Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-01-05
2001-07-10
Urban, Edward F. (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S456500, C455S525000
Reexamination Certificate
active
06259921
ABSTRACT:
The present invention generally relates to a satellite telecommunications network for mobile stations. More particularly, the invention relates to such a network in which a call set up between a mobile terminal and some other terminal, be it mobile or fixed, is conveyed in part over terrestrial network(s), such as PSTN(s) or ISDN(s). Thus, using known techniques, a call set up between two terminals, namely a mobile terminal and a fixed terminal, is conveyed: (
1
)—via a satellite link or a radio link between the mobile terminal and a terrestrial base station (or “gateway”); and (
2
)—via a terrestrial link between said base station and the fixed terminal. Similarly, a call set up between two mobile terminals is conveyed: (
1
)—via a satellite link or a radio link between one of the mobile stations and a terrestrial base station (or “gateway”); (
2
)—via a terrestrial link (PSTN) between said base station and another terrestrial base station; and finally (
3
)—via a satellite link or a radio link between the other terrestrial base station and the other mobile terminal. The type of network concerned by the invention is a network in which the terminals are mobile. In such a network, firstly each mobile terminal is capable of accessing the network from various places while it is travelling, and secondly the network is capable of identifying, locating, and reaching said terminal. For this purpose, the network stores location information for locating the terminal, which information is updated by means of a registration procedure referred to as a “location updating procedures”.
In the prior art, each mobile terminal accesses the terrestrial network firstly via a satellite and secondly via that base station which is closest to it. In the remainder of the description, the term “gateway” is used to designate a section constituted by a base station and by a Mobile Switching Center (MSC). The purpose of choosing the base station that is closest to the terminal for accessing the terrestrial network is to minimize power losses in the link between the terminal and the terrestrial base station via the satellite.
The services offered by satellite networks are superposed on the already existing services provided by terrestrial networks. That results in a possibly critical increase in traffic in terrestrial networks. Furthermore, the fact that each terminal accesses the terrestrial network via the base station that is closest to the terminal can give rise to call costs that are high.
Patent Application GB-A-2 281 014 describes a satellite telecommunications system in which a call between a mobile terminal and a fixed terminal is routed via that base station or gateway which offers the shortest routing path through the terrestrial network (PSTN). The solution proposed in that Application thus reduces traffic loading in the terrestrial network (PSTN). However, it does not solve the problem of the high call cost charged to the user.
An object of the invention is to remedy that drawback by providing a method of routing calls, and also a terminal and a base station for implementing this particularly advantageous method.
To this end, the invention provides a method of routing a call between a first terminal which is a mobile terminal and a second terminal in a global telecommunications network, it being possible for said call to be routed in said global network a)—at least in part through a satellite telecommunications network by using base stations, and b)—at least in part through a terrestrial telecommunications network connected to said base stations, said call being routed via a base station that minimizes the routing distance over which said call travels through said terrestrial telecommunications network, said method being characterized in that, prior to setting up said call, said method includes a location updating step in which the location of the first terminal is updated as being in the coverage area associated with the base station that minimizes the routing distance over which the call travels through said terrestrial telecommunications network, the updated location being different from said first terminal's current location. This step goes against the conventional location updating procedure because in this case location is updated as being in a base station coverage area which is not the coverage area in which the terminal receives a signal of maximum power. Such location updating is “forced”.
In the terrestrial network, the cost of the call charged to the user is calculated as a function of the location information as previously updated in “forced” manner, and said cost thus takes into account the real routing path followed by the call through the PSTN. Other advantages of updating the location information prior to setting up the call are to enable another call to be received, to avoid losing information transmitted to a user whose location has not been updated, etc.
In addition, whenever possible, the call is routed mainly via the satellite links, thereby avoiding overloading the terrestrial network, and reducing the cost of the call. The reduction in cost is due to the fact that a satellite network infrastructure is lower in cost than a terrestrial network infrastructure.
In a first implementation, the first terminal is a calling terminal, and the location of said first terminal is updated as being in the coverage sub-area of the base station that is closest to said second terminal which is a called terminal. A mobile terminal suitable for using this implementation includes memory means for storing association information that associates each of a plurality of called number prefixes, which are functions of call areas, with base station identification information, and means for updating location as being in an identified base station.
In a second implementation, the first terminal is a called terminal, and the location of said first terminal is updated in the base station that is closest to said second terminal which is a calling terminal. A master base station suitable for using this implementation includes means responding to location information received from the base station that is closest to said second terminal by producing location update trigger information which is transmitted to the base station that is associated with the coverage sub-area to which said first terminal belongs, which base station re-transmits said location update trigger information to the first terminal so that said first terminal updates the location as being in the coverage area of the base station that is closest to said second terminal.
REFERENCES:
patent: 5303286 (1994-04-01), Wiedeman
patent: 5481592 (1996-01-01), Azer
patent: 6009085 (1999-12-01), Lechner
patent: 6009306 (1999-12-01), Hargis
patent: 0 562 374 A1 (1993-09-01), None
patent: 2 281 014 (1995-02-01), None
patent: 2 295 296 (1996-05-01), None
Charpentier Jean
Flores Erick
Thies Roland
Totaro Antoine
Alcatel
Milord Marceau
Sughrue Mion Zinn Macpeak & Seas, PLLC
Urban Edward F.
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