Background of the invention In building a fixed telephone network, the installation of subscriber lines between the exchange and subscriber terminals is both a considerable cost item and also a measure demanding much time. Maintenance of sub- scriber lines is a major cost item also in network maintenance. In scarcely populated areas in particular, costs may be high for the individual connec- tion. One solution for reducing costs is to replace the fixed subscriber loop between exchange and subscriber terminal with a radio connection.

A system embodying a wireless subscriber loop can be imple- mented either by connecting the base stations by way of a special network element called an access node to the telephone exchange of a fixed network or by utilizing an existing mobile telephone system either as such or by re- moving some network elements and/or by simplifying some functions. The name WLL system (Wireless Local Loop System) is used in this application as a common name for these solutions.

Figure 1 shows the principle of a WLL system based on a fixed network. A wireless fixed terminal 4 comprises a radio unit equipped with an aerial and a telephone adapter connecting a standard subscriber device 5 with the terminal. The subscriber device may be an ordinary telephone, a telefax or a modem and it is connected to the terminal by pushing a standard plug into the terminal's adapter connection. The user operates the subscriber device 5 in the same way as in a normal fixed network, although a major part of the subscriber line connection is formed by a radio link between the termi- nal 4 and the base station 2. The subscriber device and the terminal can be combined to form one physical equipment 6. Each base station may serve

several subscriber terminals. The base stations are connected to a special access node 1, which for its part is connected to a standard telephone ex- change.

Access node 1 is connected to the local exchange with a multi- plexer using 2 Mbit/s PCM system of the open V2 or V5.1 type. If the local exchange supports a 2-wire connection only, the access node is connected to the exchange by converting V2 signalling into an analog 2-wire subscriber connection interface with the aid of the multiplexer. Signalling between the access node and the base stations connected to it is the signalling of an applied mobile telephone network, for example, a NMT or GSM network, however, modified in such a way that functions typical of a cellular network, such as cell handover and roaming, are left out. Thus, the subscriber must stay within the coverage area of that base station determined to it. The sub- scriber access node converts the signalling of the WLL network into signal- ling suitable for a fixed network (for example, PSTN) and, correspondingly, adapts the signalling of the fixed network into the WLL network interface.

Routing of incoming and outgoing calls is based on the subscriber data file located in the subscriber access node.

A WLL system based on a mobile telephone network is con- structed so that structural elements of some existing cellular system are applied. Hereby the signalling in the WLL system is in accordance with the system in question, the base stations are standard base stations of the sys- tem in question and the radio unit of the terminal is of the same type as the radio unit of the mobile station. The subscriber access node connecting subscribers to the standard local exchange is an important component of the WLL system. In a pure cellular system it is a mobile telephone exchange and in an applied system it is an access node to be described later.

Figure 2 shows the main structural features of a known mobile telecommunication system. The network comprises several interconnected mobile services switching centres MSC. The MSC centre may establish connections with other MSC centres or with other telecommunication net- works. Several base station controllers BSC are connected to the MSC.

Base stations BTS are connected to each base station controller. The con- nection with the mobile station MS is always through a base station. Data is collecte from the network and access nodes are configured with the aid of a network management system NMS. A billing centre collects call data records

CDR sent by the mobile services switch centres and based on these it forms the telephone bill for the subscriber.

The mobile telephone network also includes different databases.

Subscriber data is stored permanently in a home location register HLR re- gardless of the subscriber's current location. Subscriber service data, among other data, is stored in the register and routing data is stored in the visitor location register VLR. Subscriber data available from the HLR is stored in the visitor location register for the time of the subscriber's visit to the VLR area.

The mobile telephone network is suitable as such for WILL termi- nals. Information on that the subscriber is a WLL subscriber and data telling in which cell's area the subscriber resides are facts which are stored in the home location register HLR. This cell is called the subscriber's home cell.

The subscriber may have the right to receive and start calls only in the area of this cell, in Figure 2 terminal 21 could function in the cell A only. In prac- tice, such a situation might occur where the geographical location of the WLL terminal is in an area where the best audibility is obtained in more than one cell depending on radio conditions. In Figure 2 such an area is marked with the letter D and from this area the best connection can be obtained either to cell A, B or E, depending on radio conditions. Hereby these cells A, B and E are defined as home cells for the WLL subscriber. Handover may then be allowed between these base stations.

Irrespective of the subscriber's mobility, one cell or several cells can be named as home cell in a mobile station network, whereby calls started from and received in the home cell are cheaper. The applicant's patent applications FI-946091 and FI-946092 present some ways of imple- menting this. According to these, in the call establishment the exchange analyses whether the calling subscriber's location cell and/or the called sub- scriber's location cell belong to a group of special cells. Different charge rates can then be varied if the subscribers are in a group of special cells. The functions could also be based on an intelligent network IN, wherein the service switching centre SCP performs the analysis and applies the special charging basis which has been set for the group.

Principles like the one described above are also applicable to the setting of the WLL subscriber's home cell or home cells.

A prior art telephone system has several drawbacks resulting from the home cell or home cells. At present it is very problematic for the operator

to know the subscriber's home area and the cells of the home area, from which area the subscriber may make/receive a call. This is due to the fol- lowingcircumstances: The operator has no up-to-date data on the coverage area and field strengths in the billing centre BC, so when the subscriber states himself to be a WLL subscriber, he is not able at once to determine the subscriber's home area and its cell identifiers nor to store cell data of different home ar- eas in a database, such as MSC/HRL or a similar database. For this reason, the operator must get in touch with the network planning or field staff to make sure that there is a sufficiently powerful coverage area at the sub- scriber's address and to learn the home area cells and cell identifiers which can be determined for the subscriber. The fact is that it is not possible to see clearly from the address stated by the subscriber whether there is any net- work at all at the subscriber's address. Thus one must make clear if a WLL connection can be given to the subscriber and a visit must be made to the address in question to measure the network strength.

The operator has no such system wherein identifiers of cells cov- ering the subscriber's address could be stored, so that it could be possible based on the address stated by the subscriber to check which cells cover the place of location. After cell identifiers of the subscriber's home area have first been clarifie in some way, they must be stored manually in the subscriber database, one by one.

When the network is developed and cell locations and numbers are changed, the subscribers'home areas will also change, whereby the home area data of each subscriber must be checked manually for each sub- scriber and changed data must be corrected so that the subscribers can again call from their home areas. This may lead to a situation where during the work a WLL subscriber can not make or receive any calls.

The aim of this invention is to bring about such a system which has no drawbacks of the state-of-the-art system and which allows real time management of subscriber data, especially of subscriber home cells, by using a graphic user interface.

The established objective is achieved through the solutions de- fined in the independent claims.

Summary of the invention The invention is based on the insight of using a known geographic information system (GIS) so that on top of this is a special programme utiliz- ing network configuration data and cell data presently retrievable from a telephone system and digital maps of the geographical information system to determine the subscriber's home cell as a part of the subscriber data. Thus, the system as a whole is a system of controlling subscriber data and the name used for this hereinafter in this application is Subscriber Positioning System SPS.

The functionality of the subscriber positioning system or SPS is formed by management of digital maps and by their display in a GIS system and by graphic display of the coverage area and field strength of radio net- work cells on a map in a GIS system. Radio network data and cell identifiers are entered into the subscriber positioning system using a first input ar- rangement. Hereby the graphic display shows a geographical map with the desired exactness and it shows cell borderlines and, if desired, also field strength curves within cells. This can already be used for various useful purposes.

Usefulness increases when subscriber information, the sub- scriber's position included, is also supplied to the subscriber positioning system using a second input arrangement. Hereby the subscriber's position binds the subscriber to a certain point on the map and thus to a certain cell visible in the display, and according to this it can be seen whether one cell is enough as home cell or if more cells must be assigned as home cell. When a new subscriber enters the network it is easy to establish the home cell or home cells according to the position. If the position is not exact, the sub- scriber may use a display means to show the position of his terminal on the map, and based on this the operator is able forthwith to determine the home cell. The position information may be the terminal's coordinate information, street address or like.

When radio network data and subscriber data have been supplied to the system, subscriber data can be retrieved and printed out by applying different retrieval principles. It is easy to transfer identification data of the subscriber's home cells to various databases, such as the home location register HLR, the billing system etc.

When changes are made in the network, e. g. when cells are added or cell identifiersare changed, the new network configuration and the new identifiers are input to the subscriber positioning system, which will check which subscriber home cell data need to be changed.

Brief description of the drawings The invention is described in greater detail in the following by re- ferring to the enclose schematic drawings, of which Figure 1 depicts a WLL system; Figure 2 shows another WLL system; Figure 3 shows a known GIS system in a simplified form; Figure 4 shows the subscriber positioning system and its inputs; Figure 5 shows coverage areas of some cells; Figure 6 depicts a geographical area in coverage areas of cells; Figure 7 illustrates a possible view produced by the subscriber positioning system on the display; and Figure 8 shows the subscriber positioning system adapted for a mobile telephone network.

Detailed description of the invention Figure 3 shows main blocks in a geographic information system GIS known as such. According to one definition, the GIS system is an inte- grated system of computer hardware, software, and trained personnel linking topographic, demographic, utility, facility, image and other resource data that is geographically referenced. A usual way is to present different matters on a map, such as, for example, population distribution, traffic distribution etc. The system has a big database containing objects with their geographical rela- tions, software tools for processing objects and application software. The input is an abstraction of a geographical area, often a digital map.

The subscriber positioning system SPS according to the invention which is outlined in Figure 4 comprises a GIS system working in a computer and a programme built on it which produces desired outputs from given in- puts. In this example, the input in the GIS part is a map of Finland in digital form in the desired, usually small scale. It is advantageous for the map also to contain position data or at least name data of places. Position and name

data can also be transferred separately, provided that the geographical link- ing of each address to the map is attended to. The digital map is stored in a database. Other input of the subscriber positioning system SPS is radio network data, whereby the SPS shows drawn on the map of the GIS soft- ware and in a graphic form the network, the field strength of its radio cover- age, subscriber data, the home areas and the positions of the subscribers.

Henceforward a WLL subscriber is used as an example but it is clear that the subscriber also could be a subscriber in an ordinary mobile telecommunications network.

The radio network data required for the input is obtained from the network planning system. In the planning of the WLL network the network planning software is used to model the locations of network cells, their num- ber and field strengths. The cell border is formed by an area, wherein field strength has dropped below an accepted value. The result is a network con- figuration which is input to the network management system, if such a sys- tem is used. The network management system assigns a cell identifier (cell ID) for each cell. The cell identifiers are transferred to the subscriber posi- tioning system SPS.

The cell coverage area produced by the network planning system can be presented as a set of curves in accordance with Figure 5, which here shows three cells A, B and D. The thicker continuous line is the cell border and the lines inside it outline field strengths of the base station within the cell.

Information concerning cell coverage area and radio network strength, of which the curves in Figure 5 are only a part, presents the whole network and it is transferred in electronic form into the database of the subscriber posi- tioning system SPS. The transfer may take place, for example, in ASCII mode. For the system according to the invention to operate correctly, the radio network information must be consistent with the real network.

Figure 6 outlines a map given by the GIS system from the same area where the cells of Figure 5 are located. Depending on accuracy, the map may show lakes, roads, houses, hills, fields etc.

The subscriber positioning system SPS is now able to show the WLL network drawn graphically on the map and the strength of its radio coverage. In the case of Figures 5 and 6 the result could be like the one shown in Figure 7. The identifier for the cells visible on the display can also

be presented on the display or it can be made visible by clicking the mouse on the cell.

The system can be utilized even at this stage. When the customer inquires if the network has such good coverage at some geographical place that the radio connection will work, the operator may check the situation on the display. By locating the display, for example, in a shop, the seller of the terminal can check forthwith that there is sufficient audibility at the terminal's intended area of location.

When a new WLL subscriber arrives, he gives information on the location where the WLL terminal will be located. The operator inputs the location data into the system, which in a view of the type shown in Figure 7 shows the future position for the terminal, for example, with a flashing dot.

The system immediately indicates the cell in the coverage area of which the terminal is located. This cell is defined as the subscriber's home cell. The identification data of this cell is added to the subscriber database. Only calls made from this cell or received in this cell are permissible or, in a less strict case, they are cheaper than such calls of the subscriber which take place elsewhere in the network. If the dot is in position P in Figure 7, it is immedi- ately obvious that the terminal is located at the borders of cells B, D and A, whereby depending on radio conditions the best connection can be obtained with any base station of these cells. These cells are hereby defined as the subscriber's home area, that is, home cells. The cell identifiers are supplied to the subscriber database.

Correspondingly, the subscriber positioning system SPS may be used in such a way that when the subscriber complais about a poor con- nection, the subscriber's position data is input to the system, whereby it is possible to see the home area and its field strengths on the graphic display.

This allows conclusions to be drawn as regards the cause of the poor con- nection.

When a subscriber becomes a WLL subscriber it is advantageous to store in the subscriber positioning system SPS as full subscriber data as possible, for example, the subscriber's name, position, the terminal's tele- phone number and the home cell identifiers. The home cell identifier is given automatically by the system.

Retrieval and printout of subscriber data can be easily performed by various retrieval principles, for example, according to the subscriber's name, address or number.

For the WLL network to be able during a call establishment to check whether the call is permissible, the cell identification data of the sub- scriber's home area must be transferred to the home location register HLR in the case of the cellular network in Figure 2 or to the subscriber database of the subscriber access node in the case shown in Figure 1. The data may also have to be transmitted to the billing system, whereby it identifies from the received call-based CDR file that the cell is a home cell and uses a cor- responding basis for billing the price of the call. This is necessary in case of a cellular network when the subscriber device is a mobile station which can move anywhere in the network.

It is easy in the subscriber positioning system SPS to create, re- move and change subscriber data. If the subscriber's home area and posi- tion change, the new position is obtained from SPS by supplying the new home area, and this data is supplied further to the home location register HLR or to any similar register and to customer billing. If a new network con- figuration is made in the radio network's planning system, it is transferred to the SPS, whereby the SPS defines new home areas for subscribers, whose home area or home area cells have changed.

Figure 7 shows a system in accordance with the invention applied in a WLL system based on a cellular network. The cellular system may be a GSM or DCS1800 system. The latter is based on the former and differs from that mainly as regards its frequency band. The main network elements of the cellular system have been described earlier in connection with Figure 2. The subscriber positioning system SPS is connected to the cellular network so that the network planning element transmits the coverage area of the cells to the subscriber positioning system in such a form that it can be linked to the geographical map in the SPS. The network management element, which has also received the network configuration, provides the cells with cell IDs.

These are entered into the subscriber positioning system SPS and into the mobile services switching centre MSC. The cells of the WLL network with their identifiers are now available on the map in the subscriber positioning system. For each WLL subscriber, at least the position data, for example, the physical address, the subscriber's name and telephone number, are entered

into the subscriber positioning system. From this data the system gives the subscriber's home cell or home cell identifiers automatically. Together with the subscriber data mentioned above they form the subscriber data file. This is entered into the billing centre and the home location register HLR. The WLL network now has all necessary information for controlling the sub- scriber's calls. When the network configuration changes the new cell cover- age area and the new cell identifiers are entered into the subscriber posi- tioning system SPS, which automatically gives new home cells to those subscribers, whose home cells change when the network changes. The changed subscriber data is transmitted to the home location register and to the billing centre.

Correspondingly, changes in the subscriber position data are en- tered into the subscriber positioning system, which updates the subscriber file in a proper manner.

The cell coverage area data and cell identifier data may be en- tered into the subscriber positioning system SPS as a direct file transfer. In the same way, subscriber data produced by the subscriber positioning sys- tem can be transferred to the home location register or to the subscriber database of the subscriber access node and to the billing centre. It is also possible to transfer this data with a storing medium, such as a CD disk, a tape or any other such means.

On the practical level, the subscriber positioning system can be embodied in many different ways within the scope defined by the claims.

Data can be entered into the system in several different ways. Subscriber data can be entered in a centralized or decentralized manner from several operator offices. The terminal may contain a positioning system, for example a Global Positioning System GPS. Hereby the terminal may itself state its position to the subscriber positioning system. Another way is such that when the subscriber has acquired the terminal, a representative of the operator visits its place of location and using a special positioning system he registers the position, which he then reports to the system by radio or in some other way. The home cells of subscribers can possibly be defined already in the planning system of the radio network at the stage of network planning. New subscribers and changes concerning old subscribers arriving after the intro- duction are hereby entered afterwards into the subscriber positioning sys- tem. The graphic view produced by the system can also be transferred to the

display of a computer in the operator's office. Physically, the subscriber posi- tioning system can be located in connection with any network element.

The invention is suitable for use in case of a WLL network con- nected through a subscriber access node to the exchange and also in con- nection with a mobile telephone network having a cellular structure, where a WLL connection can be offered to the subscriber