Showing papers on "Handover published in 2006"
Patent•
26 Jan 2006TL;DR: In this article, a system for facilitating hard handoff adapted for use with a telecommunications network is described. But the handoff is a hard handover, and the handover is performed by a mobile transceiver.
Abstract: A system for facilitating handoff adapted for use with a telecommunications network. The system includes position equipment for determining the location of a mobile transceiver within a region containing a first cell and a second cell. A comparison circuit compares the location with a predetermined handoff area within the region and provides a control signal in response thereto. A handoff initiation circuit initiates handoff of the mobile transceiver between the first cell and the second cell in response to the control signal. In a specific embodiment, the handoff is a hard handoff. The position equipment includes Global Positioning System (GPS) equipment including a mobile unit GPS receiver and signal interface. The comparison circuit includes a positional database that stores latitudinal and longitudinal information corresponding to the predetermined handoff area. The comparison circuit also includes a Code Division Multiple Access selector. The selector begins tracking the position of the mobile transceiver when it is within a predetermined range of the predetermined handoff area. In a specific embodiment, the handoff initiation circuit includes a base station controller. The position equipment includes a base station positional detection system and a mobile unit positional detection system for determining the location of the mobile transceiver. The position database has map information depicting the coverage area of the first and second cells and the predetermined handoff area. The selector runs software for comparing the location to the map information and providing the control signal when the location is within the predetermined handoff area. The base station includes and implements instructions for completing hard handoff in response to the control signal.
281 citations
TL;DR: An analytical framework to evaluate the converged system performance and show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks is presented.
Abstract: The convergence of heterogeneous wireless access technologies has been envisioned to characterize the next generation wireless networks. In such converged systems, the seamless and efficient handoff between different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics results in handoff asymmetry that differs from the traditional intra-network handoff (horizontal handoff) problem. In the case where one network is preferred, the vertical handoff decision should be carefully executed, based on the wireless channel state, network layer characteristics, as well as application requirements. In this paper, we study the performance of vertical handoff using the integration of 3G cellular and wireless local area networks as an example. In particular, we investigate the effect of an application-based signal strength threshold on an adaptive preferred-network lifetime-based handoff strategy, in terms of the signalling load, available bandwidth, and packet delay for an inter-network roaming mobile. We present an analytical framework to evaluate the converged system performance, which is validated by computer simulation. We show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks.
264 citations
19 Jun 2006
TL;DR: The architecture and protocols of SMesh, a completely transparent wireless mesh system that offers seamless, fast handoff, supporting VoIP and other real-time application traffic for any unmodified 802.11 device, are presented.
Abstract: This paper presents the architecture and protocols of SMesh, a completely transparent wireless mesh system that offers seamless, fast handoff, supporting VoIP and other real-time application traffic for any unmodified 802.11 device. In SMesh, the entire mesh network is seen by the mobile clients as a single, omnipresent access point.Fast handoff is achieved by ensuring that each client is served by at least one access point at any time. Mobile clients are handled by a single access point during stable connectivity times. During handoff transitions, SMesh uses more than one access point to handle the moving client. Access points continuously monitor the connectivity quality of any client in their range and efficiently share this information with other access points in the vicinity of that client to coordinate which of them should serve the client.Experimental results on a fully deployed mesh network consisting of 14 access points demonstrate the effectiveness of the SMesh architecture and its handoff protocol.
205 citations
Patent•
15 Sep 2006TL;DR: In this article, the authors proposed a method of transmitting and receiving radio access information that allows a faster and an efficient way of establishing a radio connection between a terminal and a target base station while performing a handover for the terminal to a cell of the target BS.
Abstract: In a wireless mobile communications system, a method of transmitting and receiving radio access information that allows a faster and an efficient way of establishing a radio connection between a terminal and a target base station while performing a handover for the terminal to a cell of the target base station. The network transmits in advance, the radio access information and the like, to the terminal so that the terminal can be connected with the target cell in a faster manner which minimizes the total time for the handover process.
188 citations
TL;DR: This article presents and discusses limitations of recent handoff design architectures and protocols as well as outstanding challenges that still need to be addressed to achieve portable and scalable handoff solutions for continuous connectivity across wireless access networks.
155 citations
TL;DR: This work presents and evaluates practical optimizing techniques that can enhance the network capacity, maintain the VoIP quality and handle user mobility efficiently and finds that packet aggregation along with header compression can increase the number of supported VoIP calls in a multihop network by 2-3 times.
Abstract: 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
146 citations
Patent•
19 Apr 2006TL;DR: In this article, the optimization of relay station handovers and location update in a wireless network has been studied, where a request to handover a plurality of mobile stations from a first base station to a second base station may be sent.
Abstract: Various embodiments are disclosed relating to the optimization of relay station handovers and location update in a wireless network. According to an example embodiment, a request to handover a plurality of mobile stations from a first base station to a second base station may be sent. An identifier associated with the second base station for each of the plurality of mobile stations may be received. In another example embodiment, each of the identifiers is forwarded to the mobile station corresponding to the connection identifier. In another example embodiment, a location update may be performed by sending a message to a network device, such as a target base station, to provide location update information for a plurality of mobile stations. In this manner, one message may be transmitted over a wireless link to facilitate a handover or location update for a plurality of mobile stations.
143 citations
Patent•
15 Jun 2006
TL;DR: In this article, an interworking system that supports voice call continuity for a user that moves between IP-CAN and CS networks (e.g., PSTN or GSM) is presented.
Abstract: A system and method for continuous voice calls when a user switches between packet data and circuit switched access networks. In one example embodiment, the present innovations include an interworking system that supports voice call continuity for a user that moves between IP-CAN and CS networks (e.g., PSTN or GSM). In one example embodiment, the present innovations comprise a voice call continuity application server (VCC-AS) that serves as an anchor point for a voice call (i.e., it is the node from which a handover is initiated) and controls and handles voice calls to and from the user equipment (UE) regardless of the access network.
143 citations
Patent•
18 May 2006TL;DR: In this paper, the handoff of an existing communications session between a mobile handset and a fixed user is facilitated by a handoff controller implemented in a service control point, depending on the status of the fixed user and the transition of the mobile user.
Abstract: In a telecommunications network in which a mobile handset is capable of communicating in both an IP domain and a non-IP domain, the handoff of an existing communications session between the mobile handset and a fixed user is facilitated by a handoff controller implemented in a service control point The handoff controller implements different handoff methods depending on the status of the fixed user and the transition of the mobile user Additionally 80221 Media Independent Handover Function in conjunction with SIP is used to facilitate handover between IP and Non-IP points in the system
136 citations
TL;DR: A performance analysis demonstrates that significant gains in the ability to satisfy user requests for multiple simultaneous services and a more efficient use of resources can be achieved from the MUSE-VDA optimizations.
Abstract: Future wireless networks must be able to coordinate services within a diverse-network environment. One of the challenging problems for coordination is vertical handoff, which is the decision for a mobile node to handoff between different types of networks. While traditional handoff is based on received signal strength comparisons, vertical handoff must evaluate additional factors, such as monetary cost, offered services, network conditions, and user preferences. In this paper, several optimizations are proposed for the execution of vertical handoff decision algorithms, with the goal of maximizing the quality of service experienced by each user. First, the concept of policy-based handoffs is discussed. Then, a multiservice vertical handoff decision algorithm (MUSE-VDA) and cost function are introduced to judge target networks based on a variety of user- and network-valued metrics. Finally, a performance analysis demonstrates that significant gains in the ability to satisfy user requests for multiple simultaneous services and a more efficient use of resources can be achieved from the MUSE-VDA optimizations.
135 citations
TL;DR: An up-to-date, comprehensive literature survey on proposed handover schemes for LEO satellite systems, and a detailed classification of hand over schemes based on a common framework are presented.
Abstract: Low Earth Orbit (LEO) satellites will work as an important component in future data communication networks. LEO satellites provide low end-toend delays and efficient frequency spectrum utilization, making them suitable for personal communication. However, due to high satellite speed, ongoing communication using LEO constellations experiences frequent handover. In this article we provide an up-to-date, comprehensive literature survey on proposed handover schemes for LEO satellite systems. We also present a detailed classification of handover schemes based on a common framework. We first classify the schemes into link-layer and network-layer handover schemes. Link-layer handover schemes are further classified into three categories: spotbeam handover schemes, satellite handover schemes, and ISL handover schemes. Spotbeam handover schemes are categorized based on channel capacity, handover guarantee, and handover prioritization techniques. Network-layer handover schemes are also classified depending on connection transfer strategies. Finally, we compare the handover schemes using different quality of service (QoS) criteria.
Patent•
1 Nov 2006TL;DR: In this paper, the authors describe mechanisms and methods that facilitate preparation of inter-RAT and/or inter-freguency handover with respect to a mobile device (user equipment).
Abstract: Described herein are mechanisms and methods that facilitate preparation of inter- radio access technology (inter-RAT) and/or inter-freguency handover with respect to a mobile device (user equipment) . User equipment can indicate to a network servicing the user equipment that the user equipment desires to perform measurements with respect to a different frequency and/or different technology (506) . Data on the downlink channel can then be scheduled to ensure that data intended for the user equipment is not lost while the user equipment is performing the measurement (508) .
26 Jun 2006
TL;DR: A smooth MAC layer handoff scheme and a greedy smoothMAC layer handoffs scheme that scan channels in a smooth manner so that the handoff can have less impact on upper layer applications.
Abstract: The limited service range of the access points demands mobile wireless stations to handoff frequently between different cells in the IEEE 802.11 infrastructure networks. However, the handoff scheme used in the current 802.11 infrastructure networks is far from graceful. In this paper, we propose a smooth MAC layer handoff scheme and a greedy smooth MAC layer handoff scheme. Our schemes scan channels in a smooth manner so that the handoff can have less impact on upper layer applications. In order to limit the frequency of channel scanning, an adaptive mechanism is used to dynamically adjust the threshold triggering the channel scanning operations. We have implemented our handoff schemes using commodity 802.11 devices and extensive experiments have been conducted to evaluate the performance. The experimental results demonstrate that our schemes reduce packet delay and loss during handoff. Our handoff schemes are implemented in the client side only and do not require changes to access points. Therefore, our schemes can be deployed in the existing 802.11 networks.
7 May 2006
TL;DR: A fast and seamless handoff solution for IEEE 802.11 wireless LAN with IAPP is proposed based on a concept of neighbor graph, which describes the nearby access points that a mobile host may find, and selective scanning with unicast in power-save mode, pre-registration of IAPP, and frame forwarding-and-buffering mechanisms.
Abstract: Handoff is a critical issue in IEEE 802.11-based wireless networks. In this paper we propose a fast and seamless handoff solution for IEEE 802.11 wireless LAN with IAPP. It is based on a concept of neighbor graph, which describes the nearby access points (APs) that a mobile host (MH) may find. Then we further derive selective scanning with unicast in power-save mode, pre-registration of IAPP, and frame forwarding-and-buffering mechanisms. Selective scanning allows a MH to only try potential handoff targets. Pre-registration allows early transfer of a MH's security context from its old AP to new AP. The forwarding-and-buffering mechanism is to solve the packet loss problem during handoff. Our performance evaluation shows that the proposed solution can result in 90% reduction in the handoff latency from standard handoff procedure.
TL;DR: This article presents a SIP-based architecture that supports soft handoff for IP-centric wireless networks and ensures that there is no packet loss and that the end-to-end delay jitter is kept under control.
Abstract: Application-level protocol abstraction is required to support seamless mobility in next-generation heterogeneous wireless networks. Session initiation protocol (SIP) provides the required abstraction for mobility support for multimedia applications in such networks. However, the handoff procedure with SIP suffers from undesirable delay and hence packet loss in some cases, which is detrimental to applications like voice over IP (VoIP) or streaming video that demand stringent quality of service (QoS) requirements. In this article we present a SIP-based architecture that supports soft handoff for IP-centric wireless networks. Soft handoff ensures that there is no packet loss and that the end-to-end delay jitter is kept under control
Patent•
29 Dec 2006
TL;DR: In this article, a secure connection between a client device and a first security gateway is established, and the first gateway is associated with a service provider for providing a service to the client device.
Abstract: A method includes establishing a secure connection between a client device and a first security gateway, the first security gateway being associated with a service provider for providing a service to the client device, and handing off the secure connection from the first security gateway to a second security gateway. Handing off the secure connection includes sending from the first security gateway to the second security gateway security information used to encrypt and decrypt messages transmitted through the secure connection, and sending from the first security gateway to the client device an address of the second security gateway to enable the client device to initiate contact with the second security gateway.
Patent•
18 Dec 2006TL;DR: In this paper, a method and system for adjusting uplink transmission timing when sending an initial transmission to a target cell/Node-B of an evolved universal terrestrial radio access network (E-UTRAN) was proposed.
Abstract: A method and system for adjusting uplink transmission timing when sending an initial transmission to a target cell/Node-B of an evolved universal terrestrial radio access network (E-UTRAN) immediately after handover from a source cell/Node-B of the E-UTRAN. In one embodiment, a user equipment (UE) autonomously computes and applies a timing advance (TA) value based on the current source cell/Node-B timing value, cell/Node-B beacon channel reference signal measurements and knowledge of the relative time difference, (if any), between the source and target cells/Node-Bs. In another embodiment, the UE sends a scheduling request message or real data packets with the computed TA value applied to the uplink transmission timing to the E-UTRAN via pre-allocated non-contention based uplink radio resources. In an alternate embodiment, the UE sends a scheduling request message with the new computed TA value applied to the UL transmission timing to an E-UTRAN via a synchronous random access channel (RACH).
18 Apr 2006
TL;DR: An enhanced handover mechanism with new additional primitives and parameters to the media independent handover (MIH) services defined in the IEEE 802.21 can reduce handover latency for mobile IPv6 (MIPv6) by removing the router discovery time and can increase the probability that the FMIPv 6 can be performed in predictive mode.
Abstract: In this paper, we propose an enhanced handover mechanism with new additional primitives and parameters to the media independent handover (MIH) services defined in the IEEE 802.21. The proposed scheme can reduce handover latency for mobile IPv6 (MIPv6) by removing the router discovery time. Moreover, when the proposed mechanism is applied to the FMIPv6, we can increase the probability that the FMIPv6 can be performed in predictive mode by reducing the handover initiation time, thereby we can reduce the expected handover latency in the FMIPv6. In addition, with the proposed scheme, we can design the network cost-effectively by reducing coverage overlap between adjacent cells because the handover initiation time in the FMIPv6 is decreased.
TL;DR: This paper developed a network mobility testbed and implemented the network mobility (NEMO) basic support protocol and identified problems in the architecture which affect the handoff and routing performance, and extended a previously proposed route optimization (RO) scheme, OptiNets.
Abstract: Measuring the performance of an implementation of a set of protocols and analyzing the results is crucial to understanding the performance and limitations of the protocols in a real network environment. Based on this information, the protocols and their interactions can be improved to enhance the performance of the whole system. To this end, we have developed a network mobility testbed and implemented the network mobility (NEMO) basic support protocol and have identified problems in the architecture which affect the handoff and routing performance. To address the identified handoff performance issues, we have proposed the use of make-before-break handoffs with two network interfaces for NEMO. We have carried out a comparison study of handoffs with NEMO and have shown that the proposed scheme provides near-optimal performance. Further, we have extended a previously proposed route optimization (RO) scheme, OptiNets. We have compared the routing and header overheads using experiments and analysis and shown that the use of the extended OptiNets scheme reduces these overheads of NEMO to a level comparable with Mobile IPv6 RO. Finally, this paper shows that the proposed handoff and RO schemes enable NEMO protocol to be used in applications sensitive to delay and packet loss
Patent•
6 Jul 2006TL;DR: In this paper, a secure session keys context approach is proposed for wireless mobile nodes without sacrificing the security between a mobile node and wireless access points in an access network, which has all the good features, like mobility and security optimization, of the currently existing proposals of key-request, pre-authentication, and pre-distribution but also provides improved scalability for the access network and for the mobile node.
Abstract: Handoffs must be fast for wireless mobile nodes without sacrificing the security between a mobile node and wireless access points in an access network. A secure session keys context approach is shown having all the good features, like mobility and security optimization, of the currently existing proposals of key-request, pre-authentication, and pre-distribution but also providing improved scalability for the access network and for the mobile node. The new approach is compared to the existing proposals including memory requirements and especially how to reduce memory usage using a “just-in-time” transfer of security information between access points and a mobile node during a handover.
Patent•
10 Apr 2006TL;DR: In this paper, a handover of a mobile terminal is supported by a heterogeneous network handover module that is configured to provide convergence of information from at least one network interface module associated with one of a homogeneous and heterogeneous networks into a unified presentation.
Abstract: The present invention relates to supporting a handover of a mobile terminal. Preferably, the present invention performs a scan of a neighboring network different from a current network of the mobile terminal to determine the presence of an accessible link of the neighboring network for performing a handover, wherein the mobile terminal comprises a heterogeneous network handover module that is configured to provide convergence of information from at least one network interface module associated with one of a homogeneous and heterogeneous network into a unified presentation. An information message is then received from the neighboring network, wherein the information message comprises an information element associated with whether the neighboring network is capable of communicating with the heterogeneous network handover module of the mobile terminal.
Patent•
14 Jul 2006TL;DR: In this paper, a radio access network dynamically modifies a route update protocol of an access terminal in an active state that is in communication with the network, such that the access terminal reports a route-update message upon satisfaction of a condition.
Abstract: A radio access network dynamically modifies a route update protocol of an access terminal in an active state that is in communication with the network, such that the access terminal reports a route update message upon satisfaction of a condition. The condition may be related to an inter-revision hard handoff, an inter-frequency hard handoff, a RF dragging prevention, a selective resource allocation, or some combination thereof.
Patent•
7 Jul 2006TL;DR: In this article, a handover from an E-UMTS system to a GGSN is performed based on a measured signal strength of the UMTS system reported from a UE.
Abstract: A method and apparatus performs handover from a E-UMTS system to a UMTS system. An E-RAN of the E-UMTS system determines to perform the handove based on a measured signal strength of the UMTS system reported from a UE. Then, am E-CN of the E-UMTS system generates a PDP context and an MM context for the UE, and sets up a data tunnel for the UE to a GGSN of the UMTS system using the PDP/MM context. The E-CN sends to the UE a handover command message including information on an RB to be used by the UE to access the UMTS system. The UE accesses the UMTS system using the RB information, and forwards user data for the UE via a data transmission path composed of the E-CN, the data tunnel, a SGSN, and a RAN of the UMTS system.
Patent•
6 Feb 2006TL;DR: In this paper, a framework of Media-independent Pre-Authentication (MPA) is proposed, a new handover optimization mechanism that has a potential to address issues on existing mobility management protocols and mobility optimization mechanisms.
Abstract: This application describes, among other things, a framework of Media-independent Pre-Authentication (MPA), a new handover optimization mechanism that has a potential to address issues on existing mobility management protocols and mobility optimization mechanisms. MPA is a mobile-assisted, secure handover optimization scheme that works over any link-layer and with any mobility management protocol. This application also shows, among other things, an initial implementation of MPA in our testbed and some performance results to show how existing protocols could be leveraged to realize the functionalities of MPA.
Patent•
12 Oct 2006
TL;DR: In this article, an approach for coordination of communication of timing information and traffic channel control in a hybrid terrestrial/satellite mobile communications environment is presented. Butler et al. present an approach that supports inter-PLMN coordination in registration and handover of radioterminals.
Abstract: Apparatus, methods and computer program products that support inter-PLMN coordination in registration and handover operations are provided. Hysteresis is introduced in registration of radioterminals in a hybrid terrestrial/satellite mobile communications environment. Inter-PLMN handover techniques are provided, including techniques for coordination of communication of timing information and traffic channel controls.
19 Jun 2006
TL;DR: This article presents a new method to enhance both link layer and network layer handovers using geolocation information provided by a GPS system to predict the next mobile node point of attachment and the associated sub-network using the position of the mobile nodes.
Abstract: IEEE 802.11 networks are now very common and are present in various locations. While roaming through access points, a mobile node is often required to perform a link layer handover. This mechanism causes user-interceptable connection loss and breaks in time-sensitive communication, especially if a network layer handover follows the link layer handover. Many solutions attempting to improve this process have been proposed but only a few use geolocation systems in the management of the handover. In this article, we present a new method to enhance both link layer and network layer handovers using geolocation information provided by a GPS system. The idea behind our algorithm is to predict the next mobile node point of attachment and the associated sub-network using the position of the mobile nodes. This method has been implemented using the new Mobile IP daemon for GNU/Linux operating system and evaluated through two scenarios
Patent•
8 May 2006TL;DR: In this article, a multi-mode mobile station includes a first interface for wireless communication with a wireless local area network (WLAN) and a second interface for WLAN/WWAN communication.
Abstract: A multi-mode mobile station includes a first interface for wireless communication with a wireless local area network (WLAN) and a second interface for wireless communication with a wireless wide area network (WWAN). The multi-mode mobile station is associated with a particular conference bridge, through which all calls to and from the multi-mode mobile station are routed. For example, when a call involving the multi-mode mobile is established via the WLAN, the call includes a WLAN call leg that extends from the conference bridge to the multi-mode mobile station via the WLAN. To effect a handoff during the call, a WWAN call leg is established between the multi-mode mobile station and the conference bridge via the WWAN. The conference bridge bridges the WLAN and WWAN call legs. To complete the handoff, the multi-mode mobile station drops the WLAN call leg and continues the call using the WWAN call leg.
Patent•
21 Jun 2006TL;DR: In this article, power saving states of a beacon station in an ad hoc wireless local area network (WLAN) are discussed and some of the methods allow exchanging power management information among stations in the wireless network and to allow beacon station handovers.
Abstract: Methods are disclosed to support power saving states of a beacon station in an ad hoc wireless local area network (WLAN). Some of the methods allow exchanging power management information among stations in the wireless network and to allow beacon station handovers. In some methods, always-on stations are given a higher priority to become a beacon station or a beacon station handover destination. The methods achieve good power saving while minimizing beacon handover frequency.
Patent•
24 Oct 2006TL;DR: In this paper, a handoff decision function is used to determine whether to handoff user device communications from a first communication network to a second communication network, where the first and second communication networks are heterogeneous with respect to each other.
Abstract: This invention provides a system, method and apparatus for facilitating handoffs from a first communication network to a second communication network, the first communication network and second communication network being heterogeneous with respect to each other. The system, method and apparatus may further include a contextual information server, which stores contextual elements corresponding to a user device and the operating environment of the user device, and a handoff decision function module that evaluates at least one of the contextual elements to determine whether to handoff user device communications from the first communication network to the second communication network. The method and apparatus may further include obtaining at least one contextual element corresponding to a user device and the operating environment of the user device, evaluating the at least one contextual element with a handoff decision function module to establish a handoff decision, establishing a handoff decision, and notifying the user device of the handoff decision. The method for facilitating handoffs from a first communication network to a second communication network may further include receiving a received signal strength indication, receiving a link quality determination, receiving a characteristic of the user device, and determining the location of the user device.
Patent•
29 Jun 2006TL;DR: In this paper, the authors present a method of wireless communication with a mobile unit and a base station router, which may include providing, over a first channel, configuration information indicative of a second channel associated with the base station routers and the mobile unit.
Abstract: The present invention provides a method of wireless communication with a mobile unit and a base station router. The method may include providing, over a first channel, configuration information indicative of a second channel associated with the base station router and the mobile unit. The method may also include providing state information associated with the mobile unit to the base station router.