Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-01-25
2001-10-30
To, Doris H. (Department: 2632)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S426100, C455S445000, C455S554100, C455S555000
Reexamination Certificate
active
06311073
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a system for connecting a telephone switch to a fixed telephone network via a radiotelephone network, a plurality of fixed radiotelephone terminals serving to replace a cable link. Each fixed radiotelephone terminal performs functions analogous to those of a conventional portable radiotelephone terminal, but it connects a small switch or exchange to the fixed telephone network, rather than connecting a single user thereto. The system of the invention can be used to connect to a public telephone network a small switch serving a hotel or a village situated in an isolated region where it would be too expensive to lay a cable. The switch serves a group of fixed user terminals by routing calls coming from the public network. Each fixed radiotelephone terminal is used in succession with different user terminals since the user terminals are not in permanent use. A plurality of radiotelephone terminals can share a common frequency band by using time division or code division.
BACKGROUND OF THE INVENTION
The invention relates more particularly to radiotelephone networks of the GSM type, and to those of types derived from the GSM type and which include a stationary satellite, or satellites in low earth orbit (LEO). GSM type networks have the following characteristics:
a geographical zone subdivided into cells so as to enable carrier frequencies to be reused;
a gateway manages the resources of each cell concerning carrier frequencies and the plurality of channels carried by each carrier frequency; and
at least one switching center of the mobile radio service manages: calls, connections with the fixed telephone network, and databases, which databases contain the directory number, the international mobile subscriber number, and the location of each mobile subscriber.
Conventional GSM networks or networks derived therefrom are not designed to enable a plurality of subscribers to use the same user terminal. The user personalizes the terminal being used by inserting a subscriber identification module (SIM) card therein containing the international mobile subscriber identity (IMSI) which determines the account to which calls will be billed. After an initialization stage, the terminal is specified in radio messages by a temporary mobile subscriber identity (TMSI) which serves to protect the user's anonymity. In addition, an authentication procedure uses a secret key contained in the SIM card to prevent a user making fraudulent use of the IMSI or the TMSI of another user, whenever a call is made or received.
The use of a plurality of fixed radiotelephone terminals to connect a single switch to a GSM network poses a problem of coordinating the terminals, and also a problem of supplying the switch with the identity of a called line.
OBJECT AND SUMMARY OF THE INVENTION
The object of the invention is to propose a simple system for solving this problem.
The invention provides a system for connecting a telephone switch to a fixed telephone network via a radiotelephone network; the system including a plurality of fixed radiotelephone terminals for connecting the switch to the radiotelephone network, and a plurality of user terminals connected to said telephone switch, the system comprising:
call forwarding means for forwarding a call addressed to one of the user terminals and containing the directory number of the called user terminal to a mobile service switching center providing access to the called user terminal, the forwarded call containing a directory number designating a first fixed radiotelephone terminal associated with the directory number of the called user terminal; and
means situated in said center to act as follows:
if said first terminal is busy, to forward said call to a second fixed radiotelephone terminal designated by its international mobile subscriber identity number, said number being associated with the directory number of the called user terminal in the visitor location register associated with said center; and
if said second terminal is busy, to forward said call to a third fixed radiotelephone terminal designated by its international mobile subscriber identity number, said number being associated with the directory number of the called user terminal in the visitor location register associated with said center; etc. . . . , until an available fixed radiotelephone terminal is found, if any.
The system characterized in this way coordinates use of fixed radiotelephone terminals since it calls only one radiotelephone terminal at a time. It forwards a call to each of the terminals in succession until it finds a terminal that is available, however it does not perform conventional forwarding to another directory number. If the first terminal tried is not free, then the switch conditionally forwards the call to another terminal by specifying that terminal by means of its IMSI as obtained by interrogating a visitor location register (VLR) and without interrogating a home location register (HLR) on each occasion as it would if it were performing a conventional call forwarding operation. This is possible because in this application the radiotelephone terminals are fixed so they therefore always depend from the same VLR.
The conventional procedure of interrogating the HLR for each conventional call forwarding operation is very expensive in processing time. The system of the invention thus makes it possible to economize processing time in the HLR, in the VLR, and in the switching center, on each attempt.
In a preferred embodiment, the call forwarding means for forwarding a call addressed to one of the user terminals include means for sending to the mobile service switching center an IAM message containing the directory number of the called user terminal;
the mobile service switching center further including means for supplying said directory number to the radiotelephone terminal in a SETUP message; and
each of said fixed radiotelephone terminals including means for extracting the directory number of the called user terminal from the SETUP message received for setting up each call, and means for sending said number to the switch in the form of a conventional signalling message.
The system characterized in this way makes it possible in simple manner to perform direct inward dialing (DID), with the switch being capable of behaving like a switch connected to a fixed network for performing direct inward dialing.
REFERENCES:
patent: 4814763 (1989-03-01), Nelson et al.
patent: 5400390 (1995-03-01), Salin
patent: 5544227 (1996-08-01), Blust et al.
patent: 5596624 (1997-01-01), Armbruster et al.
patent: 5793859 (1998-08-01), Matthews
patent: 5818919 (1998-10-01), Berberich, Jr. et al.
patent: 5887256 (1999-03-01), Lu et al.
patent: 5896448 (1999-04-01), Holt
patent: 5966432 (1999-10-01), Buckler et al.
patent: WO 95/29565 (1995-11-01), None
patent: WO 96/24225 (1996-08-01), None
Charpentier Jean
Issenmann Edouard
Alcatel
Sughrue Mion Zinn Macpeak & Seas, PLLC
To Doris H.
LandOfFree
System for connecting a telephone switch to a fixed... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for connecting a telephone switch to a fixed..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for connecting a telephone switch to a fixed... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2613932