Abstract: As the number of Mobile IP (MIP) [C. Perkins, (1996)] users grow, so will the demand for delay sensitive real-time applications, such as audio streaming, that require seamless handoff, namely, a packet lossless Quality-of-Service guarantee during a handoff. Two well-known approaches in reducing the MIP handoff latency have been proposed in the literature. One aims to reduce the (home) network registration time through a hierarchical management structure, while the other tries to minimize the lengthy address resolution delay by address pre-configuration through what is known as the fast-handoff mechanism. We present a novel seamless handoff architecture, S-MIP, that builds on top of the hierarchical approach [H. Soliman et al. (2002)] and the fast-handoff mechanism [G. Dommety et al. (2002)], in conjunction with a newly developed handoff algorithm based on pure software-based movement tracking techniques [Z.-G. Zhou et al. (2002)]. Using a combination of simulation and mathematical analysis, we argue that our architecture is capable of providing packet lossless handoff with latency similar to that of L2 handoff delay when using the 802.11 access technology. More importantly, S-MIP has a signaling overhead equal to that of the well-known 'integrated' hierarchical MIP with fast-handoff scheme [H. Soliman et al. (2002)], within the portion of the network that uses wireless links. In relation to our S-MIP architecture, we discuss issues regarding the construction of network architecture, movement tracking, registration, address resolution, handoff algorithm and data handling.

Abstract: When carrying out a downlink handover, a source base transceiver station from which a mobile node is moving receives packets to be transmitted, via a wireless section, to the mobile node from an IP network, and copies and transfers them to a destination base transceiver station to which the mobile node is moving. On the other hand, when carrying out an uplink handover, the source base transceiver station compares the reliability of transport blocks which are received via a wireless section, from the mobile node and which are demodulated and decoded by the local station with that of transport blocks which are received via an IP network, from another base transceiver station and which are demodulated and decoded thereby, packetizes selected transport blocks with a better quality, and transmits them to a communications-partner node according to a route table, thereby implementing distribution of traffic via the IP network.

Abstract: We propose an analytical model for integrated real-time and non-real-time services in a wireless mobile network with priority reservation and preemptive priority handoff schemes. We categorize the service calls into four different types, namely, real-time and non-real-time service originating calls, and real-time and non real-time handoff service request calls. Accordingly, the channels in each cell are divided into three parts: one is for real-time service calls only, the second is for non-real-time service calls only, and the last one is for overflow of handoff requests that cannot be served in the first two parts. In the third group, several channels are reserved exclusively for real-time service handoffs so that higher priority can be given to them. In addition, a realtime service handoff request has the right to preempt non-real-time service in the preemptive priority handoff scheme if no free channels are available, while the interrupted non-real-time service call returns to its handoff request queue. The system is modeled using a multidimensional Markov chain and a numerical analysis is presented to estimate blocking probabilities of originating calls, forced termination probability, and average transmission delay. This scheme is also simulated under different call holding time and cell dwell time distributions. It is observed that the simulation results closely match the analytical model. Our scheme significantly reduces the forced termination probability of real-time service calls. The probability of packet loss of non-real-time transmission is shown to be negligibly small, as a non-real-time service handoff request in waiting can be transferred from the queue of the current base station to another one.

Abstract: A method, system and computer program are disclosed to perform a low latency inter-technology handoff of a MN from a WLAN to a cellular network. The method includes transmitting a Bearer Context from the MN for use by the cellular network, the Bearer Context containing information required to establish access network bearers in the cellular network for an ongoing Internet session of the MN; and responding to the Bearer Context with a Router Advertisement that is forwarded to the MN. The Bearer Context may be piggybacked on another message, or it may be sent as a separate message. The Bearer Context includes information expressive of: (a) a QoS requirement of an ongoing application or applications of the MN; (b) a unique identity of the MN that is recognizable by the cellular network; (c) parameters to facilitate the creation of a Point-to-Point Protocol state in the cellular network; and (d) parameters to enable establishment of packet filters in the cellular network. The method also includes authenticating and authorizing with the target cellular network for the purpose of executing handoff.

Abstract: A method and system are shown for handing off a communication stream between a mobile node and a communication endpoint from a first connection initiator to a second connection initiator while maintaining call state for the communication stream. The first connection initiator establishes a first connection to the communication endpoint in response to receiving a first connection request from the mobile node that includes a client identifier value for the mobile node. When the first connection initiator detects loss of communication with the mobile node, it sends a call-disconnect-notify (CDN) message having a cause code set to a handoff value to the connection endpoint. The connection endpoint, in response to the CDN message, stores call information for the first connection along with the mobile node's client identifier value. The first connection initiator also broadcasts a user-moved message that includes the mobile node's client identifier value and the first connection initiator's call information for the first connection. The second connection initiator, upon receiving the user-moved message, stores the first connection initiator's call information from the message along with the mobile node's client identifier value. When the second connection initiator receives a second connection request from the mobile node having the mobile node's client identifier value, it retrieves the call information from the user-moved message using the client identifier value and sends a tunnel-handoff-request message, which includes the client identifier value, to the connection endpoint. The connection endpoint retrieves its call information for the first connection using the client identifier value and sends a tunnel-handoff-response message to the second connection initiator. The second connection initiator and the connection endpoint then resume the communication stream using the call information for the first connection.

Abstract: The present invention provides a relocation of an application-specific functionality for an application that a mobile terminal (mobile node) is executing. Entities that may provide application-specific functionalities that assist the application include a location-based server (that may be associated with a supplementary service provider functionality), a transcoder proxy, and a security gateway. The relocation of the application-specific functionality with a network layer-Ievel handoff enables the mobile terminal to seamlessly execute an application that utilizes the media content from a content source that is supporting the mobile terminal before the handoff. Subsequent to the handoff, the mobile terminal registers with a current access router in order to inform the current access router about application context information. In the exemplary embodiments, the access routers and the content source support the discovery of an entity that can support the application-specific functionality and the configuration of the application-specific functionality after the handoff.

Abstract: The tremendous advancement and popularity of wireless access technologies necessitates the convergence of multimedia (audio, video, and text) services on a unified global (seamless) network infrastructure. Circuit-switched proprietary telecommunication networks are evolving toward more cost-effective and uniform packet-switched networks such as those based on IP. However, one of the key challenges for the deployment of such wireless Internet infrastructure is to efficiently manage user mobility. To provide seamless services to mobile users, several protocols have been proposed over the years targeting different layers in the network protocol stack. In this article we present a cross-layer perspective on the mobility protocols by identifying the key features of their design principles and performance issues. An analysis of the signaling overhead and handoff delay for some representative protocols in each layer is also presented. Our conclusion is that although the application layer protocol is worse than the protocols operating in the lower layers, in terms of handoff delay and signaling overhead, it is better suited as a potential mobility solution for the next-generation heterogeneous networks, if we consider such factors as protocol stack modification, infrastructure change, and inherent operational complexity.

Abstract: A communication system selection algorithm (SSA) implemented by a mobile station chooses between available systems to select a system to serve the mobile station. During initialization, the SSA causes the mobile station to scan the environment and compare available communication systems to determine the best system to provide service. After an initial system is chosen, the SSA causes the mobile station to continuously, or at discrete time intervals, scan the environment for available systems, thus allowing for a seamless switch to an available system whenever a handoff is desired. The SSA chooses the best available system based on measurements of each available system and applying preference rules defined by a service provider and/or user of the mobile station.

Abstract: The next generation of mobile systems is expected to support multiple radio access technologies, as well as diverse types of terminals, including mobile phones, personal digital assistants, and laptops, as well as personal area, moving, and sensor networks. Thus, future wireless systems will not only continue to break technological barriers in terms of new air interface capabilities, higher bit rates, mobility, security, and QoS management, but will present new end-to-end scenarios in which applications access services over multiple L2 hops and multiple IP networks. The term always best connected refers to the concept of defining a set of access selection criteria and mechanisms that allow users to get connected to various services in a nearly optimal manner. Providing QoS in this type of heterogeneous multihop environment is a challenging task because applications may be completely unaware of them scenario and the underlying layer 2 technologies that can be quite different at different hops. For instance, some wireless links may have scarce resources and highly optimized QoS mechanisms; others may not support explicit QoS handling at all. In this article we consider the use of IP-level QoS signaling as a key component to support the end-to-end QoS for various applications. We propose a small set of application programmer- and wirelesslink-friendly IP QoS parameters (wireless hints) and illustrate the use of these in a specific WLAN-to-cellular handover situation. We conclude that the proposed model, signaling protocol, and wireless information elements can efficiently support QoS in heterogeneous mobile environments.

Abstract: A method of performing an inter-RAT measurement for a handover from NB-TDD to GSM is provided A UE, as it moves from an NB-TDD Node B to a GSM cell, receives a measurement control message from the NB-TDD Node B The UE then measures the strength of a signal received from the GSM cell and verifies its identification for a predetermined measuring time If the UE successfully verifies the identification of the GSM cell for the measuring time, it reports the signal strength measurement and the verified GSM cell identification to the NB-TDD Node B If the UE fails to verify the identification of the GSM cell for the measuring time, it reports only the signal strength measurement to the NB-TDD Node B

Abstract: A system facilitates handover of a wireless transmit and receive unit (WTRU) between a cellular network and a wireless local area network (WLAN) (13). The WLAN (13) communicates with a cellular network. A location of the WTRU is determined. The coverage area of the WLAN (13) is determined. The WTRU is informed of the existence of the WLAN (13) when the WTRU approaches the coverage area of the WLAN (13). The WTRU is handed over from the cellular network to the WLAN (13) when the WTRU is in the coverage area of the WLAN (13).

Abstract: A solution for supporting relocation of an IP session of a mobile node during a network layer handover in a mobile communication system. In the method, from the application context information on the mobile node is detected a first set of capabilities of a network node that that facilitate maintaining the IP session. This first set of capabilities is queried from one or more potential next network node. Applicability of the potential next network node to the relocation of the IP session is determined by the capability information on the first set of capabilities.

Abstract: An inter system handovers in a mobile telecommunication system is performed when a dual mode user equipment (UE) covered by both GSM/GPRS network and UMTS network connects a dedicated channel and sets up a call in a BSS region where the GSM/GPRS provides coverage, and then moves to a UTRAN (UMTS Terrestrial Radio Access Network) where the UMTS provides coverage, wherein the method includes the steps of: if the dual mode UE receives an inter system handover command, i.e. from the BSS to the UTRAN, requesting GSM/GPRS data link layer to suspend a GSM/GPRS data link by a sublayer RR of GSM/GPRS network layer in the UE, requesting a GSM/GPRS physical layer to release a physical channel of the GSM/GPRS, and sending the inter system handover command to the UTRAN for authorizing a sublayer RRC of UMTS network layer in the UE to continue a call; requesting, at the RRC in the UE, a UMTS physical channel to be configured as a UMTS physical channel, and monitoring if the UMTS physical layer succeeds to have the configuration of the UMTS physical channel as requested; if the UMTS physical layer succeeds to have the configuration of the UMTS physical channel, requesting, at the RRC in the UE, a UMTS data link layer to configure a UMTS data link, and conveying information to the UTRAN through a UMTS channel that the handover between systems from the BSS to the UTRAN has been successfully performed; and sending, at the RRC, a GSM/GPRS resource release message to RR/GRR, thereby resetting the GSM/GPRS physical layer and the GSM/GPRS data link layer.

Abstract: This paper describes the session initiation protocol (SIP) based mobility in IPv6 and its performance in our laboratory testbed. For real-time mobile multimedia communication, we use SIP for signaling protocol as well as for supporting terminal mobility. While performance study for real-time mobile communication refers to several factors and their measurements, we analyze here only the handoff delay due to node mobility. In particular, we are interested to examine the delay incurred when a mobile node moves to a new link and perform the duplicate address detection (DAD) and router selection, and analyze the delay in each case. We notice that the IPv6 Linux implementation provides substantial amount of delay during node movement, which severely affects the performance of real-time applications. Therefore, we modify the Linux kernel and compare with the unaltered one. Finally, we conclude that a faster handoff is achievable in SIP based terminal mobility with intelligent modifications to unaltered Linux kernel.

Abstract: Apparatus and method for providing an automatic handoff process of a dual-mode user equipment (UE) from either a wireless local area network (WLAN) to a universal mobile telecommunications system (UMTS) or from a UMTS to a WLAN. Handoffs may be initiated by the UE, based upon user preference, signal quality, comparison of location coordinates of the UE and the system to be switched to or signal quality. The available channels of one system may be sent to the UE by the other system or the UE may monitor channels of the system to be switched to and lock on to one. The handoff may also be initiated by the UMTS, the selection being power-based.

Abstract: The present invention facilitates a handoff between cellular and wireless local area networks (WLANs). To facilitate a WLAN interface with the cellular network, a proxy packet control function (P-PCF) establishes a data tunnel to a packet data serving node (PDSN), as well as a WLAN association with a mobile terminal. The WLAN association is a tunnel, and is preferably implemented via an Access Router acting as a liaison between the proxy PCF and an Access Point. The Access Router and the proxy PCF establish an IP tunnel, which carries the WLAN user's PPP traffic. Handoffs between the cellular and WLAN networks are facilitated by effecting a same-PDSN, inter-PCF handoff wherein the communication session with the mobile terminal is effectively changed from between the PDSN and the proxy PCF to between the PDSN and a PCF associated with a base station controller facilitating the cellular access, and vice versa.

Abstract: The 4G wireless communication system is envisioned to integrate cellular network (e.g. UMTS) and wireless LAN (WLAN), in virtue of the individual coverage and capacity complementary characteristics. This paper describes a possible architecture integrating UMTS and 802.11 WLAN at SGSN. A functional entity, network interwork unit (NIU), is placed between the SGSN and WLAN access network side to hide the WLAN particularities. In this integrated architecture, mobile IP based vertical handover management increases the heterogeneous system signaling cost as well as handover latency, so one major task in the handover design is to reduce the unnecessary handover probability. This paper presents an analytical vertical handover initiation model based on the criteria of received signal strength (RSS) and distance. The handover performance evaluation criterion of interest is the handover probability. The numerical results show that our model is in line with the real cases when the distance between the base station (BS) of UMTS cell and the access point (AP) of WLAN is long or not.

Abstract: A method and system for seamlessly handing off a Mobile Node (MN) equipped with a Wireless Local Area Network (WLAN) adaptor from a cellular network such as a GRPS/UMTS network to a WLAN network without interrupting the ongoing IP connection/session. When entering a WLAN coverage area, the roaming MN sends mobility information to a WLAN Integration Gateway (WIG) node allowing the WIG node to identify the source Service GPRS Support Node (SGSN). The WIG node contacts the source SGSN to obtain PDP Context information relative to the roaming MN, and establishes a new GTP tunnel with the servicing GGSN in order to complete the handoff. The WIG node may route data traffic for the MN by assigning a new IP address to the MN and by either performing IP-in-IP encapsulation or Network Address Translation (NAT).

Abstract: A method for supporting relocation of an IP session during a network layer handover in a mobile communication system. In the method, application context information indicating activities that are advantageously executed pro-actively before the network layer handover is sent. The indicated activities are then pro-actively executed in a receiving network node. An advantage of the method and arrangement of the invention is that the pro-active actions, including pre-allocation of some critical resources for seamless handover of an ongoing IP session, facilitate timely implementation of the activities required for handing over an IP session, and/or selection of a target access router.

Abstract: The present invention provides method and apparatus for facilitating base station selection/handover by a user terminal in a distributed (e.g., cellular-type) wireless communication system. In accordance with one aspect, hysteresis is adaptively determined as a function of the variance of received signal strength fluctuations. In turn, an adaptive hysteresis factor can be obtained and used for a subsequent handover decision, for example, based on a cost function that takes into account the hysteresis. In accordance with another aspect, base station selection depends on a number of criteria, such as received signal strength, base station load, and estimated distance between a receiving user terminal and one or more base stations.

Abstract: A mobile communication system transmits a control channel having an ACK/NACK information field indicating whether packet data is received at the Node B from the particular UE when the particular UE moves from the Node B to the handover region shared by the Node B and the neighbor Node B during reception of high speed packet data from the Node B, a channel quality information (CQI) field indicating a condition of a channel over which the high speed packet data is transmitted, and a pilot signal field for power control. A radio network controller (RNC), connected to the Node and the neighbor Node B, identifies a plurality of UEs including the particular UE and other UEs, all of which are located in the handover region and receive the high speed packet data, and transmits pilot signal field position information to the UEs so that pilot signal fields that must be transmitted by the particular UE and the other UEs should not overlap with one another in the CQI field. The particular UE includes a pilot signal in a control channel at a position based on its own pilot signal field position information, and transmits the control channel.

Abstract: Current trends show that 3G cellular network and WLAN will coexist and work together to support more users with higher data rate services over a wider area In this hybrid mobile network, the WLAN provides high bandwidth data service over a small area while the 3G cellular network provides a higher mobility with lower bandwidth data service To provide seamless data service to mobile users, vertical handoff between WLAN and 3G cellular network has to be implemented We present the challenges in the vertical handoff We propose a TCP scheme for a seamless vertical handoff, and present a performance evaluation In the proposed scheme, the TCP sender and receiver use the Handoff (HO) option field in TCP header to recognize an impending handoff and a completing handoff After a vertical handoff, the sender tries to readjust its data rate, since the new network has drastically different characteristics in contrast with horizontal handoff where keeping the same data rate improves performance The proposed scheme can be implemented incrementally It is not necessary to change all of the TCP senders for compatibility since it uses an optional field in TCP header

Abstract: The Fast Handover protocol [1] provides seamless handover in wireless IP networks by minimizing handover latency. To reduce handover latency and to provide faster handover, Fast Handover uses anticipation based on layer 2 (L2) trigger information. Therefore, it incurs higher signaling costs compared with the basic Mobile IP protocol. Furthermore, since the L2 trigger is based on fluctuating wireless channel states, the handover anticipation using the L2 trigger may sometimes be incorrect. In the case of incorrect anticipation, unnecessary buffer space may be used for the purpose of providing a smooth handover. Therefore, it is essential to analyze these overhead costs, in order to evaluate and compare the performance of Fast Handover with that of the basic Mobile IP protocol. In this paper, we analyzed the overhead associated with Fast Handover including the signaling cost and the packet delivery cost. We formulated these costs based on a timing diagram and compared Fast Handover with basic Mobile IPv6 in terms of their packet loss rates and buffer requirements. Also, we studied the impact of the L2 triggering time on the total overhead cost. As a result, we found that the L2 triggering time is an important factor to consider in the optimization of handover performance.

Abstract: A method is provided for solving the mobility of a mobile trunk node (MTN) within an operated assisted mobile mesh local Ad-Hoc network. The method provides a reverse handover (RHO) when there exists another node within the local Ad-Hoc network, which is able to assume the logical role of a MTN. Before the first MTN performs the handover, existence of the other suitable MTN is determined (508). Where a suitable MTN is determined, the MTN functions are transferred to the new MTN before handover of the first MTN to a new cell of a cellular-based network. Upon transfer of the MTN functions to the new MTN (542), Ad- Hoc traffic is relayed to and from the local Ad-Hoc network via the new MTN. Enhanced tunneling (506) is proposed to minimize network traffic delays during the handover. The reverse handover also enables the first MTN to preserve its original merely Ad-Hoc local network connection.

Abstract: A cell search method for handover between an asynchronous mobile communication system's base station and a synchronous mobile communication system's base station. A border base station, which is an asynchronous base station neighboring a synchronous mobile communication network, acquires information on a GPS satellite time, a reference time of the synchronous mobile communication network, generates base station frame number (BFN) synchronized to the satellite time and a system frame number (SFN) having a predetermined offset for the BFN for each cell, generates a system information block including a difference value between the BFN and the SFN, and transmits the system information block over a common channel along with the SFN. A dual-mode mobile station receives an SFN for each cell and a system information block from the border base station, acquires the satellite time synchronization, extracts a neighbor list of synchronous base stations, including PN offset information, from the system information block, searches a neighbor cell of a synchronous system at times when the PN offsets have elapsed from the satellite time synchronization, and reports the search result to the border base station. The cell search method contributes to rapid and efficient cell search during inter-system handover.

Abstract: Techniques for avoiding handoff to a channel impaired due to frequency dependent fading, while minimizing idle mode signaling are disclosed. In one aspect, an access terminal (106) determines the assigne chancel on an access point (104) and caches the channel. In another aspect, the access terminal (106) replaces a default channel associated with an access point (104) in a cache (270) with the assigned channel. In yet another aspect, the access terminal (106) uses the cached channel associated with an access point when measuring channel quality (220) of neighbor access points for use in handoff determination (240). In yet another aspect, the access terminal (106) hands off to the cached channel of a neighbor access point (104) during handoff. Various other aspects are also presented. These aspects have the benefit of factoring in frequency dependent channel characteristics when making handoff decisions, thus avoiding handoff to an access point where the assigned channel may be impaired.

Abstract: A method for minimizing handoff latencies when a handoff is performed in a wireless network. An access point (AP) or base station associated to a current wireless station (STA) allows information required for a reassociation to the STA to be propagated to handoff-capable neighboring APs or base stations. When the STA moves, a neighboring AP or base station performs the reassociation to the STA on the basis of context. When a handoff procedure is performed, the time taken to receive context of a corresponding STA is reduced, such that a fast handoff can be implemented.

Abstract: The present invention provides a method and apparatus that enables handover of a mobile station between a cellular network and a wireless network without control intervention from the cellular network and independent of employed air interface technology. In particular, a call is connected (504) between a mobile station (202) and a remote station (204) through a media gateway (210). The media gateway is connected to the mobile station via a first connection line and to the remote station via a second connection line. Net, a communication directed to a predetermined number by the mobile station is received (520) or, in the alternative, a connection signal that includes a call header is sent to the mobile station. A third connection line between the media gateway and the mobile station is then established (524), and communication is handed-over (526, 528) from the first connection line to the third connection line.

Abstract: Fourth generation mobile communication systems are characterized by heterogeneous access networks and IP-based transport technologies. Different access technologies give users great flexibility in choosing services, which can be different in QoS support, business models, and service providers. Realization of seamless handovers to the best network section while considering QoS and AAAC (authentication, authorization, accounting and charging), calls not only for seamless handover protocols, but also intelligent handover decision strategies. The contribution of this paper is the design of a handover decision strategy in mobile all-IP networks to support seamless handover scenarios. Methods have been proposed to obtain QoS and AAAC information from candidate networks with minimum signaling overhead. New handover algorithms for wireless local area networks (WLANs) are also presented and evaluated with simulation results.