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Showing papers on "Handover published in 2000"


Patent
15 Mar 2000
TL;DR: In this paper, the authors proposed a handoff protocol for TCP sessions in a system including a client in communication with a switch and to or more devices, such as disk drives, Web servers, database servers or any other device that benefits from being clustered.
Abstract: The present invention relates to transparent access to network attached devices, such as network attached storage devices, Web servers or database servers. In particular, the present invention provides hand-off protocols that are transparent to a network client, with the advantage that physical devices can be added to, replaced on or removed from a network without reconfiguring network clients or applications running applications at levels above the network clients. One aspect the present invention is a method for handing off TCP sessions in a system including a client in communication with a switch and to or more devices. This method includes determining in the first device that a handoff should take place, identifying a second device to take over the session, sending handoff messages to and receiving an acknowledgment from the second device, and reporting the handoff to and receiving an acknowledgment from the switch. The devices applying this method may be disk drives, Web servers, database servers or any other device that benefits from being clustered. A device according to the present invention may comprise: a switch including logic for routing messages among a client and a plurality of devices and logic responsive to an instruction to reprogram its routing messages and to confirm the road reprogramming is complete; a first device including logic to determine when a TCP session should be handed off to another device, logic to instruct a second device to accept a handoff, and logic to instruct a switch to reprogram its routing of messages; wherein the second device is in communication with the switch and includes logic responsive to an instruction to accept a handoff and to confirm acceptance of the handoff. The first and second devices may be disk drives, Web servers, database servers or any other device that benefits from being clustered. Logic may be included to determine when to handoff a TCP session and to identify a second device to receive the handoff, consistent with the method of present invention.

298 citations


Journal ArticleDOI
TL;DR: The design enhancements have produced a set of highly efficient schemes that achieve significant reduction in handoff blocking rates while only incurring remarkably small increases in the new call blocking rates.
Abstract: We propose and evaluate new schemes for channel reservation motivated by the rapidly evolving technology of mobile positioning. The schemes, called predictive channel reservation (PCR), work by sending reservation requests to neighboring cells based on extrapolating the motion of mobile stations (MSs). A number of design enhancements are incorporated to minimize the effect of false reservations and to improve the throughput of the cellular system. These enhancements include: (1) reservation pooling; (2) queuing of reservation requests; (3) hybrid approach for integrating guard channels (GCs); and (4) using a threshold distance (TD) to control the timing of reservation requests. The design enhancements have produced a set of highly efficient schemes that achieve significant reduction in handoff blocking rates while only incurring remarkably small increases in the new call blocking rates. The PCR approach has also been used to solve the MINBLOCK optimization problem and has given significant improvement over the fractional guard channel (FGC) protocol. Detailed performance results of the different variations of the PCR scheme and comparisons with conventional channel reservation schemes are presented. An analytical Markov model for the hybrid predictive version of the scheme is developed and its applicability and numerical results are discussed.

238 citations


Journal ArticleDOI
TL;DR: The motivation behind micro-mobility, common characteristics that a number of proposals share and briefly describe some of the key contributions discussed by the working group are discussed.
Abstract: The IETF Mobile IP Working Group is discussing a number of enhancements to the base protocol to reduce the latency, packet loss and signaling overhead experienced during handoff. In this article, we discuss a number of "micro-mobility protocols" that extend Mobile IP with fast handoff and paging capabilities. The aim of this article is not to provide an exhaustive survey of these protocols. Rather, we discuss the motivation behind micro-mobility, present common characteristics that a number of proposals share and briefly describe some of the key contributions discussed by the working group. In the longer term there is a need to understand the differences between many of the micro-mobility proposals discussed in this article in terms of, complexity of the design choice, and performance differences. As part of that process we have recently made available the Columbia Micro-mobility Suite (CMS). The CMS software is freely available from the web (comet.columbia.edu/micromobility) and includes ns source code extensions for Cellular IP, Hawaii and Hierarchical Mobile IP.

233 citations


Patent
Walter Müller1
15 Sep 2000
TL;DR: In this article, the authors proposed a quality estimate for a current active set as well as a quality estimation for the virtual active set for inter-frequency hard handovers in wireless networks.
Abstract: A telecommunications network performs an inter-frequency hard handover for a connection with a user equipment unit (UE) by switching either from a cell or a current active set of base stations on a first frequency to a virtual active set of base stations on another (new) frequency. The inter-frequency hard handover can be an inter-frequency handover within a same system, or an inter-system handover. The virtual active set of base stations is maintained at the user equipment unit (UE), and is updated in accordance with one of several updating implementations of the invention. In a first mode of the invention for implementing virtual active set updates, the network authorizes the user equipment unit (UE) to report to the network the occurrence of certain network-specified events which are acted upon by the network for communicating virtual active set update information to the user equipment unit (UE). In a second mode of the invention, the network authorizes the user equipment unit (UE) to perform an autonomous virtual active set update upon occurrence of certain network-specified events, with inter-frequency events being reported from the equipment unit (UE) to the network and the network issuing an inter-frequency handover command. Advantageously, events which trigger intra-frequency measurements can be reused for reporting inter-frequency measurements. In another of its aspects, the present invention provides the network with a quality estimate for a current active set as well as a quality estimate for the virtual active set. The quality estimate can be utilized in a context of a handover from one UTRAN frequency to another UTRAN frequency, or even in the context of an inter-system handover (e.g., a handover between a UTRAN system and a GSM system, for example). The quality estimate can be utilized to trigger a change or switch of frequencies/systems. Certain thresholds employed in the quality estimate-utilizing handovers provide hysteresis protection.

224 citations


Patent
21 Nov 2000
TL;DR: In this paper, the authors propose a challenge/response procedure for authentication during a communication handover event in a radio communications system such as IEEE 082.11 or HIPERLAN, where the existing security association between a mobile terminal and a wireless communication network is maintained.
Abstract: An existing security association is re-established when a communication handover event occurs in a radio communications system such as IEEE 082.11 or a HIPERLAN wherein the existing security association between a mobile terminal and a wireless communication network is maintained when the communication handover occurs within the network. Authentication during a handover event is achieved by a challenge/response procedure. In accordance with the challenge/response procedure each member of a communication pair that is made up of a new access point and the mobile terminal that is experiencing a handover to the new access point sends a challenge to the other member of the communication pair. Each member of the communication pair then calculates a response to its received challenge, and these responses are sent back to the other member of the communication pair. Each member of the communication pair then compares its received response to a correct response. When these comparisons are correct, payload communication begins between the second access point and the mobile terminal.

218 citations


Book
31 Jul 2000
TL;DR: In this paper, the authors present an overview of the characteristics of mobile and personal satellite communications, including the following: 1.1.1 Mobile and Personal Satellite Communications. 2.2.1 Geometric Relations between Satellite and Earth Terminal.
Abstract: I. Basics.- 1. Introduction.- 1.1 Mobile and Personal Satellite Communications.- 1.1.1 Applications of Mobile Satellite Communications.- 1.1.2 Personal Satellite Communications.- 1.1.3 UMTS, IMT-2000.- 1.2 Broadband Multimedia Satellite Communications.- 1.3 Frequency Bands.- 1.4 Key Aspects of Satellite Communication Systems.- 2. Satellite Orbits, Constellations, and System Concepts.- 2.1 Satellite Orbits.- 2.1.1 Elliptical and Circular Orbits.- 2.1.2 Satellite Velocity and Orbit Period.- 2.1.3 Orientation of the Orbit Plane.- 2.1.4 Typical Circular Orbits.- 2.1.5 Orbit Perturbations.- 2.1.6 Ground Tracks.- 2.2 Satellite - Earth Geometry.- 2.2.1 Geometric Relations between Satellite and Earth Terminal.- 2.2.2 Coverage Area.- 2.3 Satellite Constellations.- 2.3.1 Inclined Walker Constellations.- 2.3.2 Polar Constellations.- 2.3.3 Asynchronous Polar Constellations.- 2.4 GEO System Concept.- 2.4.1 Inmarsat-3.- 2.4.2 EAST (Euro African Satellite Telecommunications).- 2.5 LEO System Concept.- 2.5.1 Globalstar.- 2.5.2 Intersatellite Links and On-Board Processing.- 2.5.3 Iridium.- 2.6 MEO System Concept.- 2.6.1 ICO.- 2.7 Satellite Launches.- 3. Signal Propagation and Link Budget.- 3.1 Satellite Link Budget.- 3.1.1 Antenna Characteristics.- 3.1.2 Free Space Loss and Received Power.- 3.1.3 Link Budget.- 3.1.4 Spot Beam Concept.- 3.2 Peculiarities of Satellite Links.- 3.2.1 Dependence on Elevation.- 3.2.2 Time Dependence of Satellite Links.- 3.2.3 Faraday Rotation.- 3.3 Signal Shadowing and Multipath Fading.- 3.3.1 Narrowband Model for the Land Mobile Satellite Channel.- 3.3.2 Satellite Channels at Higher Frequencies.- 3.3.3 Wideband Model for the Land Mobile Satellite Channel.- 3.4 Link Availability and Satellite Diversity.- 3.4.1 Concept of Satellite Diversity.- 3.4.2 Correlation of Channels.- 3.4.3 Link Availability and Satellite Diversity Service Area.- 3.5 System Implications.- 4. Signal Transmission.- 4.1 Speech Coding.- 4.1.1 Quality of Coded Speech.- 4.1.2 Overview of Speech Coding Schemes.- 4.2 Modulation.- 4.2.1 Modulation Schemes for Mobile Satellite Communications.- 4.2.2 Bandwidth Requirement of Modulated Signals.- 4.2.3 Bit Error Rate in the Gaussian Channel.- 4.2.4 Bit Error Rate in the Ricean and Rayleigh Fading Channel.- 4.3 Channel Coding (Forward Error Correction, FEC).- 4.3.1 Convolutional Coding.- 4.3.2 Block Coding.- 4.3.3 Error Protection with Cyclic Redundancy Check (CRC).- 4.3.4 RS Codes.- 4.3.5 Performance of Block Codes.- 4.3.6 Performance of Block Codes in Fading Channels.- 4.4 Automatic Repeat Request (ARQ).- 4.4.1 Stop-and-Wait ARQ.- 4.4.2 Go-Back-N ARQ.- 4.4.3 Selective-Repeat ARQ.- 4.5 Typical Error Control Schemes in Mobile Satellite Communications.- II. Satellite Systems for Mobile/Personal Communications.- 5. Multiple Access.- 5.1 Duplexing.- 5.1.1 Frequency-Division Duplexing (FDD).- 5.1.2 Time-Division Duplexing (TDD).- 5.2 Multiplexing.- 5.3 Multiple Access.- 5.4 Slotted Aloha Multiple Access.- 5.4.1 The Principle of Slotted Aloha.- 5.4.2 Throughput of Slotted Aloha.- 5.4.3 Mean Transmission Delay for Slotted Aloha.- 5.4.4 Pure Aloha Multiple Access.- 5.5 Frequency-Division Multiple Access, FDMA.- 5.5.1 Adjacent Channel Interference.- 5.5.2 Required Bandwidth for FDMA.- 5.5.3 Intermodulation.- 5.5.4 Pros and Cons of FDMA.- 5.6 Time-Division Multiple Access, TDMA.- 5.6.1 Bandwidth Demand and Efficiency of TDMA.- 5.6.2 Burst Synchronization in the Receiving Satellite.- 5.6.3 Slot Synchronization in the Transmitting TDMA Terminals.- 5.6.4 Pros and Cons of TDMA.- 5.7 Code-Division Multiple Access, CDMA.- 5.8 Direct-Sequence CDMA (DS-CDMA).- 5.8.1 Generation and Characteristics of Signature Sequences.- 5.8.2 Investigation of Asynchronous DS-CDMA in the Time Domain.- 5.8.3 Investigation of Asynchronous DS-CDMA in the Frequency Domain.- 5.8.4 Multi-Frequency CDMA, MF-CDMA.- 5.8.5 Qualcomm Return Link CDMA (Globalstar).- 5.8.6 Synchronous Orthogonal DS-CDMA with Coherent Detection.- 5.9 CDMA Receivers.- 5.9.1 PN Code Synchronization in the CDMA Receiver.- 5.9.2 Rake Receiver.- 5.9.3 CDMA Multiuser Detection.- 5.10 Characteristics of CDMA.- 5.11 CDMA for the Satellite UMTS Air Interface.- 5.11.1 The ESA Wideband CDMA Scheme.- 5.11.2 The ESA Wideband Hybrid CDMA/TDMA Scheme.- 6. Cellular Satellite Systems.- 6.1 Introduction.- 6.1.1 Concept of the Hexagonal Radio Cell Pattern.- 6.1.2 Cell Cluster and Frequency Reuse.- 6.2 Co-Channel Interference in the Uplink.- 6.2.1 Co-Channel Interference for FDMA and TDMA Uplinks.- 6.2.2 Co-Channel Interference for an Asynchronous DS-CDMA Uplink.- 6.3 Co-Channel Interference in the Downlink.- 6.3.1 Co-Channel Interference for FDMA and TDMA Downlinks.- 6.3.2 Co-Channel Interference for CDMA Downlinks.- 6.4 Bandwidth Demand and Traffic Capacity of Cellular Satellite Networks.- 6.4.1 Total System Bandwidth.- 6.4.2 Traffic Capacity per Radio Cell.- 6.4.3 Traffic Capacity of the System.- 6.4.4 Required User Link Capacity of a Satellite.- 6.4.5 Overall Network Capacity Considerations.- 7. Network Aspects.- 7.1 Architecture of Satellite Systems for Mobile/Personal Communications.- 7.2 Network Control.- 7.2.1 Tasks of Network Control.- 7.2.2 Signaling Channels of the Air Interface.- 7.3 Mobility Management.- 7.3.1 Service Area of a Gateway Station.- 7.3.2 Location Area.- 7.3.3 Registration and Location Update.- 7.4 Paging.- 7.5 Call Control.- 7.5.1 Setup of a Mobile Originating Call.- 7.5.2 Setup of a Mobile Terminating Call.- 7.6 Dynamic Channel Allocation.- 7.6.1 C/I-Based DCA.- 7.6.2 DCA Using a Cost Function.- 7.7 Handover.- 7.7.1 Handover Decision.- 7.7.2 Handover Procedure.- 7.7.3 Channel Allocation at Handover.- 7.8 Call Completion Probability.- 7.9 Routing.- 7.9.1 Routing in LEO/MEO Satellite Networks.- 7.9.2 Off-Line Dynamic ISL Routing Concept.- 7.9.3 On-line Adaptive ISL Routing.- 7.10 Integration of Terrestrial and Satellite Mobile Networks.- 8. Satellite Technology.- 8.1 Satellite Subsystems.- 8.2 Antenna Technology.- 8.2.1 GEO Antennas for Mobile Links with Spot Beams.- 8.2.2 LEO/MEO Antennas.- 8.3 Payload Architecture.- 9. Regulatory, Organizational, and Financial Aspects.- 9.1 Allocation of Frequency Bands.- 9.2 Licensing/Regulation.- 9.2.1 Granting a System License.- 9.2.2 Licensing in the USA.- 9.2.3 Licensing in Europe.- 9.2.4 Common Use of Frequency Bands by Several Systems.- 9.2.5 Global Licensing and Political Aspects.- 9.3 Financing and Marketing of S-PCN Systems.- 9.4 Operation of S-PCN Systems.- III. Satellite Systems for Broadband Multimedia Communicat ions.- 10. Multimedia Communications in Satellite Systems.- 10.1 Types of Broadband Communication Networks.- 10.1.1 Traditional Circuit-Switched Networks and the Packet-Switched Internet.- 10.1.2 New Multimedia Satellite Systems Using New Satellite Orbits.- 10.2 Multimedia Services and Traffic Characterization.- 10.2.1 Video Traffic and MPEG Coding.- 10.2.2 Self-Similar Traffic.- 10.3 ATM-Based Communication in Satellite Systems.- 10.3.1 Principles of ATM.- 10.3.2 Implications for ATM-Based Satellite Networks.- 10.4 Internet Services via Satellite Systems.- 10.4.1 Principles of TCP/IP.- 10.4.2 Internet Protocol (IP).- 10.4.3 Transport Control Protocol (TCP).- 10.4.4 TCP/IP in the Satellite Environment.- 10.4.5 IP over ATM in the Satellite Environment.- 11. ATM-Based Satellite Networks.- 11.1 System Architecture.- 11.2 Services.- 11.3 Protocol Architecture.- 11.4 ATM Resource Management.- 11.4.1 Connection Admission Control and Usage Parameter Control.- 11.4.2 Congestion Control, Traffic Shaping, and Flow Control.- 11.5 Multiple Access for ATM Satellite Systems.- 11.5.1 TDMA-Based Multiple Access.- 11.5.2 CDMA-Based Multiple Access.- 11.6 Radio Resource Management.- 11.7 Error Control.- 12. Network Dimensioning.- 12.1 Spot Beam Capacity Dimensioning for GEO Systems.- 12.1.1 Motivation and Approach.- 12.1.2 Market Prediction.- 12.1.3 Generic Multiservice Source Traffic Model.- 12.1.4 Calculation of the Spot Beam Capacity Requirements.- 12.1.5 System Bandwidth Demand Calculation.- 12.1.6 Applied Spot Beam Capacity Dimensioning: A Case Study.- 12.2 ISL Capacity Dimensioning for LEO Systems.- 12.2.1 Topological Design of the ISL Network.- 12.2.2 ISL Routing Concept.- 12.2.3 Network Dimensioning.- 12.2.4 Numerical Example.- 12.2.5 Extensions of the Dimensioning Approach.- A. Satellite Spot Beams and Map Transformations.- A.1 Map Projections and Satellite Views.- A.2 Generation of Satellite Spot Beams.- B. Parameters of the Land Mobile Satellite Channel.- B.1 Narrowband Two-State Model at L Band.- B.2 Narrowband Two-State Model at EHF Band.- B.3 Wideband Model at L Band.- C. Existing and Planned Satellite Systems.- C.1 Survey of Satellite Systems.- C.2 ACeS (Asia Cellular Satellite).- C.3 Astrolink.- C.4 EuroSkyWay.- C.5 Globalstar.- C.6 ICO (Intermediate Circular Orbits).- C.7 Inmarsat-3/Inmarsat mini-M.- C.8 Iridium.- C.9 Orbcomm.- CIO SkyBridge.- C.11 Sky Station.- C.12 Spaceway.- C.13 Teledesic.- References.

194 citations


Patent
31 Dec 2000
TL;DR: In this article, the authors propose a highly flexible base station architecture that provides extremely flexible sectorization and capacity expansion capabilities, where a base transceiver station (BTS) appliance can be interfaced with similar modules to form a higher capacity, sectorized configuration.
Abstract: A highly flexible base station architecture provides extremely flexible sectorization and capacity expansion capabilities. A base transceiver station (BTS) appliance can be interfaced with similar modules to form a higher capacity, sectorized configuration. Each BTS appliance can function as a standalone cell. In addition, multiple BTS appliances can be connected together to create a multi-sector base station in which the BTS appliances share baseband data, facilitating softer handoff. A backhaul interface module concentrates the backhaul and supports distribution and routing of packets from the network to co-located BTS appliances.

177 citations


Patent
07 Jan 2000
TL;DR: In this paper, a method and apparatus for mitigating communications interference between satellite communications systems in different orbits is disclosed, which comprises the steps of evaluating a geometrical relationship between a second ground station and the satellites in the second satellite constellation, and directing communications between the second ground-station and the second satellites according to the evaluated geometry relationship.
Abstract: A method and apparatus for mitigating communications interference between satellite communications systems in different orbits is disclosed. The method comprises the steps of evaluating a geometrical relationship between a second ground station and the satellites in the second satellite constellation, and directing communications between the second ground station and the second satellite according to the evaluated geometrical relationship. In one embodiment communications are handed over from a first satellite to another satellite when the first satellite is no longer at the highest elevation angle of visible satellites. In another embodiment, handover occurs when the first satellite drops below a minimum elevation angle.

169 citations


Patent
25 Feb 2000
TL;DR: In this paper, a method and system that enables faster acquisition of the forward link signal of a target base station in a mixed network of synchonous and asynchronous base stations is disclosed.
Abstract: A method and system that enables faster acquisition of the forward link signal of a target base station in a mixed network of synchonous and asynchronous base stations is disclosed. The serving base station transmits in a neighbor list an estimated timing error (417) between the serving base station and a target base station. By utilizing the timing information, a mobile station estimates the relative time offset (408) between forward link signals received from the serving base station and signals received from the target base station. Timing information acquired during handoff enables accurate updating of the estimated timing error (417) subsquently transmitted in the neighbor lists by the base stations.

159 citations


Patent
Justus Petersson1
18 Aug 2000
TL;DR: In this article, a quality measurement means (QMM) provided in a network control means (RNC) of a communication system (T1) monitors the transmission quality on the down link (DL) between the base transceiver station (RBS) and the subscriber station (MS).
Abstract: A quality measurement means (QMM) provided in a network control means (RNC) of a communication system (T1) monitors the transmission quality on the down link (DL) of a communication connection (CC) between the base transceiver station (RBS) and the subscriber station (MS). A network inter-frequency (IF) handover means generates a network IF measurement trigger signal (NIFTS) when the transmission quality drops under a predetermined quality measure (QoS-MS). The generated network (IF) measurement trigger signal (NIFTS) is sent to the subscriber station (MS) and an IF measurement means (IFMM) in the subscriber station (MS) starts the IF measurements in response to a receipt of the network IF measurement trigger signal (NIFTS). One example of evaluating the quality on the down link of the communication connection (CC) is to monitor the transmitted output power on the down link. Thus, the network control means (RNC) can independently generate the trigger signal without the need of measurement from the subscriber station (MS) and without an additional interference on the up link due to a transmission of such measurements and without an unnecessary reduction of the lifetime of the battery of the subscriber station (MS).

154 citations


Journal ArticleDOI
TL;DR: A call blocking criterion is imposed that ensures a system-imposed call priority independent of the traffic in the system and which adapts to changes in the offered load.
Abstract: We develop the notion of quality of service (QoS) for multimedia traffic in terms of maximum call dropping probabilities independent of system load and a predefined call blocking probability profile for the different traffic classes for wireless networks of arbitrary shape and dimension. We describe two distributed predictive admission control algorithms, independent multiclass one-step prediction (IMOSP-CS and IMOSP-RES), which provide each traffic class with a given call dropping probability and a desired call blocking probability profile. Both algorithms may be seen as extensions of the multimedia one-step prediction (MMOSPRED) algorithm previously reported, which uses prediction of the overload probability in the home and neighbor cells in deciding whether to admit new users into a multiclass cellular system. The two algorithms differ in their approach to handoff call admission. The first algorithm completely shares the bandwidth among the entering handoff users while the second implements a partition-based reservation scheme. In this paper, we additionally impose a call blocking criterion that ensures a system-imposed call priority independent of the traffic in the system and which adapts to changes in the offered load. In comparing these algorithms to each other, we focus on system throughput and class independence. Both algorithms provide appropriate throughput under both homogeneous and heterogeneous traffic loading conditions while maintaining steady call dropping probabilities for each traffic class.

Journal ArticleDOI
TL;DR: This work develops new handoff algorithms with both a negligible number of unnecessary handoffs and a negligible decision delay, using statistical pattern recognition to improve the efficiency of these algorithms.
Abstract: In wireless cellular systems, handoff algorithms decide when and to which base station to handoff. Traditional handoff algorithms generally cannot keep both the average number of unnecessary handoffs and the handoff decision delay low. They do not exploit the relative constancy of path loss and shadow fading effects at any given location around a base station. This information can in fact be used to improve the efficiency of handoff algorithms, as we do in our new handoff algorithms using statistical pattern recognition. Handoff algorithms with both a negligible number of unnecessary handoffs and a negligible decision delay can therefore be realized.

Proceedings ArticleDOI
26 Mar 2000
TL;DR: A new handoff technique is introduced which supports mobility between dissimilar networks and uses boundary cells that allow the mobile terminal to roam into a different network.
Abstract: Next-generation wireless communication is based on a global system of fixed and wireless mobile services that are transportable across different network backbones, network service providers, and network geographical boundaries. One of the most important problems for global wireless service is handoff management. In this paper, a new handoff technique is introduced which supports mobility between dissimilar networks. First, the system architecture is described, based on the concept of a boundary cell region between networks. Then a new inter-system handoff protocol is presented that uses boundary cells that allow the mobile terminal to roam into a different network. The performance of the protocol is analyzed in terms of the additional inter-system handoff signaling time and the minimum boundary cell area threshold for a successful transition within the prescribed time constraints.

Patent
Per Hans Aake Willars1
21 Mar 2000
TL;DR: In this article, a first channel is established to support a connection through a radio access network to a mobile station, and a portion of that channel is maintained for a period of time.
Abstract: Efficient channel switching procedures are provided in a mobile communications system. A first channel is established to support a connection through a radio access network to a mobile station. Subsequently, if the first channel is no longer used to support that connection, a portion of that first channel is nevertheless maintained for a period of time. That way, if the first channel is again needed to support the connection to the mobile station, the maintained portion of the first channel is simply reactivated thereby reducing channel switching costs and delays associated with channel set-up and release operations. The portion of the first channel that is maintained may be associated with resources within the radio access network. Another portion of the first channel, corresponding for example to a radio channel resource supporting the connection between the radio access network and the mobile station, may be released after the first channel is no longer being used to support the connection in order to make that radio channel resource available for other mobile connections. In one example embodiment, the first channel corresponds to a dedicated type of channel that is reserved for the connection with the mobile station, and the connection is switched to a second type of channel corresponding to a common channel that is not reserved for a particular mobile station, i.e., it is shared by plural mobile stations. In another example embodiment, the first channel is one of plural channels established between the mobile station and the radio access network in accordance with a handover operation. The invention allows the connection to be quickly and efficiently switched back from the common channel to the dedicated channel (the first example embodiment) and to a cell which previously supported the connection (in the second example embodiment).

Patent
03 Jul 2000
TL;DR: In this article, the handover of communications between fixed-infrastructure access points or other mobile Bluetooth devices formed in a scatternet is discussed. But the authors focus on the handoff of communications with a mobile Bluetooth device operable to communicate packet data with other Bluetooth devices.
Abstract: A method, and associated apparatus, facilitates handover of communications with a mobile Bluetooth device operable to communicate packet data with other Bluetooth devices. Handover of communications is effectuated between fixed-infrastructure access points or other mobile Bluetooth devices formed in a scatternet. The device to which communications are to be handed-over becomes a slave to the Bluetooth device with which communications are ongoing, thereby to permit time synchronization thereto.

Patent
21 Jan 2000
TL;DR: In this article, the authors proposed a handover protocol for a group of mobile stations having similar characteristics from a base station operating in one type of network e.g. UMTS to a base stations operating in a different type of networks (e.g., GSM, or from a first carrier frequency to a second carrier frequency both being supported by the same base station).
Abstract: A cellular communications system permits handover of a group of mobile stations (15) having like characteristics from a base station (13) operating in one type of network e.g. UMTS to a base station (16) operating in a different type of network e.g. GSM, or from a first carrier frequency to a second carrier frequency both being supported by the same base station, thereby relieving congestion in an overloaded cell by handing over a group of calls to an under-loaded one. The invention has the benefits of enabling such a handover with the minimum of signalling overhead.

Patent
Juha Back1, Tony Hulkkonen1, Kati Vainola1
03 Aug 2000
TL;DR: In this article, a method for performing an inter-system handover of a user terminal in a telecommunications network comprising a first telecommunications system operable according to a first protocol and comprising of a first service subsystem and a first access subsystem, and a second telecommunications system operating according to the second protocol, was proposed, where the user terminal storing capability data indicative of the user's capabilities for communication with the service subsystems and the access subsystems.
Abstract: A method for performing an inter-system handover of a user terminal in a telecommunications network comprising a first telecommunications system operable according to a first protocol and comprising a first service subsystem and a first access subsystem and a second telecommunications system operable according to a second protocol and comprising a second service subsystem and a second access subsystem; the user terminal storing capability data indicative of the user terminal's capabilities for communication with the service subsystems and the access subsystems.

Patent
28 Dec 2000
TL;DR: In this article, a method and apparatus for providing soft handoff in a third generation code division multiple access (CDMA) wireless communication system is presented. But the method is not suitable for the use of wireless communication devices.
Abstract: A method and apparatus for providing soft handoff in a third generation code division multiple access (CDMA) wireless communication system 34. The method comprises establishing communication between the wireless communication device 10 and the at least one serving base station 20, monitoring the reverse channel signal strength from the wireless communication device 21b, 22b, 23b, 24b, 25b, 26b from at least one neighboring base station, transmitting to a base station controller 31 the wireless communication device signal strength 21c, 22c, 23c, 24c, 25c, 26c, detected at each neighboring base station 21, 22, 23, 24, 25, 26, compiling at the base station controller 31 a list of effective neighboring base stations periodically transmitting a neighboring base station list update message 30, 32 to the wireless communication device 10, storing the effective neighboring base station list as a neighbor set in the wireless communication device 10, performing forward channel signal strength searching of the neighbor set in the wireless communication device 10 and monitoring the signals from the effective neighboring base stations to accomplish a handoff between the at least one serving base station 20 and the receiving neighboring base station 21, 22, 23, 24, 25 or 26.

Journal ArticleDOI
TL;DR: An adaptive QoS handoff priority scheme is described which reduces the probability of call handoff failures in a mobile multimedia network with a micro/picocellular architecture and exploits the ability of most multimedia traffic types to adapt and trade off QoS with changes in the amount of bandwidth used.
Abstract: For various advantages including better utilization of radio spectrum (through frequency reuse), lower mobile transmit power requirements, and smaller and cheaper base station equipment, future wireless mobile multimedia networks are likely to adopt micro/picocellular architectures. A consequence of using small cell sizes is the increased rate of call handoffs as mobiles move between cells during the holding times of calls. In a network supporting multimedia services, the increased rate of call handoffs not only increases the signaling load on the network, but makes it very difficult for the network to guarantee the quality of service (QoS) promised to a call at setup or admission time. This paper describes an adaptive QoS handoff priority scheme which reduces the probability of call handoff failures in a mobile multimedia network with a micro/picocellular architecture. The scheme exploits the ability of most multimedia traffic types to adapt and trade off QoS with changes in the amount of bandwidth used. In this way, calls can trade QoS received for fewer handoff failures. The call level and packet level performance of the handoff scheme are studied analytically for a homogeneous network supporting a mix of wide-band and narrow-band calls. Comparisons are made to the performance of the nonpriority handoff scheme and the well-known guard-channel handoff scheme.

Patent
Seo Sang Hun1, Kim Tae-Gue1, Park Tae Hun1, In-Hong Lee1, Park Sun1 
09 Aug 2000
TL;DR: In this article, a method for carrying out an idle handoff from a macrocell to a microcell (picocell) in a hierarchical cell structure includes the steps of: a) allocating different frequency assignments (FA) to the macrocell and the microcell in the same service band, to construct the hierarchical cell; b) transmitting cell structure information of neighbouring base stations and pseudo noise (PN) code from base station to mobile station; c) checking whether the mobile station is in the hierarchical cellular network by using the cell information of neighboring base station; and d
Abstract: A method for carrying out an idle handoff from a macrocell to a microcell (picocell) in a hierarchical cell structure includes the steps of: a) allocating different frequency assignments (FA) to the macrocell and the microcell in a same service band, to construct the hierarchical cell structure; b) transmitting cell structure information of neighbouring base stations and pseudo noise (PN) code from base station to mobile station; c) checking whether the mobile station is in the hierarchical cell by using the cell structure information of neighbouring base station; and d) checking whether a value of the pseudo noise (PN) code is greater than T_ADD and greater than Ec/Io of the macrocell by periodically searching the pseudo noise (PN) code of the microcell, to carrying out an idle handoff to the microcell, wherein the T_ADD represents a value of base station pilot strength required for the base station of neighbouring set to be included in a candidate set, the Ec represents a pilot energy accumulated during one pseudo noise (PN) chip period, and the Io represents a total power spectrum density within a reception bandwidth.

Patent
22 Nov 2000
TL;DR: In this article, the ratio of the load of the transmitting power on the mobile stations is controlled to suppress the communication quality difference between cells in a software handoff area, where the mobile station receives the signals from the base stations while putting them together in one and sends the SIR-Inf of the received signals to the BSs.
Abstract: PROBLEM TO BE SOLVED: To suppress the difference in speech quality between the cells in a down line when traffic and radio environment are uneven. SOLUTION: Base stations BS1 and BS2 send the same signals to a mobile station MS-A in a software handoff area. The mobile station receives the signals from the base stations while putting them together in one and sends the communication quality information SIR-Inf of the received signals to the base stations. The base station control parts 14 and 24 of the base stations BS1 and BS2 control mobile station power control parts 12 and 22 corresponding to the mobiles station in the software handoff area to suppress transmitting power if the communication quality of the downstream line becomes worse. Even when the received signal power RPt of the mobile station decreases below a prescribed value RPo and a signal PC-Inf indicating increase in the transmitting power is sent to the base stations BS1 and BS2, the base station having the deteriorated communication quality in the down line suppresses the transmitting power to the mobile station and the base station having excellent communication quality bears the transmitting power to the mobile station. The ratio of the load of the transmitting power on the mobile stations is controlled to suppress the communication quality difference between cells. COPYRIGHT: (C)2001,JPO

Patent
30 May 2000
TL;DR: In this article, a handover request with GSM-type parameters from a base station controller (BSC) through a Master Switching Center (MSC) of the GSM type network to a UTRAN core network and to a Radio Network Controller (RNC) of UMTS (Universal Mobile Telecommunications System) network, is presented.
Abstract: A method of processing a handover request from a base station controller (BSC) of a GSM (Global System for Mobile communication)-type network. The method comprises the steps of passing a handover request with GSM-type parameters from a base station controller (BSC) through a Master Switching Center (MSC) of the GSM-type network to a UMTS core network (CN) and to a Radio Network Controller (RNC) of the UMTS (Universal Mobile Telecommunications System) network, translating the GSM-type parameters to UTRAN parameters in the Radio Network Controller (RNC), and allocating UTRAN resources in response to the translated parameters.

Patent
27 Dec 2000
TL;DR: In this paper, a hand over control method and system for switching a radio base station acting as a communicating partner for mobile stations was proposed, where, when it is detected and confirmed that any one of mobile stations communicating with a radio BS becomes unable to communicate with a preset minimum band ensured, the mobile station's communicating partner is switched from the currently communicating radio BS to another radio BS.
Abstract: A hand over control method and system for switching a radio base station acting as a communicating partner for mobile stations, wherein, when it is detected and confirmed that any one of mobile stations communicating with a radio base station becomes unable to communicate with a preset minimum band ensured, the mobile station's communicating partner is switched from the currently communicating radio base station to another radio base station.

Proceedings ArticleDOI
19 Oct 2000
TL;DR: An intelligent algorithm is proposed that makes use of the user's location to simplify the procedure and results in a stable system, decreasing the signaling congestion and the call-drop probability.
Abstract: Position location of mobile terminals is expected to be one of the key services for mobile network operators in the near future. A variety of services may be offered, such as emergency-call assistance, fleet management, location-based value added services, navigation, stolen vehicle monitoring, improved network management and differential billing. Currently, network suppliers and research institutes worldwide are trying to conclude on the integration of positioning techniques, that fulfils related FCC and ETSI localization requirements, without exaggerating network costs. Furthermore, the rapidly increasing number of mobile subscribers in addition to the introduction of new circuit/packet-based data services, will cause serious traffic overload in cellular networks. Handover procedures use the signaling resources of the network and this is one of the system's parameters that has to be optimized. We propose an intelligent algorithm that makes use of the user's location to simplify the procedure and results in a stable system, decreasing the signaling congestion and the call-drop probability.

Journal ArticleDOI
TL;DR: The proposed model outperforms the existing analytical method when compared to simulation results employing all five mobility models and empirically shows that handoff traffic is a smooth process under negative exponential channel holding times.
Abstract: We present a two-moment performance analysis of cellular mobile networks with and without channel reservation. Unlike classical analysis where handoff traffic is modeled as Poisson, we characterize handoff traffic as a general traffic process and represent it using the first two moments of its offered traffic. We empirically show that handoff traffic is a smooth process under negative exponential channel holding times. We also show how one may determine customer-oriented grade-of-service parameters such as new-call blocking, handoff call blocking, and forced termination probability under the two-moment representation of traffic offered to each cell. We present extensive results validating our analysis. We compare the performance of the proposed two-moment analysis with classical single-moment analysis and simulation results. Our simulation employs five different mobility models. We show that our proposed model outperforms the existing analytical method when compared to simulation results employing all five mobility models.

Patent
23 Mar 2000
TL;DR: In this paper, the authors proposed a frame synchronization mechanism employing a downlink pilot signal, broadcasting transmitted by the base station, echoed by signature sequences transmitted by single Mobile units in the procedures foreseeing an uplink access.
Abstract: Intercell handover method in UMTS mobile systems in TDMA-SCDMA technique (and also FDMS-SDMA) with full duplexing of the TDD type. The complexity of the technique adopted requires a frame synchronization mechanism employing a downlink pilot signal, broadcasting transmitted by the base station, echoed by signature sequences transmitted by the single Mobile units in the procedures foreseeing an uplink access. The above, together with the high cipher speed (1.28 Mchip) imposed by the CDMA technique, makes inappropriate the addition of other fields to the sequence of the downlink pilot, which shall remain a pure synchronization sequence. Contrarily to the GSM, a field is missing in the synchronism burst for the transport of the system frame number FSN, absolutely necessary for the iperframe synchronism and the starting of ciphering on the channel. The information on SFN is included in the common signalling channel as other broadcasting information. This would unacceptably slow the handover and therefore a message has been created and put at disposal of the network to return the current system frame number FSN in the new cell in a dedicated mode, in reply to the HANDOVER ACCESS message sent by the Mobile (fig. 16).

Proceedings ArticleDOI
04 Jul 2000
TL;DR: A CAC which maximizes the revenue by determining the call admission decisions for each state is proposed, which outperforms the upper limit CAC while satisfying the QoS requirements.
Abstract: There is a growing interest in deploying multimedia services in mobile cellular networks. Call admission control (CAC) is a key factor in quality of service (QoS) provisioning for these services. We propose a CAC which maximizes the revenue by determining the call admission decisions for each state. A semi-Markov decision process is employed to model the cellular system. Also, the QoS requirement such as the handoff dropping probability is taken into consideration. Simulations reveal that our CAC outperforms the upper limit CAC while satisfying the QoS requirements.

Patent
18 Sep 2000
TL;DR: In this paper, a control entity determines the current or projected location of a mobile station and uses the location to identify the physical sectors and respective carrier frequencies available to serve the mobile station.
Abstract: A method and system for allocating air interface resources in a wireless telecommunications network. A control entity determines the current or projected location of a mobile station. Using the location, the control entity identifies the physical sectors and respective carrier frequencies available to serve the mobile station. The control entity then selects an optimal physical sector and respective carrier frequency and instructs the mobile station to operate in the selected physical sector using the selected carrier frequency.

Patent
06 Mar 2000
TL;DR: In this paper, a network communication system is provided for communicating a wired subnet and a wireless subnet to solve the handover problems occurred in roaming, which includes an IAPP manager program at a user level of the access point for communicating with a kernel-level device driver using system calls to perform an announce procedure and a handover procedure.
Abstract: A network communication system is provided for communicating a wired subnet and a wireless subnet to solve the handover problems occurred in roaming The system includes an IAPP manager program at a user level of the access point for communicating with a kernel-level device driver using system calls to perform an announce procedure and a handover procedure A wireless LAN card driver with a packet filter is implemented for sending signals to the IAPP manager program to perform the handover procedure upon receiving a reassociation request packet from a mobile host A wired LAN card driver is implemented for acting as an interface of the wired subnet And a bridge program with a packet filter is implemented to increase the bandwidth efficiency

Journal ArticleDOI
TL;DR: It is demonstrated here that the FIFO policy allows performance very close to that of the ideal prioritized handoff scheme and, hence, that it is a solution suitable for applications in mobile cellular networks where a high service quality is required.
Abstract: This paper deals with the performance analysis of two prioritized handoff schemes for mobile cellular networks in which handoff attempts finding all channels busy are queued for a maximum time. Fixed channel assignment is assumed. In the first prioritized handoff scheme considered, handoff attempts are queued according to the first-in-first-out (FIFO) policy. Conversely, the second scheme resorts to an ideal nonpreemptive priority queueing policy to enhance system performance. Differently from previous works, in this paper the performance analysis is carried out on the basis of a model which takes into account the event that a call may terminate when the mobile user is waiting for a handoff. Comparisons with simulation results and analytical predictions derived by means of alternative approaches highlight a better estimation accuracy for the proposed method. Moreover, it is also demonstrated here that the FIFO policy allows performance very close to that of the ideal prioritized handoff scheme and, hence, that it is a solution suitable for applications in mobile cellular networks where a high service quality is required.