WO1999039495A1

WO1999039495A1 - Procedure and system for call rerouting

Info

Publication number: WO1999039495A1
Application number: PCT/FI1999/000028
Authority: WO
Inventors: Eeva Hartikainen; Asko Suorsa
Original assignee: Nokia Networks Oy
Priority date: 1998-01-20
Filing date: 1999-01-18
Publication date: 1999-08-05
Also published as: FI980124A0; FI980124L; FI105983B; AU1970999A

Abstract

The present invention relates to a procedure for call rerouting when a subscriber line is removed from one telephone exchange to another while retaining the same subscriber number. Moreover, the present invention relates to a system for call rerouting when a subscriber line is removed from one telephone exchange to another while retaining the same subscriber number. Thanks to the invention, the switching time of calls is shortened and calls are more effectively routed to the correct address.

Description

PROCEDURE .A-STD SYSTEM FOR CALL REROUTING

The present invention relates to a procedure as defined in the preamble of claim 1 for rerouting a call after the called party has moved from one tele- phone exchange to another or has changed to another operator's system while the called party's subscriber number remains the same as before the change or move. The present invention also relates to a system as defined in the preamble of claim 3 for rerouting a call after the called party has moved from one telephone exchange to another or has changed to another operator's system while the called party retains the same subscriber number as before the change or move.

In prior art, there are two methods for im- plementing telephone number removability, which in this context means that the subscriber's subscriber number remains unchanged when the subscriber moves from one telephone exchange to another or changes to another operator's system. In the first method, after the called party has moved from one exchange to another, calls addressed to the called party are routed to the exchange from which the called party has moved away. From there, the calls are rerouted to the called party's current exchange using either redirection or number conversion. The other known method is based on an intelligent network technique in which the calling party's exchange searches a centralised database to find new routing information, based on which the call is routed directly to the called party's current ex- change .

The problem with the first prior-art method is that all calls addressed to a subscriber who has moved are switched through via the subscriber's old exchange, which takes time and wastes band capacity. In the other prior-art method, the problem is that it uses a centralised database, which may be located at a large geographic distance. In any case, it is located somewhere else than the exchange from which the call is originated. Consequently, the database queries take time. This type of databases are maintained manually, so if they are implemented in every exchange to im- prove efficiency of operation, maintaining them manually will become impossible. The problem is that the call switching time is increased, and not only for calls to subscribers who have moved but for all calls. The object of the present invention is to disclose a new type of procedure to eliminate the drawbacks described above.

A specific object of the present invention is to disclose a procedure for implementing telephone number removability so that the calls are routed to the right place already in the originating exchange, thus reducing the switching time for the call. A further object of the invention is to disclose a system for implementing telephone number removability.

As for the features characteristic of the present invention, reference is made to the claims.

In the procedure of the present invention for call rerouting after the called party has moved from one telephone exchange to another or has changed to another operator's system while the called party's subscriber number remains the same as before the move in a telephone network comprising a first telephone exchange, which comprises the calling party's subscriber line, and a second telephone exchange, which comprised the called party's subscriber line before the move, and a third telephone exchange, which comprises the called party's subscriber line after the move, the calling party's first call to the called party after the called party's subscriber line has been moved from the second telephone exchange to the third telephone exchange is routed from the first telephone exchange to the second telephone exchange, because there is no other routing information for the called number. Next, the second telephone exchange answers that the called party is not found and transmits new routing information indicating that the called party's subscriber line has been moved to the third telephone exchange. After this, the new routing information is stored in the first telephone exchange and the call is routed from the first telephone exchange to the third telephone exchange in accordance with the new routing information. In an embodiment of the procedure, calls following the first call after the move are routed on the basis of the new routing information from the first telephone exchange to the third telephone exchange.

In the system of the present invention for call rerouting after the called party has moved from one telephone exchange to another or has changed to another operator's system while the called party's subscriber number remains the same as before the move in a telephone network comprising a first telephone exchange, which comprises the calling party's subscriber line, a second telephone exchange, which comprised the called party's subscriber line before the move, and a third telephone exchange, which comprises the called party's subscriber line after the move, the first telephone exchange comprises means for analysing the called number of an outgoing call and routing the call on the basis of the analysis. The call is routed to the second telephone exchange if the analysis does not reveal any new routing information. If the analy- sis does reveal new routing information, then the call is routed accordingly to the third telephone exchange.

In an embodiment of the system, the first telephone exchange comprises means for storing the new routing information received from the second telephone exchange.

In an embodiment of the system, the second telephone exchange comprises means for analysing the called number of an incoming call and transmitting new routing information regarding removal of the called subscriber line to a third telephone exchange to the first telephone exchange. As compared with prior art, the present invention provides the advantage for subscribers that, except for the first call after the move, calls are routed to the right place already in the originating exchange, thus reducing the switching time. For the operator, the invention provides the advantage that no manual maintenance work is needed because the databases and/or analysis structures are updated automatically. Moreover, as the updates are performed in accordance with the numbers called from the exchange, the amount of data to be stored will not become as large as in a database/analysis structure comprising all numbers removed. Further, as the databases/analysis structures are decentralised so that the routing information needed by the originating ex- change of the call is found in a database/analysis structure disposed in conjunction with the same exchange, the switching time is shortened. In short, calls are more effectively routed to the correct address . In the following, the invention will be described by the aid of a few examples by referring to the attached drawing, wherein

Fig. 1 represents an embodiment of the procedure of the invention; and Fig. 2 represents an embodiment of the system of the invention.

Fig. 1 is an example illustrating an embodiment of the procedure of the invention. John Brown has moved from London to Brighton. When moving, he wanted to keep his former telephone number. When Joe Black of Oxford calls John Brown for the first time after John's move, the call is routed to the London exchange 2. However, the London exchange 2 answers that the number has been removed to another exchange and gives new routing information. The new routing information is automatically stored on a list of removed numbers in the Oxford exchange 1 and the call is routed to the Brighton exchange 3 on the basis of the new routing information. After this, calls made by Joe Black to John Brown are routed directly to the Brighton exchange 3. Thus, the new routing information is only maintained in those exchanges from which calls are made to John Brown after the move. For instance, the Edinburgh exchange, from where no one has called John Brown, has no information about the new call routing.

Fig. 2 presents an example illustrating an embodiment of the system of the invention. A first telephone exchange 4 comprises means 41 by which the called number of an outgoing call is analysed and the call is routed. Moreover, the first telephone exchange 4 comprises means 42 for storing the new routing in- formation. A second telephone exchange 5 comprises means 51 for analysing the called number of an incoming call and transmitting the new routing information to the first telephone exchange 4. The system can be implemented using traditional switching technology, i.e. without using intelligent network techniques. In the first telephone exchange 4, the called number of an outgoing call is analysed e.g. using an analysis tree 41. If the analysis does not reveal a converting number, then the call is routed in accordance with the called number. If a converting number is revealed, then the call is routed accordingly. When the call reaches the second telephone exchange 5, the number is analysed and the analysis produces information of the form "number has changed, new routing information = X.XXX" This information is returned to the first telephone exchange 4 in a signalling message defined for this purpose. In the first telephone exchange 4, the answer is processed, the analysis structure 41 is updated and the call is routed further to the third telephone exchange 6. The size of the analysis structures 41 in the first telephone exchange 4 is only in- creased by those numbers to which calls have been attempted.

The system of the invention can also be implemented using intelligent network techniques. The first 4 and the second 5 telephone exchanges are pro- vided with an intelligent network SSCP (Service Switching and Control Point) feature which comprises call switching and service control. In the first telephone exchange 4, an SSCP service 41 is executed on the called number of an outgoing call, analysing the called number. If no analysis for the number is found, then the call is continued with the number received. If an analysis is found, then a new number is obtained from a database and the call is continued with the new number. In the subscriber analysis for subscribers re- moved to a second telephone exchange 5, a trigger has been set which starts SSCP service 51 for updating the called number, which service corresponds e.g. to a message sent on the basis of the calling number to the first telephone exchange 4, giving the new called num- ber. In the first telephone exchange, the called number analysing service 41 is waiting for a response or the response starts service 42, which stores the called number. In both cases, the database is updated and the call is routed further to the third telephone exchange 6.

The invention is not restricted to the examples of its embodiments described above, but instead many variations are possible within the framework of the inventive idea defined by the claims.

Claims

1. Procedure for call rerouting after the called party has moved from one telephone exchange to another or has changed to another operator's system while the called party's subscriber number remains the same as before the move in a telephone network comprising a first telephone exchange (1) , which comprises the calling party's subscriber line, and a second telephone exchange (2) , which comprised the called party's subscriber line before the move, and a third telephone exchange (3) , which comprises the called party's subscriber line after the move, and in which procedure the first call after the move is routed from the first telephone exchange (1) to the second tele- phone exchange (2), characterised in that

- new routing information is sent from the second telephone exchange (2) to the first telephone exchange

⁽1);

- the new routing information is stored in the first telephone exchange (1) ; and

- the first call after the move is routed from the first telephone exchange (1) to the third telephone exchange (3) in accordance with the new routing information.

2. Procedure as defined in claim 1, characterised in that calls following the first call after the move are routed in accordance with the new routing information from the first telephone exchange (1) to the third telephone exchange (3) .

3. System for call rerouting after the called party has moved from one telephone exchange to another or has changed to another operator's system while the called party's subscriber number remains the same as before the move in a telephone network comprising a first telephone exchange (4) , which comprises the calling party's subscriber line, a second telephone exchange (5), which comprised the called party's sub- 8

scriber line before the move, and a third telephone exchange (6), which comprises the called party's subscriber line after the move, characterised in that the first telephone exchange (4) comprises means (41) for analysing the called number of an outgoing call and for routing the call to the second telephone exchange (5) if the analysis does not reveal any new routing information; to the third telephone exchange (6) if the analysis does reveal new routing information.

4. System as defined in claim 3, characterised in that the first telephone exchange (4) comprises means (42) for storing the new routing information received from the second telephone exchange (5) .

5. System as defined in claim 3 or 4, characterised in that the second telephone exchange (5) comprises means (51) for analysing the called number of an incoming call and transmitting the new routing information to the first telephone exchange (4) .