TRANSMITTING SUBSCRIBER IDENTITY IN MOBILE COMMUNICATION SYSTEM

Abstract: The invention relates to a method and a mobile communication system for transmitting the identity of a calling subscriber (subscriber A) to a called subscriber (subscriber B) in a mobile communication system comprising a home location register (HLR) for permanent storage of subscriber data on mobile stations (MS) registered in the network, and at least one visitor location register (VLR) for temporary storage of subscriber data on mobile stations (MS) located in the geographical area monitored by the visitor location register (VLR). The invention is characterized in that the identity of subscriber A is transmitted to the mobile services switching centre (MSC) of subscriber B via signalling that is unrelated to the speech connection.

Description: TRANSMITTING SUBSCRIBER IDENTITY IN MOBILE COMMUNICATION SYSTEM FIELD OF THE INVENTION The invention relates to a method of transmitting the identity of a calling subscriber (subscriber A) to a called subscriber (subscriber B) in a mo¬ bile communication system comprising a home location register for permanent storage of subscriber data on mobile stations registered in the network, and at least one visitor location register for temporary storage of subscriber data on mobile stations located in the geographical area monitored by the visitor loca- tion register, whereby signalling that is unrelated to the speech connection is transmitted between the switching centres and registers of the mobile commu¬ nication system. The invention further relates to a mobile communication system comprising a home location register for permanent storage of subscriber data on mobile stations registered in the network, and at least one visitor location register for temporary storage of subscriber data on mobile stations located in the geographical area monitored by the visitor location register. Signalling that is unrelated to the speech connection is transmitted between the switching centres and registers of the mobile communication system. BACKGROUND OF THE INVENTION A service usually offered by present mobile communication systems is notification of the identity of the calling subscriber (subscriber A) to the called subscriber (subscriber B) during call set-up. This enables subscriber B to identify the caller before answering the call. Figure 1 in the attached drawing illustrates mobile MS B terminating call set-up in a GSM-type mobile communication system. The Figure only shows the relevant network elements as far as call set-up signalling is con¬ cerned. At point 1 a call initiated by subscriber A is routed from the network of subscriber A (e.g. a mobile communication system PLMN or a public tele- phone network PSTN) to the Gateway MSC (GMSC) of the PLMN home net¬ work of subscriber B. The GMSC transmits an inquiry (message 2) about routing information to the home location register HLR of subscriber B. The subscriber data on the mobile station MS is permanently stored in the home location register HLR and temporarily in the visitor location register VLR in whose area the mobile station MS is located. During location update, informa- tion on the visitor location register VLR in whose area subscriber B is located is updated to the home location register HLR of subscriber B. In the example of Figure 1 , subscriber B is located in another mobile communication network PLMN. At point 3, the home location register HLR transmits to the visitor loca- tion register VLR of subscriber B a request for a roaming number to the PLMN network to be visited. The visitor location register VLR reserves a Mobile Sta¬ tion Roaming Number (MSRN) and transmits the number to the home location register HLR in a reply message 4. The home location register HLR forwards the roaming number in message 5 to the GMSC of the home PLMN which in- quired about the routing information. On the basis of the roaming number, the GMSC can then route the call to the mobile services switching centre MSC of subscriber B in the PLMN network visited, if necessary via a transmitting tran¬ sit network, as in Figure 1 , in a set-up message 6. Information on the identity of subscriber A is transmitted to subscriber B in a Calling Line Identity (CLI) field of the set-up message 6. The above kind of transmission of the calling subscriber identity is not always successful, e.g. when subscriber B is located in the area of another PLMN, as in Figure 1. Although call set-up is possible between different networks, all networks do not support the network signalling used in the transmission of the calling subscriber identity. In these cases the called subscriber is notified, in accordance with point 1.4 (version 4.4.1) of the recommendation GSM 02.81 , that the CLI is not available. BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to enable transmission of the identity of a calling subscriber to subscriber B even if call set-up does not sup- port transmission of calling subscriber identity, e.g. because subscriber B is located in the area of another network. This new type of transmission of the identity of subscriber A is achieved with the method of the invention, which is characterized that the identity of subscriber A is transmitted to the mobile services switching centre of subscriber B via signalling that is unrelated to the speech connection. The invention further relates to a mobile communication system de¬ scribed in the preamble, which, according to the invention, is characterized in that it is arranged to transmit the identity of subscriber A to the mobile services switching centre of subscriber B via signalling that is unrelated to the speech connection. The invention is based on the idea that the subscriber identity is transmitted in signalling traffic between the switching centres and registers of the mobile communication system, preferably before a call is established. The advantage of such a method for transmission of the identity of subscriber A is that the identity of subscriber A can be transmitted to sub¬ scriber B irrespective of the signalling protocols of the networks used for call set-up. A further advantage of the invention is that the identity of subscriber A can be transmitted to subscriber B to the area of another network, e.g. abroad. LIST OF DRAWINGS In the following the invention will be described in greater detail with reference to the accompanying drawings, in which Figure 1 illustrates call set-up in a GSM system, and Figure 2 shows transmission of subscriber A identity CLI according to the method of the invention. DETAILED DESCRIPTION OF THE INVENTION The present invention can be applied to any mobile communication system. By way of example, the invention will be described below in connec- tion with the pan-European digital mobile communication system GSM. As to a more detailed description of the GSM system, reference is made to GSM rec¬ ommendations and the publication 'The GSM System for Mobile Communica¬ tions", M. Mouly & M. Pautet, Palaiseau, France, 1992, ISBN:2-9507190-0-7. Figure 1 illustrates signalling associated with call set-up, previously described in connection with state-of-the-art call set-up. In the following the invention will be described in more detail by means of a preferred embodiment with reference to Figure 1. In this embodiment the transmission of subscriber A identity is associated with message 3 of Figure 1. Using MAP signalling of the GSM system, the home location register HLR transmits a roaming number re- quest by a PROVIDE_ROAMING_NUMBER message to the visitor location register VLR. In the preferred embodiment of the invention, the identity of the calling subscriber, e.g. the phone number or the ISDN number, is added to the PROVIDE_ROAMING_NUMBER message, thus enabling identification of subscriber A. As to the other messages of Figure 1 , call set-up in a mobile communication system utilizing the method of the invention conforms with the above described state-of-the-art technique. Figure 2 illustrates the transmission of the CLI under call set-up ac¬ cording to the preferred embodiment of the invention. The calling subscriber (subscriber A) states his/her identity when initiating a call. At point 1 this infor- mation is forwarded via the PLMN home network of subscriber B to the GMSC in a manner known per se. At point 2 the GMSC forwards the CLI to the home location register HLR of subscriber B, e.g. in connection with the inquiry about routing information. In accordance with the invention, at point 3 the PRO- VIDE_ROAMING_NUMBER message of the request for a roaming number forwards the CLI from the home location register HLR to the visitor location register VLR, which stores the CLI. In accordance with prior art, the visitor lo¬ cation register VLR answers the request for a roaming number by allocating a roaming number MSRN to the call and by transmitting it to the home location register HLR (point 4), which forwards the roaming number to the GMSC for routing of the call (point 5). Once the set-up message 6 arrives from the GMSC, possibly via a public telephone network or another transit network to the mobile services switching centre MSC of subscriber B in the PLMN net¬ work being visited, the MSC makes an inquiry about subscriber data to the visitor location register VLR and receives in the answer, among other things, the identity of subscriber A. The MSC forwards the identity of subscriber A to subscriber B in a manner known per se. The invention has been described above by way of an example with reference to Figures 1 and 2, in a case when call set-up is carried out via the GMSC of the home network of subscriber B. When subscriber A is located in the same network as the home location register HLR of subscriber B, the call does not have to be routed via the GMSC of subscriber B. Neither is there any need for the GMSC of Figure 1 if the switching centre of subscriber A or the gateway MSC of the network of subscriber A has the capacity to communicate directly with the home location register of subscriber B. In this case the call initiated by subscriber A does not have to be transmitted to the GMSC, but instead the switching centre of subscriber A, e.g. a mobile services switching centre, or the gateway MSC of the network of subscriber A transmits the rout¬ ing inquiry direct to the home location register HLR of subscriber B (message 2' in Figure 1). The home location register HLR transmits a roaming number request to the visitor location register VLR in accordance with the above de¬ scribed embodiment of the invention by forwarding the identity of subscriber A in message 3. In a reply message 4 the home location register HLR gets a roaming number MSRN in accordance with the set-up signalling described above. The home location register HLR transmits to the switching centre of subscriber A or the network gateway MSC of subscriber A the roaming number MSRN reserved by the visitor location register VLR in message 5' of Figure 1. Having received this message, the switching centre or the network gateway MSC of subscriber A routes the call to the mobile services switching centre of subscriber B, possibly via a transit network. Transmission of the identity of subscriber A according to the present invention is also applicable when both subscriber A and subscriber B are lo¬ cated in the home PLMN of subscriber B. A prerequisite for the use of the method of the invention is that the CLI has been transmitted to the home loca¬ tion register HLR of subscriber B. The drawings and the description related thereto are only intended to illustrate the idea of the invention. The details of the mobile communication system and the method for transmitting the identity of subscriber A of the in¬ vention may vary within the scope of the claims. Even though the invention has been described above mainly in connection with MAP signalling, the method can be realized by utilising other kinds of signalling between the mo- bile services switching centres and registers of a mobile communication sys¬ tem.

Claims: CLAIMS 1. A method of transmitting the identity of a calling subscriber (subscriber A) to a called subscriber (subscriber B) in a mobile communication system comprising a home location register (HLR) for permanent storage of subscriber data on mobile stations (MS) registered in the network, and at least one visitor location register (VLR) for temporary storage of subscriber data on mobile stations (MS) located in the geographical area monitored by the visitor location register, whereby signalling that is unrelated to the speech connection is transmitted between the switching centres (GMSC, MSC) and registers (HLR, VLR) of the mobile communication system, characterized in that the identity of subscriber A is transmitted to the mobile services switching cen¬ tre (MSC) of subscriber B via signalling that is unrelated to the speech con¬ nection. 2. A method as claimed in claim ^characterized in that the identity of subscriber A is transmitted before call set-up. 3. A method as claimed in claim 1 or 2, characterized in that the home location register (HLR) transmits to the visitor location register (VLR) the identity of subscriber A in connection with a request for routing in¬ formation. 4. A method as claimed in claim 3, characterized in that the identity of subscriber A is transmitted in a MAP PROVIDE_ROAMING_NUM- BER message. 5. A method as claimed in any one of the preceding claims, characterized in that subscriber B is located in a visited network. 6. A mobile communication system comprising a home location register (HLR) for permanent storage of subscriber data on mobile stations (MS) registered in the network, and at least one visitor location register (VLR) for temporary storage of subscriber data on mobile stations (MS) located in the geographical area monitored by the visitor location register (VLR), whereby signalling that is unrelated to the speech connection is transmitted between the switching centres (GMSC, MSC) and registers (HLR, VLR) of the mobile communication system, characterized in that the mobile communica¬ tion system is arranged to transmit the identity of subscriber A to the mobile services switching centre (MSC) of subscriber B via signalling that is unrelated to the speech connection. 7. A mobile communication system as claimed in claim 6, char¬ acterized in that the home location register (HLR) is arranged to transmit the identity of subscriber A to the visitor location register (VLR) in connection with a request for routing information. 8. A mobile communication system as claimed in claim 7, char¬ acterized in that the home location register (HLR) is arranged to transmit the identity of subscriber A in a MAP PROVIDE_ROAMING_NUMBER mes¬ sage. 9. A mobile communication system as claimed in claim 6, 7 or 8, characterized in that subscriber B is located in a visited network.

Inventors: HUOTARI SEPPO, HUOTARI, SEPPO
Applicants: HUOTARI SEPPO, NOKIA TELECOMMUNICATIONS OY, HUOTARI, SEPPO
Application year: 1997
Main classification: H04Q7
IPC codes: H04M1, H04M3, H04Q7