Showing papers on "Handover published in 2007"

Methods and system for performing handover in a wireless communication system

Abstract: A method and system for performing handover in a third generation (3G) long term evolution (LTE) system are disclosed. A source evolved Node-B (eNode-B) makes a handover decision based on measurements and sends a handover request to a target eNode-B. The target eNode-B sends a handover response to the source eNode-B indicating that a handover should commence. The source eNode-B then sends a handover command to a wireless transmit/receive unit (WTRU). The handover command includes at least one of reconfiguration information, information regarding timing adjustment, relative timing difference between the source eNode-B and the target eNode-B, information regarding an initial scheduling procedure at the target eNode-B, and measurement information for the target eNode-B. The WTRU then accesses the target eNode-B and exchanges layer 1/2 signaling to perform downlink synchronization, timing adjustment, and uplink and downlink resource assignment based on information included in the handover command.

Proactive Scan: Fast Handoff with Smart Triggers for 802.11 Wireless LAN

Abstract: It has been a challenging problem to support VoIP-type delay sensitive applications in an 802.11 wireless LAN, because the standard handoff procedure implemented in many current 802.11 products occurs a delay deem unacceptable to VoIP users. To reduce this delay, we have developed a fast handoff scheme called Proactive Scan. It employs two new techniques. The first is to decouple the time-consuming channel scan from the actual handoff, and to eliminate channel scan delay by doing scan early and interleaving it with ongoing traffic in a non-intrusive way. The second technique is a smart trigger that takes into account both uplink and downlink quality and explicitly addresses the link asymmetry which has yet not been touched in previous work. Through implementation and experimentation study, we have shown that Proactive Scan does provide fast handoff and satisfactory performance to VoIP applications. Further, it is a software-only client-only solution that any mobile device can use in any existing 802.11 networks.

Load balancing for cellular/WLAN integrated networks

Abstract: The interworking between heterogeneous third-generation cellular networks and wireless local area networks is one promising evolution approach to fourth-generation wireless networks, which can exploit the complementary advantages of the cellular network and WLANs. Resource management for the 4G-oriented cellular/WLAN integrated network is an important open issue that deserves more research efforts. In this article we present a policy framework for resource management in a loosely coupled cellular/WLAN integrated network, where load balancing policies are designed to efficiently utilize the pooled resources of the network. A two-phase control strategy is adopted in the load balancing policies, in which call assignment is used to provide a statistical quality of service guarantee during the admission phase, and dynamic vertical handoff during the traffic service phase is used to minimize the performance variations. Numerical results are presented to demonstrate that the proposed load balancing solution achieves significant performance improvement over two other reference schemes

Optimal Joint Session Admission Control in Integrated WLAN and CDMA Cellular Networks with Vertical Handoff

Abstract: This paper considers optimizing the utilization of radio resources in a heterogeneous integrated system consisting of two different networks: a wireless local area network (WLAN) and a wideband code division multiple access (CDMA) network. We propose a joint session admission control scheme for multimedia traffic that maximizes overall network revenue with quality of service (QoS) constraints over both the WLAN and the CDMA cellular networks. The WLAN operates under the IEEE 802.11e medium access control (MAC) protocol, which supports QoS for multimedia traffic. A novel concept of effective bandwidth is used in the CDMA network to derive the unified radio resource usage, taking into account both physical layer linear minimum mean square error (LMMSE) receivers and characteristics of the packet traffic. Numerical examples illustrate that the network revenue earned in the proposed joint admission control scheme is significantly larger than that when the individual networks are optimized independently with no vertical handoff between them. The revenue gain is also significant over the scheme in which vertical handoff is supported, but admission control is not done jointly. Furthermore, we show that the optimal joint admission control policy is a randomized policy, i.e., sessions are admitted to the system with probabilities in some states

An experimental comparison of handover methods.

Abstract: INTRODUCTION With the increase in shift pattern work for junior doctors in the NHS, accurate handover of patient clinical information is of great importance. There is no published method that forms the gold standard of handover and there are large variations in practice. This study aims to compare the reliability of three different handover methods. PATIENTS AND METHODS We observed the handover of 12 simulated patients over five consecutive handover cycles between SHOs on a one-to-one basis. Three handover styles were used and a numerical scoring system assessed clinical information lost per handover cycle. RESULTS After five handover cycles, only 2.5% of patient information was retained using the verbal-only handover method, 85.5% was retained when using the using the verbal with note taking method and 99% was retained when a printed handout containing all patient information was used. CONCLUSIONS When patient information is handed over by the verbal only method, very few facts are retained; therefore, this method should be avoided whenever possible. Verbal handover with note taking is shown to be an effective method of handover in our study, although we accept that this is an artificial scenario and may not reflect the reality of a busy hospital. Nearly all information is retained by the printed handout method but this relies on the handout being regularly updated.

Combined SINR Based Vertical Handoff Algorithm for Next Generation Heterogeneous Wireless Networks

Abstract: Next generation heterogeneous wireless networks offer the end users with assurance of QoS inside each access network as well as during vertical handoff between them. For guaranteed QoS, the vertical handoff algorithm must be QoS aware, which cannot be achieved with the use of traditional RSS as the vertical handoff criteria. In this paper, we propose a novel vertical handoff algorithm which uses received SINR from various access networks as the handoff criteria. This algorithm consider the combined effects of SINR from different access networks with SINR value from one network being converted to equivalent SINR value to the target network, so the handoff algorithm can have the knowledge of achievable bandwidths from both access networks to make handoff decisions with QoS consideration. Analytical results confirm that the new SINR based vertical handoff algorithm can consistently offer the end user with maximum available bandwidth during vertical handoff contrary to the RSS based vertical handoff, whose performance differs under different network conditions. System level simulations also reveal the improvement of overall system throughputs using SINR based vertical handoff, comparing with the RSS based vertical handoff.

Optimized FMIPv6 Using IEEE 802.32 MIH Services in Vehicular Networks

Abstract: In this paper researchers describe an optimization scheme for handover procedures as found in the fast handover for mobile IPv6 (FMIPv6) protocol using a media independent handover (MIH) service. Radio access discovery and candidate access router (AR) discovery problems with FMIPv6 are addressed using the lower three layers' information found in the mobile node/router (MN/MR) as well as the neighboring access network. The static and dynamic L2 and L3 information is stored in an Information Element Container presented herein alongside a special caching device that is maintained by MN/MR that reduces anticipation time. This then increases probabilities of proper prediction for FMIPv6. A cross-layer protocol mechanism is presented that makes intelligent handover decisions, improving the quality of service (QoS) parameters. Analysis and simulations of the presented systems are presented.

Active service redirection for a private femto cell

Abstract: A femto cell at a customer premises, such as an IP-based femto Base Transceiver System (IP-BTS), can be configured as a “private access” node intended to service a limited set of mobile stations. However, mobile stations not associated with the private femto cell may acquire and lock onto the femto BTS. To avoid service blockages in such cases, the private femto BTS will allow call access attempts by, and call deliveries to, a non-associated mobile station, despite the “private access” configuration. However, upon completion of call set-up, the non-associated mobile station is directed to initiate handoff, from the private femto cell coverage provided by the femto BTS into a cell coverage of a base station of the macro network, to conserve femto cell resources for use in servicing calls of the associated mobile station(s).

Optimized FMIPv6 Using IEEE 802.21 MIH Services in Vehicular Networks

Abstract: In this paper, we optimize the handover procedure in the fast handover for mobile IPv6 (FMIPv6) protocol by using the IEEE 802.21 media independent handover (MIH) services. FMIPv6 is used to enhance the performance of handovers in mobile IPv6 and its basic extension for network mobility (NEMO), i.e., the fundamental mobility management protocols used in vehicular networks. With the aid of the lower three layers' information of the mobile node/router (MN/MR) and the neighboring access networks, we tackle the radio access discovery and candidate access router (AR) discovery issues of FMIPv6. We introduce an "information element container" to store static and dynamic layer 2 (L2) and layer 3 (L3) information of neighboring access networks and propose to use a special cache maintained by the MN/MR to reduce the anticipation time in FMIPv6, thus increasing the probability of the predictive mode of FMIPv6 operation. Furthermore, we propose a cross-layer mechanism for making intelligent handover decisions in FMIPv6. The lower layer information of the available links obtained by MIH services and the higher layer information such as quality-of-service (QoS) parameter requirements of the applications are used by a policy engine to make intelligent handover decision. We will show through analysis and simulations of the signaling procedure that the overall expected handover (both L2 and L3) latency in FMIPv6 can be significantly reduced in the proposed mechanism.

Enhanced Route Optimization for Mobile IPv6

Abstract: This document specifies an enhanced version of Mobile IPv6 route optimization, providing lower handoff delays, increased security, and reduced signaling overhead. [STANDARDS-TRACK]

Grey Prediction Based Handoff Algorithm

Abstract: As the demand for higher capacity in a cellular environment increases, the cell size decreases. This fact makes the role of suitable handoff algorithms to reduce both number of handoffs and handoff delay more important. In this paper we show that applying the grey prediction technique for handoff leads to considerable decrease in handoff delay with using a small number of handoffs, compared with traditional hystersis based handoff algorithms. Keywords— Cellular network, Grey prediction, Handoff.

Fast handoff support for wireless networks

Abstract: Systems and methods for providing fast handoff support by transferring information are provided. Additionally, a generic protocol message format is presented which allows the transfer of information used in the handoff. The generic protocol allows a gateway to request contexts or session information and send information that allows tunnel setup and mapping to other connections. The session, tunnel, and mapping information allow the gateways to switch packet processing operations without causing disruption to the packet flow. Further, in inter-gateway handoffs or inter-access network handoffs, fast and seamless handoffs are provided so the mobile station keeps the same IP address and the session continues.

System and method for optimizing authentication procedure during inter access system handovers

Abstract: Disclosed is a method and system of deriving new keys for accessing a new system. The method enables an optimized authentication procedure during handover form an existing system to a new system by using the existing system access keys. The user equipment that is accessing the new system receives a temporary ID during handover preparation which enables the user equipment to perform a fast re-authentication. The method uses existing system access keys to derive system access keys for the new network.

A roaming gateway

Abstract: A roaming gateway has at least one IP network interface, and at least one cellular network interface, and inter-working functions for inter-working between a wireless IP network and a cellular network. The inter-working functions communicate with user devices in an IP network according to a machine-level subscribe-and-notify event package protocol for managing handover of mobile devices roaming between IP and cellular networks. They also poll a cellular network for subscriber status on that cellular network in the absence of a mobility event package. The inter-working functions comprise HSS functionality programmed to access data on a HLR of a cellular network and to perform HSS operations using said data. The gateway applies routing policies specific to call types, allowing or disallowing the anchoring of calls originating in either an IP network or a cellular network based on number prefixes. The inter- working functions comprise an application server programmed to communicate with a user device as a client. The server provides a staging point for cellular supplementary services while anchoring calls, retrieving configurations from cellular network elements and applying appropriate routing based on these configurations and the current state of a call.

An Overview of Handoff Techniques in Cellular Networks

Abstract: Continuation of an active call is one of the most important quality measurements in the cellular systems. Handoff process enables a cellular system to provide such a facility by transferring an active call from one cell to another. Different approaches are proposed and applied in order to achieve better handoff service. The principal parameters used to evaluate handoff techniques are: forced termination probability and call blocking probability. The mechanisms such as guard channels and queuing handoff calls decrease the forced termination probability while increasing the call blocking probability. In this paper we present an overview about the issues related to handoff initiation and decision and discuss about different types of handoff techniques available in the literature. Keywords—Handoff, Forced Termination Probability, Blocking probability, Handoff Initiation, Handoff Decision, Handoff Prioritization Schemes.

Performance Evaluation of Received Signal Strength Based Hard Handover for UTRAN LTE

Abstract: This paper evaluates the hard handover performance for UTRAN LTE system. The focus is on the impact that received signal strength based hard handover algorithm have on the system performance measured in terms of number of handovers, time between two consecutive handovers and uplink SINR for a user about to experience a handover. A handover algorithm based on received signal strength measurements has been designed and implemented in a dynamic system level simulator and has been studied for different parameter sets in a 3GPP UTRAN LTE recommended simulation scenario. The results suggest that a downlink measurement bandwidth of 1.25 MHz and a handover margin of 2 dB to 6 dB are the parameters that will lead to the best compromise between average number of handovers and average uplink SINR for user speeds of 3 kmph to 120 kmph.

Capacity optimisation in a cellular wireless network

Abstract: Embodiments of the invention relate to cellular wireless networks and are particularly suited to networks including different types of base stations. So-called femtocell base stations are typically deployed within a subscriber's premises and operate at low transmit power, providing a very limited area of wireless coverage. A femtocell is typically deployed within the area of wireless coverage of a conventional macrocell type of base station, and if handover from a macrocell is performed on the basis of the best signal to noise plus interference ratio, a connection is likely to be transferred to another macrocell rather than to a femtocell. However, in view of the low density of user equipments capable of transceiving with a femtocell, the femtocell could potentially provide a greater data rate to the user equipment terminal than is possible with a macrocell. A cellular wireless network according to an embodiment of the invention employs a method of handover algorithm that has dependence on both a measure of signal quality such as signal to noise plus interference ratio and on a measure of loading of the base station. The handover algorithm is thereby able to weight selection of a base station on the basis of data rate, and intelligently engineer handover to a femtocell.

Method and system for handoff between wireless networks

Abstract: A method and system for operating a standalone client in a dual-mode mobile communications device to hand off a call between first and second wireless networks operating under different communications protocols, using SIP and ISUP signaling.

A Novel Fuzzy Logic Vertical Handoff Algorithm with Aid of Differential Prediction and Pre-Decision Method

Abstract: In this paper, we propose a novel vertical handoff decision algorithm for overlay wireless networks consisting of cellular and wireless local area networks (WLANs). The target network is selected using a fuzzy logic-based normalized quantitative decision algorithm which, in addition to usual parameters such as the current received signal strength (RSS) and the available bandwidth, also takes a prediction of the RSS into account, resulting in a more accurate handoff. The RSS prediction is obtained using a differential prediction algorithm that has good accuracy. Furthermore, to reduce system load, a pre-decision method is employed before actual handoff decision to filter out users with high mobility or low RSS from using the WLAN. Simulation results show that the proposed algorithm can reduce the call-dropping probability as well as unnecessary handoffs in heterogeneous network environments.

Transferring a communications exchange

Abstract: Methods and systems for transferring a communications exchange using a mobile handset (128) are described. A radio frequency (RF) signal is transmitted from a mobile handset to a base station to provide a communications exchange. The communications exchange exists between the mobile handset and a first communications device (104). The mobile handset automatically detects a second communications device when it is in close proximity to the second communications device. The second communications device is capable of receiving a call handoff. If the mobile handset is in close proximity to the second communications device, then a transfer request including information associated with the second communications device is received from the second communications device. The transfer request is accepted and the communications exchange is seamlessly transferred to the second communications device form the mobile handset.

Performance Analysis of Handover Measurements and Layer 3 Filtering for Utran LTE

Abstract: Handover is one of the key functionalities which tries to keep a user equipment (UE) connected to the best base station (eNodeB). Handover is usually based on the downlink received signal strength (RSS) and carrier-to-interference ratio (CIR) measurements. Processing of the handover measurement is usually done in Layer 1 (LI) and Layer 3 (L3) by the UE, and handover is initiated by the serving eNodeB if certain event criteria are met. L3 filtering can be done in linear domain or decibel (dB) domain. A hard handover algorithm based on the downlink RSS and CIR measurements along with linear and dB domain L3 filtering has been studied by using a dynamic system level simulator for a 3GPP UTRAN LTE recommended scenario. The results suggest that RSS measurement with linear or dB domain L3 filtering is a better criterion for handover in terms of reduced number of handovers for a small penalty on the downlink CIR.

Inter-system handoffs in multi-access environments

Abstract: Systems and methods according to these exemplary embodiments provide for handing off user equipment between different access networks, e.g., a high rate packet data (HRPD) system and a long term evolution (LTE) system. An existing mobile IP session can be maintained by the UE during the handoff.

Method and apparatus for dynamically creating and updating base station neighbor lists

Abstract: The invention includes a method and apparatus for creating a base station neighbor list at a target base station in a wireless network including a plurality of base stations. A method includes obtaining information for creating the base station neighbor list, creating the base station neighbor list using the obtained information, and storing the base station neighbor list. The obtained information includes at least one of geographic locations of ones of the base stations, network status information associated with the wireless network, and pilot signal strength measurement feedback information. The base station neighbor list includes a subset of the base stations of the network. The base stations of the base station neighbor list may be prioritized using at least a portion of the obtained information. The base station neighbor list may be updated periodically, or in response to changes to the obtained information. The base station neighbor list is distributed from the base station to wireless user devices served by the base station for use by the wireless user devices in making handoff decisions.

Terminal-Controlled Mobility Management in Heterogeneous Wireless Networks

Abstract: The coexistence of multiple access technologies deployed by different operators is fundamental for future fourth-generation mobile networks. In spite of this heterogeneity, seamless interoperator/intersystem mobility is a mandatory requirement. In this article we present a seamless mobility management approach that does not require changes to existing network infrastructure. The novelty of the proposed approach is that mobility management is fully controlled by the terminal, and network selection is user-centric, power-saving, cost-aware, and performance-aware. Total mobility management, including interface management, handover decision, and execution, is also detailed

Handover adaptation for dynamic load balancing in 3gpp long term evolution systems

Abstract: The long-Term Evolution (LTE) of the 3GPP (3rd Generation Partnership Project) radio access network is in early stage of specification. Self-tuning and self-optimisation algorithms are currently studied with the aim of enriching the LTE standard. This paper investigates auto-tuning of LTE mobility algorithm. The auto-tuning is carried out by adapting handover parameters of each base station according to its radio load and the load of its adjacent cells. The auto-tuning alleviates cell congestion and balances the traffic and the load between cells by handing off mobiles close to the cell border from the congested cell to its neighbouring cells. Simulation results show that the auto-tuning process brings an important gain in both call admission rate and user throughput.

Re-synchronization of temporary UE IDS in a wireless communication system

Abstract: Techniques for re-synchronizing Cell Radio Network Temporary Identifiers (C-RNTIs) in a wireless communication system are described. In one design, a user equipment (UE) sends a random access preamble for random access. A base station receives the random access preamble, assigns a Temporary C-RNTI to the UE, and sends a random access response including the Temporary C-RNTI. The UE uses the Temporary C-RNTI as a C-RNTI for itself if a valid C-RNTI is not already available. The UE discards the Temporary C-RNTI and uses the valid C-RNTI if available. The UE sends a transmission after receiving the random access response, and the transmission may include the valid C-RNTI if available. For handover, the base station (a target base station) receives a handover request from a source base station, assigns the valid C-RNTI to the UE, and sends the valid C-RNTI to the source base station for forwarding to the UE.

Method and system for maintaining session continuity

Abstract: A method and a system for maintaining session continuity, in which the system includes: a Handover Source Function (HOSF), a Handover Destination Function (HODF), a Handover Anchor Function-Control Plane (HOAF-CP) and a Handover Anchor Function-User Plane (HOAF-UP). The method includes: a first user establishing a connection through the HOSF with the HOAF-CP and the HOAF-UP which correspond to a second user, so as to establishing a session with the second user; during session handover, the HODF that corresponds to the HOSF establishing another connection with the HOAF-CP and HOAF-UP though which the first user continues the session with the second user, so as to maintain the session continuity. When the access address or the access means of the terminal changes, or even the terminal changes during a session, embodiments of the present invention can logically replace the connection before the handover with a new connection to ensure the session continuity.

Transmission and reception of system information upon changing connectivity or point of attachment in a mobile communication system

Abstract: Method for informing a mobile terminal on target cell-specific system information to facilitate a mobility procedure such as handover or cell reselection in a mobile communication network. Further a radio resource control apparatus, a mobile terminal and a system comprising the radio resource control apparatus and the mobile terminal are provided. The invention suggests improvements to current mobility procedures so as to reduce the interruption time implied by the procedures. More specifically, it is proposed to include at least one pointer to target cell-specific system information to a control message, such as a handover indication or connection release message, pointing the mobile terminal to system information in the target cell relevant for system access and/or to perform mobility procedures. Further, a portion of the target cell-specific system information may also be comprised in the control message.

Movement-Aware Vertical Handoff of WLAN and Mobile WiMAX for Seamless Ubiquitous Access

Abstract: This paper addresses a movement-aware vertical (MAV) handover algorithm between WLAN and Mobile WiMAX for seamless ubiquitous access. An MAV handover algorithm is proposed in this paper to exploit movement pattern for avoiding unnecessary handovers in the integrated WLAN and Mobile WiMAX networks. If a mobile station (MS)'s velocity is high and its movement pattern is irregular, unnecessary handovers likely occur more frequently. Therefore, the MS velocity and moving pattern are important factors for the handover decision procedure. To avoid unnecessary handovers, the MAV handover algorithm adjusts the dwell time adaptively and predicts the residual time in the cell of target base station (BS). Consequently, the adaptive dwell timer of MAV handover algorithm allows an MS a better connection as long as possible. Our simulation results show that the reduction of unnecessary handovers by leads to significant throughput improvements.