Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-08-17
2003-09-30
Maung, Nay (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432100, C455S433000, C455S528000
Reexamination Certificate
active
06628950
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to management of barring of incoming calls in a mobile telecommunications system.
BACKGROUND OF THE INVENTION
FIG. 1
shows network elements and their mutual relations in connection with routing of a call in a known mobile telecommunications network PLMN (Public Land Mobile Network). The presented network is in accordance with the GSM system used as an example in this example. In this connection, a network means a mobile telecommunications network operated by one operator. The solid lines in the figure depict connections comprising both signalling and call connection whereas dashed lines depict such connections which comprise signalling only. The network includes base transceiver stations BTS able via a radio path to set up connections with mobile stations MS of mobile subscribers, base station controllers BSC controlling base transceiver stations and mobile services switching centres MSC. Under the MSC in the hierarchy there are typically several base station controllers BSC, while under these there are several base transceiver stations BTS. The call connections which have been set up pass from base transceiver station BTS via the base station controller BSC to the mobile services switching centre MSC, which connects calls either back to base station controllers under itself, to other mobile services switching centres MSC or to a fixed public switched telephone network PSTN or integrated services digital network ISDN. In addition, the network includes a network management system NMS which may be used for collecting information on the network state and for supplying information and programmes to other network elements.
It is characteristic of mobile telecommunications networks that the geographic location of mobile stations may change. For this reason, the network must maintain information on the locations of mobile subscribers. In the network of
FIG. 1
, this information is distributed to a home location register HLR and to visitor location registers VLR located in connection with mobile services switching centres MSC. The HLR, which is always in the subscriber's own home network, contains unchanging subscriber information and information on the subscriber's location with VLR precision. Information on the subscriber's reachability and on the more precise location with so-called location area precision is stored in the VLR located in connection with the subscriber's current mobile services switching centre VMSC.
FIG. 2
shows routing of a call. The figure names calling subscriber A's home network PLMNA, called subscriber B's home network HPLMNB and network VPLMNB visited by subscriber B. PLMNA, HPLMNB and VPLMNB may all be the same network operated by one operator (internal call of one operator) or networks operated by two or three different operators. The figure shows a case where subscriber A too is a mobile subscriber. If subscriber A is a fixed network subscriber, routing is exactly similar, but the GMSCA (Gateway MSCA) of subscriber A in the figure will be replaced with the GE (Gateway Exchange) of the fixed network.
FIG. 3
shows the signalling required when setting up a call. When setting up a call terminating in mobile station B, a connection is first set up with an initial address message IAM based on subscriber B's subscriber number MSISDN(B) with the GMSCB (Gateway MSCB). The GMSCB asks for routing information from subscriber B's home location register HLRB with SRI (Send_Routing_Info). Having received Send_Routing_Info, the HLRB performs a subscriber information check which is described more closely hereinafter. If no barrier to the incoming call is found in the subscriber information check, the HLRB will request the MSRN (Mobile Subscriber Roaming Number) from subscriber B's present visitor location register VLRB with PRN (Provide_Roaming_Number). VLRB returns the MSRN number to HLRB in a PRN_ACK message. HLRB relays the MSRN to GMSC by a SRI_ACK message. GMSC sets up a connection with subscriber B's MSCB using the identifying MSRN of called subscriber B.
Payments for calls are determined so that the calling subscriber, that is subscriber A, always pays for that part of the call which is between subscriber A and the home network of the called subscriber, that is subscriber B. The principle is that subscriber A, who does not know the location of subscriber B, will not have to pay any unpredictably high price for the call he makes. When outside his home network or when using a call forwarding service, subscriber B will pay for that part of the call which is forward from his home network. Hence when e.g. subscriber A is in Sweden and calls a New Zealand subscriber in Finland, subscriber A will pay for the part of the call from Sweden to New Zealand, while subscriber B will pay for the part going from New Zealand to Finland.
When far away from his own network, a subscriber may have to pay a considerable price for the calls he receives. For this reason, barring services for incoming calls are defined in GSM. Such services are e.g. BAIC (Barring of All Incoming Calls) and BIC-Roam (Barring of Incoming Calls when Roaming). Information about these barring services is stored in the subscriber's home location register HLR.
The flow chart in
FIG. 4
shows a subscriber information check of a call performed by the called subscriber's home location register HLRB. Having received a SRI request (point
401
), HLRB will search its database for the address of the called subscriber's current visitor location register VLRB. At point
403
HLRB examines if the call is barred. If the call is not barred, progress will be made to point
404
, where a PRN request is sent to VLRB, and the MSRN number received in response to the request is relayed to the exchange which made the routing information inquiry (point
406
). If the subscriber has activated barring of incoming calls, HLRB will not send the Provide_Roaming_Number request of the signalling diagram in
FIG. 3
to subscriber B's visitor location register VLRB, but will send (point
411
) an error message SRI_ERROR to the exhange which made the routing information inquiry SRI, stating barred call as the reason code.
In addition to checking of barring of incoming calls shown in
FIG. 4
, HLR also checks other matters, such as the existence of the called subscriber, any changes in the subscriber number, unconditional call forwarding to another number, and permission to the requested service. However, these are not essential from the viewpoint of the invention presented in this application, nor are they shown in the figure for this reason.
ETSI (European Telecommunications Standards Institute) is specifying a so-called optimal routing of calls for the GSM system, besides the normal call routing method presented above. The basic idea of optimal routing of calls is to use the straightest route possible between subscriber A and subscriber B as shown in FIG.
5
. The home network of subscriber B does not necessarily take part in the call otherwise than as regards HLR signalling. By using optimal call routing, costs of calls between exchanges or centres can be saved and thus the total price of the call can be reduced.
The MoU (Memorandum of Understanding, the organisation of GSM operators) has imposed two requirements on the implementation of optimal routing:
1. use of optimal routing must not cause any price increase for any user, and
2. one subscriber always pays for one leg of the call at least in the first stage of the service.
Since it can not be assumed that the price of different legs of a call is 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. The total cost of the call is hereby typically on the same level as a call made to the mobile station inside the same country.
Since optimal routing aims at routing the call using as direct a route as possible, it must be possible to make the HLR request at a
Haumont Serge
Verkama Markku
Maung Nay
Nokia Corporation
Sobutka Philip J.
Squire Sanders & Dempsey L.L.P.
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