Reference Manual

Self Test and Supervision
40.4.5 Radio Transmission and Reception
Purpose
The transceiver is tested during traffic by a radio test loop function.
The purpose is to detect a faulty transceiver by detecting an error in the
signal strength or in the number of bit errors.
Preconditions and Initiation
The test requires two unused ATSR (AirTime Slot Resources) separated
by three timeslots. The radio test loop function is initiated when the
application software is started and is activated every fifth minute and is
performed only if resources are available.
Description
The transceiver is tested by sending a dummy burst to the transmitter
unit and looped back internally to the radio receiver unit. The test is
performed in two steps, a primary test and, if necessary, a retest if the
primary test fails. All loops are performed on the diversity channels A
and B and the results from these channels are combined. A fault report
is issued if at least one channel indicates an error. All transceivers are
tested.
The output power to the antenna is turned off for the ATSR used in the
loop. The primary test issues one dummy burst. The signal level of the
looped burst for both the A- and B-channel returning to the receiver unit
is compared with the sent burst and must exceed a lowest level. The
number of detected bit errors must be less than a maximum permitted
level. If the test is passed, the test is terminated and no fault is indicated.
If the primary test fails, a retest is performed. This test issues a
preconfigured number of dummy bursts, and for each of these bursts,
the looped signal level must exceed the lowest level. If the lowest lewel
is not exceeded, the test is terminated and a fault is indicated.
The presence of an interferer is detected by measuring the mean signal
level of all the looped bursts. This is done for both the A- and B-
channels. If the signal exceeds a maximum defined level, an interferer
is considered present.
If no interferer can be detected a final test of the bit error rate is
conducted. If the number of bit errors exceeds a maximum permitted
number a fault is reported. If all configured retests have failed and not
recovered, the transceiver is blocked by the BSC.
40.4.6 Transmitter Antenna
Purpose
Transmitting characteristics are monitored in order to detect if an
antenna has been damaged.
EN/LZT 720 0008 R1A
2001-06-26
309 (421)
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