traditional handoff mechanisms employed at STAs introduce a few hundred milliseconds delay, which is far longer than what can be tolerated by some multimedia streams such as voice over Internet protocol (VoIP), it is a challenging issue for supporting seamless handoff service in IEEE 802.11 networks. In this paper, we propose a pre-scan based fast handoff scheme within an IEEE 802.11 enterprise wireless local area network (EWLAN) environment. The proposed scheme can help STA obtain the best alternative AP in advance after the pre-scan process, and when the handoff is actually triggered, STA can perform the authentication and reassociation process toward the alternative AP directly. Furthermore, we adopt Kalman filter to minimize the fluctuation of received signal strength (RSS), thus reducing the unnecessary pre-scan process and handoffs. We performed simulations to evaluate performance, and the simulation results show that the proposed scheme can effectively reduce the handoff delay.

A Proactive mobile‐initiated fast handoff scheme using the multihomed approach

AbstractMobile IP (MIP) defines a mobility management for mobile users to continuously access data when the currently attachment is changed to another network. However, when mobile node (MN) roams between network segments, the handoff latency results in packet losses and transmission delay. In this paper, we propose a multihomed fast handoff scheme (MFH‐MIP) to decrease the handoff cost. In the proposed MFH‐MIP scheme, each MN is implemeted with the link layer trigger and multihomed techniques. Based on the link layer trigger, MN can collect signal strengths of nearby access points (APs) and switch to a new link automatically when the old link becomes unsuitable to connect. Using the multihomed technique, MN can prepare for handoff using two (or more) interfaces, in which (i) one is connected with the old link to receive packets and (ii) the other one is used to access nearby APs and select the most suitable one as the new link, in parellel. In this way, MN can continuously transmit and receive packets during handoff. Based on the proposed method, MN can roam smoothly among different networks in the wireless environment. Copyright © 2008 John Wiley & Sons, Ltd.

DeuceScan: Deuce-Based Fast Handoff Scheme in IEEE 802.11 Wireless Networks

The IEEE 802.11 standard has enabled low-cost and effective wireless local area network (WLAN) services. It is widely believed that WLANs will become a major portion of the fourth-generation cellular system. The seamless handoff problem in WLANs is a very important design issue to support the new astounding and amazing applications in WLANs, particularly for a user in a mobile vehicle. The entire delay time of a handoff is divided into probe, authentication, and reassociation delay times. Because the probe delay occupies most of the handoff delay time, efforts have mainly focused on reducing the probe delay to develop faster handoff schemes. This paper presents a new fast handoff scheme (i.e., the DeuceScan scheme) to further reduce the probe delay for IEEE-802.11-based WLANs. The proposed scheme can be useful to improve wireless communication qualities on vehicles. A spatiotemporal approach is developed in this paper to utilize a spatiotemporal graph to provide spatiotemporal information for making accurate handoff decisions by correctly searching for the next access point. The DeuceScan scheme is a prescan approach that efficiently reduces the layer-2 handoff latency. Two factors of stable signal strength and variable signal strength are used in our developed DeuceScan scheme. Finally, simulation results illustrate the performance achievements of the DeuceScan scheme in reducing handoff delay time and packet loss rate and improving link quality.

Enhanced fast handoff scheme for heterogeneous wireless networks

Mobility management, integration and interworking of existing wireless systems are important factors to obtain seamless roaming and services continuity in next generation or 4G wireless networks (NGWN/4G). Although, several IPv6-based mobility protocols as well as interworking architectures have been proposed in the literature, they cannot guarantee seamless roaming, especially for real-time applications. Moreover, mobility management protocols are designed for specific needs, for example, the purpose of IPv6-based mobility schemes consists of managing users roaming while ignoring access network discovery. This paper proposes an efficient handoff protocol, called enhanced Handoff Protocol for Integrated Networks (eHPIN), which carries out localized mobility management, fast handoff, and access network discovery. It alleviates services disruption during roaming in heterogeneous IP-based wireless environments. Performance evaluation results show that eHPIN provides significant gain with respect to signaling traffic overhead cost, handoff latency, packet delivery cost, handoff failure and packet loss compared with existing IPv6-based mobility schemes.

Fast-handoff support in IEEE 802.11 wireless networks

With the advance of wireless local area network (WLAN) technology, handoff support has become one of the most important issues in IEEE 802.11 WLANs. However, the current IEEE 802.11 specification does not provide the fast handoff required for real-time multimedia applications. To support fast handoff in IEEE 802.11 networks, a number of fast-handoff schemes have been proposed in the literature. In this article we review these fast-handoff schemes and analyze their advantages and disadvantages qualitatively. After that, important design considerations for mobility support in future IEEE 802.11 networks are suggested. Also, we introduce a fast-handoff framework which adaptively meets different application requirements via a cross-layer approach.

Performance Optimizations for Deploying VoIP Services in Mesh Networks

In the recent past, there has been a tremendous increase in the popularity of VoIP services as a result of huge growth in broadband access. The same voice-over-Internet protocol (VoIP) service poses new challenges when deployed over a wireless mesh network, while enabling users to make voice calls using WiFi phones. Packet losses and delay due to interference in a multiple-hop mesh network with limited capacity can significantly degrade the end-to-end VoIP call quality. In this work, we discuss the basic requirements for efficient deployment of VoIP services over a mesh network. We present and evaluate practical optimizing techniques that can enhance the network capacity, maintain the VoIP quality and handle user mobility efficiently. Extensive experiments conducted on a real testbed and ns-2 provide insights into the performance issues and demonstrate the level of improvement that can be obtained by the proposed techniques. Specifically, we find that packet aggregation along with header compression can increase the number of supported VoIP calls in a multihop network by 2-3 times. The proposed fast path switching is highly effective in maintaining the VoIP quality. Our fast handoff scheme achieves almost negligible disruption during calls to roaming clients

Adaptive RSVP Path Fast Handoff Scheme in Wireless/Mobile Networks

Adaptive RSVP Path Fast Handoff Scheme in Wireless/Mobile Networks

Fast handoff scheme based on mobility prediction in public wireless LAN systems

Recently, wireless LAN systems have been widely deployed for public mobile Internet services. Public wireless LAN systems can provide high speed Internet connectivity using portable devices such as laptop computers, personal digital assistants (PDAs), etc. In public wireless LAN systems, reliable user authentication and mobility support are essential issues. However, re-authentication during handoff procedures causes long handoff latency and this affects the quality of service in real-time multimedia applications. A fast handoff scheme based on mobility prediction is proposed. In this scheme, a mobile host entering the area covered by an access point (AP) performs authentication procedures for multiple APs, rather than just the current AP. These multiple APs are selected by a prediction method called the frequent handoff region (FHR) selection algorithm, which takes into account users' mobility patterns, service classes, etc. Since a mobile host is registered and authenticated for an FHR in advance, handoff latency resulting from re-authentication can be significantly reduced. Simulation results show that the proposed scheme is more efficient than other schemes in terms of handoff delay and buffer requirements.

ACM SIGCOMM computer communication review

At some point in the future, how far out we do not exactly know, wireless access to the Internet will outstrip all other forms of access bringing the freedom of mobility to the way we access the we...

A Fast Handoff Management Scheme in ATM-Based Personal Communication Networks

Future wireless personal communication networks will likely have infrastructures based on asynchronous transfer mode (ATM) networks. It is a challenge to support seamless, fast handoffs in such an environment. We propose a fast handoff management scheme using permanent virtual connections (PVCs) reserved between neighboring base stations (BSs). In the proposed scheme, the handoff can be quickly performed by rerouting the communication path via the PVCs. Handoff calls are distributively controlled only by the corresponding BSs without the involvement of any ATM switches. ATM cell sequence integrity during handoff can be maintained by the BSs. In order to dimension the PVC, we analytically derive the probability of handoff blocking due to the lack of PVCs. We give some numerical examples of PVC dimensioning. The proposed scheme can be utilized in the future IMT-2000 networks accommodating various narrowband services in the range of several kbps to several hundreds kbps.

Scanning the literature

There are inherent difficulties in supporting mobility in ATM networks, due to its connection oriented nature. Once mobile users moves out of certain geographic areas, the ongoing connections for the mobile users have to be rerouted. A suitable connection rerouting schemes must exhibit a number of features including: low handoff latency, efficient routes, minimal disruption to the network traffic as well as the necessary route updates. This paper propose and studies 5 different connection rerouting schemes in ATM-based wireless networks. Extensive experiments show that one of the schemes demonstrates superior performance, seems to be ideally suited for the connection rerouting. This scheme is executed in two phrases, real-time and non-real-time: 1) to execute very fast handoff (reroute) scheme using chaining in a real-time with measured time of 6.5 ms; and 2) reroute the connection in non-real-time to achieve more efficient routes if necessary. The conclusion this paper reaches is that simple handoff schemes coupled with a suitable connection management architecture are sufficient for low-bit-rate multimedia application in the ATM-based wireless networks.

Scanning the literature

There are inherent difficulties in supporting mobility in ATM networks, due to its connection oriented nature. Once mobile users moves out of certain geographic areas, the ongoing connections for the mobile users have to be rerouted. A suitable connection rerouting schemes must exhibit a number of features including: low handoff latency, efficient routes, minimal disruption to the network traffic as well as the necessary route updates. This paper propose and studies 5 different connection rerouting schemes in ATM-based wireless networks. Extensive experiments show that one of the schemes demonstrates superior performance, seems to be ideally suited for the connection rerouting. This scheme is executed in two phrases, real-time and non-real-time: 1) to execute very fast handoff (reroute) scheme using chaining in a real-time with measured time of 6.5 ms; and 2) reroute the connection in non-real-time to achieve more efficient routes if necessary. The conclusion this paper reaches is that simple handoff schemes coupled with a suitable connection management architecture are sufficient for low-bit-rate multimedia application in the ATM-based wireless networks.