Application Note IFR 2968 Frequently Asked Questions by Clive Rodmell The IFR 2968 TETRA Radio Test Set is the industry standard for testing TETRA mobiles and base stations during design, manufacture, service and repair. This application note answers common questions concerning the capabilities and configuration of the IFR 2968, and provides solutions to common problems that may arise during testing. For the very latest specifications visit www.aeroflex.
Introduction TETRA is a complex system with many features and a high degree of customisation to suit the requirements of individual networks and groups of end users. The IFR 2968 is therefore a complex product providing configuration to match the mobiles and base stations under test and supporting the diversity of features and operational behaviour. Inevitably the IFR 2968 requires some user familiarisation and experience in order to achieve the greatest benefit from it.
Section 2 Questions: Testing mobile and base station transmitters Q3.12: Can the 2968 generate PRBS for testing AACH, BSCH and SCH/HD channel types? Q2.1: How do I use the 2968 to control the mobile to transmit at a particular power level? Q3.13: Can the IFR 2968 test base station receivers? Q2.2: Why is the mobile power level approximately 5 dB too high or too low? Q2.3: Can I use the 2968 to control the mobile power directly, as with GSM? Q2.
Phase 3.2 software? plan and channel number? Q5.9: Why has the AUTORUN PARAMETERS menu changed in the Phase 3.2 software? Q6.13: Can I test a TETRA mobile that does not conform to the ETSI channel numbering? Q5.10: Why is 'TEST MODE REGISTRATION' not in System Parameters in Phase 3.2? Q6.14: Can I ignore channel plans and channel numbers and set the 2968 frequency in Hz? Q5.11: What has happened to mobile terminated SDS types 1, 2, 3 and 4 in Phase 3.
Q9.4: Can the IFR 2968 test other base station components besides the transceiver? Q1.3: Do I have to return the IFR 2968 to IFR for the software upgrade? Q9.5: Can I store and recall different TETRA system set-ups on the IFR 2968? A1.3: No, this is not normally necessary. The software upgrade will normally be performed by your local IFR Approved Service Center, either on your premises or by return to a local service center, as agreed between you and the IFR Approved Service Center.
• Multiple Group Attachments, group detachment and group modification fully displayed • Configurable Trunking Timers and Call Timers • DTMF digits displayed during a call • Mobile Originated Direct Mode call set-up and clear down (requires Option 32) w.r.t. Phase 3.1. Q1.7: What functionality will I gain by purchasing Option 32 TETRA Direct Mode? A1.6: The "2968 PHASE 3" option enables your IFR 2968 to be upgraded to the latest Phase 3.2 software. The Phase 3.
band/tri-band GSM mobiles, not the 1800 MHz or 1900 MHz bands. Dual band and tri-band GSM mobiles are supported by the IFR 2935 and IFR 2967 radio test sets. IFR 2968 + Option 30 TETRA MS + Option 31 TETRA BS IFR 2968 + Option 30 TETRA MS IFR 2968 + Option 31 TETRA BS Q1.17: Does the IFR 2968 support Tetrapol? Further options can be purchased at a later date if not purchased initially. Please contact your local IFR sales representative or distributor for a quotation. Q1.
Level, and by two of the parameters in the 2968 SYSTEM PARAMETERS menu, "ACCESS PARAMETER" and "MAX TX LEVEL". The calculation is as follows: • Take the 2968 RF GEN level, which will be in -ve dBm, and make it +ve. • Add the ACCESS PARAMETER, which is in -ve dBm, range -53dBm to -23dBm. • The result is the mobile's transmit power, subject to some modifications.
the PTT pressed. If you are testing in Direct Mode, you will not be able to set up a duplex call, so you should simply release and repress the PTT to continue measuring. Q2.8: Why does my TETRA mobile or base station exhibit excessive vector error? A2.
erence sensitivity level (-112 dBm) with a correctly functioning mobile. TETRA mobiles need to be able to receive a signal from the base station (test set) that meets or exceeds the 'minimum Rx level for access'. The default value for this parameter on the IFR 2968 is -125 dBm, and you should ensure that this value is set prior to performing receiver sensitivity tests, in order to avoid call dropping. Q3.4: Why doesn't 'TT' RF Loopback work with my mobile? A3.
34 and 35 for details of testing receiver sensitivity using audio SINAD. There is also another T1 signal defined which the 2968 does not generate: Q3.9: What is the difference between MER, BER and RBER? • A3.9: MER is Message Erasure Rate, and it applies to TETRA channel types that include a parity check (e.g. the signalling channels such as SCH/F and the Class 2 bits in the speech frame). BER is Bit Error Rate and it applies to TETRA channel types that do not include a parity check (e.g.
channel type 8 (SCH/F) in frame 18 in timeslot 1. It does not generate an uplink T1 type 8 (SCH/F) signal in frames 1 to 17 for testing base station receiver Message Erasure Rate (MER), although the SCH/F in frame 18 could be used for this purpose. The 2968 synchronises the timing of its uplink T1 type 7 signal to that expected by the base station.
After you have set the 2968 correctly for the required uplink scrambling, it may be necessary to re-start the BER measurement on the base station so that it can re-synchronise its BER measurement to the correct PRBS. Note that the 2968 manual test screen display of the MCC/MNC/ BCC parameters always shows the values indicated by the base station synchronisation burst, whether or not it is auto updating to these values.
formance is poor. Q4.4: What is the IFR 2968 generating when it is set to 'test tone'? A4.4: It is generating a TETRA encoded version of a 1 kHz tone, representing a level of approximately 12 dB below the theoretical maximum output level. The test tone is pre-computed data that is stored in the 2968, hence the frequency and level are fixed. It is not generated in real time from an audio signal since the 2968 does not have a TETRA codec.
parameter is used in autotest to determine the BER / RBER / MER limits to be applied to the receiver sensitivity tests. Q5.6: Does the IFR 2968 test DGNA (Dynamic Group Number Assignment)? A5.6: No. The IFR 2968 generally supports only those protocol functions that are required to enable the test set to perform parametric tests on the mobile, or to obtain useful information about the configuration and capabilities of the mobile.
A5.16: TETRA mobiles can only make and receive group calls to or from groups that they have successfully attached to the network. Normally a TETRA mobile will attach one or more groups at registration, and you will be able to subsequently change the currently selected group. Ensure that the 2968 is not displaying "GSSI: NO GROUPS ATTACHED". If it is, this could be because the mobile group selection is explicitly set to 'NO GROUP', or because the mobile has not been configured with any group identities.
Q6.5: The essential network parameters have been set correctly but the mobile still does not register to the IFR 2968. Is there anything else that needs to be checked? A6.5: Refer to 'Annex C: Troubleshooting when a mobile does not register' in the IFR application note 'Testing TETRA mobiles with the IFR 2968' for further assistance. Q6.6: The mobile registers to the IFR 2968 but call set-up fails. What is wrong? A6.
Firstly, use the 2968 in base station test mode ([SYSTEM] [TETRA base], requires Option 31 TETRA BS) to determine the frequency of the base station. Select channel plan NO PLAN ([SET-UP] [channel plan] [NO PLAN]) and go to [MANUAL] mode. Ensure that your antenna is connected to the TNC port in 2-port duplex mode with maximum sensitivity (refer to 'Off-Air Base Station testing' in the 2968 Phase 3.2 TETRA supplement issue 10, chapter 5, page 8).
0 Hz Therefore channel plan = TETRA 800+0 MS (zero offset), channel = 2697 does not test Mobile Terminated Direct Mode call set-up, i.e. it does not simulate a Direct Mode mobile setting up a call to other Direct Mode mobiles. Note: the ETSI numbering scheme permits a small overlap of the 100 MHz bands (2.4 MHz overlap), since the channel numbering extends to 4095. For example, a base station covering 395.000 MHz to 400.
LOG in 'view all layers' mode since these messages only appear at MAC and MLE layers. For information on the SYSINFO and SYNC parameters that can be changed, refer to the 2968 Phase 3.2 manual issue 10, chapter 3 pages 6 to 16; chapter 4 pages 2 to 3; chapter 11 pages 1 to 4. Section 8 Q&A: Testing mobiles with encryption and authentication Q8.1: Can I test TETRA mobiles that use encryption and / or authentication? A8.1: Yes.
the necessary security measures associated with handling the authentication keys and algorithms. Q8.10: How can I test a TETRA mobile that uses mutual authentication? A8.10: Mutual authentication involves the mobile authenticating the network as well as the network authenticating the mobile. This functionality is specified for TIPv5, and is always initiated by the TETRA network.
Q9.6: Why doesn't the store / recall facility work when I try to store /recall TETRA settings? A9.6: The IFR 2968 store/recall facility incorporates both internal stores and external stores; external stores use a memory card. The internal stores (numbered 00 to 19) only store the settings relating to the 'NO SYSTEM' analogue functionality of the 2968.
For the very latest specifications visit www.aeroflex.
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