CA2260139A1 - Method and apparatus for inter-system handoff within a plural hyperband supporting cellular telephone network - Google Patents
Method and apparatus for inter-system handoff within a plural hyperband supporting cellular telephone network Download PDFInfo
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- CA2260139A1 CA2260139A1 CA002260139A CA2260139A CA2260139A1 CA 2260139 A1 CA2260139 A1 CA 2260139A1 CA 002260139 A CA002260139 A CA 002260139A CA 2260139 A CA2260139 A CA 2260139A CA 2260139 A1 CA2260139 A1 CA 2260139A1
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- 238000000034 method Methods 0.000 title claims description 33
- 238000005259 measurement Methods 0.000 claims abstract description 78
- 238000012795 verification Methods 0.000 claims abstract description 41
- 230000010267 cellular communication Effects 0.000 claims abstract description 15
- 238000004891 communication Methods 0.000 claims description 30
- 238000012545 processing Methods 0.000 claims description 11
- 230000011664 signaling Effects 0.000 claims 4
- 210000004027 cell Anatomy 0.000 description 141
- 230000009471 action Effects 0.000 description 16
- 230000009977 dual effect Effects 0.000 description 11
- 230000008569 process Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 5
- 230000004044 response Effects 0.000 description 3
- 238000012790 confirmation Methods 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
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- 210000000712 G cell Anatomy 0.000 description 1
- 101000861034 Homo sapiens Cytochrome c oxidase subunit 3 Proteins 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
- H04W36/144—Reselecting a network or an air interface over a different radio air interface technology
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Abstract
A cellular telephone network (10) includes plural system areas (32) each having a plurality of cells (12). The system areas do not support cellular communications in all of the same hyperbands. When a verification signal strength measurement (118, 218) is needed, a message (114, 116) is sent from a first one of the system areas to a second one of the system areas, with the message including not only an identification for measurement of the traffic channel currently being used by a mobile station, but also an identification of the hyperband within which that traffic channel exists. The report (120, 122) on the results of the requested measurement and hyperband capabilities of target cell is then sent from the second system area to the first system area. From this information, the first system area may confirm (124, 224) that the measurement was made or was attempted in the proper hyperband and thus determine whether the second system would be able to support mobile station operation with respect to hyperband in the event of an inter-system hand off.
Description
METHOD AND APPARATUS FOR INTER-SYSTEM
HANDOFF WITHIN A PLURAL HYPERBAND SUPPORTING
CELLULAR TELEPHONE NETVVORK
Technical Field of the Invention The present invention relates to cellular telephone networks and, in particular,to inter-system handoff of mobile stations in connection with a plural hyperbandsupporting cellular telephone network.
0 Description of Related Art North American cellular communications have historically been implemented solely in the 800 MHZ Cellular hyperband. The Cellular hyperband is assigned twofrequency bands (commonly l~Çelled to as the A frequency band and the B frequency band) for carrying and controlling communications. The most recent evolution in cellular cl mm.~nications services involves the adoption of three additional hyperbands for use in h~ndling mobile and personal communications. Of these additional hyperbands, only the Personal Communication Services (PCS) hyperband in the 1900MHZ frequency range has been completely defined. The PCS hyperband is specified to include six dirre-e~-L frequency bands (A, B, C, D, E and F).
HANDOFF WITHIN A PLURAL HYPERBAND SUPPORTING
CELLULAR TELEPHONE NETVVORK
Technical Field of the Invention The present invention relates to cellular telephone networks and, in particular,to inter-system handoff of mobile stations in connection with a plural hyperbandsupporting cellular telephone network.
0 Description of Related Art North American cellular communications have historically been implemented solely in the 800 MHZ Cellular hyperband. The Cellular hyperband is assigned twofrequency bands (commonly l~Çelled to as the A frequency band and the B frequency band) for carrying and controlling communications. The most recent evolution in cellular cl mm.~nications services involves the adoption of three additional hyperbands for use in h~ndling mobile and personal communications. Of these additional hyperbands, only the Personal Communication Services (PCS) hyperband in the 1900MHZ frequency range has been completely defined. The PCS hyperband is specified to include six dirre-e~-L frequency bands (A, B, C, D, E and F).
2 o Each one of frequency bands specified for the Cellular and PCS hyperbands is allocated a plurality of voice or speech (traffic) channels, as well as access or control channel(s). The control ch~nn~lc are used to control or supervise the operation of mobile stations by means of information transmitted to and received from the mobile stations. Such information may include incoming call signals, outgoing call signals, page signals, page response signals, location registration signals, voice channel ~c~i~...,.~..l.~, m~int.,n~nce instructions, and cell selection or reselection instructions as a mobile station travels out of the radio coverage of one cell and into the radio coverage of another cell. The traffic channels are used to carry subscriber telephonic communications as well as messages requesting mobile station ~si~t~nce in making3 o hand-off evaluations and controlling the hand-off operation. The control and traffic r.h~nnr.l~ may operate in either an analog mode, a digital mode, or a combination mode.
As the cellular telephone network has been upgraded to accommodate the newly made available hyperbands, inst~nc~s have arisen where one cellular system area does not support the same hyperbands as its adjacent cellular system area. Thus, for ex~mp'e, a first cellular system area may support cellular operations in both the Cellular 5 and PCS hyperbands, while an adjacent, second cellular system area incon~ictently supports cellular operations only in the Cellular hyperband. This presents a communications problem when mobile stations roam between the two service areas, as it may become necessary for a mobile station to switch between the hyperbands as well as switch traffic çh~nnçl~ at the point of hand-off Furthermore, of perhaps even 10 more concern with respect to communications is that the included verification process, wherein signal strength measurements are made from the target cell on the traffic channel currently being used by the mobile station, may be improperly pe~ 1~1 Illed or the results may be erroneous if the service area does not support the hyperband within which the mobile station is currently operating. Accordingly, there is a need then for 15 a system and method for supporting inter-system hand-off, and in particular the included verification process, wherein the system and method accounts for differences and inconsistencies between system supported hyperbands.
SUMMARY OF THE INVENTION
In a cellular telephone network inrlllrline plural system areas having inconsistent 2 o hyperband support, a message sent from a first one of the system areas to a second one ofthe system areas requ~stine the making of a verification signal strength measurement includes not only an identification of the traffic channel currently being used by a mobile station, but also an identification of the hyperband within which that traffic channel exists. Responsive thereto, a measurement is made, if possible, from the2 5 second system area in the identified hyperband on the traffic channel currently being used by the mobile station. A report on the results of the requested verification measurement is then sent from the second system area to the first system area for further processing. This report preferably includes an indication of the hyperband within which the verification measurement, if any, was made. From the report, the first 3 o system area can confirm the hyperband capabilities of the second system area, and thus deterrnine whether the second system area would support mobile station operation in the event of an inter-system hand-off.
In co~ ;on with the hand-offofthe mobile station from the first system area to the second system area, the first system area requests from the second system area the ~c!~;g~ of a traffic channel. Responsive to that request, the second system area selects a traffic channel within a supported hyperband and reports on the selected ch~nnel, as well as the hyperband within which that selected trafflc channel exists, to the first system area. From that report, the first system area can confirm the hyperband capabilities of the second system area, and thus determine whether the second system 0 area would support mobile station operation in the event of an inter-system hand-off BRIEF DESCR~PTION OF THE DRAWINGS
A more complete unders~n~in~ of the method and a~palal~ls of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:
FIGURE 1 is a cell diagram illustrating an exemplary cell configuration for a plural hyperband sul)po~ ~;..g cellular telephone network in which the present invention may be implem~nterl;
FIGURES 2A-2B are signal flow and network operation diagrams illustrating operation of the network of FIGIJRE 1 in connection with a verification-type hand-off 2 0 of a mobile station from a cell within a first system area to a cell within a second system area; and FIGURES 3A-3B are signal flow and network operation diagrams illustrating operation of the network of FIGURE 1 in connection with a blind-type hand-off of a mobile station from a cell within a first system area to a cell within a second system 2 5 area.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is now made to FIGURE I wherein there is shown a cell diagram illustrating an exemplary cell configuration for a plural hyperband supporting cellular telephone network l0 in which the present invention may be implemented. The cellular telephone network 10 operates in accordance with one of a number of known air interface types in~ ng~ for example, a digital time division multiple access (TDMA) protocol. In a digital TDMA cellular telephone network, for example, each cell 12 operates with an ~csigned set of tr~n~mi~eion frequencies selected from one or more 5 of the available hyperbands. The set of frequencies assigned to each cell 12 includes frequencies supporting both at least one control channel and a plurality of traffic channels, with the control and traffic channels operable in either or both an analog and/or a digital mode. Sets of ~signed frequencies are di~lenl for adjacent cells 12, and such sets are not repeated for use by other cells except for those cells that are far 0 enough away from each other to minimi7e the likelihood of adjacent or co-channel interference.
In the network 10, a base station 14 is provided for each of the cells 12. The base stations 14 engage in sim~llt~neous comm-~niC~tions with plural mobile stations 16 operating roughly within the area of the associated cell 12. The control channel15 a~signPd to each cell 12 is used to carry system control signals between the base station 14 and proximately located mobile stations 16, and also to assist in the network with mobile station cell reselection. Such control signals include call originations, page signals, page ~ onse signals, location l~g,~Ll~lion signals, traffic channel ~ nmPnts, m~int~n~nce instructions, and cell selection or re-selection instructions. The traffic 20 channels provided in each cell 12 are used to carry subscriber voice or data communications between the base station 14 and proximately located mobile stations 16 and also to assist in the hand-offoperation.
The base stations 14 are illustrated as being positioned at or near the center of each ofthe cells 12. However, depending on geography and other known factors, the 2 5 base stations 14 may instead be located at or near the periphery of, or otherwise away from the centers of, each of the cells 12. In such instances, the base stations 14 may broadcast and communicate with mobile stations 16 located within the cells 12 using directional rather than omni-directional ~nt~nn~c. Each one of the base stations 14 in~ dec a ~ Pr, a receiver, and a base station controller (none shown) connected 3 0 to an antenna (also not shown) in a manner and with a configuration well known in the art.
The base stations 14 further communicate via sign~lin~ links and voice trunks 22 with a central control station, co.. ~ ly referred to as a mobile switching center 18, which functions to control operation of the network 10. The mobile switching centers 18 are interconnected with each other and to the public switched telephone networl~
(PSTN) 20 by ~ign~ling links and voice trunks 24. The mobile switching centers 18 operate to selectively connect subscriber voice and data communications to the mobile stations 16 through its base stations 14. Thus, the mobile switching center 18 controls system operation through and in response to the tr~n~mi~sion of control signals over the control cl,~; ~n~lc to set-up on the traffic ch~nnels calls that are either ori~in~ted by or termin~ted at the mobile stations 16. The mobile switching center 18 further controls, through and in response to control and traffic channel tr~nemi~sions, the handoffofa subscriber comm~.nir~tion from a traffic channel of one cell 12 to a traffic channel of another cell as the subscriber mobile station 16 roams throughout thecellular service area during an ongoing communication.
It is common within one overall cellular service area to have a plurality of system areas 32 (differenti~ted from each other by the fact that they have different system identifications (SIDs) and perhaps have different service providers). A
boundary 34, passing between cells 12 along the border between two system areas 32, is shown in bold in FIGURE 1 to delimit the physical extent of each of the illustrated 2 o system areas. In this illustrated example, it will be noted that the cells 12 within two system areas 32 are served by dirrelellt mobile switching centers 18.
North American cellular communications have historically been implemented solely in the 800 MHZ Cellular hyperband. The most recent evolution in cellular comml.- tion~ services involves the adoption of three additional hyperbands for use 2 5 in h~n~ling mobile and personal cnmm--nications. Of these additional hyperbands, only the Personal Communication Services (PCS) hyperband in the 1900 MHZ frequency range has been completely defined. In the network 10 illustrated in FIGVRE 1, mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband. The mobile switching center 3 C 18(2) for system area 32(2), however, supports mobile station 16 operation only in the -r CA 02260139 l999-01-ll Cellular hyperband. Thus, there exists in the network 10 inconsistent hyperband support between the plurality of system areas 32.
There are a number of mobile stations 16 shown operating within the service area of the network 10. These mobile stations 16 may comprise Cellular hyperbandonly capable mobile stations, PCS hyperband only capable mobile stations, or dual frequency (Cellular and PCS hyperband) capable mobile stations. With respect to the Cellular hyperband only capable mobile stations, they may operate in an analog mode only or in a dual (analog and digital) mode. With respect to the PCS hyperband only capable mobile stations, they operate in a digital mode only. Finally, with respect to o the dual frequency (Cellular and PCS hyperband) capable mobile stations, they may operate in a digital mode only or in a dual (analog and digital) mode. It will, of course, be understood that Cellular hyperband only capable mobile stations may operate within the cells 12 of both system areas 32(1) and 32(2) of FIGURE 1 using any of the traffic or control channel frequçnci~s ofthe Cellular hyperband. PCS hyperband only capable mobile stations, however, may operate within the cells 12 of system area 32(1) using any of the traffc or control channel frequencies of PCS hyperband. Dual frequency (Cellular and PCS hyperband) capable mobile stations may operate within the cells 12 of both system areas 32(1) and 32(2), and use traffic or control channel frequencies of both the Cellular and PCS hyperbands while in system area 32(1), but may only use 2 o traffic or control channel frequencies of the Cellular hyperband while within system area 32(2).
As the mobile stations 16 move within the service area of the network 10, there will be ;..~ çs where a mobile station will pass between two cells 12 within a single system area 32, or from one cell in a first system area 32(1) to another cell in a second system area 32(2). In moving between the cells 12, the mobile stations 16, in conjunction with base station 14 information and orders exchanged with and between the mobile switching centers 18, have an opportunity through hand-offto change the base station through which cellular radio communications are being effectl.~ted For example, mobile station 16(1) is shown moving in the direction of arrow 26 from system area 32(1) into system area 32(2). Because the network 10 supports pluralhyperbands and in~l~ldçs single and multiple hyperband supporting system areas 32, by .
CA 02260139 l999-01-ll moving between cells and cl~ gil~g base stations as a result thereof, the mobile stations ] 6 may not only change the traffic or control channel frequency used for communication, but may further change the hyperband over which communications are being effectll~ted. It is important in such instances of inter-system hand-off that the 5 mobile switching centers 18 be informed not only of the hyperband within whichcommunications are being effected in the currently serving cell, but also of thehyperband capabilities for communication within the target cell.
Reference is now made in combination to FIGU~ES 1 and 2A-2B wherein FIGU3~ES 2A-2B are signal flow and network operation diagram illustrating operation 0 of the network I 0 of FIGURE 1 in connection with a verification-type hand-off of a mobile station 16(1) from a cell 12(1) within a first system area 32(1) to a cell 12(2) within a second system area 32(2). In this instance, the mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband, while the mobile switching center 18(2) for system area 32(2) supports mobile station 16 operation in the Cellular hyperband only. The mobile station 16(1), operating if capable in accordance with known mobile assisted hand-off (MAHO) principles, periodically makes downlink signal strength measul t~lllt;ll~S 100 on the traffic channel (of cell 12(1)) that is currently being used, and also periodically makes downlink signal strength measurements 102 on the control2 o channels of network identified cells 12, including cell 12(2), which neighbor the cell 12(1). These signal strength measurements are reported 104 to the base station 14(1) for the currently serving cell 12(1). The base station 14(1) concurrently makes uplink signal strength measuleme..ls 106 on the traffic channel that is currently being used by the mobile station 16(1).
2 5 The base station 14(1) processes the mobile station 16(1) reported 104 downlink signal strength measu~ (100 and 102), if available, and the base station made uplink signal strength measurements (106) to determine first whether a hand-off is necec~ry (action 108) and second, if yes, to which cell or cells the hand-offcould and/or should preferably occur (action 110). In this example, it is assumed that the 3 o base station 14(1) determines 108 from deteriorating measured uplink and/or downlink signal strengths that a hand-offis necessaly. It is further assumed that an identification 110 is made of cell 12(2) in system area 32(2) as the prerel- ed target cell for hand-off.
A request 112 for hand-off inclu.ling information comprising an identification of the currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time s}ot (for a digital traffic channel) carrying the cellular communication, and the target cell 12(2) for hand-off, is then sent by the base station 14(1) to the serving mobile switching center 18(1). A hand-offif approved in this instance would comprise an inter-system hand-offbecause the target cell 12(2) is served by a mobile switching center 18(2) (serving system area 32(2)) di~elel.~ from the mobile swieching o center 18(1) serving the current cell 12(1) (serving system area 32(1)). The foregoing description is only an example of the procedure used in making the detel lnillaLion to in~titllte a hand-off.
The currently serving mobile switching center 18(1) then signals 114 the mobile switching center 18(2) associated with the target cell 12(2) requesting verification of base station 14(2) comm~lnic~tions capability with the mobile station 16(1). The signal 114, like the request 112 sent by the base station 14(1), includes information COIII~ ing an id~ntifi~ ~tion ofthe currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, the target cell 12(2) for hand-off, and the hyperband capabilities of the mobile station. Responsive thereto, the mobile switching center 18(2) signals 116 the base station 14(2) for the target cell 12(2) to make a verifying signal strength measurement (action 118) on the traffic channel currently being used by the mobile station 16(1) in the currently serving cell 12(1). This measurement 2 5 should take into account the hyperband within which that traffic channel exists, and perhaps, if l~ecess~y, the time slot (for a digital traffic channel) carrying the cellular communication.
The base station 14(2) then reports 120 the results of the verification signal strength measurement to the mobile switching center 18(2), which then forwards 122 the results back to the mobile switching center 18(1). This report 120 not only identifies whether the verification signal strength measurement was successful, but also CA 02260139 l999-01-ll identifies the particular hyperband within which the verification measurement, if any, was made, along with an identification of the hyperband capabilities of the cell. The results are then processed (action 124) by the mobile switching center 18(]) to determine whether a hand-off to target cell 12(2) should be made. This determination takes into account not only the success and strength of the verification measurement, but also the hyperband capabilities of both the mobile station 16(1) and the target cell 12(2). If the deterrnin~tion is ~ a~ e, the mobile switching center 18(1) signals 126 the mobile switching center 18(2) requesting assignment (and reservation) of a traffic channel (and time slot therein for a digital traffic channel) for hand-off to the target cell 0 12(2). Both the base station 14(2) and mobile switching center 18(1) are then informed 128 ofthe ~c~ignment by the mobile switching center 18(2) ofthe traffic channel (and hyperband within which that traffic channel exists) in the target cell 12(2). The mobile switching center 18(1) then confirms (action 130) the propriety ofthe assigned traffic channel and hyperband in view of mobile station 16(1) communications capabilities, and signals 132 the mobile station 16(1) via the base station 14(1) for the currently serving cell 12(1) with a handover command directing the mobile station to switch to the ~igned traffic channel (and time slot therein if âppl Opl iate) in the target cell 12(2) .
The mobile station 16(1) then tunes to and ~cc~s~es 134 the assigned traffic channel (in the proper time slot). When the base station 14(2) detects the mobile station access 2 o (action 136), the mobile switching centers 18(1) and 18(2) are informed 138, and the call is switched 140 to the mobile switching center 18(2) for further handling to complete the hand-off procedure.
The operation ofthe network 10 in connection with the verification-type hand-off procedure illustrated in FIGURE 2 may be better understood by reference to the following examples.
In a first example, the mobile station 16(1) comprises a PCS hyperband only capable mobile station which operates only in digital mode, and is currently utili7.ing digital traffic channel number 1 of cell 12(1) in the PCS hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) and determines that a hand-offis necessary 108.
The base station 14(1) further determines that cell 12(1), among perhaps other WO 98/03031 PCT/SE97/0~246 neighboring cells 12, co.l.p.ises a c~ntlid~te target cell for that hand-of~. The base station 14(1) then requests 112 a hand-offfrom the mobile switching center 18(1).
This request inf.hldçs an identification of not only traffic channel number 1, but also that traffic channel number 1 is within the PCS hyperband. This is important because the Cellular hyperband may also include a traffic channel number 1, and absent an identification of the hyperband, the traffic channel number identification provided may be ambiguous with respect to a system area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strengtho measurement (action 118) within the PCS hyperband on the traffic channel number 1 currently being used by the mobile station 16(1). Because the service area 32(2)supports cellular operations in the Cellular hyperband only, the base station 14(2) cannot make the requested verification signal strength measurement in the PCS
hyperband. Accordingly, the base station 14(2) may report 120 and 122 that it cannot make the requested verification signal strength measurement. Alternatively, the base station 14(2) may mistakenly make the verification signal sllen~ measurement on traffic channel number l of the Cellular hyperband, and the report 120 and 122 will include an indication that the measurement was made (albeit improperly) in the Cellular hyperband. In either case, the processing 124 ofthe report confirms the Cellular only 20 hyperband capabilities oftarget cell 12(2), and determines that a hand-offto target cell 12(2) is not possible with respect to PCS hyperband mobile station 16(1). That cell is then discarded as a viable target cell for hand-off. Accordingly, for PCS hyperband only capable mobile station 16(1)~ no attempt is made to hand-offto a cell in a service area 32(2) that supports only Cellular hyperband operations.
2 5 In a second example, the mobile station 16(1) comprises a Cellular hyperband only capable mobile station which operates in either an analog only mode or a dual analog/digital mode, and is currently utilizing traffic channel number 2 in the Cellular hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100~ 102 and/or 106) and determines that a 3 0 hand-off is neces~ry 108. The base station 14(1) further determines that cell 12(1), among perhaps other neighboring cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a hand-off from the mobile switching center 18(1). This request includes an identification of not only traffic channel number 2, but also that traffic channel number 2 iS within the Cellular hyperband. This is important because the PCS hyperband may also include a traffic 5 channel number 2, and absent an identification of the hyperband, the traffic channel idçntifiç~tion provided may be ambiguous with respect to a system area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strengtho measurement (action 118) within the Cellular hyperband on the traffic channel number 2 currently being used by the mobile station 16(1). Because the service area 32(2) supports cellular operations in the Cellular hyperband only, the base station 14(2) should be capable of making the requested verification signal strength measurement in the Cellular hyperband. The measurement may then be made but be ~lncl~cces~fill,15 it~ ;"g iml~ffici~nt signal strength for mobile station 16(1) communication with base station 14(2). The measurement may also fail to be made. perhaps because the base station 14(2) iS not functioning properly Alternatively, the measurement may be made and be sllcces~fi~l, indicating sufficient signal strength for mobile station 16(1) commlmic~tiQn with base station 14(2). In any of the foregoing cases, the report 120 and 122 from the base station 14(2) includes an indication conr.. ,l-g that a Cellular hyperband measurement was to be made.
If the measurement is made and is successful, or if the measurement fails to be made, the processing 124 confirms the Cellular only hyperband capabilities of target cell 12(2), and may then result in the selection and approval of the target cell 12(2) for hand-of~: The mobile switching center 18(2) iS then cign~led 126 to request ~ignment (and reservation) of a traffic channel for hand-off to the target cell 12(2). In order to maximize the chances of a succç.s~ful hand-off~ the assigned traffic channel typically comprises an analog traffic channel within the Cellular hyperband. Following confirmation 130 ofthe selected channel. a handover command 132 is broadcast to the mobile station 16(1) via the base station 14(1). The ~e~igned traffic channel is then accessed 134 by the mobile station 16(1), and the call is switched 140 to the mobile CA 02260l39 l999-Ol-ll switching center 18(2) for further h~ntlline to complete the hand-off procedure.Alternatively, if the measurement is made but is unsuccessful (indicating insufficient signal strength), the processing 124 again confirms the Cellular only hyperband capabilities oftarget cell 12(2), and d~te~ nes that a hand-off is not possible. That cell 5 12(2) is then discarded as a viable target cell for hand-off, and no attempt is made to hand-offto that cell.
In a third example, the mobile station 16(1) comprises a dual frequency (Cellular and PCS hyperband) capable mobile station which operates in either a digital only mode or a dual analog/digital mode, and is currently utili7:ine traffic channel 0 number 3 in the Cellular hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) and determines that a hand-off is necess~ry 108. The base station 14(1) further determines that cell 12(1), among perhaps other neighboring cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a 15 hand-off from the mobile switching center 18(1). This request includes an id~ntifil~tion of not only trafiic channel number 3, but also that traffic channel number 3 is within the Cellular hyperband. This is important because the PCS hyperband may also include a traffic channel number 3, and absent an identification of the hyperband, the traffic channel identification provided may be ambiguous with respect to a system 2 o area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) pelrol.,l a verifying signai strength measurement (action 118) within the Cellular hyperband on the traffic channel number 3 currently being used by the mobile station 16(1). Because the service area 32(2) 25 supports cellular operations in the Cellular hyperband only, the base station 14(2) should be capable of making the reqllested verification signal strength measurement in the Cellular hyperband. The measurement may then be made but be unsuccessfi~l, in-lir.~tine in~llffi~ie.nt signal strength for mobile station 16(1) communication with base station 14(2). The measurement may also fail to be made, perhaps because the base 3 0 station 14(2) is not functioning properly. Alternatively, the measurement may be made and be succes~fill~ indicating sufficient signal strength for mobile station 16(1) comm~lniç~tion with base station 14(2). In any ofthe foregoing cases, the report 120 and 122 from the base station 14(2) includes an indication co~lr~lllling that a Cellular hyperband measurement was to be made.
If the measurement is made and is succes.~ful, or if the measurement fails to bemade, the proces~ing 124 confirms the Cellular only hyperband capabilities of target cell 12(2) and may then result in the selection and approval of the target cell 12(2) for hand-of~ The mobile switching center 18(2) is then signaled 126 to request a.csi~nmçnt (and reservation) of a traffic channel for hand-off to the target cell 12(2). In order to maximize the chances of a s~lccessful hand-off, the ~c~igned traffic channel typically 0 comprises an analog traffic channel in the Cellular hyperband. No change in the hyperband being used by the mobile station 16(1) is necessary. Following conr~""~tion 130 ofthe selected channel, a handover command 132 is then broadcast to the mobile station 16(1) via the base station 14(1). The assigned traffic channel is then acce.csed 134 by the mobile station 16(1), and the call is switched 140 to the mobile switching center 18(2) for further h~ndling to complete the hand-off procedure. Alternatively, if the measurement is made but is unsuccessful (indicating insufficient signal strength), the processing 124 again COIlr~ S the Cellular only hyperband capabilities of target cell 12(2), and determines that a hand-o~is not possible. That cell 12(2) is then discarded as a viable target cell for hand-off, and no attempt is made to hand-offto that cell.
In a fourth example, the mobile station 16(1) comprises a dual frequency (Cellular and PCS hyperband) capable mobile station which operates in either an analog only mode or a dual analog/digital mode~ and is currently utili7.ing traffic channel number 4 in the PCS hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) anddetermines that a hand-offis n~cç~ y 108. The base station 14(1) further determines that cell 12(1), among perhaps other neigl-bo~"~g cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a hand-offfrom the mobile switching center 18(1). This request in~illdP,s an identification of not only traffic channel number 4, but also that traffic channel number 4 is within the PCS hyperband.
3 o This is important because the Cellular hyperband may also include a traffic channel -T . ~.
CA 02260139 l999-01-ll WO 98/03031 PCT/SE97tO1246 number 4, and absent an identification of the hyperband, the traffic channel identification provided may be ambiguous.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strength5 measurement (action 118) within the PCS hyperband on the traffic channel number 4 currently being used by the mobile station 16(1). Because the service area 32(2)supports cellular operations in the Cellular hyperband only, the base station 14(2) cannot make the requested verification signal strength measurement in the PCS
hyperband. Accordingly, the base station 14(2) may report 120 and 122 that it cannot o make the requested verification signal strength measurement. Alternatively, the base station 14(2) may mistakenly make the verification signal strength measurement on traffic channel number 4 of the Cellular hyperband, and the report 120 and 122 will include an indication that the measurement was made (albeit improperly) in the Cellular hyperband. In either case, the processing 124 of the report confirms the Cellular only 5 hyperband capabilities oftarget cell 12(2), and accordingly may result in a discarding of cell 12(2) as a viable target cell for hand-off Alternatively, the cell 12(2) may be retained as the best available option for hand-offin spite ofthe inability to make a verification signal strength measurement on traffic channel number 4 of the PCS hyperband. This is because the mobile station 20 16(1) is dual frequency (Cellular and PCS hyperband) capable. Through processing 124, the target cell 12(2) is then selected and approved for hand-off. The signal 126 is then sent to mobile switching center 18(2) to request ~.cignment (and reservation) of a traffic channel for hand-offto the target cell 12(2). In order to maximize the chances of a successful hand-off, the assigned traffic channel typically comprises an 2 5 analog traffic channel in the Cellular hyperband. Following confirmation 130 of the s~lected channel, a handover CO~ n(l 132 is broadcast to the mobile station 16(1) via the base station 14(1). A hyperband change from PCS to Cellular is effect~l~ted. and the assigned traffic channel is ~ccç~sed 134 by the mobile station 16(1). The call is then switched 140 to the mobile switching center 18(2) for further handling to complete the 3 0 hand-off procedure.
Reference is now made in combination to FIGURES I and 3A-3B wherein FIGURES 3A-3B and signal flow and network operation diagrams illustrating operation of the network of FIGI~RE I in connection with a blind-type hand-off of a mobile station 16(1) from a cell 12(1) within a first system area 32(1) to a cell 12(2) within a second system area 32(2). The blind-type hand-off differs from the verification-type hand-off of FIGURES 2A-2B, as will be seen, primarily with respect to the point in time at which the verification signal strength measurement is made.
The mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband, while the 0 mobile switching center 18(2) for system area 32(2) supports mobile station 16 operation in the Cellular hyperband only. The mobile station 16(1), operating inaccordance with known mobile assisted hand-off (MAHO) principles, periodically makes downlink signal strength measule~ 200 on the traffic channel (of cell 12(1)) that is currently being used, and also periodically makes downlink signal strength measu,e,l,t;.,ls 202 on the control t~ nn~l~ of network identified cells 12, including cell 12(2), which nei~llbol the cell 12(1). These signal strength measurements are reported 204 to the base station 14(1) for the currently serving cell 12(1). The base station 14(1) concurrently makes uplink signal strength measurements 206 on the traffic channel that is currently being used by the mobile station 16(1).
The base station 14(1) processes the mobile station 16(1) reported 204 downlink signal strength measu,~",e"l~ (200 and 202), if available. and the base station made uplink signal strength measurements (206) to determine first whether a hand-off is necP.c~.y (action 208), and second, if yes, to which cell or cells the hand-off should pl~ bly occur (action 210). In this example, it is assumed that the base station 14(1) 2 5 determines 208 from deteriorating measured uplink and downlink signal strengths that a hand-offis l-~cç~,y. It is further a~s.lmed that an identification 210 is made of cell 12(2) in system area 32(2) as the target cell for hand-off. A request 212 for hand-off inr.lutling i"Çul,.,alion comprising an identification ofthe currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 3 o 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, and the target cell 12(2) for hand-off, is then sent by the base station 14(1) to the serving mobile switching center 18(1).
A hand-off if approved in this in~t~nce would comprise an inter-system hand-off because the target cell 12(2) is served by a mobile switching center 18(2) (serving system area 32(2)) dilI~relll from the mobile switching center 18(1) serving the current cell 12(1) (serving system area 32(1)). The roregoh~g description is only an example of the procedure used in making the determination to institute a hand-off.
The currently serving mobile switching center 18(1) then signals 214 the mobile switching center 18(2) associated with the target cell 12(2) requesting ~Csignment (and reservation) of a traffic channel (and time slot therein for a digital trafflc channel) for o hand-offto the target cell 12(2). The signal 214, like the re~uest 212 sent by the base station 14(1), includes i~ ion cO.ll~Jl;s.llg an identification of the currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, the target cell 12(2) for hand-off, and the hyperband capabililies of the mobile station. Responsive thereto. the mobile switching center 18(2) signals 216 the base station 14(2) for the target cell 12(2) to make a verifying signal ~ n~ measurement (action 218) on the traffic channel currently being used by the mobile station 16(1) in the currently serving cell 12(1). This measurement should take into account the hyperband within which thattraffic channel exists, and perhaps, if necessary, the time slot (for a digital traffic channel) carrying the cellular communication. The base station 14(2) then reports 220 the results of the verification signal strength measurement to the mobile switching center 18(2). If the verification was S~lCCe~fill, both the base station 14(2) and mobile switching center 18(1) are then inro,l"ed 222 ofthe ~.cignmP.nt by the mobile switching center 18(2) of the traffic channel (and hyperband within which that traffic channel exists) in the target cell 12(2). This differs from the process of FIGURE~ 2A-2Bwhere verifi~.~tion was pe.r~llned prior to requesting ac~ignmPnt of the traffic channel.
The mobile switching center 18(2) then forwards 226 the results of the verific~tion and ~;g~.,..l,..l back to the mobile switching center 18(1). This report 226 3 o not only identifies whether the verification signal strength measurement was successful, but also ide.ntifiPc the particular hyperband within which the measurement, if any, was .. . .
CA 02260139 l999-01-ll made, along with an idPntific~tion of the hyperband capabilities of the cell. The results are then processed (action 228) by the mobi}e switching center 18(1) to determine whether a hand-offto target cell 12(2) should be made. This detel -l.ina~ion takes into account not only the success and strength of the verification measurement, but also the hyperband c~p~hi'itie.c of both the mobile station 16(1) and the target cell 12(2). If the determination is alllll.la~ e, the mobile switching center 18(1) then confirms (action 230) the proprietary of the ~.csigned channel and hyperband in view of mobile station 16(1) comm~mic~tionc r~p~hilitiec and signals 232 the mobile station 16(1) via the base station 14(1) for the currently serving cell 12(1) with a handover con~ dlld directing the mobile station to switch to the assigned traffic channel (and time slot therein if appropriate) in the target cell 12(2). The mobile station 16(1) then tunes to and ~ccesses 234 the assigned traffic channel (in the proper time slot). When the base station 14(2) detects the mobile station access (action 236), the mobile switching centers 18(1) and 18(2) are informed 238, and the call is switched 240 to the mobile switching center 18(2) for further h~n~lling to complete the hand-offprocedure.
The operation of the networlc 10 in connection with the blind-type hand-off procedure illustrated in FIGURES 3A-3B may be better understood by reference again to the examples discussed above with respect to FIGIJRES 2A-2B. The primary difference with respect to FIGURES 2A-2B and its examples comprises the point in2 o time at which the mobile switching center 18(1) requests that base station 14(2) for the target cell 12(2) perform verifying signal strength measurement within the design~ted hyperband on the decien~ted traffic channel currently being used by the mobile station 16(1). In FIGURES 3A-3B with respect to each of those four examples, the verification signal strength measurement is not made until after the request for25 a~;g~"~l of a traffic channel in the target cell 12(2) has been made. Otherwise, the hand-offprocess and results remain the same.
Although pl~--ed embodiments ofthe method and apparatus ofthe present invention have been illustrated in the accompanying Drawings and described in the roregoing Detailed Description, it will be understood that the invention is not limited 3 0 to the embodiments disclosed, but is capable of numerous rearrangements, , . .
modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
As the cellular telephone network has been upgraded to accommodate the newly made available hyperbands, inst~nc~s have arisen where one cellular system area does not support the same hyperbands as its adjacent cellular system area. Thus, for ex~mp'e, a first cellular system area may support cellular operations in both the Cellular 5 and PCS hyperbands, while an adjacent, second cellular system area incon~ictently supports cellular operations only in the Cellular hyperband. This presents a communications problem when mobile stations roam between the two service areas, as it may become necessary for a mobile station to switch between the hyperbands as well as switch traffic çh~nnçl~ at the point of hand-off Furthermore, of perhaps even 10 more concern with respect to communications is that the included verification process, wherein signal strength measurements are made from the target cell on the traffic channel currently being used by the mobile station, may be improperly pe~ 1~1 Illed or the results may be erroneous if the service area does not support the hyperband within which the mobile station is currently operating. Accordingly, there is a need then for 15 a system and method for supporting inter-system hand-off, and in particular the included verification process, wherein the system and method accounts for differences and inconsistencies between system supported hyperbands.
SUMMARY OF THE INVENTION
In a cellular telephone network inrlllrline plural system areas having inconsistent 2 o hyperband support, a message sent from a first one of the system areas to a second one ofthe system areas requ~stine the making of a verification signal strength measurement includes not only an identification of the traffic channel currently being used by a mobile station, but also an identification of the hyperband within which that traffic channel exists. Responsive thereto, a measurement is made, if possible, from the2 5 second system area in the identified hyperband on the traffic channel currently being used by the mobile station. A report on the results of the requested verification measurement is then sent from the second system area to the first system area for further processing. This report preferably includes an indication of the hyperband within which the verification measurement, if any, was made. From the report, the first 3 o system area can confirm the hyperband capabilities of the second system area, and thus deterrnine whether the second system area would support mobile station operation in the event of an inter-system hand-off.
In co~ ;on with the hand-offofthe mobile station from the first system area to the second system area, the first system area requests from the second system area the ~c!~;g~ of a traffic channel. Responsive to that request, the second system area selects a traffic channel within a supported hyperband and reports on the selected ch~nnel, as well as the hyperband within which that selected trafflc channel exists, to the first system area. From that report, the first system area can confirm the hyperband capabilities of the second system area, and thus determine whether the second system 0 area would support mobile station operation in the event of an inter-system hand-off BRIEF DESCR~PTION OF THE DRAWINGS
A more complete unders~n~in~ of the method and a~palal~ls of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:
FIGURE 1 is a cell diagram illustrating an exemplary cell configuration for a plural hyperband sul)po~ ~;..g cellular telephone network in which the present invention may be implem~nterl;
FIGURES 2A-2B are signal flow and network operation diagrams illustrating operation of the network of FIGIJRE 1 in connection with a verification-type hand-off 2 0 of a mobile station from a cell within a first system area to a cell within a second system area; and FIGURES 3A-3B are signal flow and network operation diagrams illustrating operation of the network of FIGURE 1 in connection with a blind-type hand-off of a mobile station from a cell within a first system area to a cell within a second system 2 5 area.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is now made to FIGURE I wherein there is shown a cell diagram illustrating an exemplary cell configuration for a plural hyperband supporting cellular telephone network l0 in which the present invention may be implemented. The cellular telephone network 10 operates in accordance with one of a number of known air interface types in~ ng~ for example, a digital time division multiple access (TDMA) protocol. In a digital TDMA cellular telephone network, for example, each cell 12 operates with an ~csigned set of tr~n~mi~eion frequencies selected from one or more 5 of the available hyperbands. The set of frequencies assigned to each cell 12 includes frequencies supporting both at least one control channel and a plurality of traffic channels, with the control and traffic channels operable in either or both an analog and/or a digital mode. Sets of ~signed frequencies are di~lenl for adjacent cells 12, and such sets are not repeated for use by other cells except for those cells that are far 0 enough away from each other to minimi7e the likelihood of adjacent or co-channel interference.
In the network 10, a base station 14 is provided for each of the cells 12. The base stations 14 engage in sim~llt~neous comm-~niC~tions with plural mobile stations 16 operating roughly within the area of the associated cell 12. The control channel15 a~signPd to each cell 12 is used to carry system control signals between the base station 14 and proximately located mobile stations 16, and also to assist in the network with mobile station cell reselection. Such control signals include call originations, page signals, page ~ onse signals, location l~g,~Ll~lion signals, traffic channel ~ nmPnts, m~int~n~nce instructions, and cell selection or re-selection instructions. The traffic 20 channels provided in each cell 12 are used to carry subscriber voice or data communications between the base station 14 and proximately located mobile stations 16 and also to assist in the hand-offoperation.
The base stations 14 are illustrated as being positioned at or near the center of each ofthe cells 12. However, depending on geography and other known factors, the 2 5 base stations 14 may instead be located at or near the periphery of, or otherwise away from the centers of, each of the cells 12. In such instances, the base stations 14 may broadcast and communicate with mobile stations 16 located within the cells 12 using directional rather than omni-directional ~nt~nn~c. Each one of the base stations 14 in~ dec a ~ Pr, a receiver, and a base station controller (none shown) connected 3 0 to an antenna (also not shown) in a manner and with a configuration well known in the art.
The base stations 14 further communicate via sign~lin~ links and voice trunks 22 with a central control station, co.. ~ ly referred to as a mobile switching center 18, which functions to control operation of the network 10. The mobile switching centers 18 are interconnected with each other and to the public switched telephone networl~
(PSTN) 20 by ~ign~ling links and voice trunks 24. The mobile switching centers 18 operate to selectively connect subscriber voice and data communications to the mobile stations 16 through its base stations 14. Thus, the mobile switching center 18 controls system operation through and in response to the tr~n~mi~sion of control signals over the control cl,~; ~n~lc to set-up on the traffic ch~nnels calls that are either ori~in~ted by or termin~ted at the mobile stations 16. The mobile switching center 18 further controls, through and in response to control and traffic channel tr~nemi~sions, the handoffofa subscriber comm~.nir~tion from a traffic channel of one cell 12 to a traffic channel of another cell as the subscriber mobile station 16 roams throughout thecellular service area during an ongoing communication.
It is common within one overall cellular service area to have a plurality of system areas 32 (differenti~ted from each other by the fact that they have different system identifications (SIDs) and perhaps have different service providers). A
boundary 34, passing between cells 12 along the border between two system areas 32, is shown in bold in FIGURE 1 to delimit the physical extent of each of the illustrated 2 o system areas. In this illustrated example, it will be noted that the cells 12 within two system areas 32 are served by dirrelellt mobile switching centers 18.
North American cellular communications have historically been implemented solely in the 800 MHZ Cellular hyperband. The most recent evolution in cellular comml.- tion~ services involves the adoption of three additional hyperbands for use 2 5 in h~n~ling mobile and personal cnmm--nications. Of these additional hyperbands, only the Personal Communication Services (PCS) hyperband in the 1900 MHZ frequency range has been completely defined. In the network 10 illustrated in FIGVRE 1, mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband. The mobile switching center 3 C 18(2) for system area 32(2), however, supports mobile station 16 operation only in the -r CA 02260139 l999-01-ll Cellular hyperband. Thus, there exists in the network 10 inconsistent hyperband support between the plurality of system areas 32.
There are a number of mobile stations 16 shown operating within the service area of the network 10. These mobile stations 16 may comprise Cellular hyperbandonly capable mobile stations, PCS hyperband only capable mobile stations, or dual frequency (Cellular and PCS hyperband) capable mobile stations. With respect to the Cellular hyperband only capable mobile stations, they may operate in an analog mode only or in a dual (analog and digital) mode. With respect to the PCS hyperband only capable mobile stations, they operate in a digital mode only. Finally, with respect to o the dual frequency (Cellular and PCS hyperband) capable mobile stations, they may operate in a digital mode only or in a dual (analog and digital) mode. It will, of course, be understood that Cellular hyperband only capable mobile stations may operate within the cells 12 of both system areas 32(1) and 32(2) of FIGURE 1 using any of the traffic or control channel frequçnci~s ofthe Cellular hyperband. PCS hyperband only capable mobile stations, however, may operate within the cells 12 of system area 32(1) using any of the traffc or control channel frequencies of PCS hyperband. Dual frequency (Cellular and PCS hyperband) capable mobile stations may operate within the cells 12 of both system areas 32(1) and 32(2), and use traffic or control channel frequencies of both the Cellular and PCS hyperbands while in system area 32(1), but may only use 2 o traffic or control channel frequencies of the Cellular hyperband while within system area 32(2).
As the mobile stations 16 move within the service area of the network 10, there will be ;..~ çs where a mobile station will pass between two cells 12 within a single system area 32, or from one cell in a first system area 32(1) to another cell in a second system area 32(2). In moving between the cells 12, the mobile stations 16, in conjunction with base station 14 information and orders exchanged with and between the mobile switching centers 18, have an opportunity through hand-offto change the base station through which cellular radio communications are being effectl.~ted For example, mobile station 16(1) is shown moving in the direction of arrow 26 from system area 32(1) into system area 32(2). Because the network 10 supports pluralhyperbands and in~l~ldçs single and multiple hyperband supporting system areas 32, by .
CA 02260139 l999-01-ll moving between cells and cl~ gil~g base stations as a result thereof, the mobile stations ] 6 may not only change the traffic or control channel frequency used for communication, but may further change the hyperband over which communications are being effectll~ted. It is important in such instances of inter-system hand-off that the 5 mobile switching centers 18 be informed not only of the hyperband within whichcommunications are being effected in the currently serving cell, but also of thehyperband capabilities for communication within the target cell.
Reference is now made in combination to FIGU~ES 1 and 2A-2B wherein FIGU3~ES 2A-2B are signal flow and network operation diagram illustrating operation 0 of the network I 0 of FIGURE 1 in connection with a verification-type hand-off of a mobile station 16(1) from a cell 12(1) within a first system area 32(1) to a cell 12(2) within a second system area 32(2). In this instance, the mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband, while the mobile switching center 18(2) for system area 32(2) supports mobile station 16 operation in the Cellular hyperband only. The mobile station 16(1), operating if capable in accordance with known mobile assisted hand-off (MAHO) principles, periodically makes downlink signal strength measul t~lllt;ll~S 100 on the traffic channel (of cell 12(1)) that is currently being used, and also periodically makes downlink signal strength measurements 102 on the control2 o channels of network identified cells 12, including cell 12(2), which neighbor the cell 12(1). These signal strength measurements are reported 104 to the base station 14(1) for the currently serving cell 12(1). The base station 14(1) concurrently makes uplink signal strength measuleme..ls 106 on the traffic channel that is currently being used by the mobile station 16(1).
2 5 The base station 14(1) processes the mobile station 16(1) reported 104 downlink signal strength measu~ (100 and 102), if available, and the base station made uplink signal strength measurements (106) to determine first whether a hand-off is necec~ry (action 108) and second, if yes, to which cell or cells the hand-offcould and/or should preferably occur (action 110). In this example, it is assumed that the 3 o base station 14(1) determines 108 from deteriorating measured uplink and/or downlink signal strengths that a hand-offis necessaly. It is further assumed that an identification 110 is made of cell 12(2) in system area 32(2) as the prerel- ed target cell for hand-off.
A request 112 for hand-off inclu.ling information comprising an identification of the currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time s}ot (for a digital traffic channel) carrying the cellular communication, and the target cell 12(2) for hand-off, is then sent by the base station 14(1) to the serving mobile switching center 18(1). A hand-offif approved in this instance would comprise an inter-system hand-offbecause the target cell 12(2) is served by a mobile switching center 18(2) (serving system area 32(2)) di~elel.~ from the mobile swieching o center 18(1) serving the current cell 12(1) (serving system area 32(1)). The foregoing description is only an example of the procedure used in making the detel lnillaLion to in~titllte a hand-off.
The currently serving mobile switching center 18(1) then signals 114 the mobile switching center 18(2) associated with the target cell 12(2) requesting verification of base station 14(2) comm~lnic~tions capability with the mobile station 16(1). The signal 114, like the request 112 sent by the base station 14(1), includes information COIII~ ing an id~ntifi~ ~tion ofthe currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, the target cell 12(2) for hand-off, and the hyperband capabilities of the mobile station. Responsive thereto, the mobile switching center 18(2) signals 116 the base station 14(2) for the target cell 12(2) to make a verifying signal strength measurement (action 118) on the traffic channel currently being used by the mobile station 16(1) in the currently serving cell 12(1). This measurement 2 5 should take into account the hyperband within which that traffic channel exists, and perhaps, if l~ecess~y, the time slot (for a digital traffic channel) carrying the cellular communication.
The base station 14(2) then reports 120 the results of the verification signal strength measurement to the mobile switching center 18(2), which then forwards 122 the results back to the mobile switching center 18(1). This report 120 not only identifies whether the verification signal strength measurement was successful, but also CA 02260139 l999-01-ll identifies the particular hyperband within which the verification measurement, if any, was made, along with an identification of the hyperband capabilities of the cell. The results are then processed (action 124) by the mobile switching center 18(]) to determine whether a hand-off to target cell 12(2) should be made. This determination takes into account not only the success and strength of the verification measurement, but also the hyperband capabilities of both the mobile station 16(1) and the target cell 12(2). If the deterrnin~tion is ~ a~ e, the mobile switching center 18(1) signals 126 the mobile switching center 18(2) requesting assignment (and reservation) of a traffic channel (and time slot therein for a digital traffic channel) for hand-off to the target cell 0 12(2). Both the base station 14(2) and mobile switching center 18(1) are then informed 128 ofthe ~c~ignment by the mobile switching center 18(2) ofthe traffic channel (and hyperband within which that traffic channel exists) in the target cell 12(2). The mobile switching center 18(1) then confirms (action 130) the propriety ofthe assigned traffic channel and hyperband in view of mobile station 16(1) communications capabilities, and signals 132 the mobile station 16(1) via the base station 14(1) for the currently serving cell 12(1) with a handover command directing the mobile station to switch to the ~igned traffic channel (and time slot therein if âppl Opl iate) in the target cell 12(2) .
The mobile station 16(1) then tunes to and ~cc~s~es 134 the assigned traffic channel (in the proper time slot). When the base station 14(2) detects the mobile station access 2 o (action 136), the mobile switching centers 18(1) and 18(2) are informed 138, and the call is switched 140 to the mobile switching center 18(2) for further handling to complete the hand-off procedure.
The operation ofthe network 10 in connection with the verification-type hand-off procedure illustrated in FIGURE 2 may be better understood by reference to the following examples.
In a first example, the mobile station 16(1) comprises a PCS hyperband only capable mobile station which operates only in digital mode, and is currently utili7.ing digital traffic channel number 1 of cell 12(1) in the PCS hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) and determines that a hand-offis necessary 108.
The base station 14(1) further determines that cell 12(1), among perhaps other WO 98/03031 PCT/SE97/0~246 neighboring cells 12, co.l.p.ises a c~ntlid~te target cell for that hand-of~. The base station 14(1) then requests 112 a hand-offfrom the mobile switching center 18(1).
This request inf.hldçs an identification of not only traffic channel number 1, but also that traffic channel number 1 is within the PCS hyperband. This is important because the Cellular hyperband may also include a traffic channel number 1, and absent an identification of the hyperband, the traffic channel number identification provided may be ambiguous with respect to a system area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strengtho measurement (action 118) within the PCS hyperband on the traffic channel number 1 currently being used by the mobile station 16(1). Because the service area 32(2)supports cellular operations in the Cellular hyperband only, the base station 14(2) cannot make the requested verification signal strength measurement in the PCS
hyperband. Accordingly, the base station 14(2) may report 120 and 122 that it cannot make the requested verification signal strength measurement. Alternatively, the base station 14(2) may mistakenly make the verification signal sllen~ measurement on traffic channel number l of the Cellular hyperband, and the report 120 and 122 will include an indication that the measurement was made (albeit improperly) in the Cellular hyperband. In either case, the processing 124 ofthe report confirms the Cellular only 20 hyperband capabilities oftarget cell 12(2), and determines that a hand-offto target cell 12(2) is not possible with respect to PCS hyperband mobile station 16(1). That cell is then discarded as a viable target cell for hand-off. Accordingly, for PCS hyperband only capable mobile station 16(1)~ no attempt is made to hand-offto a cell in a service area 32(2) that supports only Cellular hyperband operations.
2 5 In a second example, the mobile station 16(1) comprises a Cellular hyperband only capable mobile station which operates in either an analog only mode or a dual analog/digital mode, and is currently utilizing traffic channel number 2 in the Cellular hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100~ 102 and/or 106) and determines that a 3 0 hand-off is neces~ry 108. The base station 14(1) further determines that cell 12(1), among perhaps other neighboring cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a hand-off from the mobile switching center 18(1). This request includes an identification of not only traffic channel number 2, but also that traffic channel number 2 iS within the Cellular hyperband. This is important because the PCS hyperband may also include a traffic 5 channel number 2, and absent an identification of the hyperband, the traffic channel idçntifiç~tion provided may be ambiguous with respect to a system area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strengtho measurement (action 118) within the Cellular hyperband on the traffic channel number 2 currently being used by the mobile station 16(1). Because the service area 32(2) supports cellular operations in the Cellular hyperband only, the base station 14(2) should be capable of making the requested verification signal strength measurement in the Cellular hyperband. The measurement may then be made but be ~lncl~cces~fill,15 it~ ;"g iml~ffici~nt signal strength for mobile station 16(1) communication with base station 14(2). The measurement may also fail to be made. perhaps because the base station 14(2) iS not functioning properly Alternatively, the measurement may be made and be sllcces~fi~l, indicating sufficient signal strength for mobile station 16(1) commlmic~tiQn with base station 14(2). In any of the foregoing cases, the report 120 and 122 from the base station 14(2) includes an indication conr.. ,l-g that a Cellular hyperband measurement was to be made.
If the measurement is made and is successful, or if the measurement fails to be made, the processing 124 confirms the Cellular only hyperband capabilities of target cell 12(2), and may then result in the selection and approval of the target cell 12(2) for hand-of~: The mobile switching center 18(2) iS then cign~led 126 to request ~ignment (and reservation) of a traffic channel for hand-off to the target cell 12(2). In order to maximize the chances of a succç.s~ful hand-off~ the assigned traffic channel typically comprises an analog traffic channel within the Cellular hyperband. Following confirmation 130 ofthe selected channel. a handover command 132 is broadcast to the mobile station 16(1) via the base station 14(1). The ~e~igned traffic channel is then accessed 134 by the mobile station 16(1), and the call is switched 140 to the mobile CA 02260l39 l999-Ol-ll switching center 18(2) for further h~ntlline to complete the hand-off procedure.Alternatively, if the measurement is made but is unsuccessful (indicating insufficient signal strength), the processing 124 again confirms the Cellular only hyperband capabilities oftarget cell 12(2), and d~te~ nes that a hand-off is not possible. That cell 5 12(2) is then discarded as a viable target cell for hand-off, and no attempt is made to hand-offto that cell.
In a third example, the mobile station 16(1) comprises a dual frequency (Cellular and PCS hyperband) capable mobile station which operates in either a digital only mode or a dual analog/digital mode, and is currently utili7:ine traffic channel 0 number 3 in the Cellular hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) and determines that a hand-off is necess~ry 108. The base station 14(1) further determines that cell 12(1), among perhaps other neighboring cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a 15 hand-off from the mobile switching center 18(1). This request includes an id~ntifil~tion of not only trafiic channel number 3, but also that traffic channel number 3 is within the Cellular hyperband. This is important because the PCS hyperband may also include a traffic channel number 3, and absent an identification of the hyperband, the traffic channel identification provided may be ambiguous with respect to a system 2 o area 32 supporting plural hyperbands.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) pelrol.,l a verifying signai strength measurement (action 118) within the Cellular hyperband on the traffic channel number 3 currently being used by the mobile station 16(1). Because the service area 32(2) 25 supports cellular operations in the Cellular hyperband only, the base station 14(2) should be capable of making the reqllested verification signal strength measurement in the Cellular hyperband. The measurement may then be made but be unsuccessfi~l, in-lir.~tine in~llffi~ie.nt signal strength for mobile station 16(1) communication with base station 14(2). The measurement may also fail to be made, perhaps because the base 3 0 station 14(2) is not functioning properly. Alternatively, the measurement may be made and be succes~fill~ indicating sufficient signal strength for mobile station 16(1) comm~lniç~tion with base station 14(2). In any ofthe foregoing cases, the report 120 and 122 from the base station 14(2) includes an indication co~lr~lllling that a Cellular hyperband measurement was to be made.
If the measurement is made and is succes.~ful, or if the measurement fails to bemade, the proces~ing 124 confirms the Cellular only hyperband capabilities of target cell 12(2) and may then result in the selection and approval of the target cell 12(2) for hand-of~ The mobile switching center 18(2) is then signaled 126 to request a.csi~nmçnt (and reservation) of a traffic channel for hand-off to the target cell 12(2). In order to maximize the chances of a s~lccessful hand-off, the ~c~igned traffic channel typically 0 comprises an analog traffic channel in the Cellular hyperband. No change in the hyperband being used by the mobile station 16(1) is necessary. Following conr~""~tion 130 ofthe selected channel, a handover command 132 is then broadcast to the mobile station 16(1) via the base station 14(1). The assigned traffic channel is then acce.csed 134 by the mobile station 16(1), and the call is switched 140 to the mobile switching center 18(2) for further h~ndling to complete the hand-off procedure. Alternatively, if the measurement is made but is unsuccessful (indicating insufficient signal strength), the processing 124 again COIlr~ S the Cellular only hyperband capabilities of target cell 12(2), and determines that a hand-o~is not possible. That cell 12(2) is then discarded as a viable target cell for hand-off, and no attempt is made to hand-offto that cell.
In a fourth example, the mobile station 16(1) comprises a dual frequency (Cellular and PCS hyperband) capable mobile station which operates in either an analog only mode or a dual analog/digital mode~ and is currently utili7.ing traffic channel number 4 in the PCS hyperband. As the mobile station 16(1) moves, the base station 14(1) processes available signal strength measurements (100, 102 and/or 106) anddetermines that a hand-offis n~cç~ y 108. The base station 14(1) further determines that cell 12(1), among perhaps other neigl-bo~"~g cells 12, comprises a candidate target cell for that hand-off. The base station 14(1) then requests 112 a hand-offfrom the mobile switching center 18(1). This request in~illdP,s an identification of not only traffic channel number 4, but also that traffic channel number 4 is within the PCS hyperband.
3 o This is important because the Cellular hyperband may also include a traffic channel -T . ~.
CA 02260139 l999-01-ll WO 98/03031 PCT/SE97tO1246 number 4, and absent an identification of the hyperband, the traffic channel identification provided may be ambiguous.
The mobile switching center 18(1) then requests (with signals 114 and 116) that base station 14(2) for the target cell 12(2) perform a verifying signal strength5 measurement (action 118) within the PCS hyperband on the traffic channel number 4 currently being used by the mobile station 16(1). Because the service area 32(2)supports cellular operations in the Cellular hyperband only, the base station 14(2) cannot make the requested verification signal strength measurement in the PCS
hyperband. Accordingly, the base station 14(2) may report 120 and 122 that it cannot o make the requested verification signal strength measurement. Alternatively, the base station 14(2) may mistakenly make the verification signal strength measurement on traffic channel number 4 of the Cellular hyperband, and the report 120 and 122 will include an indication that the measurement was made (albeit improperly) in the Cellular hyperband. In either case, the processing 124 of the report confirms the Cellular only 5 hyperband capabilities oftarget cell 12(2), and accordingly may result in a discarding of cell 12(2) as a viable target cell for hand-off Alternatively, the cell 12(2) may be retained as the best available option for hand-offin spite ofthe inability to make a verification signal strength measurement on traffic channel number 4 of the PCS hyperband. This is because the mobile station 20 16(1) is dual frequency (Cellular and PCS hyperband) capable. Through processing 124, the target cell 12(2) is then selected and approved for hand-off. The signal 126 is then sent to mobile switching center 18(2) to request ~.cignment (and reservation) of a traffic channel for hand-offto the target cell 12(2). In order to maximize the chances of a successful hand-off, the assigned traffic channel typically comprises an 2 5 analog traffic channel in the Cellular hyperband. Following confirmation 130 of the s~lected channel, a handover CO~ n(l 132 is broadcast to the mobile station 16(1) via the base station 14(1). A hyperband change from PCS to Cellular is effect~l~ted. and the assigned traffic channel is ~ccç~sed 134 by the mobile station 16(1). The call is then switched 140 to the mobile switching center 18(2) for further handling to complete the 3 0 hand-off procedure.
Reference is now made in combination to FIGURES I and 3A-3B wherein FIGURES 3A-3B and signal flow and network operation diagrams illustrating operation of the network of FIGI~RE I in connection with a blind-type hand-off of a mobile station 16(1) from a cell 12(1) within a first system area 32(1) to a cell 12(2) within a second system area 32(2). The blind-type hand-off differs from the verification-type hand-off of FIGURES 2A-2B, as will be seen, primarily with respect to the point in time at which the verification signal strength measurement is made.
The mobile switching center 18(1) for system area 32(1) supports mobile station 16 operation in both the Cellular hyperband and the PCS hyperband, while the 0 mobile switching center 18(2) for system area 32(2) supports mobile station 16 operation in the Cellular hyperband only. The mobile station 16(1), operating inaccordance with known mobile assisted hand-off (MAHO) principles, periodically makes downlink signal strength measule~ 200 on the traffic channel (of cell 12(1)) that is currently being used, and also periodically makes downlink signal strength measu,e,l,t;.,ls 202 on the control t~ nn~l~ of network identified cells 12, including cell 12(2), which nei~llbol the cell 12(1). These signal strength measurements are reported 204 to the base station 14(1) for the currently serving cell 12(1). The base station 14(1) concurrently makes uplink signal strength measurements 206 on the traffic channel that is currently being used by the mobile station 16(1).
The base station 14(1) processes the mobile station 16(1) reported 204 downlink signal strength measu,~",e"l~ (200 and 202), if available. and the base station made uplink signal strength measurements (206) to determine first whether a hand-off is necP.c~.y (action 208), and second, if yes, to which cell or cells the hand-off should pl~ bly occur (action 210). In this example, it is assumed that the base station 14(1) 2 5 determines 208 from deteriorating measured uplink and downlink signal strengths that a hand-offis l-~cç~,y. It is further a~s.lmed that an identification 210 is made of cell 12(2) in system area 32(2) as the target cell for hand-off. A request 212 for hand-off inr.lutling i"Çul,.,alion comprising an identification ofthe currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 3 o 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, and the target cell 12(2) for hand-off, is then sent by the base station 14(1) to the serving mobile switching center 18(1).
A hand-off if approved in this in~t~nce would comprise an inter-system hand-off because the target cell 12(2) is served by a mobile switching center 18(2) (serving system area 32(2)) dilI~relll from the mobile switching center 18(1) serving the current cell 12(1) (serving system area 32(1)). The roregoh~g description is only an example of the procedure used in making the determination to institute a hand-off.
The currently serving mobile switching center 18(1) then signals 214 the mobile switching center 18(2) associated with the target cell 12(2) requesting ~Csignment (and reservation) of a traffic channel (and time slot therein for a digital trafflc channel) for o hand-offto the target cell 12(2). The signal 214, like the re~uest 212 sent by the base station 14(1), includes i~ ion cO.ll~Jl;s.llg an identification of the currently serving cell 12(1), the traffic channel being used for communication with mobile station 16(1) in cell 12(1), the hyperband within which that traffic channel exists, the time slot (for a digital traffic channel) carrying the cellular communication, the target cell 12(2) for hand-off, and the hyperband capabililies of the mobile station. Responsive thereto. the mobile switching center 18(2) signals 216 the base station 14(2) for the target cell 12(2) to make a verifying signal ~ n~ measurement (action 218) on the traffic channel currently being used by the mobile station 16(1) in the currently serving cell 12(1). This measurement should take into account the hyperband within which thattraffic channel exists, and perhaps, if necessary, the time slot (for a digital traffic channel) carrying the cellular communication. The base station 14(2) then reports 220 the results of the verification signal strength measurement to the mobile switching center 18(2). If the verification was S~lCCe~fill, both the base station 14(2) and mobile switching center 18(1) are then inro,l"ed 222 ofthe ~.cignmP.nt by the mobile switching center 18(2) of the traffic channel (and hyperband within which that traffic channel exists) in the target cell 12(2). This differs from the process of FIGURE~ 2A-2Bwhere verifi~.~tion was pe.r~llned prior to requesting ac~ignmPnt of the traffic channel.
The mobile switching center 18(2) then forwards 226 the results of the verific~tion and ~;g~.,..l,..l back to the mobile switching center 18(1). This report 226 3 o not only identifies whether the verification signal strength measurement was successful, but also ide.ntifiPc the particular hyperband within which the measurement, if any, was .. . .
CA 02260139 l999-01-ll made, along with an idPntific~tion of the hyperband capabilities of the cell. The results are then processed (action 228) by the mobi}e switching center 18(1) to determine whether a hand-offto target cell 12(2) should be made. This detel -l.ina~ion takes into account not only the success and strength of the verification measurement, but also the hyperband c~p~hi'itie.c of both the mobile station 16(1) and the target cell 12(2). If the determination is alllll.la~ e, the mobile switching center 18(1) then confirms (action 230) the proprietary of the ~.csigned channel and hyperband in view of mobile station 16(1) comm~mic~tionc r~p~hilitiec and signals 232 the mobile station 16(1) via the base station 14(1) for the currently serving cell 12(1) with a handover con~ dlld directing the mobile station to switch to the assigned traffic channel (and time slot therein if appropriate) in the target cell 12(2). The mobile station 16(1) then tunes to and ~ccesses 234 the assigned traffic channel (in the proper time slot). When the base station 14(2) detects the mobile station access (action 236), the mobile switching centers 18(1) and 18(2) are informed 238, and the call is switched 240 to the mobile switching center 18(2) for further h~n~lling to complete the hand-offprocedure.
The operation of the networlc 10 in connection with the blind-type hand-off procedure illustrated in FIGURES 3A-3B may be better understood by reference again to the examples discussed above with respect to FIGIJRES 2A-2B. The primary difference with respect to FIGURES 2A-2B and its examples comprises the point in2 o time at which the mobile switching center 18(1) requests that base station 14(2) for the target cell 12(2) perform verifying signal strength measurement within the design~ted hyperband on the decien~ted traffic channel currently being used by the mobile station 16(1). In FIGURES 3A-3B with respect to each of those four examples, the verification signal strength measurement is not made until after the request for25 a~;g~"~l of a traffic channel in the target cell 12(2) has been made. Otherwise, the hand-offprocess and results remain the same.
Although pl~--ed embodiments ofthe method and apparatus ofthe present invention have been illustrated in the accompanying Drawings and described in the roregoing Detailed Description, it will be understood that the invention is not limited 3 0 to the embodiments disclosed, but is capable of numerous rearrangements, , . .
modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
Claims (15)
1. A cellular telephone network, comprising:
a first system area having a plurality of cells including a first cell, the first system area supporting cellular communications on traffic channels in both a first and a second hyperband;
a second system area having a plurality of cells including a second cell, the second system area supporting cellular communications on traffic channels in the first hyperband but not the second hyperband;
a mobile station moving through the network from the first cell into the second cell and engaged in a cellular communication on a traffic channel of either the first or second hyperbands; and means for signaling from the first system area to the second system area of a request for the second system area to perform a verification signal strength measurement on the traffic channel being used by the mobile station, the requestincluding an identification of the traffic channel being used as well as an identification of the first or second hyperband within which that traffic channel exists.
a first system area having a plurality of cells including a first cell, the first system area supporting cellular communications on traffic channels in both a first and a second hyperband;
a second system area having a plurality of cells including a second cell, the second system area supporting cellular communications on traffic channels in the first hyperband but not the second hyperband;
a mobile station moving through the network from the first cell into the second cell and engaged in a cellular communication on a traffic channel of either the first or second hyperbands; and means for signaling from the first system area to the second system area of a request for the second system area to perform a verification signal strength measurement on the traffic channel being used by the mobile station, the requestincluding an identification of the traffic channel being used as well as an identification of the first or second hyperband within which that traffic channel exists.
2. The network as in claim 1 wherein the first system area includes means for identifying the second cell as a target cell for hand-off of the mobile station.
3. The network as in claim 2 wherein the second system area performs the requested verification signal strength measurement from the target second cell.
4. The network as in claim 1 further including means for signaling from the second system area to the first system area of a report on the results of the requested verification signal strength measurement and hyperband capabilities of the target cell.
5. The network as in claim 4 wherein the first system area further includes means for processing the report on the results of the requested verification signal strength measurement to determine whether the second system area can support mobile station communications with respect to hyperband in the event of a hand-off from the first cell to the second cell.
6. In a cellular telephone network including:
a first system area having a plurality of cells including a first cell, the first system area supporting cellular communications on traffic channels in both a first and a second hyperband; and a second system area having a plurality of cells including a second cell, the second system area supporting cellular communications on traffic channels in the first hyperband but not the second hyperband;
a method for performing verification signal strength measurements in connection with a potential hand-off from the first cell to the second cell of a mobile station engaged in a cellular communication on a traffic channel of either the first or second hyperbands, comprising the steps of:
signaling from the first system area to the second system area of a request for the second system area to perform a verification signal strength measurement on the traffic channel being used by the mobile station, the request including an identification of the traffic channel being used as well as an identification of the first or second hyperband within which that traffic channel exists; and considering by the second system area of the identified hyperband in connection with the making and reporting of the verification signal strength measurement.
a first system area having a plurality of cells including a first cell, the first system area supporting cellular communications on traffic channels in both a first and a second hyperband; and a second system area having a plurality of cells including a second cell, the second system area supporting cellular communications on traffic channels in the first hyperband but not the second hyperband;
a method for performing verification signal strength measurements in connection with a potential hand-off from the first cell to the second cell of a mobile station engaged in a cellular communication on a traffic channel of either the first or second hyperbands, comprising the steps of:
signaling from the first system area to the second system area of a request for the second system area to perform a verification signal strength measurement on the traffic channel being used by the mobile station, the request including an identification of the traffic channel being used as well as an identification of the first or second hyperband within which that traffic channel exists; and considering by the second system area of the identified hyperband in connection with the making and reporting of the verification signal strength measurement.
7. The method as in claim 6 further including the step of identifying the second cell as a target cell for hand-off of the mobile station.
8. The method as in claim 7 further including the step of performing the requested verification signal strength measurement from the target second cell.
9. The method as in claim 6 further including the step of signaling from the second system area to the first system area of a report on the results of the requested verification signal strength measurement and hyperband capabilities of target cell.
10. The method as in claim 9 further including the step of processing the report on the results of the requested verification signal strength measurement to determine whether the second system area can support mobile station communications with respect to hyperband in the event of a hand-off from the first cell to the second cell.
11. A method for operating a cellular telephone network, comprising the steps of:
detecting with respect to mobile station communication operation in a first cella need to perform a hand-off, the mobile station having certain hyperband communications capabilities, identifying a target second cell associated with a second system as a candidate cell for hand-off;
requesting that the second cell perform a verification signal strength measurement, the request identifying a traffic channel currently being used by a mobile station in the first cell as well as identification of the hyperband within which that channel exists;
attempting to perform the verification signal strength measurement in the identified traffic channel and hyperband;
reporting results of the attempted verification signal strength measurement and hyperband capabilities of target cell; and processing the report on the results of the requested verification signal strength measurement to determine whether the second cell would support mobile station communications with respect to its certain hyperband communications capabilities in the event of a hand-off from the first cell to the second cell.
detecting with respect to mobile station communication operation in a first cella need to perform a hand-off, the mobile station having certain hyperband communications capabilities, identifying a target second cell associated with a second system as a candidate cell for hand-off;
requesting that the second cell perform a verification signal strength measurement, the request identifying a traffic channel currently being used by a mobile station in the first cell as well as identification of the hyperband within which that channel exists;
attempting to perform the verification signal strength measurement in the identified traffic channel and hyperband;
reporting results of the attempted verification signal strength measurement and hyperband capabilities of target cell; and processing the report on the results of the requested verification signal strength measurement to determine whether the second cell would support mobile station communications with respect to its certain hyperband communications capabilities in the event of a hand-off from the first cell to the second cell.
12. The method as in claim 11 wherein the first cell supports mobile station communications in both a first hyperband and a second hyperband.
13. The method as in claim 12 wherein the second cell supports mobile station communications in the first hyperband but not the second hyperband.
14. The method as in claim 13 wherein the step of processing further includes the steps of:
determining from the results of the requested verification signal strength measurement that the second cell supports mobile station communications in the first hyperband but not the second hyperband; and determining whether the mobile station is capable of operation in the first hyperband.
determining from the results of the requested verification signal strength measurement that the second cell supports mobile station communications in the first hyperband but not the second hyperband; and determining whether the mobile station is capable of operation in the first hyperband.
15. The method as in claim 14 further including the steps of:
requesting a traffic channel in the first hyperband for mobile station hand-off to the second cell; and transmitting a handover command to the mobile station specifying operation in that traffic channel of the first hyperband.
requesting a traffic channel in the first hyperband for mobile station hand-off to the second cell; and transmitting a handover command to the mobile station specifying operation in that traffic channel of the first hyperband.
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| US68078096A | 1996-07-16 | 1996-07-16 | |
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| CA002260139A Abandoned CA2260139A1 (en) | 1996-07-16 | 1997-07-08 | Method and apparatus for inter-system handoff within a plural hyperband supporting cellular telephone network |
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| DE10259349B4 (en) * | 1978-02-01 | 2005-05-04 | Intel Corporation, Santa Clara | Portable communication device that enables a wireless network to communicate with another wireless network, and associated method |
| US6157835A (en) * | 1998-03-02 | 2000-12-05 | Ericsson Inc. | System and method for detecting and handling system and capability changes in handoffs of cellular calls |
| FI106518B (en) * | 1998-06-26 | 2001-02-15 | Nokia Networks Oy | The handover procedure |
| US6885866B1 (en) | 1998-06-26 | 2005-04-26 | Nokia Corporation | Handover-method in a cellular radio system with two frequency bands |
| USRE47895E1 (en) | 1999-03-08 | 2020-03-03 | Ipcom Gmbh & Co. Kg | Method of allocating access rights to a telecommunications channel to subscriber stations of a telecommunications network and subscriber station |
| US6687237B1 (en) * | 1999-04-01 | 2004-02-03 | Nortel Networks Limited | Methods and systems for facilitating a multi-mode multi-pilot hard handoff |
| US7212821B2 (en) | 2003-12-05 | 2007-05-01 | Qualcomm Incorporated | Methods and apparatus for performing handoffs in a multi-carrier wireless communications system |
| US7047009B2 (en) | 2003-12-05 | 2006-05-16 | Flarion Technologies, Inc. | Base station based methods and apparatus for supporting break before make handoffs in a multi-carrier system |
| DK1808029T6 (en) * | 2004-11-03 | 2019-07-22 | Vringo Infrastructure Inc | Intersystem handover of a mobile terminal capable of a first and a second radio access network |
| SE0402782D0 (en) * | 2004-11-10 | 2004-11-10 | Ericsson Telefon Ab L M | Method and arrangement in a telecommunication system |
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| US5697055A (en) * | 1994-10-16 | 1997-12-09 | Qualcomm Incorporated | Method and apparatus for handoff between different cellular communications systems |
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- 1997-07-08 CA CA002260139A patent/CA2260139A1/en not_active Abandoned
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20010709 |