3G Post Processing RF Analysis Summary
Definitions
• Pilot pollution:
The presence of more than a pilot with level difference within 5-8 dB causing low Ec/No all of them are strong but no one is strong enough to be dominant regarding that they are of the same frequency
• Missing Neighbor:
The presence of a detected neighbor with high RSCP for a period without adding to the AS causing degradation in Ec/NoIt may cause pilot pollution as this high neighbor neither added to AS nor it is low enough to be neglected (from the point of view of interference).
• Overshooting
It is a case like missing neighbor but the difference is that in case of overshooting the mentioned neighbor is far from the detection position while in case of missing neighbor the neighbor is near the detection position.
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Dropped calls:
Cause
|
Ways
to discover
|
Recommendation
|
Pilot
pollution
|
Finding
AS, MN & DN with relatively near RSCP levels (within 5-8dB) all of them
are high
|
Down
tilt the antennas of the surrounding sites to decrease the interference caused
by them to have dominant cells
|
Low
RSCP
|
The
RSCP level is too low(less than -90) causing low Ec/No
|
Add
a site in this area to improve the coverage
|
Missing
neighbor
|
Finding
a high DN but check the cell file to make sure that it is near the detection
position.
It
can be noticed from WCDMA missing neighbor window but make sure that it is a
real problem as TEMS report missing neighbor after a certain time while this
neighbor may be added to AS after a longer time than that of the TEMS.
In
WCDMA missing neighbor window we can notice 2 priorities :
1st
priority where the missing neighbor must be added as the first member in AS
and has higher RSCP and Ec/No than the strongest AS member.
2nd
priority where it has lower or equal RSCP than strongest AS member.
|
Add
this neighbor to AS
|
Overshooting
|
Finding
a high DN but check the cell file to make sure that it is far from the
detection position. Check the cells by cell ID.
|
Down
tilt the antenna to AS
|
DT
problem
|
Noticing
a mobile disconnection
|
No
need to solve
|
UL
interference
|
It
can be found from System information message SIB 7
It
can be noticed also by monitoring the layer 3 messages and detecting that DL
messages are successive without UL messages for a while
Also
we notice that UE Tx power increases gradually until it reaches its maximum after
checking the distance between the UE and Node B and make sure that the
increasing power is not due to the distance.
The
RSCP is a sign to determine the distance between UE and Node B.
|
Continue
to observe the performances of this cell and try to decrease the percentage
of soft HO on this cell.
|
Unidirectional
missing neighbor
|
Noticing
the DT direction, if the call dropped in one direction and continued in the
other as a result that a neighbor is defined in a direction and missing (DN
in the problem direction with high RSCP) in the other.
|
Define
this neighbor as bidirectional neighbor.
|
Wrong
parameters
|
It
can be noticed by finding strange AS updates
|
Check
the parameters of soft HO
|
TEMS
problem
|
Noticing
blocked or dropped call on the map without finding it in layer 3 messages
|
No
need to solve
|
DL
Interference
|
There
is no DL layer 3 messages sent and noticing successive UL messages.
The
Ec/No is very low although the RSCP is good.
|
Check
traffic performance on this cell.
Check
soft HO parameters.
Check
Inter-RAT HO parameters.
|
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|
Cause
|
Ways to discover
|
Recommendation
|
|
Interference
|
Noticing DL successive messages without UL reply
or vice versa.
|
Continue to observe this area
|
|
Congestion
|
Presence of call attempt retries.
Notice the call scenario for the blocking if the
mobile camped on this cell in another time with a good quality and
performance then this cell maybe congested.
|
Adjust soft handover parameters to decrease SHO on
this cell.
Check the 3G phase in the nearest sites in this
area.
Add a micro in this area to handle traffic there.
|
|
Not RF problem
|
Presence of reject or noticing a failure in any
request from RNC to CN.
|
Continue to observe A-interface
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