EXTENDED FUNCTIONALITY IN MOBILE TELEPHONE NETWORK

Abstract: In a cellular mobile telecommunication system there is possibility to make change of base of calls in progress to other mobile telephone networks. The invention deals with a method to collect information necessary to make possible to make a change of base. Said information is collected without aid from the network operator in the second mobile telephone network. Necessary information is collected from the second mobile telephone network by measuring of signals. The following processing of the information aims at deciding which base stations in this second network which are so located that it is possible to make change of base to them. This means in most cases which base stations which, in the measured area, have sufficient signal strength to constitute candidate for change of base from base station in the delivering network.

Description: EXTENDED FUNCTIONALITY IN MOBILE TELEPHONE NETWORK TECHNICAL FIELD In a cellular mobile telecommunication system there is possibility to change base for call in progress from a first mobile telephone network to a second mobile telephone network. The invention deals with a method to collect information which is utilised to automatically set parameters of the first mobile telephone network, the delivering network, which is condition for that change of base shall be possible to perform. Said information is collected without aid from the network operator in the second mobile telephone network. PRIOR ART Previous solutions to set parameters in the delivering network has implied active participation from concerned network operators. At a performed patent state investigation the following documents have been found: Dl. GB 2310111 D2. EP 725552 Document Dl shows a procedure for synchronisation between different base stations, also between such which belong to different networks. The synchronisation is arranged by means of a device which transmits reference pulses, which are adjusted in accordance with the transmission delay. Document 2 shows a method for transmission of parameters from a telecommunication system for wireless telephony, preferably a DECT-system, to a cellular mobile telephone system. The parameters are transferred in given transfer zones between the systems. Neither of the documents includes explicitly, or in combination, the suggested technology. TECHNICAL PROBLEM A mobile telephone is adapted to be used within a mobile telephone network, PLM . A PLMN covers a geographical area and is run by a network operator. The geographical area does not normally extend beyond the borders of a country, but the network also can have a more limited range depending on that a network operator can have been given concession to carry on mobile telephony within only a part of a country. Especially during a construction period the geographical area may also be limited due to that the network operator's establishment does not cover the whole area where he/she has possibility to run mobile telephony. Concession to run mobile telephony can be given to more than one network operator, at which it within a geographical area may exist competition between a number of network operators. Mobile telephones in a cellular mobile telephone network are connected to a base station which belongs to the network operator of the network. A base station has a radio coverage area which is limited by the range of the base station. Outside this radio coverage area other base stations have a radio coverage area, so that in the ideal case the whole surface is covered by the radio coverage areas of different base stations. At transit between the radio coverage areas of base stations, change of base has to be made to another base station which belongs to the same network operator, so that the mobile telephone shall be able to maintain the contact with the mobile telephone network. Such change of base can also be made during call in progress, and then it is normally made without the conversing parties noticing that change of a base has been made . In for instance the mobile telephone standard for GSM, there also is the possibility to effect change of base between different mobile telephone networks, which can be run by different network operators, during and between calls. This can be made both within a nation and across national borders. Change of base then is made from a base station which belongs to a first mobile telephone network where the call is established, after this called "delivering network", to a base station which belongs to a second mobile telephone network, after this called "receiving network". To make this possible during a call is, however, required that the delivering network has knowledge of detailed information about the base stations in the receiving network. In mobile telephone systems with network controlled change of base, for instance in GSM, the mobile telephone network must have knowledge of signal levels from base stations in the neighbourhood of the mobile telephone, measured from the mobile telephone. When measured signal level shows that connection to another base station is advantageous, change of base is initiated. In order to get basic data for the mobile telephone network for decision of change of base, each mobile telephone measures signal levels of neighbouring base stations. This in its turn implies that the base station transmits signals to the mobile telephones and transmits information about the base stations which shall be measured, and that the result from the measurement then is transmitted to the base station. This information is transmitted to the mobile telephones in form of a so called "list of neighbours". In order to create this list of neighbours, the mobile telephone network must have access to information about the base stations. Within each mobile telephone network, the network operator sees to it that the mobile telephone network is loaded with necessary information about the base stations. If change of base shall be made to another mobile telephone network, the base station also must be provided with the necessary information regarding the other network. Today this is achieved by the two involved network operators exchanging information with each other manually, or via some type of automatic connection. As soon as a small change in any of the networks, the co-operating network operator, however, must immediately be informed. In other case there is no possibility to make change of base during a call in progress. This implies that the delivering network must have access to this information immediately when the change is made, to make it possible to maintain the service level aimed at. Such an arrangement, which implies an immediate exchange of information between independent organisations, is very difficult to maintain. The close co-operation required to make it possible for all parties to continously have access to right information is further made difficult if the network operators are competing . TECHNICAL SOLUTION The here described technical solution is based on a cellular mobile telephone network, for instance a GSM- network. In order to make possible change of base to other mobile telephone networks during call in progress, information must be collected for setting of parameters. According to the invention, the necessary basic data are collected from the receiving network by signal measuring. The subsequent processing of the information intends to decide which base stations in the receiving network which are so located that it will be possible to make a change of base to them. This means in most cases which base stations which, in the measured area, have sufficient signal strength to constitute candidate for change of base from base station in the delivering network. The method is used in mobile telephone networks or similar systems where change of base can be made between base stations belonging to two different networks. This is, for instance, usable in, and between, all networks based on the GSM-standard, i.e. GSM 900/1800/1900 and GSM-R. Change of base between different networks and systems are also expected to be possible in future systems, such as UMTS. The method can be used both between networks within a nation and between networks which are in different nations. ADVANTAGES A mobile telephone network is built to cover a country or a part of a country. If a mobile telephone user passes the border of the area which is covered by the mobile telephone network to which the telephone is connected, call in progress is normally disconnected. Through co-operation between network operators there are functions and routines so that the mobile telephone can establish contact with the new mobile telephone network after such a border having been passed. After that the user can use the telephone for new calls. By an extended bilateral co-operation between two network operators there will be possibilities to exchange information so that change of base during call in progress also can be made at change of base to base station in another mobile telephone network. A network operator in a telecommunication network can, at need, for instance effect a change of base of calls between networks, by the suggested method collect necessary parameter data. The method makes it possible for a network operator in a network to collect these parameter data without assistance from the party which represents the other network. The suggested method can be used at crossing of a border between countries. In that way a call in progress can proceed apart from that the border has been passed. When a network operator has concession for mobile telephony within only a part of a country, or the network has been built out only within a smaller area, call in progress can, according to the described method, proceed without the user being disturbed when a limit of the network operator's area is passed. At such disturbances, or at so heavy traffic load that the network operator has no resources to manage all traffic which is required within his/her radio coverage area, he/she in the same way has possibility to utilise other network operators within the same geographical area. Established mobile telephone calls then can be transferred to another network operator and by that good quality and access in the network can be maintained. LIST OF FIGURES Figure 1 shows collection of data by placed measuring receiver . Figure 2 shows collection of data by means of existing mobile telephones. EXPLANATION OF TERMS Delivering network Mobile telephone network where the call is established and from which the change of base is made. Change of base Handover. (Switching to other BTS) BSC Base Station Controller (Control unit for base stations). BTS Base station in cellular mobile telephone network. GSM Global System for Mobile communication . Receiving network Mobile telephone network to which change of base is made. MS Mobile Telephone NE Network Element; connection controlling unit in telecommunication network, for instance BTS, BSC. PLMN Mobile telephone network which is managed by a network operator. SMS Short Message Service (Short text message; service in GSM for packet switched data) . DETAILED DESCRIPTION The description below refers to the figures of the enclosed drawings . The invention is based on that within a first mobile telephone network, the delivering network, measurements collection and processing of information is made which relates to a second mobile telephone network, the receiving network. In the area where the first mobile telephone network operator wants that change of base shall be possible to make, in addition to base stations in the own mobile telephone network also to base stations in a neighbouring mobile telephone network, measuring receivers are arranged for collection of information. Such an area can be a border area of a mobile telephone network, which is run by a second mobile telephone network operator, and where the first mobile telephone operator's network does not have radio coverage. The area also can have coverage by the first mobile telephone network operator's network, but he/she may need to have the possibility to in certain situations transfer established calls to another operator. The processing of information intends to decide which base stations in the receiving network which it can be suitable to change base to. This means in most cases which base stations which, in the measured area, have sufficient signal strength to constitute candidate for change of base from respective base station in the delivering network. When a list has been made with information about all base stations which may be subject to change of base, the information is transformed into parameter setting commands which are fed into the network elements of the network. In for instance GSM each connected mobile telephone is arranged to make measurements of signal strength etc for neighbouring base stations. The result of the measurements are transmitted from the mobile telephone to the base station to which the mobile station is connected, in order to later be utilised by BSC for analysis and decision of change of base. Information about base stations, or "neighbouring cells", for which the mobile telephone shall make such measurements is transferred to the mobile telephone in a "list of neighbouring cells". According to the here described invention this list of neighbouring cells is extended with neighbouring cells which are located within another mobile telephone network. When a mobile telephone makes measurements about neighbouring cells, this information will apply for both neighbouring cells within the own network and neighbouring cells within the other network. By that there will be a possibility that BSC decides that the mobile telephone shall make a change of base to base station within another mobile telephone network. By this arrangement a better service consequently will be offered the network operator's customers . PREFERRED EMBODIMENT In the area where a first mobile telephone network operator wants that change of base shall be possible to make, in addition to base stations in the own mobile telephone network also to base stations in a second mobile telephone network, specific measuring receivers (1) are placed. The measuring receivers are arranged to measure necessary information about the receiving network, for instance cell identity and used frequency. If the need for such measuring is limited to a few smaller areas, this described embodiment is favourable. The embodiment can also be suitable if the receivers are integrated with, or are placed together with, the base stations in a standardised arrangement . The measuring receivers are placed in that part of a first network operator's radio coverage area where there a change of base to a PLMN, which is managed by another network operator, can be of interest. This can be at the periphery of the radio coverage area, in order to in that way make possible change of base to base station within a PLMN with a radio coverage area outside that of the first network operator's. It also can be favourable to place measuring receivers within the first network operator's radio coverage area in order to create a possibility to, for instance at lack of resources, make change of base to a base station within another PLMN but in the same geographical area. The placed measuring receivers transmit the measured information to a device (2) for processing and generation of commands. The result of the processing then is transferred to the network element in question (3) such as BSC and base stations so that information about base stations in the neighbouring network can be entered in the list of neighbouring cells which is transmitted to connected mobile telephones. By that BSC will have access to information which is needed as basic data for decision and initiation of measures for change of base. The measuring receivers can for instance be placed together with a base station, or be built in as a part of a base station, to from this place make necessary measuring. As an alternative, the measuring receivers can be placed in other places within the radio coverage area of the base station. ALTERNATIVE EMBODIMENT According to an alternative embodiment all existing mobile telephones (21) connected to a first mobile telephone network, the delivering network (25) , are used as measuring receivers. The mobile telephones are arranged to measure on one or more of the frequencies which have been allocated the second mobile telephone network, the receiving network (24). Necessary parameters are transferred to a device (22) for processing and generation of commands. The result is then transferred to network elements in question (23) and is utilised in the same way as has been described above. Algorithm and processing procedure can be transmitted via data message to the mobile telephones, for instance as SMS- message in GSM-system. After that the mobile telephones are ready to serve as measuring receivers. This embodiment therefore does no require any change in existing equipment, neither in MS nor in BTS, but all changes can be made in software and procedures. This embodiment, however, requires a more complicated data processing than the one described above . The in this embodiment described simpler introduction without installation in plants or other existing equipment also means that one rapidly will have radio coverage of a larger geographical measuring area. The invention is not limited to the above presented embodiments, but can in addition be subject to modifications within the frame of the following patent claims and the idea of invention.

Claims: PATENT CLAIMS 1. A method to, in a first cellular mobile telephone network, collect information, for instance cell identity and frequency about cells in a second cellular mobile telephone network so that a list over neighbouring cells of base stations for which measurements shall be made by the mobile telephone, and which are required for decision of change of base, can be created and transmitted to mobile telephones in the first mobile telephone network, c h a r a c t e r i s e d in that the information is collected by measuring by means of measuring devices, which are within the radio coverage area of base stations within the first mobile telephone network. 2. A method as claimed in patent claim 1, c h a r a c t e r i s e d in that said information is collected by the network operator who manages the first mobile telephone network, without participation from the network operator who manages the second mobile telephone network. 3. A method as claimed in patent claim 1 or 2 , c h a r a c t e r i s e d in that the cellular networks are GSM networks . 4. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that change of base from a base station in the first mobile telephone network to a base station in the second mobile telephone network is made possible during call in progress . 5. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that the first mobile telephone network is located in one nation, and the second mobile telephone network in another nation. 6. A method as claimed in any of patent claims 1 to 4 , c h a r a c t e r i s e d in that the two mobile telephone networks are located in the same nation. 7. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that said collected information constitutes basic data for extension of the list of neighbouring cells which is transmitted to mobile telephones which are connected to the first mobile telephone network, with neighbouring cells which are located within the second mobile telephone network. 8. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that measuring receivers (1) for collection of said information about cells in the second mobile telephone network are placed in that part of the radio coverage area of the first mobile telephone network where change of base to a base station in the second mobile telephone network may be of interest. 9. A method as claimed in patent claim 8, c h a r a c t e r i s e d in that said measuring receivers are integrated with, or placed together with, the base stations in a standardised arrangement. 10. A method as claimed in patent claim 8 or , c h a r a c t e r i s e d in that said measuring receivers are placed in the periphery of the radio coverage area of the first mobile telephone network in order to make measuring of data regarding base stations in the second mobile telephone network with a radio coverage area outside the radio coverage area of first mobile telephone network. 11. A method as claimed in any of patent claims 1 to 8 , c h a r a c t e r i s e d in that all existing mobile telephones (21) connected to a first mobile telephone network (25) are used to collect necessary information, for instance cell identity and frequency, regarding cells in the second mobile telephone network (24) . 12. A method as claimed in patent claim 11, c h a r a c t e r i s e d in that said mobile telephones are arranged to measure on one or more of the frequencies which have been allocated to the second mobile telephone network (24) . 13. A method as claimed in patent claim 11 or 12, c h a r a c t e r i s e d in that algorithm and processing procedures are transferred via data message to the mobile telephones, which after that operate as measuring receivers . 14. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that the measured information is transferred to a device (2, 22) for processing and generation of commands with after that following transfer of results to current network elements (3, 23), such as BSC and base stations. 15. A method as claimed in any of the previous patent claims, c h a r a c t e r i s e d in that change of base from one base station in the first mobile telephone network to a base station in the second mobile telephone network can be made at such distorsion, or at such heavy traffic load, that the resources to manage the traffic which is required is not momentary sufficient within the first mobile telephone network.

Inventors: LJUNGGREN TOMMY, LJUNGGREN, TOMMY
Applicants: LJUNGGREN TOMMY, TELIA AB, LJUNGGREN, TOMMY, TELIA AB (PUBL)
Application year: 1999
Main classification: H04Q7
IPC codes: H04W36, H04W48