Call Performance Issues

Got some reading which i though useful for u who work on network performance or fault management, kinda action that can taken in solving common issue in 3G network.

Behaviour	Problem	Description	Possible solutions
Call set-up failure Call drop	Poor coverage area	If problem is poor coverage, this means poor RSCP (<-95 dBm) thus also the EcNo derades very rapidly (< -12 dB) when the coverage border is reached.	Check Antenna line installation (antenna position and quality, cable length and quality). Check that CPICH powers are balanced between the studied cells. Check presence of shadowing obstacles. Add a site to the area.
Call set-up failure Call drop	Poor dominance area.	No main server in the area, too many cells with weak CPICH level. CPICH EcNo is usually very bad even the RSCP is good e.q. RSCP –80…-90 dBm but EcNo about –10 dB	Use buildings and other environmental structures to isolate cell(s) coverage. Down tilt antennas to make cells dominant and limit effects of interfering cell(s). Check antenna bearing. Add a site.
Call set-up failure Call drop	Pilot Pollution	Bad CPICH Ec/Io (<-12 dB) level although CPICH RSCP level is good. High site in the neighbourhood may cause interference.	Find interfering cell from Scanner results. Adjust antenna bearing and down tilt or lower the antenna height (too much tilt will break the dominance). Add interfering cell to the neighbour of the serving cell.
Dropped call/SHO failure	Missing neighbour	A good usable neighbour is present within cells coverage area, can cause DL interference if it is not in the active set. Swapped sectors in WBTS.	Check scanner data and look for missing neighbours. Check the cabling in antenna line.
Call set-up Failure Call drop	High PrxTotal due to UL External interference	The PrxTotal level is significantly higher than expected in no/low load conditions.	Try to figure the possible area/direction of the interference by checking PrxTotal level on neighbouring cells. Alternatively use spectrum analyser & directive antenna to locate interferer. Inform operator/regulator about the found conditions. Check if auto tuning range is large enough (20 dB).
Call set-up failure Call drop	High PrxToatal due to wrong MHA settings	The PrxTotal level is significantly higher than expected in no/low load conditions. MHA settings should be checked, see more in reference [7]	In case of MHA is used in BTS check MHA and cables loss parameters, otherwise PrxTotal value will be too high. (If MHA parameter is set to ON, Cable loss parameter is used, Cable loss = Real MHA gain = Feeder loss parameter)
Call set-up failure Call drop	High Prxtotal due to Installation problems	The PrxTotal level is significantly higher than expected in no/low load conditions.	Check the antenna installation as the last alternative in high PrxNoise case.
Cell set-up failure	Bad RRC connection set-up success rate due to slow Ue cell reselection	RRC connection set-up complete message not heard by BTS.	Set parameters so that reselection process will start earlier: Qqualmin, Sintrasearch and Qhyst2 as per latest recommendation [8]
Long call set-up time	Long time interval for sync between RNC and BTS before connection	The value of Parameter N312 is too high: maximum number of “in sync” indications received from L1 during the establishment of a physical channel	Use smaller value N312 (2, recommendation is 4). Use Actix for checking the call set-up delay (L3 messages). Use call set-up time optimisation feature Dynamic setting of “ActivationTimeOffset” (possible in RAN1.5.2 ED2) enables 200 to 500ms reduction for set up delay.
Dropped call	SHO to wrong cell will cause drop call.	Overshooting cell come temporarily into active set and forces a suitable serving cell to be dropped out. Later RSCP suddenly drops in the “wrong cell” and causes a dropped call because there is no neighbour defined.	Pan away overshooting cell if it is too close to the serving cell, otherwise apply down tilting as well.
Dropped call	Cell suffering from UL interference = DL (CPICH) coverage much bigger than UL coverage	As the UE Tx power is not enough for target cell synchronisation, the SHO fails which will cause call drop later.	Use cell individual offset (negative value) parameter to balance the DL and UL coverage. Check traffic direction of in-car UEs to decide which cell requires offsets.
Dropped call	DL CPICH coverage <>	Cell with lower CPICH power than the surrounding is having “too good” UL performance, as this cells’ UL cannot be used efficiently due to SHO is decided upon DL (CPICH Ec/No).	Use cell individual offset (positive value) parameter to balance the DL and UL coverage. Note: Cell individual offsets are not taken into account when calculating the added cell Tx power.
Dropped call	Round the corner effect	The call drops due to too rapid CPICH coverage degradation for Cell A, and therefore there is not enough time for SHO.	Use cell individual offset (positive value) parameter to balance the DL and UL coverage. Note: Cell individual offsets are not taken into account when calculating the added cell Tx power.
Dropped call/SHO failure	Too many neighbours	In SHO area the number of combined neighbouring cells become more than 31. HO list is created using RNC algorithm in the final stage some of the neighbours will randomly be removed.	Delete unnecessary neighbours. Improve dominance.