WO2000064212A1

WO2000064212A1 - Number portability between mobile telephone networks

Info

Publication number: WO2000064212A1
Application number: PCT/GB2000/001529
Authority: WO
Inventors: Joseph Jones
Original assignee: New World Technology Limited
Priority date: 1999-04-19
Filing date: 2000-04-19
Publication date: 2000-10-26
Also published as: AU4131200A

Abstract

There is described a method and apparatus for effecting instant portability of mobile phone numbers between different mobile phone networks. When a subscriber wishes to change from an original mobile telephone network to a new network, a 'freephone' link is established from the original network to the new network, and calls to the subscriber's number are diverted to the 'freephone' number. The new network includes means for discriminating calls made to the 'freephone' number, and further diverts these calls to a temporary phone number assigned to the transferring subscriber's new handset operating on the new network. The result is an instantly-implementable solution to the problem of transferring from one mobile telephone network to another while retaining the same mobile telephone number, since during the transfer period calls directed to the original mobile telephone number will be diverted via the 'freephone' link to the new network, and passed to the subscriber's new network handset.

Description

NUMBER PORTABILITY BETWEEN MOBILE TELEPHONE NETWORKS

The present invention relates to telecommunications, particularly mobile telephones, and is concerned with overcoming difficulties encountered in a subscriber transferring his mobile telephone to a new service network.

To provide a mobile telephone service, a network operator establishes a network of radio transceiver stations covering the area within which the telephone service is to be provided. Each station is linked to a central telephone exchange, which in turn is linked to terrestrial telephone networks, and to exchanges of other networks, using land lines. Each subscriber to the mobile telephone service is provided with a handset capable of radio communication with any of the transceiver stations of the network. Each handset has its own unique telephone number, by which the transceiver stations of the network identify the handset for communication therewith. In order to make a call using the handset, the subscriber simply dials the number to be called, irrespective of whether that number identifies another mobile handset belonging to the same or another mobile telephone network operator, or whether it identifies a telephone line in a land line system. The handset then makes a radio transmission which is received by a transceiver station of the network, and is routed from there to the network exchange. The network exchange then identifies the number either as a number belonging to the same mobile telephone service, a number belonging to a different mobile telephone service, or a land line number. The network exchange then forwards the call. In the case of a call to another handset of the same mobile telephone service, the exchange passes the call to the transceiver station most conveniently positioned in relation to the called handset, and that transceiver station then makes contact with the called handset. In the case of a call to a handset belonging to a different mobile telephone service, the network exchange makes a connection via land line to the network exchange of the other mobile telephone service, and the call is then forwarded to the transceiver station of the other service which is most conveniently placed to communicate with the called handset. Selection of the appropriate transceiver station is made in either case by the handset periodically emitting a positioning signal which is received by its nearest transceiver stations, one of which then adds that handset to a list of the handsets considered to be within its area, and notifies the network exchange so that calls to that handset are directed to that transceiver station. In the case of a call to a land line number, the call is forwarded from the network exchange to the land line service, which then directs the call to the appropriate telephone instrument.

When a subscriber to a mobile telephone network wishes to subscribe to a different network, perhaps because of dissatisfaction with the quality or cost of the service provided by the original network, it has hitherto usually been the case that the network operator on the "new network" provides the subscriber with a new handset, which has a different telephone number from the handset of the "old network" . Such a change therefore presents considerable inconvenience to the subscriber^", in that he or she must notify all of his or her colleagues and friends of the new number. When the telephone is used extensively in a business context, the effect on a business of such a change in telephone number can be detrimental.

In some cases, the new network does not issue the subscriber with a new handset, but simply supplies a new

SIM (Subscriber Identification Module) chip or card to be used in the subscriber's existing handset. For the subscriber to use both networks, it is necessary for the original SIM card to be inserted in the handset when the handset is to make and receive calls on the 'old* network, and the new SIM card to be inserted when the handset is to make calls on the new network. SIM cards are small and readily lost, and can be damaged by- frequent mishandling. Contemplation of these inconveniences by the subscriber may lead to the subscriber deciding to remain with the old network, despite not being totally satisfied with the service provided. The free market in mobile telephone services is thus distorted, and true competition is not achieved.

Recently in the UK, the governmental regulating body and the four mobile telephone network operators have established procedures by which a subscriber can transfer from one network to another, while keeping his original mobile telephone number. However, among these established procedures there is set down a notice period allowed for the original network to "release" the subscriber to the new network. This notice period is approximately two weeks or may be slightly longer, and is principally provided to give the 'old network' an opportunity to ensure that the subscriber has no outstanding charges. However this notice period may be used by the original network to contact the subscriber with an improved service offer in an effort to retain the subscriber on the original network.

At the end of the ' notice period ' , the original network instigates a permanent diversion of the subscribers ' calls from his original number to the number of his new handset on the new network.

When transferring between networks under these procedures, the subscriber may receive a new handset connected to the new network with a temporary number or a SIM module, to change his original handset to receive and send calls on the temporary number. During the notice period, therefore, calls dialled to the original number will be routed through the original network to the original handset, and calls dialled to the temporary number will be routed through the new network to the new handset.

If the subscriber wishes to continue to receive calls made to his original number, but to make calls using the new handset and network, the subscriber is obliged to carry both handsets with him, and use the original handset to answer incoming calls and the new handset to make outgoing calls .

If the subscriber wishes to make the transfer immediately to use the new network for both incoming and outgoing calls, the subscriber must first notify his friends and colleagues of the temporary phone number, and at the end of the notice period must again advise his friends and colleagues that he has now reverted to the original telephone number.

In view of the inconvenience involved in notifying friends and colleagues of firstly the temporary number and then the reversion to the original telephone number, and to avoid carrying either two handsets or a handset and a loose SIM card with them, most subscribers adopt the practice of continuing to use the original handset for both incoming and outgoing calls during the notice period, and only make use of the new handset after the notice period has elapsed and calls to the original number will be received via the new network on the new handset .

This practice is disadvantageous to the new network in two main respects. The first is that the new handset remains unused until the end of the notice period, and the subscriber thus does not become familiar with the new handset and with the services offered by the new network, making a change less attractive. Secondly, any calls made by the subscriber within the notice period are made on the original handset, generating call revenue for the original network and denying it to the new network.

An objective of the present invention is to provide a telecommunication method and apparatus which enables a mobile telephone subscriber to transfer his subscription from a first network operator to a second network operator while maintaining his original telephone number, in such a way that the transfer takes immediate effect in relation both to incoming and outgoing calls.

A further objective of the present invention . is to provide a telecommunication method and apparatus which enables callers to contact a transferred subscriber via his new network during the "notice period", using his original telephone number, without or substantially without additional cost to the caller or the subscriber.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of the routing of a call through a mobile telephone network;

Figure 2 is a schematic illustration of a first stage of the transfer operation;

Figure 3 is a schematic illustration of the routing of a call to a transferred subscriber's new handset using the divert line between exchanges .

Figure 4 illustrates the additional devices installed in the new network's exchange for a first call routing method;

Figure 5 is a flow chart showing the progress of an incoming call to the original network exchange using the first routing method;

Figure 6 is a flow chart showing the progress of an incoming call through the new network exchange using the first routing method.

Figure 7 is a schematic diagram similar to Figure 4, illustrating devices installed in the new network's exchange for a second call routing method. Figure 8 is a flow chart showing the progress of an incoming call through the original network exchange using the second routing method; and

Figure 9 is a flow chart showing the progress of an incoming call through the new network exchange using the second routing method.

Referring now to figure 1, there is shown a mobile telephone network comprising a network exchange 1, a first transceiver station 2 , and a second transceiver station 3. The network exchange 1 is connected via land lines to the terrestrial telephone system at a land line exchange 4, to which land line telephones 5 are connected. A number of mobile telephone handsets 6, 7 are arranged to transmit and receive telephone calls to and from the nearest or most appropriate respective transceiver station 2, 3. For example, if the calling subscriber's handset 6 is in the area of the first transceiver station 2, and the called subscriber's handset 7 is in the area of the second transceiver station 3, a call from handset 6 to the subscriber's handset 7 will be transmitted to the first transceiver station 2 , and from there to the network exchange 1. At the network exchange 1, the transceiver stations 2 and

3 will be interrogated to determine which transceiver station is closest to the subscribers handset 7 , and the call will then be sent to the second transceiver station 3 and re-transmitted to the subscriber ' s handset 7.

Similarly, if a network subscriber 7 calls a land-based telephone 5, the call will be received by the closest transceiver station 3 and routed to the network exchange 1, from where it will be passed to the land line exchange

4 and onward to the land-based telephone 5.

If a call is made from a land-based telephone 5 to a mobile handset 7, the call first passes to the land line exchange 4. The dialled prefix to the called number identifies the network to which the called number belongs, and the land line exchange 4 routes the call via land line 4a to the appropriate network exchange 1. Each network has a number of prefixes which uniquely identify subscribers by their network. The network exchange 1 interrogates the transceiver stations of its network to determine the appropriate transceiver station for the mobile handset 7 being called. The network exchange 1 then routes the call to the appropriate transceiver station for transmission to the handset 7. Figure 2 shows the conventional transition situation when a subscriber transfers from an original network to a new network. The new network comprises a new network exchange 21, first and second transceiver stations 22 and 23, and new network handsets 26 and 27. The new network exchange 21 is connected to the land line exchange 4 as previously described in relation to figure 1. The network described in figure 1 is reproduced in figure 2 as the "original network", with like reference numbers attaching to like components.

As previously described, when the subscriber wishes to transfer to a new network yet keep his original telephone number, the transfer process includes a transition period during which the subscriber's original handset 7 operates on the original network with his original telephone number, and a new handset 27 operates on the new network with a temporary telephone number unique to the new handset 27. If the subscriber wishes to carry with him only the new handset 27, but also wishes to receive calls directed to the original telephone number during the transition period, the subscriber can arrange for the original network to divert his calls using its existing call-divert facility via line 30 to the temporary number of his new handset 27. This has the disadvantage, however, that a redirection fee, payable by the subscriber, attaches to each call, which may excessively inflate the charge per minute for the call.

A redirected call to the original handset is intercepted at the original network exchange 1, and routed via land line 30 to the new network exchange 21, from whence it passes to the appropriate transceiver station 22 or 23 of the new network for transmission to the new handset 27.

Figure 3 shows an embodiment of the present invention enabling a subscriber to "instantly" transfer to a new network at minimum cost. The elements shown in figure 3 correspond substantially to those shown in figure 2 , and like elements are given like reference numbers. In a first routing method of the present invention, when a subscriber wishes to transfer from his original network to a new network, the new network arranges for a "least cost route" 31 to be opened between the original network exchange 1 and the new network exchange 21. In practice, the new network exchange issues a "freephone" number for each subscriber and the subscriber requests the original network exchange to use its existing call diverting facility to divert all incoming calls to the original handset 7 onto this freephone number, and these "freephone" diverted calls are routed via the "freephone" link 31 on the land line system to the exchange 21 of the new network.

At the new network exchange, incoming calls which have been routed to the new network exchange are subjected to a separating process in a separating section 33 of the exchange 21. The separating section is shown in greater detail in figure 4. The separating section 33 comprises an incoming call discriminator 34 and a correlating unit 35. The correlating unit 35 stores the "freephone" numbers issued to the transferring subscribers in a memory, and each "freephone" number is linked to the temporary number issued to the new handset 27 of the transferring subscriber.

As the incoming calls are received at the new network exchange, the incoming call discriminator 34 distinguishes between dialled calls directed to existing telephone numbers of the new network, and calls directed to the specified "freephone" numbers issued to transferring subscribers. The new network exchange routes the incoming calls to existing subscribers ( "regular calls") through the exchange in the normal way, and directs them to the appropriate transceiver station for onward transmission to the existing subscribers' handsets .

Calls identified by the incoming call discriminator as being directed to the specified "freephone" numbers are routed to the correlating unit 35, and the address information (the "freephone" number) associated with the call is replaced by the temporary phone number with which that "freephone" number is uniquely associated. For example, an incoming call to the new network exchange directed to the "freephone" number 0800 12345 will be routed by the incoming call discriminator 34 to the correlating unit 35, where the address information associated with the call will be replaced by the temporary phone number "temp 2". The call is then passed through the exchange as if it were a call to the temporary number "temp 2", and will be directed to the transceiver station appropriate to the new handset 27 of the transferring subscriber.

The routing method of the invention is thus implemented firstly by using the conventional "divert" facility of the original network to divert calls directed to the subscriber's original number to the low cost link 31 which is set up by the new network using a unique number for each transferring subscriber. Such a call diversion facility can be rapidly set up, as it involves only a request by the subscriber and the use of conventional equipment already provided at the original network exchange.

At the new network exchange, a correlating unit 35 including a memory for storing related pairs of "freephone" numbers and temporary phone numbers is set up. In the first routing method described, a unique "freephone" number is issued to each transferring subscriber and thus, an incoming call to that "freephone" number is clearly intended for the transferring subscriber. The incoming call discriminator 34 selects the "freephone" calls by comparing the address information associated with each call with the standard "0800" prefix, and directs the "freephone" calls to the correlating unit 35, which then replaces the "freephone" number with the unique temporary number issued to that transferring subscriber. The call is then routed to the new handset 27, and thus reaches the subscriber at minimal extra cost. It is foreseen that the new network may absorb the cost of setting up this freephone number and call diversion, in order to facilitate the " instant" transfer of the subscriber from the original network to the new network.

Figure 5 is a flow chart illustrating the sequence of events at the original network exchange. At step 1, an incoming call directed to the subscriber ' s original number arrives at the exchange. At step 2, it is determined whether the subscriber has arranged a "divert" facility for calls to that number. If no such facility has been arranged, the incoming call is forwarded to the dialled number. Since the call is an incoming call to the network exchange, the dialled number must be a number of the subscriber on the network. At step 3, the call is forwarded to the dialled number and proceeds to step 4, where the transceiver stations of the network are interrogated to select the appropriate transceiver station for that handset at that time. The call is then forwarded to the transceiver, where at step 5 it is transmitted to the handset.

If at step 2 it is determined that the dialled number has an activated "divert" facility, the flow proceeds to step 6 where the number to which calls are to be diverted is determined. This is preferably done at the exchange by consulting a look up table correlating the original number and the "divert" number. The flow then proceeds to step 7 where the call is forwarded to the "divert" number. In step 8 is determined whether the " divert "number is a number on the network. If it is, the flow then proceeds to step 4. If the "divert" number is not on the network, the flow proceeds to step 9 and the call is routed to the land line exchange for onward transmission to the "divert" number.

Figure 6 is a flow chart showing the sequence of events for an incoming call to the new network exchange. At step one, an incoming call to the new network exchange is detected. At step 2 the incoming call discriminator 34 determines whether or not the call is directed to a specified "least-cost" number. If the call is directed to an existing subscriber's number, the flow proceeds to step 3 and the call is forwarded to the dial number. At step 4 the transceiver stations of the new network are interrogated to select the appropriate transceiver station for that handset at that time. The call is then forwarded to the transceiver, where at step 5 it is transmitted to the subscriber's new handset 27.

If at step 2 the incoming call is found to be directed to a "least-cost" number, the flow proceeds to step 6 the correlating unit 35 finds the temporary phone number corresponding to that "least-cost" number. At step 7 the call is forwarded to the temporary number, and the flow proceeds to step 4.

An alternative method of routing calls to the transferring subscriber will now be described with reference to figures 7, 8 and 9.

The alternative method also requires of the subscriber to arrange for his original network exchange to divert calls, as explained above with reference to figure 3. In this alternative method, however, the new network exchange issues only a single "freephone" number, and all the transferring subscribers have their calls diverted, at the original network exchange, on to this "Divert Number". The calls diverted on to this Divert Number include data identifying the number originally called, i.e. the number of the subscriber on the original network.

At the new network exchange, an incoming call discriminator 34 separates regular calls from calls to the Divert Number. Regular calls are routed to the transceiver station, while calls to the Divert Number are sent to a correlator 35. In the correlator 35, there is stored a relationship between the original number of the subscriber on the original network and the temporary number of the subscriber on the new network. The correlator 35 retrieves from the call information the number originally called, i.e. the original number of the subscriber on the original network, determines the temporary number to which the call should be routed, and forwards the call to the transceiver station for transmission to the temporary number.

Figure 8 shows the operations performed at the original network exchange in this second routing method. In step 1, an incoming call is detected at the original network exchange. At step 2 it is determined whether the number called the is on the list for diversion. If it is a "regular call", and is forwarded to the dialled number via the appropriate transceiver station in steps 3 to 5.

If the subscriber has requested diversion of calls to the Divert Number, the original network exchange identifies the number of the subscriber originally called, and forwards the call to the Divert Number via the landline exchange in steps 6 to 8. Figure 9 is a flow chart showing the operations performed at the new network exchange. At step 1 an incoming call is detected, and at step 2 it is determined whether the incoming call is directed to the Divert Number. If not it is a "regular call", and is forwarded to the dialled number via the appropriate transceiver station in steps 3 to 5.

If the call is to the Divert Number, the flow passes to step 6, where the new network exchange extracts data from the call information identifying the number of the subscriber originally dialled, in the correlator 35. In step 7, the correlator 35 determines the temporary number corresponding to the originally-dialled number, for example by consulting a look-up table. At step 8, the call is forwarded to the temporary number and the flow passes to steps 4 and 5 for transmission.

The second routing method of the invention is thus implemented by using the conventional "divert" facility of the original network exchange to divert calls directed to transferring subscribers on to the Divert Number. In practice, the new network will set up a low-cost link 31 using the Divert Number, and the call diversion facility is requested by the subscriber to the original network to effect call diversion to the Divert Number.

At the new network exchange, the correlating unit 35 includes a memory for storing, for each subscriber, the original number of the subscriber on the original network and their respective temporary number on the new network. The correlating unit 35 must also include data extraction means for removing from the call information the original number dialled by the caller, means to retrieve the temporary number corresponding to the originally dialled number, and means to forward the call to the appropriate transceiver station for transmission to the handset on the new network associated with that temporary number.

The invention thus provides an instantly-implementable and instantly effective solution to the difficulty of a subscriber transferring from one mobile telephone network to another while keeping his original mobile telephone number. The link 31 with its unique number can be set up at short notice, and the subscriber can request that original network exchange 1 divert calls via the link 31 to the new network exchange 21 using the existing "call divert" facilities. The new network exchange, once equipped with an incoming call discriminator 34 and a correlating unit 35, can identify the original subscriber and route calls to the relevant temporary number stored in memory in the correlating unit 35. Once these operations have been completed, any call made to the subscriber's original mobile phone number will be automatically routed to the subscriber's new handset 27. At the end of the notice period, the link 30 may be deactivated and its number may be removed from the memory of the correlation unit 35.

Claims

1. A telecommunication method for routing a call directed to a first handset connected to a first mobile telephone network to a second handset connected to a second mobile telephone network, comprising the steps of: establishing a link between an exchange of the first network and an exchange of the second network; diverting, at the first network exchange, calls directed to the first handset on to the link, each call including data representative of the identity of the first handset; identifying, at the second network exchange, calls directed to the link; storing in a memory a correlation between the identity of the first handset and a temporary phone number associated with the second handset; and directing, at the second network exchange, calls received over the link to the temporary phone number of the second handset on the basis of the identifying data.

2. A telecommunication method according to claim 1, wherein a link having a unique telephone number is established between the exchange of the first network and the exchange of the second network for each first handset, and wherein the memory stores a correlation between the unique telephone number of the link and the temporary telephone number associated with the second handse .

3. A telecommunication method according to claim 1, wherein calls transmitted over the link include data identifying the first handset, and wherein the memory stores a correlation between the identity of the first handset and the temporary telephone number associated with the second handset.

4. A telephone system comprising: a first telephone exchange to which at least one first handset is connectable; a second telephone exchange linked to the first telephone exchange via a link; call discriminating means associated with the second telephone exchange for identifying calls directed via the said link; correlating means associated with the second telephone exchange and including a memory for storing data identifying the first handset and a respective temporary phone number associated with a second handset linked to the second exchange; wherein the call discriminating means is arranged to direct incoming calls received via the said link to the correlating means, and wherein the correlating means is arranged to identify said first handset and attach to the call the corresponding temporary phone number; and call forwarding means arranged to forward the call to the telephone instrument identified by the temporary phone number.

5. A telephone system according to claim 4 , wherein a respective link having a unique identifier is associated with each of said first handsets, and wherein the correlating means includes means to identify said first handset on the basis of the unique identifier of its respective link.

6. A telephone system according to claim 4,wherein the first telephone exchange includes means to attach data identifying the first handset to a call transmitted over the link, and the correlating means of the second telephone exchange includes means to extract the said data and means to identify said first handset on the basis of the extracted data.

7. A telephone system according to any of claims 4 to 6, wherein the first telephone exchange is part of a mobile telephone network.

8. A telephone system according to any of claims 4 to 7, wherein the second telephone exchange is part of a mobile telephone network.

9. A telephone system according to any of claims 4 to 8, wherein the link is a least-cost, or toll-free link.

10. A telephone exchange for a telephone system according to claim 5, comprising: means to receive calls directed to a telephone number having a predetermined prefix; call discriminating means for identifying calls directed to telephone numbers having said predetermined prefix; correlating means including a memory for storing a plurality of telephone numbers having said predetermined prefix and a like number of temporary phone numbers each associated with one of said plurality of telephone numbers; wherein the call discriminating means is arranged to direct incoming calls directed to telephone numbers having said predetermined prefix to the correlating means, and wherein the correlating means is arranged to substitute the telephone number of the incoming call with the temporary phone number stored in the memory and associated with the telephone number of the incoming call; and call forwarding means arranged to forward the call to the telephone instrument identified by the temporary phone number.

11. A telephone exchange for a telephone system according to claim 6, comprising: means to receive calls diverted to a predetermined telephone number ("Divert Number") and including data identifying the originally-dialled "first" telephone number from which the calls have been diverted; call discriminating means for identifying calls directed to said predetermined telephone number; correlating means including means for extracting the said identifying data from a received call to determine the originally-dialled telephone number, memory means for storing a plurality of "first" telephone numbers and a like number of temporary telephone numbers each associated with one of said "first" telephone numbers; wherein the call discriminating means is arranged to direct incoming calls directed to said predetermined number to the correlating means, and wherein the correlating means is arranged to extract from the incoming call the data identifying the "first" telephone number, and to determine a corresponding temporary telephone number associated with the identified "first" telephone number; and call forwarding means arranged to forward the call to the telephone instrument identified by the said corresponding temporary telephone number.