Call control method

Call Control Method

FIELD OF THE INVENTION

This invention relates to incoming call barring management in a mobile communication system.

Background of the invention

The network elements related to the PLMN (Public Land Mobile Network) call routing of a known mobile communication network and their mutual relations are shown in Figure 1. The network shown is in accordance with the GSM system used as an example in this application. In this context, network means a mobile network operated by a single operator. The solid lines in the figure describe connections comprising both signaling and a call connection, and the dashed lines describe connections involving only signaling. The network includes base transceiver stations (BTS), which can establish connections to mobile subscriber equipment MS (Mobile Station), base station controllers BSC (Base Station Controller) controlling base stations and mobile services switching centers MSC (Mobile services Switching Center). Hierarchically, below the MSC, there are typically a plurality of base station controllers BSC, and below these, in turn, a plurality of base stations BTS. The established call connections pass from the base station BTS via the base station controller BSC to the exchange MSC, which connects calls either back to the subordinate base station controllers, to the other exchanges MSC or to the public switched telephone network PSTN (Public Swiched Telephone Network) or ISDN (Integrated Services Digital Network). The network also includes a network management system (NMS), which can be used to collect information about the status of the network and to enter data and programs into other network elements.

It is characteristic of mobile networks that the geographical location of mobile stations may change. For this reason, the network must maintain information about the location of mobile subscribers. This information is distributed in the network of Figure 1 to the Home Location Register (HLR) of the subscriber and to the Visitor Location Register (VLR) connected to the MSC of the mobile services switching centers. The HLR, which is always in the subscriber's own home network, contains unchanged subscriber information and information about the subscriber's location with VLR accuracy. The VLR connected to the VMSC of the subscriber's current mobile switching center stores information about the subscriber's reachability and more precise location with the accuracy of the so-called location area.

The routing of the call is shown in Figure 2. The caller is named in the figure

Subscriber A's home network PLMNA, called B's subscriber's home network HPLMNB and B's subscriber's visited network VPLMNB. The PLMNA, HPLMNB, and VPLMNB may all be the same network operated by one operator (intra-operator call), or networks operated by two or three different operators.

The figure shows a case where the A-subscriber is also a mobile subscriber. If the A-subscriber is a fixed network subscriber, the routing is completely similar, only the A-subscriber's transit mobile switching center GMSCA (Gateway

MSCA) will be replaced by the Gateway Exchange (GE).

The signaling required for call set-up is shown in Figure 3.

When establishing a call terminating for mobile station B, a connection is first established with the Initial Address Message (IAM) based on the subscriber number MSISDN (B) of the subscriber B to the transit center GMSCB of the subscriber B.

MSCB). The GMSCB requests routing information from the B-subscriber's home location register HLRB 20 with a routing information request SRI (Send_Routing_lnfo). Upon receipt of the routing information request, the HLRB performs the subscriber information check described in more detail below. If there is no obstacle to the incoming call in the subscriber information check, request the Mobile Subscriber Roaming Number (MSRN) from the current visitor register of the HLRB B subscriber by saying PRN (Provide_Roaming_Number). The VLRB returns the MSRN number HLRBJIe in the message PRN_ACK. The HLRB forwards the MSRN to the GMSCJIe by saying SRI_ACK. The GMSC connects to the B-subscriber exchange MSCB using the MSRN identifying the desired B-subscriber.

The charges for the calls are determined in such a way that the calling, i.e. A-subscriber mak30 always receives a call from the part between the A-subscriber and the called, i.e. B-subscriber's home network. The principle is that an A-subscriber who does not know the location of the B-subscriber does not have to pay an unpredictably high price for the call he makes. When outside his home network or using the call transfer service, the B-subscriber pays for the call share forwarding from his home network.

Thus, for example, when an A-subscriber in Sweden calls a New Zealand subscriber in Finland, the A-subscriber pays for the call share from Sweden to New Zealand and the B-subscriber for the call from New Zealand to Finland.

When away from their own network, the subscriber may have to pay a considerable price for the calls he receives. For this reason, incoming call barring services have been defined in GSM. Such services include Barring of All Incoming Calls (BAIC) and Barring of Incoming Calls when Roaming (BIC-Roam) outside the home network. Information about these restriction services is stored in the subscriber's home location register HLR.

The subscriber information check performed by the home location register HLRB of the called subscriber of the call is illustrated in the flowchart of Figure 4. Upon receiving the SRI request (step 401), the HLRB searches its database for the VLRB address of the current visitor location register of the called subscriber. At 403, the HLRB examines whether the call is barred. If the call is not barred, proceed to step 404, where a PRN request is sent to the VLRBJ, in response to which the received MSRN is forwarded to the exchange that made the routing information request (step 406). If the subscriber has activated blocking for incoming calls, the HLRB does not send the roaming number request shown in the signaling diagram of Figure 3 to the BL subscriber's visitor location register VLRB but sends (step 411) an error message SRI_ERROR to the exchange that made the routing information request with the reason code.

In addition to the incoming call barring check shown in Figure 4, the HLR also checks other issues, such as the existence of the called subscriber, the number change, the absolute reversal of the number to another number, and the authorization of the requested service. However, these are not relevant to the invention of this application and are therefore not shown in the figure.

ETSI (European Telecommunications Standards Institute) is specifying the GSM system in addition to the normal call routing method described above, the so-called optimized call routing. The basic idea of ​​optimized call routing is to use the most direct route between subscriber A and subscriber B, as shown in Figure 5. Subscriber B's home network may not participate in the call except for HLR signaling. By using optimal call routing, call costs between exchanges can be saved and thus the total cost of the call can be calculated.

The Memorandum of Understanding (MoU) of GSM operators has set two requirements for the implementation of optimal routing:

1. the use of optimal routing must not lead to an increase in the price of the call for any user; and

2. at least in the first phase of the service, one call share is always paid by one subscriber.

Since the price of the different parts of the call cannot be assumed to be known in the first stage of optimal routing, optimal routing is used in the first stage of the service only if GMSCA and VMSCB or VMSCB and HLRB are in the same country. In this case, the total price of the call is typically the level of the price of a call made to a domestic mobile station.

Since the goal of optimal routing is to route a call using the most direct route possible, it must be possible to perform an HLR query at the earliest possible stage. If the A-subscriber is a mobile station according to the same mobile communication system as the B-subscriber, the query can be made by the A-subscriber's transit center GMSCA, which supports optimal routing. If the A-subscriber is not a mobile station according to the same system as the B-subscriber, the call must be routed to a network element that can make HLR queries, for example by means of a pre-agreed pre-selection.

Consider the establishment of a call using optimal routing with reference to Figure 6, which shows the signaling used in call setup. The GMSCA checks the address of the B-subscriber belongs to the GSM subscriber and, if the GMSCA supports the optimal routing (OR1 = Y), sends a routing information request to the SRI (B, OR) for the optimal routing to the HLRBJI. The HLRB receives the routing information request. If the HLRB supports optimal routing (OR2 = Y) it checks whether at least one of the following conditions OR3 is fulfilled:

• GMSCA is in the same country as the VMSCB • HLRB is in the same country as the VMSCB

If at least one of the conditions is met (condition OR3 = Y) and there are no other obstacles to call establishment, the HLRB sends a Provide Roaming Number (PRN) request to the VLRB. In the future, the conditions OR3 will be changed in the direction that the call can be optimally routed whenever the call using the optimized route is not more expensive for the A and B subscribers than for a normally routed call.

If the VLRB supports optimal routing (OR4 = Y), it returns the roaming number in the MSRN HLRBJIe PRN_ACK message. The HLRB sends the roaming number MSRN to the GMSCA, which establishes a direct connection to the VMSCB by means of the MSRN included in the IAM message.

If one of the conditions OR2, OR3 or OR4 is not fulfilled, the HLRB sends an error message SRI_ERROR to the GMSCA. If the GMSCA receives this error message or does not itself support optimal routing (OR1 = N), it establishes the call using the normal method shown in Figure 3.

Next, the operation of the HLRB in optimal routing shown in Figure 7 will be considered. In addition to the checks shown in the figure, the HLR also checks other things, such as the existence of the called subscriber, the change of number, the absolute reversal of the number to another number, the barring of all incoming calls (BAIC) and the authorization of the requested service. However, these are not relevant to the invention of this application and are therefore not shown in the figure.

Upon receiving the routing information request SRI (B, OR) for optimal routing (step 702), the HLR supporting the optimal routing searches at its database in step 704 the address of the B-subscriber's visitor location register VLRB. In step 705, it is checked whether the call is blocked, for example due to the activated BICRoam service. If the call is not barred, the above-mentioned optimal routing condition OR3 is checked. If OR3 = Y, a roaming number request (step 707) is sent to the VLRBJI, resulting in the roaming number MSRN being returned to the GMSCAJI in step 709.

If the HLR does not support optimal routing (OR2 = N), an error message SRI_ERROR is sent to the GMSCAJI, in response to which the GMSCA starts to establish a call with the normal call set-up method according to Figure 3. If the call is barred, an error message SRI_ERROR is sent to the GMSCA with the reason code “call barred”, in response to which the GMSCA terminates the call set-up. If the optimal routing condition OR3 is not fulfilled, a subscriber information request PSI (Provide_Subscriber_-information) is sent to the VMSCB, in response to which the VMSCB returns information about the subscriber's availability status. If the subscriber is not reachable, call forwarding defined in the non-reachable state CFNRc (Call Forwarding on Not Reachable) is examined, and if the subscriber is reachable, the error message SRI_ERROR is returned to the GMSCAJI.

In response to the error message SRI_ERROR, the GMSCA establishes a call using normal routing.

If the B-subscriber MSB is outside his home network with the BIC-Roam service activated, the call is prevented from being established. The problem with the prior art 5 is that this is done even if receiving the call would be considerably cheaper for the B-subscriber due to the optimal routing than the price of a normally routed call, in many cases even free of charge. However, the basis of the entire BIC-Roam service is to reduce the call charges of the B-subscriber, so blocking incoming cheap calls is not in line with the basic idea of ​​the service 10. It is an object of the present invention to obviate or at least reduce this shortcoming of the prior art. This object is achieved by a method as defined in the independent claim.

Brief description of the invention

The idea of ​​the invention is to determine, on the basis of the location information of the called subscriber, a number of permitted network elements from which incoming calls are forwarded to the called subscriber. Calls from outside this set will be blocked. In the context of the invention, the subscriber's location information can be defined, for example, as • the country in which the subscriber last updated the location, • the network to which the subscriber last updated the location, or · the network element VLR to which the subscriber last updated the location.

A number of allowed network elements can be defined, for example, as exchanges whose identifier fulfills a certain condition. For example, all calls from exchanges in the same country or the same operator can be defined to be forwarded to the so-called subscriber. Calls from, for example, certain countries or the exchanges of certain operators can also be defined as forwarding.

The invention can advantageously be applied in conjunction with BIC-Roam for incoming call blocking operating outside the home network. With the method of the invention, the barring of incoming calls can be bypassed if the reception of the call causes little or no cost to the B-subscriber due to the optimal routing.

According to a preferred embodiment, when the BICRoam service is activated, only those optimally routable calls coming from the network where the subscriber is currently present are forwarded to the subscriber.

According to another preferred embodiment, when the BIC-Roam service is activated, only those optimally routable calls coming from the country where the subscriber is currently located are forwarded to the subscriber.

The function according to the invention is preferably implemented in the home location register of the called subscriber, where the check according to the invention is added to the check routines. The check examines which network element of the calling subscriber is and to which visitor location register the subscriber called by the VLRB has last made a location update. An incoming call is forwarded if the calling subscriber's network element belongs to the set of network elements defined for the called subscriber's location information, from which incoming calls the called subscriber has specified to receive.

According to a preferred embodiment of the invention, the information associated with the subscriber's location information about the network elements from which the subscriber is ready to receive incoming calls is divided into categories. Class division can be used to define several sets of network elements per visitor register from which incoming calls are forwarded. In this way, the subscriber can easily define the appropriate class by choosing to receive those calls that are not too expensive for him to receive.

picture List

The invention will be explained in more detail with reference to the accompanying drawings, in which Figure 1 shows a network topology of a prior art cellular radio network, Figure 2 shows call routing using normal routing, Figure 3 shows prior art signaling using normal routing, Figure 4 shows prior art home location register operation using normal routing, Figure 5 shows the routing of a call using optimized routing, Fig. 6 shows prior art signaling using optimized routing, Fig. 7 shows prior art home location register operation using optimal routing, Fig. 8 shows an example of functionality according to the invention implemented in a home location register, Fig. 9 shows an example of a visitor location register specific list according to the invention, of which incoming call barring is bypassed and Figure 10 shows another example of the functionality according to the invention implemented in the home location register.

Detailed description of the invention

The operating principle of the invention is shown in the operation diagram of the home location register HLR shown in Fig. 8. Upon receiving the routing information request, the SRI HLR checks the location information VLRB of the subscriber called in step 803. In step 804, it is checked whether the calling subscriber network element GMSCA belongs to the set ALLOWED_ADDR (VLRB) corresponding to the called subscriber location information VLRB. The set ALLOWED_ADDR (VLRB) is the set of network elements from which incoming calls are forwarded to the VLRB to the subscriber who performed the location update. If the GMSCA belongs to the set, the call set-up is continued according to the prior art from step 805. If the GMSCA does not belong to the set, the call set-up is blocked in step 811 by the error message SRI_ERROR with the reason code “call barred” sent to the GMSCA.

At its simplest, the method can be implemented by specifying to be forwarded only calls from the country or network where the subscriber last performed a location update. In this case, it is not necessary to store information about the permitted network elements on a location-by-location basis, but a simple comparison of the location information and the country or network code of the calling subscriber's network element at the call set-up stage is sufficient. For example, in the system of Figure 8, comparison 804 would only compare the country or country and network codes of the transit center GMSCA and the visitor location register VLR. If more degrees of freedom are desired for defining the set of allowed network elements, information about the permitted network element sets for location information must be stored in the network.

A preferred embodiment of the invention will be considered in more detail below, in which the invention is applied together with the blocking of incoming calls outside the home network. In this case, the method lightens the call barring so that, despite the barring activated by the called subscriber, the calls coming from among the predefined network elements are forwarded to the subscriber. Because the purpose of activated call barring is to avoid the high call costs caused by incoming calls, the subscriber typically does not want to receive incoming normally routed calls through his home network. Therefore, optimal routing is also required for outgoing calls.

The method according to the invention, combined with the blocking of incoming calls outside the home network BIC-Roam, is implemented in its simplest form by bypassing the blocking of calls routed only within one country (or network). It should be noted that such a call is always optimally routed. The method can be implemented in the called subscriber's home location register simply by adding a condition to the calling subscriber's network element to the BIC-Roam activity checkpoint, where call barring is bypassed if the calling and called subscribers are in the same country (or network).

The operation of an exemplary embodiment of the invention in a situation where a New Zealand subscriber with an MSISDN number +64 21 123456 is moving in Norway will be investigated. The subscriber has activated the incoming call barring BIC-Roam operating outside the home network. In the subscriber operator's home location register HLR, number +64 21 77, three different categories for blocking bypass are defined for the network of the operator who has entered into a joint subscription or roaming agreement with each subscriber's home network operator. The table in Figure 9 shows the addresses of the VLRB of the visitor location register in the left column. An asterisk indicates a so-called wild card, i.e. +46 705 * means all addresses whose initials CC + NDC (Country Code + National Destination Code) is +46 705 (country code CC = 46 and network code NDC = 705). The remaining three columns corresponding to the different categories each contain a set of initials of the addresses of the MSCs of the exchanges or, more generally, of the network elements. The lists define, on a VLRB basis, the number of exchanges from which incoming call barring outside the home network is bypassed for incoming optimally routed calls.

Suppose now that a New Zealand subscriber in our example has made a location update to the visitor location register VLRB with address +47 90 12, i.e. CC = 47 (country = Norway) and NDC = 90 (operator = TelenorMobil AS). In this case, blocking incoming calls outside the home network is bypassed for optimally routed incoming calls to him in the following cases:

• if the subscriber has been assigned a block 1 for blocking bypass, a bypass is performed if the A-subscriber's exchange number starts with +47 90 (ie the call comes from the same operator's network), • if a 2-blocker is defined for blocking bypass 47 (ie the call comes from the networks of the same country) and • if block 3 is defined for blocking bypass, is made if * the number of the A-subscriber's exchange starts +358 40 (ie the call comes from the Finnish Telecom Finland network), * the number of the A-subscriber's exchange starts +46 705 (ie the call comes from the Swedish Telia Mobitel network), * the number of the A-subscriber's exchange starts 46 707 (ie the call comes from the Swedish Comvik network), * the number of the A-subscriber's exchange starts from +46 708 (ie the call comes from the Swedish Europolitan network) or * the number of the A-subscriber exchange starts from +47 (ie the call comes from the networks of the same country).

In the preferred embodiment of the invention, the arrangement according to the invention does not cause changes in network elements other than the home location register HLRB of the B-subscriber. In addition, of course, the network management system NMS must be able to create and transmit to the home location register HLRB the information to be connected to the location information of the mobile station according to the invention about the network elements from which the optimally routable calls to the subscriber are to be routed.

An example of operation according to the invention in an HLRB supporting optimal routing is shown in Figure 10. After receiving a routing information request SRI (B, OR) for optimal routing (step 1002), the HLR first checks the subscriber's current visitor location register VLRB address (step 1003). Next, it is checked (item 1004) whether the visitor location register is in the same country as HLRB itself. If the result of the check is positive, the condition of optimal routing is also met. In this case, the optimal routing is continued to point 1008 where the roaming number request PRN is sent to the VLRBJ.

Only situations in which the subscriber is outside his home network, i.e. situations in which point 1004 proceeds to the non-branch, are relevant to the present invention. In step 1005, it is checked whether the condition of optimal routing is fulfilled. In the first step of optimal routing, at step 1005, it is checked whether the GMSCA transit center of subscriber A is in the same country as the visitor location register VLRB of subscriber B. If the condition is met, check (item 1006) whether the BIC-Roam blocking of incoming calls outside the home network is activated. If the BIC-Roam is not activated, the optimal routing according to the prior art is continued by proceeding to step 1008. If the BIC-Roam is activated, proceed to step 1007, where it is checked according to the invention whether the set incoming call barring can be overridden. The check compares the GMSCA address of the A-subscriber's transit center that sent the routing information request with the ALLOWED_-ADDR (VLRB) register of the B-subscriber according to Figure 9 stored in the HLRB. The register contains information about the network elements from which incoming calls outside the home network can be overridden. If the GMSCA address is found in the visitor location register of the B-subscriber from the VRLB list, the call can be routed to the B-subscriber. In this case, proceed to step 1008, where a roaming number request PRN is sent to the VLRBJ. The VLRB responds by sending the roaming number MSRN, which is forwarded in an SRI_ACK message to the GMSCA of the A-subscriber transit center that made the routing information request.

At 1009, it can be seen that the B-subscriber's visited network PLMNB (and the B-subscriber's visitor location register VLRB) does not support optimal routing. If the BIC-Roam is bypassed based on the optimal routing, the error message SRI_ERROR with the reason code call denied is returned to the GMSCAJI.

If the check in step 1007 finds that the GMSCA is not found in the list in Figure 9 of the VLRB, proceed to step 1031, where the call is barred.

If the check in step 1005 states that the conditions for optimal routing are not met, proceed from step 1005 to step 1021. This step checks the activity of the BIC-Roam service. If BIC-Roam is active, proceed to step 1031, where the call is barred. If the check in step 1021 states that the BIC-Roam is not activated, the subscriber information request PSI is sent to the VLRBJI according to the state of the art (step 1022). In response to a subscriber information request (step 1023), the VLR returns information on whether the B-subscriber is unavailable to the network. If subscriber B is unreachable, call forwarding (not shown) is examined. Otherwise, an error message SRI_ERROR is returned to the GMSCA, in response to which the GMSCA establishes a connection to the BSC's transit center GMSCB.

In addition to the checks shown in Figure 10, the HLR also checks other things, such as the existence of the called subscriber, the change of number, the absolute reversal of the number to another number, the barring of all incoming calls (BAIC) and the authorization of the requested service. However, these are not relevant to the invention of this application and are therefore not shown in the figure.

The operation of HLRB in different cases is considered below. The examples assume that all network elements support optimal routing.

Let us first examine the situations in which the subscriber blocking bypass class is defined as 1. In this case, according to the information stored in the table in Figure 9, incoming calls are blocked if the GMSCA address of the A-subscriber's exchange is not +47 90. Therefore, only calls routed internally by the same operator are allowed in this category.

Consider a situation where an attempt is made to call a subscriber from the network of the same Norwegian operator from a mobile switching center GMSCA with the number +47 90 22. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB based on its number analysis of +64 21 77 B subscriber numbers. The HLRB receives the request and starts implementing the function shown in Figure 10. At 1003, it is found that the B-subscriber has made a location update in the visitor location register +47 90 12. The check in step 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to step 1005. Condition 1005 for optimal routing is met, so proceed to step 1006, where it is found that the BIC-Roam service is activated. This moves to step 10 07, where the table in Figure 9 states, according to barring class 1, that incoming calls to the VLRB are allowed from exchanges with an initial number of +47 90. GMSCA fulfills this condition.

The operation thus proceeds to steps 1008, 1009 and 1010, where the VLRBJ is requested to have a roaming number which is forwarded to the GMSCA.II. The GMSCA routes the call directly to the B-subscriber.

Next, a situation is considered in which the subscriber blocking bypass class is 1 and an attempt is made to call the subscriber from the network of another Norwegian operator from the mobile switching center GMSCA with the number +47 20 22. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB +64 21 77 B- on the basis of its number analysis of the subscriber's number. The HLRB receives the request and starts implementing the function shown in Figure 10. At 1003, it is found that the B-subscriber has made a location update in the visitor location register +47 90 12. The check at 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to

1005. Optimal routing condition 1005 is satisfied, so proceed to

1006, where it is detected that the BIC-Roam service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 1, that incoming calls to the VLRB from the exchange +47 20 22 are not allowed. Upon receipt of this message, the GMSCA suspends the call set-up. The same applies to a call from Finland to the center on +358 40 11.

Next, let's examine the situations in which the subscriber blocking bypass class is defined as 2. In this case, incoming calls according to the table in Figure 9 are blocked if the GMSCA address of the A-subscriber's exchange is not +47. This category therefore allows calls routed within the same country.

Let us first consider again the situation where an attempt is made to call a subscriber from the network of the same Norwegian operator from a mobile switching center GMSCA with the number +47 90 22. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB based on its number analysis of the +64 21 77 B subscriber number . The HLRB receives the request and starts implementing the function shown in Figure 10. In step 1003, it is found that the B-subscriber has made a location update in the visitor location register +47 90 12. The check in step 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to step 1005. Optimal routing condition 1005 is fulfilled, so proceed to step 1006 where BIC-Roam the service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 2, that incoming calls to VLRB are allowed from exchanges with a +47 prefix. The GMSCA fulfills this condition, so the operation proceeds to steps 1008, 1009, and 1010, where the VLRBJ is requested to have a roaming number that is forwarded to the GMSCA. The GMSCA routes the call directly to the B-subscriber.

Consider next a situation in which an attempt is made to call a subscriber from the network of another Norwegian operator from the mobile switching center GMSCA with the number +47 20 22. The subscriber blocking bypass class is still 2. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the called subscriber's home location register +64 21 77 BBased on the number analysis of the subscriber's number. The HLRB receives the request and starts implementing the function shown in Figure 10. At step 1003, it is found that the B-subscriber has made a location update to the visitor location register +47 90 12. The check at step 1004 finds that the GMSCA is not 15 in the same country as the HLRB, so proceed to step 1005. Optimal routing condition 1005 is fulfilled, so proceed to step 1006 where the BIC-Roam service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 2, that incoming calls to the VLRB are allowed from exchanges with an initial number of +47. The GMSCA 20 implements this condition, so the operation proceeds to steps 1008, 1009, and 1010, where the VLRB is requested to have a roaming number that is forwarded to the GMSCA. The GMSCA routes the call directly to the B-subscriber.

Let us consider another situation in which an attempt is made to call a subscriber from the Finnish operator's network from the mobile switching center GMSCA, whose number is +358 40 11, and the subscriber blocking bypass class is 2. GMSCA sends a routing information request SRI (B, OR) for optimal routing to HLRB +64 21 77 B based on a number analysis of the subscriber’s number. The HLRB receives the request and starts implementing the function shown in Figure 10. In step 1003, the visitor location30 of the B subscriber has been updated to register +47 90 12. The check in step 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to step 1005. It is assumed here that the HLRB has a procedure that also allows two countries to provided that the conditions specified by the MoU at the beginning of the application are met. In this case, the optimal routing condition 1005 to35 is fulfilled, so we proceed to step 1006, where it is found that the BIC-Roam service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9 according to barring class 2 that incoming calls to the VLRB are not allowed from the exchange +358 40 11. The operation thus proceeds to step 1031, where the call is barred by sending a GMSCA.He SRI_ERROR message with reason code . Upon receipt of this message, the GMSCA suspends the call set-up.

Finally, let us consider the case where the subscriber barring bypass class is defined as 3. In this case, according to the information stored in the table of Figure 9, the barring of incoming calls is skipped if the GMSCA address 10 of the A-subscriber exchange starts with the number series 358 40.

Let us first consider again the situation where an attempt is made to call the subscriber from the network of the same Norwegian operator from the mobile switching center GMSCA with the number +47 90 22. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB +64 21 77 by. The HLRB receives the request and starts implementing the function shown in Figure 10. At step 1003, it is found that the B-subscriber has made a location update to the visitor location register +47 90 12. The check at step 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to step 1005. Condition 1005 of the optimal routing 20 is fulfilled, so proceed to step 1006 service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 3, that incoming calls to the VLRB are allowed from exchanges with an initial number of +47. The GMSCA implements this condition, so the operation proceeds to steps 1008, 1009, and 1010, where 25 VLRBJs are requested to have a roaming number that is forwarded to the GMSCAJI. The GMSCA routes the call directly to the B-subscriber.

Consider next a situation where an attempt is made to call a subscriber from the network of another Norwegian operator from a mobile switching center GMSCA with the number +47 20 22 and a subscriber blocking bypass class of 3. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB +64 21 77 Based on the number analysis of the B-subscriber's number. The HLRB receives the request and starts implementing the function shown in Figure 10. At 1003, it is found that the B-subscriber has made a location update to the visitor location register +47 90 12. The amendment at 1004 finds 35 that the GMSCA is not in the same country as the HLRB, so proceed to

1005. Optimal routing condition 1005 is satisfied, so proceed to

1006, where it is detected that the BIC-Roam service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 3, that incoming calls to the VLRB are allowed from exchanges with an initial number of +47. The GMSCA implements this condition, so the operation proceeds to steps 1008, 1009, and 1010, where the VLRBJ is requested to have a roaming number that is forwarded to the GMSCAJI. The GMSCA routes the call directly to the B-subscriber.

Consider further the situation in which an subscriber with a blocking bypass class of 3 is tried to call from the Finnish operator's network .MobSCA +358 40 11. The GMSCA sends a routing information request SRI (B, OR) for optimal routing to the HLRB +64 21 77 B based on a number analysis of the subscriber’s number. The HLRB receives the request and starts implementing the function shown in Figure 10. In step 1003, it is found that the B-subscriber has made a location update to the visitor location register +47 90 12. The check in step 1004 finds that the GMSCA is not in the same country as the HLRB, so proceed to step 1005. It is assumed here that the HLRB has a procedure that allows optimal routing if the conditions specified by the MoU at the beginning of the application are met. In this case, the optimal routing condition 1005 is fulfilled, so it proceeds to step 1006, where it is found that the BIC-Roam service is activated. This proceeds to step 1007, where it is stated from the table in Figure 9, according to barring class 3, that incoming calls to the VLRB are allowed from exchanges with a prefix of +47, +46 705, +46 707, +46 708 or +358

40. The GMSCA implements this condition, so the operation proceeds to steps 1008, 1009, and 1010, where the VLRBJ is requested to have a roaming number that is forwarded to the GMSCAJI. The GMSCA routes the call directly to the B-subscriber.

The use of optimal routing and blocking of incoming calls outside the home network is not necessary for the operation according to the invention. According to the invention, allowing incoming calls only from certain network elements can also be used without the optimal routing service or the blocking of incoming calls activated outside the home network. However, combining the invention with these services is one rather advantageous embodiment.

The information about the allowed network elements from which incoming calls are forwarded can be determined either on the basis of location data only or on the basis of both location data and mobile subscriber. The invention is not limited to the method of storing the bulk information of network elements shown in the example of Fig. 9. The information can also be stored in a way other than in tabular form. An arbitrary number of categories can be defined, for example only one. Incoming calls can be defined to be forwarded, for example, from all network elements of one operator or one country, such as mobile switching centers. In doing so, the information described in Figure 9 describing the location information of the B-subscriber among the allowed network elements may not be required. For example, check 1007 of Figure 10 then simply compares the country codes or country and network codes of the A-subscriber network element GMSCA and the B-subscriber visitor location register.

Of course, the set of allowed network elements can also be defined by defining those forbidden network elements from which incoming calls are not forwarded to the called subscriber. In this case, the set of allowed network elements is a negation of the set of forbidden network elements among all network elements.

The depth of numerical analysis of the VLRB and GMSCA addresses of the network elements used in the network element comparison may also vary. Numerical analysis is preferably performed either at the country level of the network by analyzing the country code CC alone or at the operator level by checking both the country code CC and the network code NDC.

The analysis preferably performed in the home location register HLR according to the invention can be carried out as soon as the network element of the calling subscriber, the location information of the called subscriber (i.e. the address of the VLRB, for example) are known. The analysis can also be performed at some other stage, e.g.

As will be apparent, embodiments of the invention are not limited to the exemplary embodiments set forth above, but may vary within the scope of the appended claims.