GB2056818A - Traffic route testing in a telecommunications network - Google Patents

Abstract

In a telecommunications network, for traffic route testing, there is a central unit per network section (which section may include several exchanges) and which controls a number of remote units distributed over the network section at the exchanges thereof by transmitting to them all data needed for a sequence of test calls via a switched line. The remote units each stores in its memory the data sent from the central unit, and they each perform their own test calls independently under control of the stored data and store the test results in their memories. These results are periodically requested by the central unit. A data connection between the central unit and one of the remote units is needed only during the data input and the request of results, and the remote units work independently during the substantially longer test phase. Hence only a small number of line circuits and modems are needed in the central unit, and nevertheless a large number of simultaneous test calls can be performed in a network section. The central control can be handled by a processor of small capacity since it does not perform any real- time work.

Description

SPECIFICATION Traffic route testing in a telecommunications network This invention relates to a method of and an arrangement for testing traffic routes in a telecommunication exchange, which involves the making of test calls.

With the aid of the traffic route test the grade of service of a telecommunication network can be checked, and, if the tests are performed at short intervals the grade of service can be monitored. The test is done by setting up test calls between different points of the network. By grade of service we mean the availability of the telecommunication network to a subscriber, i.e. whether and after what period of time the subscriber who has lifted the handset receives "dial" tone, whether and after what period of time after "dialling" the ringing tone occurs, whether the line loss for both directions of transmission lies within given values, whether the metering is correct, whether the release is done correctly, and so on.

As already mentioned, to test traffic routes test calls are set up by test apparatus to test stations provided with automatic answering devices and arranged within the different exchanges of the network and based on the results of the test calls there is given evidence of the grade of service. Methods of and arrangement for testing traffic routes are known. In the simplest there is only tested whether and within how long a caller receives "dial" tone. With more sophisticated methods there is set up a complete connection with testing of both directions of transmission. The present method is of the last-mentioned kind.

In "Ericsson-Review" 3/74 p. 80-87 there is described a traffic route tester setting up complete two-way-connections. Such a tester co-operates with a central processor as the controlling unit at a central point of the network, which processor controls traffic-producing units in the exchanges via modems and switched lines or via through-connected lines which units set up test calls to other exchanges and transmit back the test results.

The number of the simultaneously-performable test calls within the network is given by the number of the modems and/or throughconnected lines available for the central unit.

The number of test calls per time unit performable via a modem or a through-connected line is given by the time needed to set up the call and to transmit back the result.

It is desirable to use a traffic route test not only for receiving statistical data concerning the grade of service of a telecommunication network, but also for monitoring the grade of service in an almost realtime manner. For this purpose a rather large number of test calls per time unit between two exchanges is needed to receive the desired realtime knowledge of the grade of service. With the above-mentioned known traffic route tester this would need a large number of modems with the corresponding cost of the exchange housing the central unit with non-chargeable test traffic or a large number of expensive through-connected lines and further a very fast processor in the central unit due to the large data traffic.

It is thus an object of the invention to provide a method of and an arrangement for testing traffic routes enabling the monitoring of the grade of service in a realtime manner without the above drawbacks.

According to the invention there is provided a method of traffic route testing in a telecommunication network using a central unit and a number of remote units, wherein test calls are set up between calling stations and automatic answering stations, wherein the central unit transmits to each of the remote units the data needed to perform a sequence of test calls, wherein the remote unit stores said data and based thereon sets up independently the test calls, detects the test results and stores them, and wherein the central unit requests the test results from each of the remote units so that a data connection between the central unit and the respective remote unit is set up only during the data transmission.

An embodiment of the invention will now be described with reference of the accompanying drawings in which Fig. 1 is a block diagram of the central unit of a traffic route tester embodying the invention, and Fig. 2 is a block diagram of a remote test unit.

The central unit NQTC, Fig. 1, consists of a processor 11, a memory unit 12, e.g. a floppy-disk store, a teletyper 1 3 as the input/ output device and a number of modems 1 4 via which the central unit is connected to the telecommunication network and which contain devices to set up calls with the remote test units under the control of the processor 11.

The central unit NQTC has the following task: (a) handling of the man-machine dialog; (b) handling of the network data such as: subscriber numbers of the modem connections to all remote units NQTC, subscriber lines and categories of all NQTR's, subscriber number of all answering stations of the network, and admissible thresholds for fault rates; (c) storage of the test sequences and initialisation of the tests by calling up the various NQTR's and transmitting the test data to them; (d) collecting test result data from the individual NQTR's; and (e) interpretation and printing of the test results.

The remote unit NQTR shown in Fig. 2 comprises a microprocessor 21 with an additional memory 22 having a PROM-part and a RAM-part, two call generators 23 and 24, a voice frequency transmitter/receiver 25, one or more answering stations 26 and a modem 27, which parts are interconnected by a data bus 28. Further there is a power supply unit 29 to provide power for all these units from the exchange battery.

Within a telephone network or network portion there is provided only one central unit NOTC as shown in Fig. 1 whereas the remote test unit is provided for each exchange for which the trunks and switching paths are to be tested, The remote test unit NQTR contains, as already mentioned, both the calling and the answering portion for test calls so that different devices can be used in common.

Pure answering stations would be possible which when they are called would,-for example, send back a voice frequency signal. However, it is desirable for the check of the grade of service of a network portion to be complete. To achieve this, each exchange of a network portion should be able to call up each other exchange of this portion for test connections in which case each exchange needs both calling and answering stations so that the combination of the calling and the answering portion into a remote test unit NQTR suggests itself.

As above mentioned the arrangement for the automatic traffic route test consists of remote units NQTR in every exchange and a central unit NOTC which is equipped once per network portion.

The remote units NQTR work under the control of their microprocessors as self-standing units, and carry out test calls to automatic answering stations in the same exchange and in all other exchanges and store the test results. For this reason the remote unit NQTR has a number of subscriber lines (up to 20) which are used to set up such calls. The automatic answering stations are also connected to subscriber lines. The remote unit NQTR can set up two calls at the time via one of a maximum of 10 subscriber lines. The remote unit NQTR receives the data for the test calls to be carried out through a data interchange via modems from the central unit NQTC. The latter requests the test results periodically and evaluates them.It is always the central unit NQTC which performs the active role to set up data connections between NQTC and NQTR, which central unit calls the different remote units NQTR via the switching network on demand or periodically. The operating and the supervision of the whole system is done exclusively at the place of the central unit NQTC.

The working principle of the automatic traffic route test will now be described in more detail. In the central unit NQTC, all data relating to the test sequences to be carried out periodically, to the subscriber numbers of the modem connections to the different remote units NQTR, to the subscriber lines, to categories of the different connections in the remote units, to the subscriber numbers of the answering stations in the different exchanges, and to the admissible fault rates are stored in memory 1 2. When the starting time of an automatic test sequence occurs or if a distinct test sequence is manually started by a manmachine dialog the central unit NQTC sets up a data connection via the switching network to the modem connection of the respective remote unit NQTR and transmits via this data connection all data relating to the subscriber numbers to be used and their categories, to the subscriber numbers of the answering stations to be called, to the type of test calls (with/without meter pulse test, with/without synchronization, time intervals, starting times to the parameter of the exchange, and to the start and stop time of the test.

The remote unit NQTR then carries out tha test calls independently and classifies the results per answering station, per type of fault and per calling line. The central unit NQTC scans periodically all remote units NQTR and asks for results of the tests via a data connection.

The data received are then handled by the- central unit NQTC into a statistical overview and printed out in accordance with the mode of printing, i.e. periodically or immediately if a threshold for a fault rate is exceeded. All test data needed can be altered by a man-machine dialog via the input/output device 14. The last look of this data is stored in the memory 1 2 so that said data are not lost in case of a mains breakdown.

With the aid of the present arrangement the following types of tests can be carried out: (a) quality of service test for all routes; (b) quality of service test for a predeterminate route per exchange; and (c) test with holding the line in case of a fault.

The test results can be printed out in the following different ways: (a) per route, on demand or periodically; (b) per route if a certain threshold for the fault rate is exceeded; (c) per calling line on demand; (d) per calling line if a certain threshold for the fault rate is exceeded.

The faults can be classified per route according to the following types: (i) no dial tone; (ii) route busy; (iii) subscriber busy; (iv) no ringing tone; (v) no answering signal; (vi) no metering; (vii) wrong metering; (viii) loss too high in the speed path; and (ix) wrong release.

The tests can be performed with measuring the delay between two meter pulses or with out meter test. It is obvious that with a meter test the holding time per call is longer and consequently less test calls can be made per time unit.

The tests can be run in a synchronous or an asynchronous mode. In the synchronous mode the calls from the various remote units NQTR are started in fixed time intervals and with staggered delays, in such that never more calls have to be answered simultaneously than there are answering stations in an exchange. Thus a falsification of the test results due to busy answering stations can be avoided.

As can be seen from the above there is a division of labour between the central unit NQTC and the remote unit NQTR, the latter being kept as simple and passive as possible.

The remote unit NQTR contains in the PROMportion of its memory 22 only the programs allowing the independent establishment of calls ordered by the central unit NQTC and the-storage of the results in counters of the memory. The remote unit NQTR does not interpret the test results but only transmits them to the central unit NQTC on request of the latter, which subsequently interprets the test results and prints them out.

All semi-permanent data for a specific test sequence are sent from the central unit NQTC via modem and switched line to the remote unit NQTR and stored there in the RAMportion of store 22. Therefore no back up memory is needed in the remote units NQTR and alterations of these data can be carried out simply by means of a man-machine dialog at the central unit NQTC.

It is obvious that these data are lost in the case of a mains failure. If power is restored the remote unit NQTR makes an automatic restart but it then waits until the central unit NQTC calls on it the next time to transmit the semi-permanent data anew.

Summarizing the above, with the present traffic route tester the remote units NQTR are so designed and equipped that they are able to set up the test calls independently and to store the results, whereas the central unit NQTC is so designed and equipped that it can communicate periodically with the remote units NQTR to request therefrom test results and to send them data for new test sequences.

This design of the central unit NQTC and the remote units NQTR has the following advantages: (a) since each remote unit NQTR can perform independently one or more test calls there is no longer a limitation of the number of the test calls to be performed simultaneously within a network section, i.e. the information concerning the quality of service obtained by the test calls approaches a realtime level of information; (b) the central unit NQTC is discharged from real-time control duties so that a processor of small capacity can handle the traffic route test; (c) a data connection between the central unit NQTC and one of the remote units NQTR is only needed for a short time to request the test results and start a new test sequence, which data transmission can be done via switched line. Thus the central unit NQTC only needs a small number of line circuits with modems since it can communicate with the different remote units NQTR in a timespaced manner. Hence the additional test traffic for the exchange housing the central unit remains within admissible limits.

Claims (11)

1. A method of traffic route testing in a telecommunication network using a central unit and a number of remote units, wherein test calls are set up between calling stations and automatic answering stations, wherein the central unit transmits to each of the remote units the data needed to perform a sequence of test calls, wherein the remote unit stores said data and based thereon sets up independently the test calls, detects the test results and stores them, and wherein the central unit requests the test results from each of the remote units so that a data connection between the central unit and the respective remote unit is set up only during the data transmission.

2. A method according to claim 1, and wherein the data connections between the central unit and the remote units are set up via switched lines and modems.

3. A method according to claim 1 or 2, and wherein the data needed for the test calls are stored in the remote unit and can be altered electrically so that the data traffic between the central unit and the remote units is limited to alterations of the stored data, to the start order for a sequence of test calls and to the request of the test results.

4. A method according to claim 3, wherein a synchronous mode of operation is used for the remote units, so as to avoid an answering station being called when it has a test call in process, the test calls being performed in a fixed time scheme under the control of the central unit, and wherein time interleaving of the calls to a distinct answering station is used by a suitable choice and starting of the test sequences of the individual remote units.

5. A method according to claim 1, 2, 3 or 4, and wherein the central unit interprets the test results requested'from the individual remote units prints them out and gives an alarm if the number of faults exceeds a given threshold value.

6. Arrangement for carrying out the method according to claim 1, 2, 3, 4 or 5, and which includes one central unit per net work section and a number of remote units distributed over the network section for setting up and/or answering test calls to and/or from other remote units.

7. Arrangement according to claim 6, and wherein the central unit comprises a small processor, a memory unit, a data input/output device and a number of modems.

8. Arrangement according to claim 6 or 7, and wherein each remote unit includes a microprocessor, an additional memory, at least one call generator, a voice frequency receiver, a modem and a power supply unit.

9. Arrangement according to claim 8, and wherein the remote unit further includes a voice frequency transmitter and an automatic answering station.

1 0. An arrangement for the performance of traffic route testing in a multi-exchange telecommunications network, wherein at a central exchange there is located a central control unit and at each of a number of exchanges at which test calls are to be set up there is provided a remote unit, wherein the route testing involves the establishment of test calls by the remote units, wherein to initiate a series of tests the central unit transmits data appropriate to the tests to be performed to the remote unit to be responsible for the performance of those tests, wherein the remote unit stores such data in its own memory, performs the tests and records the results of such tests in its own memory, wherein when the central unit requires the test results it sends to the remote unit in question a request for those results, as a result of which the remote unit sends those results to the central unit for use threat and wherein the transmission between the central unit and the remote unit is effected wholly under the control of the central unit and via the switched network.

11. A method of traffic route testing in a telecommunication network, substantially as described with reference to the accompanying drawings.

1 2. Apparatus for traffic route testing in a telecommunication network, substantially as described with reference to the accompanying drawings.