Abstract:
The test facility tests whether the services subscribed to by a user in a subscribed network are also available in a visited network. Because the network functions and services should be tested in the same way as a customer actually uses them, they preferably have to be tested from the subscriber network interfaces. The subscriber network interfaces are especially important at the air interface and at the switched network for conventional analogue and ISDN telephone services (Integrated Services Digital Network). However, for special tests internal interfaces of a GSM network (Global System for Mobile Communication) are also of significance such as the A-Interface at the Mobile Switching Center (MSC) of a GSM network.

Description:
BACKGROUND OF THE INVENTION 
     The invention covers the field of cellular mobile telephones. It relates to a test facility and a method for its operation for the permanent monitoring of the services provided by a GSM network (Global System for Mobile Communication). In particular checks are made whether the services subscribed to by a user in his/her home network or at his/her home location are also available in the visited network or location respectively. Apart from these so-called roaming tests it is also of interest as to with what quality the services offered in the GSM network are available. Because the network functions and services should be tested in the same way as a customer actually uses them, they logically have to be tested from the customer network interfaces. The customer network interfaces at the air interface are of particular importance, i.e. to the mobile station (MS), and at the switched network for conventional analogue and ISDN telephone services (Integrated Services Digital Network). However, for special tests internal interfaces of the GSM network are also of significance such as the so-called A-Interface at the MSC (Mobile Switching Center). 
     Mobile communication networks such as the GSM (Global System for Mobile Communication) are experiencing increasing customer numbers due to good availability, fast connection capabilities and worldwide ability for contact under the same number. To ensure that such a highly complex system functions efficiently and reliably under varied peripheral conditions, a series of measures is necessary. One of these measures is the almost continuously conducted testing of the various functions of networks and the services provided which are subject to constant modifications, especially expansions. Since a radio transfer is exposed to substantially greater interference effects overall than a transfer by cable, the testing of the so-called air interface, i.e. the radio link between the mobile customer terminal, the mobile station (MS), often just called Handy, and the so-called base station, i.e. the sending/receiving station at a fixed location, is therefore on one hand especially important. On the other hand the number of interfaces is also increasing rapidly at other locations, as explained below, so that it can be useful to include these in tests if reliable results are to be obtained. 
     For testing the air interface within a mobile communication network the use of automated test facilities for alternate routing and toll billing, is already known. Such a facility and the appropriate operating method are described in German patent document DE 196 20 164. The test facility described in this document consists essentially of a special mobile station (MS), also known as Handy, which is equipped with a wire-bound interface, a multiplexor to hold and alternately operate several data modules, i.e. SIMs (Subscriber identity Modules), and a computer which controls the whole facility. Instead of a SIM the MS contains an adapter module which is connected to the multiplexor via cable in such a way that each of the SIMs contained in the multiplexor is emulated in the MS. The selection of the respectively required SIM and the control of the entire test process are performed by the control computer which has to be connected to the MS and to the multiplexor for this purpose. 
     Undoubtedly the facility described in DE 196 20 164 already permits an automated test of alternate routing and toll billing. The disadvantage however is that a multitude of multiplexors have to be placed at different locations in order to conduct tests that extend across an entire network and, if necessary, several countries. Such extended tests have today become indispensable because of the continuously increasing roaming possibilities. Roaming is the use of an MS outside the home network in which it is registered and in whose data banks its data is stored. 
     In addition the focus on testing of the air interfaces alone is no longer sufficient because the number of other gateways is also increasing. As a result of the steadily increasing number of network operators to which deregulation in many countries is contributing, the number of gateways between mobile communication networks on the one hand is growing as well as the number of network gateways to switched networks and between these networks. Therefore it is appropriate and necessary to also include switched network gateways in the tests. 
     This is connected to the fact that a SIM is required in all network accesses which are to be tested, for the international and national roaming test from each network or from each location within a network respectively. The configuration with distributed SIMs demands a substantial effort with regard to establishing the configuration. On one hand the number of roaming agreements grows with the increase in mobile communication networks, on the other hand, with the increase in customers, the number of MSC (Mobile Switching Center) and therefore the locations within the network necessarily rise. In order to guarantee the total availability of the services for network subscribers and roaming customers at any time tests have to be performed with each SIM at each location which in turn requires a large number of SIMs at each location. The expansion of the networks, usually nationally if not internationally, makes the maintenance of these extensive sets of locally distributed SIMs more difficult and requires substantial effort in terms of material and time. 
     SUMMARY OF THE INVENTION 
     It is therefore the task of the invention to establish a test facility and a test method which is capable of solving the problems outlined. For this, it should be possible to perform tests efficiently for already existing data networks as centrally as possible from a single location. In other words, it will be possible to use the invention immediately without any change or extension to existing mobile communication networks. It will furthermore be adaptable in the respect that it can be adapted to network changes or expansions using a simple modification, preferably of the software, at a central location when the roaming agreements as well as the number of customers and the resulting increase in Home Location Register (HLR) grow which require a change of one or more tests or parts thereof. 
     These tasks are solved in principle by the fact that according to the invention at least one central server is provided which can adopt a multitude of SIMs, and that a large number of geographically distributed mobile stations equipped with adapter modules or mobile stations simulated by software processes can access this central server via at least one existing data network so that each SIM can be emulated in each of the distributed mobile stations. Further forms of the invention can be derived from the instant disclosure and, details can be collected from the following description. 
     The test facility according to the invention not only makes it possible to continuously monitor the availability of the services provided, but also to alter these tests constantly and, whenever necessary, to adapt them to the growing demands efficiently. In particular the following tests should be performed or the following services should be tested respectively: 
     Basic Services, i.e. the basic services which are available to every customer 
     Supplementary Services, i.e. the supplementary services such as call forwarding, call suspending 
     Data and fax services, i.e. non-linguistic services that can process many MS 
     Toll estimation, i.e. the toll billing, calculation and, if necessary, display 
     International Roaming, i.e. the trunking scheme outside the home country 
     National Roaming, i.e. the trunking scheme outside the location in which the relevant SIM is registered. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     To follow an embodiment of the invention is described in detail in conjunction with the figures. 
     In the figures below 
     FIG. 1 shows a general view of the test facility 
     FIG. 2 shows a test module for air interfaces 
     FIG. 3 shows the central SIM server 
     FIG. 4 shows details of the control unit 
     FIG. 5 shows a test module for A-Interfaces 
     FIG. 6 shows a test module for switched net interfaces 
     FIG. 7 shows an example how to connect the SIM server to the GSM network 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In order to use the services provided by a GSM network the confidential algorithms which are stored in the SIM and the key which is dependent on the network operator are necessary for authentication, identification and coding. Without this information it is not possible to utilize the services offered. 
     The test system essentially uses test modules (TM) which provide test accesses via so-called A-Interfaces, air interfaces and/or conventional switched network interfaces. The functions of the MS are simulated at an A-Interface using software processes. At an air interface commercially available MS are used. Both test methods use real SIMs for reasons of confidentiality regarding the algorithms and keys. Normally the SIMs are either located directly in the mobile stations (MS) or the software process accesses a SIM directly. But because there is a larger number of spatially distributed MS and software processes present in a test system the number of SIMs required is normally also provided at each location. In other words, depending on the type of test a certain selection and number of SIMs have to be made available continuously or temporarily at each location or at certain locations respectively. It is obvious that this is time-consuming and costly because of the spatial distribution. This problem is solved by the centralized SIM card server (SKS) according to the invention. Such a centralized SKS additionally offers two further advantages. Firstly, the number of required SIMs is reduced and secondly, temporary allocations of all SIMs can be actioned from the central SKS, i.e. a central work place. 
     The test system according to the invention then uses the data communication already available between Mobile Switching Centers (MSCs), Visitor Location Registers (VLRs) and Home Location Registers (HLRs) for testing as well. In each GSM network a cross-linking of the VLRs and HLRs exists in the appropriate routing in order to check the data and registrations of users. This existing function is now also used for networking of test modules (TM) and SKS. It is known to the expert that separate addresses have to be defined for each TM and SKS and that routing within the network has to be configured accordingly. 
     In order to perform roaming and mobile service tests the following data is of importance and needs to be determined before the test commences: 
     Test data, i.e. SIM dependent data such as the International Mobile Subscriber Identity (IMSI) or the Mobile Station Integrated Service Digital Network Number (MSISDN); 
     Test cases, i.e. prepared test cases that can be compiled to form a test campaign in order to obtain particular test objectives using for example the international roaming tests as specified in a Memorandum of Understanding of the International Expert Group (MoU IREG); 
     The system configuration, i.e. number of test modules (TM), positions and addresses of the SIMs, network addresses etc. 
     To follow an embodiment of the test system will now be described in detail using the figures. 
     In FIG. 1 the test system is shown in a typical environment. A GSM network  10 , a ISDN or PSTN network  20  (PSTN stands for Public Switched Telecommunication Network) and a data network  30  form the basic structure of the network. While the GSM network in this example has a fixed connection to the ISDN/PSTN network the other connections are interfaces to be tested for which test modules are provided: a test module  1  for an air interface between the GSM network  10  and the data network  30 , a test module  2  for a so-called switched network interface between the switched ISDN/PSTN network  20  and the data network  30  as well as a test module  3  for an A-Interface between a Mobile Switching Center (MSC) of a GSM network  10  and the data network. The test modules which are shown as simple box elements in FIG. 1 are in reality complex arrangements as will be explained in more detail below. Furthermore in FIG. 1 the SIM card server (SKS)  4  is shown which is connected to the GSM network  10  via cable  41  and to the data network  30  via cable  42 , and the test control unit (TCU)  5  which is connected to the data network via connection  52 . 
     It is known to the expert that the test modules are functionally connected to the respective networks  10 ,  20  and  30 , for example via cables  13 ,  23  and  33  for the test accesses, via cables  12 ,  22 ,  32  and  52  as control connections (control links) between the test modules (TM)  1  and  3 , the SKS  4  and the TCU  5 , and via  11 ,  31  and  41  for communication between the test modules  1  and  3  and the SKS  4 . The test access  13  can be performed via a cable or the air, i.e. a radio connection. The remaining connections are self-explanatory. 
     In FIG. 2 the test module  1  for the air interface is shown in detail. In this example two mobile stations (MS)  112  and  112 ′ are connected to a local control unit  111 . The MS  112  and  112 ′ contain, as known previously, no SIM but one adapter each inserted in place of the SIM. The MS  112  and  112 ′ and the adapter (not shown) are connected to the control unit  111 . Since it is known the MS  112  and  112 ′ are capable of communicating with the mobile communication network  10  (GSM in FIG. 1) via radio  13  or cable. The control unit  111  is also connected to the mobile communication network  10  via cable  11  and to the data network  30  (FIG. 1) via cable  12 . The function of the test module  1  is as follows: 
     The test module  1  receives all data required for carrying out the test from the TCU  5  via the data network  30  and cable  12 . As a rule this is a so-called test campaign which consists of a sequence of single test cases, i.e. test cases or test calls. In order to avoid time collisions of the test calls the test modules are coordinated by a time slot. 
     The test campaign is stored in the control unit  111 . The latter works through the individual test cases step by step at a predetermined start time. Then it controls the individual MS  112  and  112 ′ and transfers the required test parameters such as MSISDN number, test files etc, to them via the serial interface. At the same time the control unit  111  establishes communication with the SKS  4  via cable  11  and the mobile radio network  10 . The address of the SIM belonging to a test case is transferred together with test data from the TCU  5  via cable  12 . 
     FIG. 3 shows the central SIM card server (SKS)  4 . Subscriber Identification Modules, i.e. SIMs, are commonly also called SIM cards; with exception of the SKS the expression SIM will preferably be used in this context. 
     The SIM card server (SKS)  4  in FIG. 3 consists of a local control unit  411 , an internal controller  412 , a 2 Mbit/s-Interface  413 , a SIM controller  414  and a number of SIM card units  415 . The local control unit  411  establishes communication between the TCU  5  and the internal controller  412  via the data network  30 . The configuration of the SKS  4  such as the querying of the SIM data, positions etc, is carried out via the local control unit  411  and the link  42  to the TCU. The internal controller  412  controls the communication of the interface  41  of interface  413  to the GSM network  10 . The SIM controller  414  routes the messages arriving from the test modules  1  and  3  to the addressed SIMs and the answers back to the test modules respectively. 
     FIG. 4 shows the test control unit  5  (control unit TCU) in detail. Inside this unit the test cases required which are in turn stored in units  513 , are created from single test steps stored in storage units  511  with the help of a test case editor  512 . Using a test sequence editor  514  test cases are transformed into test sequences which are stored in readily retrievable form in units  516 . By combining the test sequences from storage unit  516  with configuration data from the SIMs placed in the SKS  4  and the operator specific data via units  515 ,  517  and  518 , the aforementioned running test campaigns are created, i.e. extensive test procedures which are stored in unit  519 . Via the operating console  521  the test data is acquired as specific data concerning the operator, SIM data etc. 
     With the help of the scheduler  520  a test campaign can be executed automatically through time control. In short, the control unit  5  will ensure that the individual components of the test cases, together with all necessary parameters, are loaded into the appropriate test modules  1 ,  2  and  3 . 
     Each of the test modules  1 ,  2  and  3  then implements the relevant test cases at its respective interface. Since the test parameters mentioned also include the position and address of the SIMs, each of the test modules  1  and  3  is capable of communicating with the SIM predetermined by the test case, in the SKS  4  via the GSM network  10 . 
     In this way all test cases contained in a test campaign are executed. At the end of a test campaign the results determined are stored in the control unit  5  and edited for a later display, symbolized by printout  522 , for example in graphic or alphanumeric form. 
     In FIG. 5 the test module  3  for the A-Interfaces is shown. Similar to the SKS  4  described above this module consists of a local control unit  311 , an internal controller  312 , a 2 Mbit/s interface  313  for test access to the A-Interface  33  and a second 2 Mbit/s interface  314  for connection via cable  31  with the SKS  4 . The local control unit  311  establishes communication between the TCU  5  and the internal controller  312 . In test module  3  the MS are emulated on the internal controller using software processes. For authentication this controller  312  communicates with the SKS  4  via the interface  314  and the link  31 . 
     In FIG. 6 the test module  2  for the switched network interfaces is shown. This test module is assembled in a similar way to the test module  1  as described above. It consists of a control unit  211  and two or more modems  212  and  212 ′ which permit the test access to the switched network via links  23  and  23 ′. According to demand these modems  212  are equipped for analogue connections or ISDN connections. The test process is similar to test module  1  with the difference that in this case no connection to the SKS  4  is required. 
     Finally, in FIG. 7 the concept of the invention is illustrated. Shown are the GSM network  10  with some of its accesses, in particular the Mobile Switching Centers (MSC)  70 ,  71  and  72  and by way of example a Base Transceiver Station BTS  75 , i.e. a base station for sending and receiving, which enables radio connection to the mobile stations  1  and  1 ′ shown. Some of the components which exist in reality such as the data network  30  and the control unit  5  are not shown in FIG. 7 in order to retain clarity. In addition the networking of several test modules  1  and  3  with the SKS  4  is shown. The networking is carried out via the MSC  70 ,  71  and  72  and the data channels available in the GSM network  10 ; the MSCs and also the data channels are required for the operation of the system and are therefore available anyway. For this purpose each of the test modules  1  to  3  as well as the SKS  4  feature a 2 Mbit/s interface for the connection to the so-called C/D interface of a MSC. For each test case requiring a SIM the associated test module  1  or  3  is sending a relevant message (for example “RAND” a message commonly used for authentication) to the address of the affected SIM within the SKS  4  as well as the point code, i.e. the IP address of the SKS  4 . This address enables on one hand the data network  30 . to route messages to the correct address and on the other hand enables SKS  4  to forward messages to the required SIM. Each message carries at least the identification (sender address) of the test module in order to be able to route the answers to the querying test module. 
     At the same time each of the test modules (TM)  1 ,  2  or  3  as well as the SKS  4  can be connected to a 2 Mbit/s trunk either directly or via a multiplexor (MUX)  73 ,  74 . As only one time slot with 64 Kbit/s is required per test module or SKS  4  this time slot can simply be extracted from a 2 Mbit/s trunk using a MUX  73  or  74 . The connection established in this way is used exclusively for communication between the SKS  4  and the respective TM. The additional load for the network is minute because only a few messages are required per trunking scheme and mobile station. 
     The SIM card server  4  can be assembled in modular form from units whereby a single SKS unit, shown in FIG. 7 as SKS  4 ′ and SKS  4 ″, can handle up to  568  SIMs and make them available to a test system with several test modules  1  and  3 . These SKS units can be arranged either integrated or separately. If they are arranged separately the units can be set up at the same location as well as at different locations. Several of the test modules  1  and  3  and several test cases can then access each of the SKS units in a quasi-parallel way, i.e. a virtually entire parallel operation is possible. If necessary, several SKS units can be integrated so that the number of SIMS available for the tests can in practice be increased to any desired level. 
     The separate data network which, for example, can be developed as a LAN or WAN or also as a X  25  network is also being used for controlling and configuring the test system and for transferring the results. 
     The following list of reference characters is presented in detail in order to provide the expert with a detailed impression of an embodiment of the invention in conjunction with the figures and the aforementioned description. 
     LIST OF REFERENCE CHARACTERS 
     FIG. 1 General View 
       1  Test module for the air interface 
       2  Test module for the ISDN or analogue interface 
       3  Test module for the A-Interface 
       4  SIM card server (SKS), in FIG. 7 also  4 ′ and  4 ″ one unit each 
       5  Test control unit (TCU) 
       10  Global System for Mobile Communication (GSM) 
       11  Data link from test module  1  to SKS  4  via GSM network  10   
       12  Control link from test module  1  to the TCU  5  via data network  30   
       13  Radio connection to the GSM network  10   
       20  Switched network, for example Integrated Services Digital Network (ISDN) and/or Public Switched Telecommunication Network (PSTN) 
       22  Control link from test module  2  to the TCU  5   
       23  Test connection for analogue and/or ISDN telephone services 
       30  Data network, for example a LAN, WAN or X  25  network between the TCU  5 , the SKS  4  and the test modules  1 ,  2  and  3   
       31  Data link from the test module  3  to the SKS  4   
       32  Control link from the test module  3  to the TCU  5   
       33  A-Interface (at the Mobile Switching Center, MSC, see FIG. 7) 
       41  Data link from the SKS  4  to the test modules  1  and  3   
       42  Control link from the TCU  5  to the SKS  4   
       52  Control link from the TCU  5  to the SKS  4  and the test modules  1 ,  2  and  3   
     FIG. 2 Test Module for the Air Interface 
       11  Data link to the SKS  4  via GSM network  10   
       12  Control link to the TCU  5  via data network  30   
       13 ,  13 ′ Radio connections to the GSM network  10   
       111  Local control unit 
       112 ,  112 ′ Mobile stations (MS) 
     FIG. 3 Central SIM Card Server (SKS) 
       41  Data link to the test modules  1  and  3  via GSM network  10   
       42  Control link to the TCU  5  via data network  30   
       411  Local control unit for communication with the TCU  5   
       412  Internal controller for communication with the test modules  1  and  3   
       413  Interface for connection to the GSM network  10   
       414  Controller for the SIM card unit  415   
       415  Modular SIM card unit with a multitude of SIMs 
     FIG. 4 Control Unit, Test Control Unit (TCU) 
       52  Control cable to the test modules  1 ,  2  and  3  and to the SKS  5   
       511  Memory for test steps 
       512  Test case editor 
       513  Memory for test cases 
       514  Test sequence editor 
       515  Entry of the test data, manually or machine readable test data 
       516  Memory for test sequences 
       517  Memory for test data 
       518  Editor for test data and creation of feasible test campaigns 
       519  Memory for test campaigns 
       520  Scheduler for control of the chronological test process 
       521  Operating unit 
       522  Output of the test results 
     FIG. 5 Test Module for the A-Interface 
       31  Data link to the SKS  4  via GSM network  10   
       32  Control link to the TCU  5  via data network  30   
       33  A-Interface (test access at Mobile Switching Center, MSC, see FIG. 7) 
       311  Local control unit for communication with the TCU  5   
       312  Internal controller for communication with the A-Interface  33  and the SKS  4   
       313  Interface for connection to the A-Interface  33  (test) 
       314  Interface for connection to the GSM network  10   
     FIG. 6 Test Module for the Switched Network Interface 
       22  Control link to the TCU  5  via data network  30   
       23 ,  23 ′ Test access to analogue and/or ISDN telephone services of network  20   
       211  Local control unit for communication with the TCU  5   
       212 ,  212 ′ Modems 
     FIG. 7 Example for Connection of a SIM Server to a GSM Network 
       1 ,  1 ′ Test module for the air interface 
       3  Test module for the A-Interface 
       4 ,  4 ′ SIM server, one unit each 
       10  GSM network 
       11 ,  11 ′ Data links 
       13 ,  13 ′ Radio connections 
       31  data link 
       33  A-Interface 
       41 ,  41 ′ Data links 
       70  Mobile Switching Center (MSC) 
       71 ,  72  further MSCs 
       73 ,  74  Multiplexor (MUX) 
       75  Base Transceiver Station (BTS) for radio connection 
       70 - 75  are internal components of the GSM  10