Fault No. SO CF I2A:33
Fault name RX diversity lost
Related faults SO CF RU:40 – Antenna
AO RX I2A:1 – RX path lost on A receiver side
AO RX I2A:2 – RX path lost on B receiver side
AO RX I2A:3 – RX path lost on C receiver side
AO RX I2A:4 – RX path lost on D receiver side
Description An imbalance in signal strength between the receiver paths has been
detected for one, or several, TRXs. Depending on which of the RX
paths that have the lowest signal strengths, one or several of the related
faults are also issued.
Note: To avoid false alarms the fault has a long filter time, the actual
length of which depends on the traffic load. The fault may occur several
days after installation. Despite the long filter time, a single MS can
cause an alarm if the call is made when the traffic load is low and the
call continues for a long time in an area with poor coverage. When the
traffic load increases, the alarm normally ceases. To correct this kind of
alarm, the radio cell planning needs to be revised.
Action Follow the instructions below until the fault is corrected:
Note: Due to the long filter time, do not use reset until the actions have
• Use the issued RX I2A faults to identify which RXs, and thereby which
RX path, are faulty. The RX path identifies which antenna connection
should be investigated.
Note: If other alarms are issued on the same RX path, this might also
be the cause of the RX Diversity alarm. If present, correct these alarms
• Ensure that cables are connected to the correct CDUs and antennas.
The ’Radio’ view in the OMT shows how the IDB is defined regarding
• Check that the correct RX Diversity mode is defined in the BSC (RX
parameter RXD with possible values A, B, AB, and ABCD). See antenna
setup in OMT Radio view for help.
• Check that the ALNA/TMAs, if used, are working correctly. This can
be done by monitoring the ALNA/TMA power consumption in the OMT
and comparing it with the expected power consumption.
• Check all radio cables, connectors and other passive radio equipment,
for example with Antenna System SWR tests.
• Check the antennas.