WO1999044386A1 - Verification continue de stations mobiles aux fins d'operations de transfert - Google Patents

Verification continue de stations mobiles aux fins d'operations de transfert Download PDF

Info

Publication number
WO1999044386A1
WO1999044386A1 PCT/SE1999/000184 SE9900184W WO9944386A1 WO 1999044386 A1 WO1999044386 A1 WO 1999044386A1 SE 9900184 W SE9900184 W SE 9900184W WO 9944386 A1 WO9944386 A1 WO 9944386A1
Authority
WO
WIPO (PCT)
Prior art keywords
base station
handoff
mobile station
mobile
verification
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE1999/000184
Other languages
English (en)
Inventor
Tomas Lundborg
Göran Carlsson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Priority to BR9908288-8A priority Critical patent/BR9908288A/pt
Priority to CA002321304A priority patent/CA2321304A1/fr
Priority to AU27516/99A priority patent/AU2751699A/en
Publication of WO1999044386A1 publication Critical patent/WO1999044386A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength

Definitions

  • the present invention relates generally to cellular radio telecommunication systems. More specifically, the invention relates to an improved technique for performing verification of mobile stations for handoff operations.
  • a mobile switching center In a basic cellular telecommunication system, a mobile switching center (MSC) is linked to a plurality of base stations by a series of digital transmission links.
  • the base stations are geographically dispersed to form an area of coverage for the system.
  • Each base station (BS) is designated to cover a specified area, known as a cell, in which two way radio communication can take place between a mobile station (MS) and the BS in the associated cell.
  • MS mobile station
  • a handoff procedure is initiated to transfer the communication link from the present BS to the next BS in order to continue the connection. Since the handoff involves oversight from the MSC, valuable system resources are consumed for each of the many MSs requiring handoffs.
  • FIG. 1 A simplified cellular radio telecommunication system is depicted comprising an MSC and base stations BSl and
  • BSl and BS2 is represented by line 110.
  • BSl has an initial established connection with the MS within its cell.
  • a handoff to BS2 is therefore initiated when the relative signal strength associated with BS2 indicates that BS2 is deemed more suitable for continuing the connection i.e. signal strength associated with BS2 is typically stronger than that of the current connection. This condition typically occurs in the proximity of cell border 110.
  • the MSC then sends the appropriate commands over transmission links 115 to the BSs in order to execute the handoff.
  • the MSC when the MSC receives a handoff request for an MS, the MSC signals the BS targeted for handoff directing it to perform a verification in order to determine if the base station can sufficiently communicate with the MS. The MSC then waits for a confirmation signal back from the BS targeted for handoff indicating that the MS has been verified prior to proceeding with the handoff.
  • the verification is usually performed for a very short period of time and typically requires much signaling activity from the MSC. Consequently, a reduction in the involvement of the MSC during verification can significantly reduce the loading on the system.
  • Fig. 2 depicts a typical signaling sequence involved in a D-AMPS handoff operation from an originating BSl to a neighboring BS2.
  • BSl sends a handoff request DHOFFREQ to the MSC, as shown in step 200.
  • the MSC follows with a command VERIFYMS to BS2 to initiate a verification procedure to determine if the radio link between the MS and BS2 is satisfactory.
  • BS2 performs the verification procedure by tuning a receiver to receive the uplink signals the MS is currently transmitting to BSl, in which the signals are only evaluated for a very short time.
  • BS2 When the uplink signals have been received satisfactorily or if a preset time period has elapsed, BS2 sends a response MSVERIFIED to the MSC at step 210 which includes an indication of whether the verification was successful. If successful, the MSC signals BS2 with a STARTVC command (step 215) to set up a digital traffic channel (DTC), which includes setting up a frequency and timeslot for the new connection. After the DTC has been set up, BS2 signals the MSC with a VCSTARTED acknowledgment message at step 220 to notify the MSC that a traffic channel has been set up.
  • DTC digital traffic channel
  • the MSC issues a handoff order to BSl with a STARTHOFF command (step 225) which BSl then forwards to the MS (step 230).
  • the MS responds back with an acknowledgment (step 235) to BSl which terminates the connection with the MS and sends a message HANDOFFSYNC (step 240) to the MSC to confirm the release of the MS from the connection with BSl.
  • the MS tunes to the new frequency of the new traffic channel establishing a connection with BS2 in step 245.
  • BS2 signals the MSC in step 250 to confirm that the handoff was completed with a HANDOFFCONF message indicating that the communication link has been completely transferred to cell 2.
  • the invention discloses a method and apparatus for reducing the loading on a cellular telecommunication system by reducing the involvement of the mobile switching center (MSC) in recurring tasks such as the verification process for mobile station handoffs.
  • a mobile station In a cellular telecommunication system having an MSC linked to a plurality of base stations, a mobile station (MS) has an established wireless connection with a first base station (BSl).
  • BS2 second base station
  • BS2 eavesdrops on the uplink transmissions sent by the MS to BSl.
  • BS2 immediately initiates a verification procedure on the MS, prior to a handoff being initiated, and analyzes the uplink signals to determine if a satisfactory connection can be established with BS2.
  • a handoff message is relayed to BS2 via the MS in the slow associated control channel (SACCH) on the digital traffic channel (DTC).
  • SACCH slow associated control channel
  • DTC digital traffic channel
  • the present invention provides a method in which handoffs are performed with improved efficiency since the verification step will have been completed or be underway before the time the handoff occurs.
  • the verification of the mobile station is preemptive and carried out in the "background" by neighboring base stations thereby substantially reducing the participation of the MSC by eliminating several communication steps with the associated base stations.
  • the verification procedure has improved reliability since it is performed over a relatively longer period of time. This is because the verification starts well before a handoff procedure is initiated by the currently connected BS i.e. at the time when BS2 is first able to receive uplink signals from the MS.
  • Fig. 1 illustrates a mobile station handoff from one base station to a neighboring base station in a cellular telecommunication system
  • Fig. 2 depicts a signaling sequence involved in a typical prior art handoff procedure
  • Fig. 3 illustrates the verification process operating in accordance with an embodiment of the present invention.
  • Fig. 4 depicts a signaling sequence for a handoff procedure operating in accordance with the embodiment.
  • Fig. 5 illustrates an exemplary application of the continuous verification function.
  • a primary motivation of the present invention is to reduce system loading by reducing the involvement of the MSC in recurring tasks such as overseeing the verification process during handoff operations.
  • the MSC is burdened with directing the verification procedure after a handoff decision has been made involving the currently connected BS.
  • an improved method of performing verification of mobile stations (MSs) in handoff operations without substantially involving the MSC is described.
  • verification on the MS is performed by all neighboring base stations (BSs) capable of receiving signals from the MS while it is still in communication with the originating BS.
  • BSs base stations
  • those that can adequately receive signals from the MS will immediately initiate verification of the MS in anticipation of a handoff. Since a neighboring BS will likely be the target for handoff, the verification will be completed by the time the actual handoff is performed.
  • Fig. 3 illustrates the verification process utilized in a simplified two-cell radio telecommunication system operating in accordance with the exemplary embodiment.
  • An MS initially located in cell 1 is maintaining a connection with BSl i.e. transmissions of uplink 315 and downlink 320 signals are made between the MS and BSl.
  • BS2 and in addition to the primary transceivers 325, is an array of receivers 330 configured to receive signals from MSs operating in neighboring cells.
  • Receivers in the receiver array 330 are capable of listening to active frequencies of the neighboring - 7 -
  • BS2 Upon reception of the uplink signals, BS2 immediately begins a verification procedure on the MS.
  • the verification procedure typically includes signal strength measurements and the evaluation of the signal based on the measurements by, for example, determining the color code and evaluating various statistics such as the number of satisfactory measurement samples.
  • the verification of the MS by BS2 will be completed satisfactorily without requiring the involvement of the MSC.
  • the verification is effectively performed in the "background" by the neighboring base stations which are constantly monitoring MSs that are within receiving range in anticipation of a handoff.
  • Another advantage of the method is that the verification that takes place is typically performed over a relatively longer time than that performed in the prior art and thus is more reliable. It should be noted that the application of the invention to a telecommunication system comprising a large number of base stations, having equivalent equipment and capability, is readily attained and that the simplified embodiment was given for purposes of illustration.
  • Fig. 4 illustrates a typical signaling sequence for a handoff procedure operating in accordance with the exemplary embodiment.
  • the embodiment represents a signaling sequence used in a cellular system operating in accordance with the Digital Advanced Mobile Phone System (D-AMPS) standard.
  • D-AMPS Digital Advanced Mobile Phone System
  • a mobile station traveling within a cell served by an originating BSl, with which it has an established connection, towards a neighboring cell served by BS2.
  • BSl detects that the signal strength of the connection is getting weaker and determines, based on recent signal strength measurements, that a handoff to a more suitable cell served by BS2 should be undertaken.
  • BSl sends a message in a presently existing Slow Associated Control Channel (SACCH) on the digital traffic channel (DTC) to the MS to indicate that BSl wishes to initiate a handoff to BS2.
  • SACCH Slow Associated Control Channel
  • DTC digital traffic channel
  • the MS receives this message and retransmits it on the current uplink frequency, as shown in step 410.
  • the message is also received by BS2 since it is tuned to and listening to MS transmissions for verification.
  • BS2 After receiving the relayed SACCH message from BSl via the MS, BS2 sends a handoff request HOFFREQ to the MSC in step 415.
  • the handoff request includes the cell identification of BSl and associated channel information for use by the MSC.
  • the HOFFREQ indicates to the MSC that the verification has been completed satisfactorily.
  • the MSC issues a command STARTVC to BS2 to start transmitting and receiving on a specified frequency and timeslot.
  • the MSC then issues a handoff order to BSl by sending a STARTHOFF command in step 420.
  • the STARTHOFF command includes information on the new frequency and timeslot to be used.
  • BSl then sends a handoff message to direct the MS (step 425) who then responds back with a mobile acknowledgment in step 430.
  • the connection with BSl can be released and a message HANDOFFSYNC indicating same is sent to the MSC in step 435.
  • the MS retunes to the specified frequency to establish a connection with BS2 at step 440.
  • BS2 signals the MSC confirming the handoff is completed by sending a HANDOFFCONF message in step 445.
  • the communication link has been completely transferred to cell 2 at this point.
  • the MS is capable of repeating the message received on the SACCH from BSl to BS2 as illustrated in step 410.
  • the concept of utilizing the MS as a relay mechanism for transmitting information between base stations further reduces the necessity for the information to be sent from BSl to the MSC to be passed on to BS2.
  • the handoff procedure of the present invention eliminates several communication steps between the MSC and base stations as compared to the prior art handoff procedure, thereby significantly reducing the loading on the system.
  • the technique of the present invention is especially suitable for applications involving many fast occurring handoffs in a short amount of time such as fast moving traffic along highways, for example. - 9 -
  • Fig. 5 illustrates an application for continuous verification function as described.
  • An array of receivers 520 is placed in BS 515 which continuously listen to MS uplink transmissions of active frequencies of neighboring cells served by BS 505 and BS 510.
  • a receiver in the array searches the spectrum by scanning for frequencies that are being used by MSs communicating with neighbor base stations such as BS 505 and BS 510.
  • the scanning pattern may follow a succession algorithm such as, for example, round robin or any other suitable model.
  • a receiver in the array is assigned to continuously listen to that particular MS.
  • the searching for active frequencies may follow a predetermined list of neighbor frequencies.
  • the listening procedure of the receivers is relatively straightforward since the direction of oncoming traffic and the operating frequencies of the adjacent cells are known.
  • an MS traveling in either direction along a highway 500 will initially have an established connection with either BS 505 or BS 510.
  • BS 515 who is the target of the handoff, will perform the verification on the oncoming traffic as described above.
  • the handoff will be more efficiently handled since the verification step will have been completed by the time the handoff is performed to BS 515.
  • there is increased reliability of the verification because it is performed over a relatively longer period of time i.e. the verification starts at the time the MS enters into the receiving range of receivers 520 of BS 515.
  • the verification procedure can be further corroborated by detecting whether the MS is moving toward or away from BS 515 by analyzing whether the signal strength is increasing or decreasing.
  • the embodiment of the present invention not only reduces system signaling for improved efficiency but also produces much more reliable handoffs.
  • the result is a more accurate verification process that is continuous in nature and is better able to confirm the location of the correct MS.
  • Those skilled in the art will appreciate that the prior art verification procedure only measures very brief bursts of data in which the - 10 -
  • color code is analyzed in order to determine where the MS is located relative to the BS.
  • GSM Global System for Mobile Communication
  • PDC Personal Digital Cellular
  • AMPS Advanced Mobile Phone System

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé et un appareil destinés à la vérification continue d'une station mobile aux fins d'opérations de transfert dans un système de télécommunication cellulaire. Dans un mode de réalisation de l'invention, une station mobile (MS) est en radiocommunication avec une première station de base (BS1). Une deuxième station de base (BS2) reçoit les transmissions sens montant envoyées à BS1 à partir de MS dès qu'elle passe en mode réception. BS2 initie immédiatement une procédure de vérification sur la MS pour déterminer si une communication satisfaisante a été établie. L'opération de vérification est initiée par la deuxième station de base avant qu'une procédure de transfert ne soit initiée, ce qui réduit la quantité de signalisation entre le MSC et les stations de base associées. La vérification étant anticipée, elle a lieu sur un temps relativement long, ce qui entraîne une amélioration de la fiabilité de transfert.
PCT/SE1999/000184 1998-02-26 1999-02-12 Verification continue de stations mobiles aux fins d'operations de transfert Ceased WO1999044386A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BR9908288-8A BR9908288A (pt) 1998-02-26 1999-02-12 Processos de transferência da conexão de estação móvel de uma primeira estação base para uma segunda estação base e de realização de verificação sobre uma estação móvel por uma segunda estação base antes de uma transferência e sistema de telecomunicação celular
CA002321304A CA2321304A1 (fr) 1998-02-26 1999-02-12 Verification continue de stations mobiles aux fins d'operations de transfert
AU27516/99A AU2751699A (en) 1998-02-26 1999-02-12 Continuous verification of mobile stations for handoff operations

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US3093198A 1998-02-26 1998-02-26
US09/030,931 1998-02-26

Publications (1)

Publication Number Publication Date
WO1999044386A1 true WO1999044386A1 (fr) 1999-09-02

Family

ID=21856758

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1999/000184 Ceased WO1999044386A1 (fr) 1998-02-26 1999-02-12 Verification continue de stations mobiles aux fins d'operations de transfert

Country Status (5)

Country Link
AR (1) AR014662A1 (fr)
AU (1) AU2751699A (fr)
BR (1) BR9908288A (fr)
CA (1) CA2321304A1 (fr)
WO (1) WO1999044386A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001049061A1 (fr) * 1999-12-29 2001-07-05 Qualcomm Incorporated Algorithme de transfert souple ameliore et systeme de communication sans fil destines a des systemes amcr de troisieme generation
EP1871130A1 (fr) * 2006-06-20 2007-12-26 Alcatel Lucent Méthode de transfert cellulaire et station de base dans un réseau de communication radio
US20130279478A1 (en) * 2010-12-22 2013-10-24 Telefonaktiebolaget L M Ericsson (Publ) Methods and Arrangements in a Cellular Communication System
EP2491739A4 (fr) * 2009-10-22 2017-09-06 Samsung Electronics Co., Ltd. Système de communication pour détecter un terminal affecté et assurer la coordination d'interférence dans des environnements multi-cellule

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0504122A2 (fr) * 1991-03-15 1992-09-16 Telefonaktiebolaget L M Ericsson Changement de cellule assisté par les cellules voisines dans un système de communication cellulaire
WO1997031487A2 (fr) * 1996-02-23 1997-08-28 Nokia Telecommunications Oy Transfert dans un systeme de communication mobile

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0504122A2 (fr) * 1991-03-15 1992-09-16 Telefonaktiebolaget L M Ericsson Changement de cellule assisté par les cellules voisines dans un système de communication cellulaire
WO1997031487A2 (fr) * 1996-02-23 1997-08-28 Nokia Telecommunications Oy Transfert dans un systeme de communication mobile

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
NOERPEL A ET AL: "HANDOVER MANAGEMENT FOR A PCS NETWORK", IEEE PERSONAL COMMUNICATIONS, vol. 4, no. 6, December 1997 (1997-12-01), pages 18 - 24, XP000734433 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001049061A1 (fr) * 1999-12-29 2001-07-05 Qualcomm Incorporated Algorithme de transfert souple ameliore et systeme de communication sans fil destines a des systemes amcr de troisieme generation
US6430414B1 (en) 1999-12-29 2002-08-06 Qualcomm Incorporated Soft handoff algorithm and wireless communication system for third generation CDMA systems
KR100746871B1 (ko) * 1999-12-29 2007-08-07 퀄컴 인코포레이티드 제 3 세대 ｃｄｍａ 시스템들을 위한 소프트 핸드오프 알고리즘 및 무선 통신 시스템
EP1871130A1 (fr) * 2006-06-20 2007-12-26 Alcatel Lucent Méthode de transfert cellulaire et station de base dans un réseau de communication radio
WO2007147704A1 (fr) * 2006-06-20 2007-12-27 Alcatel Lucent Procédé de transfert et station de base dans un réseau de communications radio
US8755803B2 (en) 2006-06-20 2014-06-17 Alcatel Lucent Handover method and base station for a radio communication network
EP2491739A4 (fr) * 2009-10-22 2017-09-06 Samsung Electronics Co., Ltd. Système de communication pour détecter un terminal affecté et assurer la coordination d'interférence dans des environnements multi-cellule
US20130279478A1 (en) * 2010-12-22 2013-10-24 Telefonaktiebolaget L M Ericsson (Publ) Methods and Arrangements in a Cellular Communication System

Also Published As

Publication number Publication date
AU2751699A (en) 1999-09-15
AR014662A1 (es) 2001-03-28
BR9908288A (pt) 2000-10-31
CA2321304A1 (fr) 1999-09-02

Similar Documents

Publication Publication Date Title
KR100975715B1 (ko) 이동통신 시스템에서의 핸드오프 결정 방법 및 이를 지원하는 시스템
US6845238B1 (en) Inter-frequency measurement and handover for wireless communications
JP4021620B2 (ja) セルラー移動無線システムにおけるハンドオフを改善する方法およびシステム
CA2344482C (fr) Procede de transfert robuste dans un systeme de communication sans fil
CA2262926C (fr) Procede et dispositif de transfert intersysteme fiable dans un systeme amcr
US7162247B2 (en) Autonomous base station set up and soft handoff
US6438377B1 (en) Handover in a mobile communication system
EP0872152B1 (fr) Verification adaptative de presence de station mobile
US5327575A (en) Directional handover control in digital mobile radio systems employing MAHO
US6449482B1 (en) Creation of overlapping cells when using multi casting
US8787910B2 (en) Apparatus and method for terminal handover between systems using different frequency allocations
KR20060136277A (ko) 이동통신 시스템에서의 핸드오프 결정 방법
KR20160004003A (ko) 핸드오버 방법 및 그 장치
EP1750472A1 (fr) Appareil et méthode pour le transfert dans un système de communication
US8477726B2 (en) Method, system and device for mobile station handover
EP0986927B1 (fr) Relance dirigee pour etablissement de communication
WO1999044386A1 (fr) Verification continue de stations mobiles aux fins d'operations de transfert
MXPA00008278A (en) Continuous verification of mobile stations for handoff operations
KR100654374B1 (ko) 이동통신 시스템의 기지국 장치, 이동통신 시스템의 기지국에서의 비콘 신호를 이용한 데이터 송수신 방법 및 핸드오프 방법
WO2025113928A1 (fr) Mobilité déclenchée par couche 1/couche 2
KR20070060458A (ko) 휴대인터넷시스템의 핸드오버용 스캐닝 간소화 방법
GB2364854A (en) Determining necessity for handoff based on past experience of other mobiles
HK1137521A (en) Apparatus and method for wireless communications

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG UZ VN YU ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
ENP Entry into the national phase

Ref document number: 2321304

Country of ref document: CA

Ref country code: CA

Ref document number: 2321304

Kind code of ref document: A

Format of ref document f/p: F

WWE Wipo information: entry into national phase

Ref document number: PA/a/2000/008278

Country of ref document: MX

NENP Non-entry into the national phase

Ref country code: KR

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase