DE4215422A1 - RECEPTION DEVICE FOR A DIAGNOSTIC SUB-SYSTEM FOR A REMOTE BASE STATION - Google Patents

Abstract

Radio system infrastructure equipment is provided which comprises base station transceiver equipment 20 for communication with a mobile transceiver and diagnostic transceiver equipment 35 associated with the base station transceiver equipment for generating test signals and feeding them to the base station transceiver equipment. A loopback facility is provided within the infrastructure equipment for looping back a signal received from the diagnostic transceiver equipment at a point within the infrastructure equipment. This signal is returned to the diagnostic transceiver equipment, where it is tested, for example by comparison with the original signal, and faults are diagnosed. The test signal may be looped back from various points so that various parts of the equipment may be tested. In order to facilitate a loop back via the public service telephone network 30 without the test signal being cancelled by echo cancellers 31, 32, a maintenance terminal unit is connected to the network 30 and incorporates means for receiving a signal from the network, means for storing the signal, and means for automatically retransmitting the signal to the network after a predetermined delay, (Fig. 6). <IMAGE>

Description

The present invention relates to Radio base stations, such as cellular radio base stations and finds mainly in GSM (Groupe Speciale Mobile) pan-European digital cellular radio systems Application. The invention is cellular in others Applicable to systems such as the PCN.

Overview of the state of the art

In the TACS (Total Access Communication System), ie in the United Kingdom analog cellular radio system, it is known to provide a loop-back facility for issuing test calls. The device is shown in FIG. 2. There, a base transceiver station (BTS) 10 is connected to a mobile switching center (MSC) 11 , which in turn is connected to a public services telephone network (PSTN) 12 . The transceiver base station 10 is in communication with a test mobile unit 13 that is capable of moving in the area. For the purpose of a loopback test, feedback test, feedback tests, the test mobile unit 13 is stationary at the base area. The operation of the loopback test is the following. In the MSC 11 , a test signal is generated, transmitted to the BTS and in turn transmitted via an RF interface to the test mobile unit 13 . In the test mobile unit 13 , the signal is returned from the receiving channel to the corresponding transmission channel, transmitted to the BTS 10 , and forwarded to the MSC 11 , where it is compared to the original signal. In this way, the connections from the MSC to the mobile unit 13 can be tested. The feedback signal on the test mobile unit is an audio signal.

In the arrangement described above, each System unit makes a call to the test mobile unit stop, may continue to receive audio traffic (audio traffic) they settle and then the returning one Watch news traffic. The arrangement is however in terms of its application and functioning limited.

The British patent application with the number 90 07 330.5 of Motorola Ltd. describes a diagnostic subsystem for remote base stations (remote base station diagnostic Subsystem RBDS), which together with a Transceiver base station is created and with this is connected via a bidirectional RF coupler. The RBDS has an ability to simulate certain Functions of a test mobile unit.

According to the present invention, a Radio system infrastructure equipment specified consisting from a transceiver base station equipment Communication with a mobile transceiver and a diagnostic transmitting / receiving equipment that the Transceiver base station equipment for generating Test signals and for supplying these to the Associated with transmitting / receiving base station equipment, the invention being characterized by Facility within the infrastructure equipment to Returning one of the diagnostic transceiver equipment received signal to a point within the Infrastructure equipment, to redirect this signal to the diagnostic transceiver and for testing  of the returned signal, thereby error within of the infrastructure equipment.

The infrastructure equipment preferably comprises multiple parallel resources (e.g. parallel RCUs, parallel transcoders, parallel modems) and the diagnostic transmission / reception equipment includes a Control device, with the multiple parallel Resources is coupled to a selected one Communication wire through the multiple parallel Build resources using the resources selected under control of the diagnostic transmission / reception equipment can be tested.

The infrastructure equipment preferably comprises multiple serial elements (eg one or more Transmit / receive base stations, one Base Station Controller, one or more Transcoderkarten, an MTU, an IMF and a PSTN) and the diagnostic transmission / reception equipment comprises a Control device using the multiple serial Elements, possibly via an OMC (operation maintenance center) to select one Elements in which the point of feedback of the signal to be held. The equipment can be first and second serial elements (eg a BSC and a switch site) have, wherein the first serial element with the Diagnostic transmit / receive equipment is coupled and the second serial element with the Diagnostic transmit / receive equipment via the first serial Element is coupled, and wherein the first and second serial element is a control device for the Communication of control signals with each other during having a normal, non-diagnostic operation, and wherein the first serial element further comprises a  Simulation device for simulating Has control signals to the second serial element, if a signal coming from the Diagnosis Transceiver Equipment was received in the the first serial element is returned to thereby a normal operation for the second serial element to simulate. This feature has the advantage that it Punches of the second serial element while a diagnostic feedback to the first serial element is performed minimized.

The invention allows at least in its preferred Embodiment, that a feedback device by a central facility (the RBDS), which the Results of the test for locating errors in the System can be controlled. It should be noted be that the direction opposite to the return conventional systems is exactly the opposite. The order allows errors in the system based on the test returns to locate.

Another aspect of the invention is in the Presence of a maintenance connection unit (maintenance Terminal unit), which a connection means for Connecting a Public Telephone System (PSTN) which memory, delay and Reproducing means for receiving a signal from the PSTN, to save these and automatic Retransmission of this to the PSTN after a given Delay time has. This unit allows one Build back the entire way through the System goes through from end to end without doing so the feedback signal by Echoausschalter, which between the radio infrastructure system and the PSTN can be provided, can be turned off.

Brief description of the drawings

Fig. 1 shows a cellular radio system according to the present invention.

Fig. 2 shows a conventional cellular radio system.

Fig. 3 shows details of a base station controller according to the implementation of a preferred embodiment of the present invention.

Fig. 4 shows a flow chart for an example of a test routine.

Fig. 5 shows a detail of a transcoder card of Fig. 2 according to a second preferred embodiment of the invention.

Fig. 6 shows a maintenance terminal unit according to an embodiment of the present invention.

The abbreviations used below are based on Examples explained.

BSC Base Station Controller - Base Station Controller. This control unit is the one that immediately controls a BTS. A BSC can control several BTSs. BTS Base Transceiver Station - Transceiver Station. This cellular transmitting / receiving base station communicates with the mobile units within a cell. CPSIM Call Processing Simulator - details below. DRI Digital Radio Interface - digital radio interface. DriX Digital Radio Interface Extender Card - digital radio interface extension card. This is the communication circuit for the DRI. EC Echo Canceller - Echo-breaker. This is an echo canceller of conventional design of the echoes that result from the connection to the PSTN turns off. GSM Groupe Speciale Mobile. IMF Inter-working function - interim working function. The IWF translates modem modulated data from the PSTN into packet data according to the GSM format and vice versa. KSW Kiloport Switch - Kilo Switch. LAN Local Area Network - local area network. MSC Mobile Switching Center - mobile control center. This represents an element of any cellular radio system that controls handoff and other aspects of overall message traffic management. MSI Mega Stream Interface - Mega Stream Interface. This represents the connection from the MSC to the base site. MTU Maintenance Termination Unit - closer below. OMC Operation Maintenance Center - Maintenance Operations Center. this is a Processing center that communicates with all base stations and switches in the system to centrally report activities and errors. PCN Personal Communications Network - personal communication network PSTN Public Service Telephone Network - public telephone network. RAI Routine Antenna Integrity - see below. RBDS Remote Base Station Diagnostic Subsystem - remote base station diagnostic system. RCU Radio Channel Unit - Radio Channel Unit. This is a multi-channel transmitter / receiver in the BTS. RXCDR Remote Transcoder Card - remote transcoder card. This represents a voice encoder / decoder arranged with the MSC. TACS Total Access Communicate System. This represents an existing in the United Kingdom analog cellular radio system. XCDR Transcoder Card Transcoder Card. This represents a speech encoder / decoder co-located at the base site.

Detailed description of a preferred embodiment

In Fig. 1 an overall block diagram of important elements of the GSM system is shown. The system includes a BTS 20 , a BSC 21 , a series of transcoder cards 22 , an MSC 23, and an OMC 24 . Associated with the MSC is an IWF 26 . The MSC is connected to the PSTN 30 via echo-off switches, two of which are shown ( 31 and 32 ). The BTS 20 is connected to an RBDS 35 by means of an RF coupler 36 . Other parallel antennas may be provided (not shown), each having its own coupler. These antennas operate different sectors of the base site or allow diversity (multiple receive). The RBDS 35 is described in British Patent Application No. 90 07 330.5 and moreover has additional functions which are described below. A LAN 37 is provided which connects the RBDS 35 to the BTS 20 and is responsible for control and data.

The BTS 20 , BSC 21 , RBDS 35, and associated elements are generally (but not necessarily) located at the base site 38 . The KSW 22 , the MSC 23 , the IWF 265 and the echo cancellers 31 and 32 are generally (but not necessarily) located at the switch location 39 . An MSL 40 connects the base site 38 to the switch site 39 . The two locations can be in the same location.

The general operation of the above elements is described in the GSM guidelines with the exception of RBDS 35 .

In Fig. 1, a number of dashed lines representing loop feedback tests, designated A to E, according to a preferred embodiment of the present invention are shown. In each of these loop feedback tests, a signal is generated by the RBDS 35 , fed to the BTS 20 via the coupler 36 and fed back to the RBDS at a selected point in the system where a test can be made, for example a comparison of the generated signal with the feedback Signal. Where an error is detected, this is reported to the OMC 24 .

The loop feedback tests A to E are performed in described in more detail below.

Loop return A

The first loop feedback test to be described is indicated by the dashed arrow A and is established at the base site 38 .

In Fig. 3, the BTS 20 is shown in more detail. It comprises 5 RCUs 40 to 44 , an RF combiner 45 , a preselector 46 , and a 6-way splitter 47 . The combiner 45 is a filtering network that directs various transmission signals of different frequencies to different antennas. There are a number of receiving antennas (e.g., 6 pieces) connected to the preselector 46 . One of them is shown as antenna 48 r. Also, a number of Ubertragungsantennen (z. B. 6) is provided, which are connected to the combiner 45, one of which is shown as an antenna 48 t.

The RBDS 35 is connected to the preselector 46 by an RF coupler 36 r and the combiner 45 is connected to the RBDS 35 via the coupler 36 t. Assigned to each RCU is a DRIX 50 to 54 and a DRI 55 to 59 . The DRIs 55 to 59 are connected to a bus 60 . Connected to the bus is a processor 62 and an MSI 617 . The MSI is in communication with the MSC 23 of FIG. 2. The processor 62 is in communication with the LAN 37 .

The loop return A, as shown in Figure 2, is accomplished by hardware by passing the signal from the RBDS received by the combiner and by one of the RCU (e.g., RCU 44 ) through the associated DRIX and by attributing this signal in the DRI 59 from the reception channel to the corresponding transmission channel. The associated signal is then fed back to the RBDS 35 through the DRIX 54 through the RCU 44 and through the combiner 45 .

The receive and transmit channels are at different frequencies and different time slots. The DRI 59 stores digital signals, delays them to the appropriate transmission slot, and reads them out of memory again during this slot. The RCU 44 receives the signal from the DRIX and transmits it at the appropriate transmission frequency.

Example - RAI test (routine antenna integrity test)

As an example of a test established by the RBDS in a return call by the DRI 59 of the BTS 20 , the RAI test is described. A flow chart of the test is described in FIG . The test shows two beneficial features of the return capability: (A) resource selection in the loop return path and (B) isolation of resource usage within the return path.

In the cellular system, the system elements (resources) through the base site and through the switch in not trivially assigned. To locate errors, It is therefore desirable to be able to Test call from the RBDS along a preselected path through the system. This is done by the RBDS using the system element selection in the Loop feedback as described below reached.

In Fig. 4, the routine integrity test (step 100 ) is initiated by the RBDS. In step 101 , the command SYSSTAT-REQ0 is sent from the RBDS to the BTS via the LAN 37 to obtain the hopping status (skip state) from the processor 62 of the BTS. In this way, the RBDS requests the status of "frequency hopping" in the BTS, whether it is enabled or not. If the hopping status is activated (step 102 ), an HOP-DIS-REQ command is sent from the RBDS to the BTS, resulting in the deactivation of hopping in the base site (step 103 ). The system is now ready for the test. The RBDS sends a command received. The table is read from the processor 62 to the RBDS over the LANs. By examining this table, the RBDS has the ability to select a particular system subscriber in the base site for a test. In particular, the RBDS may select a particular channel and select different antennas for testing according to its frequency. In step 105 , the RBDS selects the channel for the test and sends the command BTS-CHAN-REQ to reserve that channel in the base site. In this way, a channel that will test a particular transmission antenna is selected. It will be understood that the same principle can be applied to each base site of system subscribers, both software and hardware (eg, by RCUs). In step 106 , the RBDS sends the command LOOP-REQ0 to the BTS, causing the DRI 59 to assign the received channel to the transmission channel. At this time, a software routine called CPsim is implemented as follows.

In order to set up a call to test the loopback, signaling between the base site 38 and the switch site 39 would normally be required. It would be preferable in a test operation that occurs only locally in the base site to avoid that this operation has any effects on the switch. In order to make the test call as unsound as possible and to avoid the amount of unnecessary signaling on the long link between the base site 38 being large, the BSC makes use of a call processing simulator CPsim. This simulates the signaling that the base site would expect from the switch during call setup.

The CPsim software emulates the signaling associated with the build-up of the loop feedback test, thereby avoiding the switch and signaling channel on the control interface (the A interface) being involved via the MSI 40 between the MSC 39 and the base site 38 .

In this way, the loop feedback is established and the RAI (routine antenna integrity test) (step 107 in Figure 4 ) is executed. The test may for example consist of a simple measurement of the voltage standing wave ratio (VSWR).

The test is carried out by a normal cellular radio signal which is modulated with an audio test signal via the advance selector 46 and the fragment is transmitted 47, wherein the two-way switch 49 r is located, from the RBDS to the RCU 44, as shown in its upper position. When the signal is returned, it is transmitted to the antenna 48 t. By switching the switch 49 t from its upper position to its lower position and by comparing the strengths of the signals from the combiner 45 and signals reflected from the antenna 48 t, a VSWR measurement can be made from the RBDS. Alternatively, the RBDS simply measures the reflected power and compares it to the initial transmission power as reported via the LAN 37 . The process may be repeated for another channel belonging to a different frequency and antenna.

In addition to the described example of a loopback test at the base site, it will be apparent to those skilled in the art that other site tests can be made. Further loop feedback paths will be described below with reference to FIG .

Loop feedback B

This loop return path is in the transcoder card 22 . The loop feedback is established by means of a command from the RBDS to the OMC 24 and from the OMC to the transcoder card 22 . The transcoder card 22 comprises 30 separate transcoders, each having its own digital signal processor. The command from the RBDS causes a selected one of the transcoders to return an audio signal (after the transcoding operation) and return the signal on the opposite channel to the RBDS. The transcoder transcodes the signal from a 30 Kbps rate to a 64 Kbps rate, returns it, and transcodes it back to the low rate. The RBDS may perform a spectrum analysis to analyze the returned signal. The transcoder on each channel can be tested by establishing calls to each channel in sequence. If the transcoder card 22 is remotely located at the MSC, as shown in Fig. 2, this must be coordinated by the OMC. Alternatively, if the transcode card is located at the base site 38 , the system element may be selected by the RBDS without involving the OMC.

FIG. 5 shows a hardware implementation of the loop feedback. The figure shows a transcoder card 22 comprising a bus 160 , a processor 162, and an MSI 167 , similar to the equivalent units in the base site 38 .

The processor 162 interfaces with the LAN 137 , which extends around the switch site 39 . Connected to the bus 160 are five XCDRs 170 through 174 connected to the MSC 23 . The XCDRs include digital signal processors and encoder / decoder (codec software) for performing the transcoder function.

Referring now to Figure 5, loopback is shown as occurring in XCDR 174 . Under the control of the processor 162 , the XCDR 174 decodes the message traffic on its receive channel (ie, received from the BSC 21 ) from a low data rate of 13 Kbps audio encoding according to the GSM guidelines to a higher rate of 64 Kbps in digital audio format It distributes to its transmission channels (ie, it is transmitted to the BSC 21 ) in the appropriate transmission slot, encodes it at a 13 Kbps rate, and transmits it to the BSC for return to the RBDS 35 .

On the RBDS 35 , the returned signal can be compared with the original signal. The signals can not be compared bit by bit as significant distortions will occur during the transcoder process. The transcoder is designed to retain the characteristics of human speech and, correspondingly, would require a human ear to decide if the quality of the speech has been preserved. However, other methods are used for these purposes of the test. In a preferred embodiment, the audio signal generated by the RBDS is a pure sine wave and spectral analysis is performed on the returned signal. In particular, the harmonic of the returned signal is analyzed and if it does not fall within expected constraints, an error is registered and reported to the OMC 24 .

Loop feedback C

The loop feedback C is performed in the MSC 23 . It allows the RBDS to set up a call and forward an audio signal to the MSC, which redirects the message traffic to the RBDS for verification. The OMC is requested by the RBDS to select a particular path through the MSC so that each part of the MSC can be tested and errors isolated.

Loop feedback D

The loop return D is executed in the IWF 26 . A data signal is transmitted from the RBDS through the BTS 20 and BSC 21 to the MSC 23 . Since the signal is a data signal, the MSC 23 routes the call to the IWF 26 , which translates it into a normal telephone modem signal. Instead of forwarding the modem signal to the PSTN 30 , the IWF returns the signal, translates it back into the GSM data format, and passes it back to the BSC 21 and the BTS 20 . The RBDS receives the feedback signal and can compare the transmitted data with the received data.

Loop feedback E

One problem that arises in attempting to loop feedback through the PSTN is the use of echo cancellers 31 and 32 . A returned signal with no delay would be detected by the echo cancellers as a long echo and be removed. In order to facilitate PSTN loopback in the GSM system, according to a preferred embodiment of the invention, it is proposed to provide a maintenance termination unit (MTU), which will be described below. The MTU is a self-contained entity connected to any PSTN with its own PSTN phone number. The MTU is shown in FIG . It comprises a switching device 200 , a loop return with a fixed attenuator 201 , D / A nd A / D converters 202 and 203 , a RAM memory 204 and a control device 205 . In addition, the MTU includes other standard circuits, which need not be further described.

The RBDS initiates a call to the only telephone number of the MTU in the PSTN. The PSTN forwards the call to the MTU and when the call is received, the MTU is activated. The time before the incoming call is answered is adjustable. Once the call is answered, the MTU operates in two different operations, as determined by the switch means 200 . In the first mode (indicated by the above position of the switching means), audio signals are simply fed back from the receiving line to the transmission line, whereby a weak attenuation by the weaker 201 is made. In an alternative operation (indicated by the lower position of the switching device 200 ), the signal is digitalized by the A / D converter 202 at the standard PCN rate of 64 Kbps and stored digitally in the RAM 204 . Ten seconds of data are recorded containing all the conduction activities (tones, voices, pops, crackles). During this recording process, the MTU detects periods of silence by detecting a number of consecutive samples having a smaller than a prescribed amplitude and then plays back the ten seconds of data through the D / A converter 203 to the transmission line. It will be understood that if the signal is periodic, it makes no difference whether the last ten seconds, the first ten seconds or any other part of the signal being retransmitted, provided that the signal is present for a sufficiently long period before Retransmission has been stored so that the operating period of the Echoausschalter 31 and 32 is exceeded, is used. There may be another delay between the end of the receive operation and the start of the retransmission operation.

The effect of the MTU is to store, delay and reproduce the received signal after a period of ten seconds, which is outside the range of operation of the echo cancellers 31 and 32 . Thus, the reproduced audio signal is not turned off by the echo cancellers and is received at the RBDS to be compared with the transmitted signals.

In this way, a complete path through the GSM system to be tested by the mobile unit to the PSTN.

Claims (9)

A radio system infrastructure system comprising a transceiver station for communicating with a mobile transceiver, a diagnostic transceiver associated with the transceiver station for generating test signals and forwarding them to the transceiver station, characterized by means ( 20 , 22 , 23 , 26 , 200 ) within the infrastructure for returning a signal received from the diagnostic transceiver ( 35 ) at a point within the infrastructure, returning it to the diagnostic transceiver, and testing the returned signal thereby diagnosing faults within the infrastructure facility. 2. Installation according to claim 1, in which the infrastructure system comprises multiply parallel system elements ( 40-44 , 55-59 , 26 , 170-174 ) and the diagnostic transmitting / receiving system comprises a control device which is coupled to the multiply parallel system elements, to set up a selected communication path through the multiple parallel system elements, whereby the selected system elements can be tested under control of the diagnostic transceiver. 3. Installation according to claim 2, wherein the multiply parallel system elements radio transmitter / receiver units ( 40-44 , 55-59 ) include. 4. Plant according to claim 2, wherein the multiply parallel system elements comprise parallel transcoders ( 170-174 ). The system of claim 2 including an intermediate workstation ( 26 ) having a plurality of modems for translation between packet data format and modem data format, and wherein the multiple parallel system elements comprise a plurality of modems. 6. Plant according to at least one of the preceding Claims in which the infrastructure investment multiple times includes serial elements and the Diagnostic Transceiver a controller which is coupled to the multiple serial elements is to select an item where the item is to Returning the signal is made. The system of at least one of the preceding claims, comprising first ( 38 ) and second ( 39 ) serial elements, wherein the first serial element is coupled to the diagnostic transceiver and the second serial element is coupled to the diagnostic transceiver is coupled across the first serial element, and wherein the first and second serial elements comprise control means for communicating control signals therebetween during normal non-diagnostic operation, and wherein the first serial element ( 38 ) further comprises simulating means (CPsim) for simulating control signals from the second serial element when a signal received from the diagnostic transceiver is returned to the first serial element to thereby simulate normal operation for the second serial element. 8. Plant according to at least one of the preceding Claims, further comprising a connection to a public telephone network (PSTN), one Maintenance port unit that connects to the PSTN and has a memory, delay and Reproduction device for receiving a signal from the Has a diagnostic transmission / reception system by the PSTN, this signal is saved and automatically sent to the Diagnostic transmission / reception system according to a predetermined Retransmission period. A maintenance terminal unit having connection means for connection to a public telephone network (PSTN) having echo-out switches ( 31 , 32 ), having storage, delay and reproduction means ( 204 , 205 ) for receiving a signal from the PSTN on a receive line for storage of this signal and automatically retransmitting to the PSTN on a corresponding transmission line after a predetermined delay period exceeding the period of operation of the echo canceller has elapsed.