Call drop caused by forward interference

Typical case:
As MS moves, its Rx power is increasing;
As MS moves, the strongest pilot Ec/Io is decreasing and is not enough for demodulation requirement, F-FER increases very fast until call drop;
As MS moves, MS Tx power is normal and will not tend to maximum;
After call drops, MS will initialize and stay in previous pilot, but origination call is difficult and call drop is very easy to happen. MS may stay in one new pilot and the signal stabilization is decided by interference source.

Analyzing:
MS Rx power is increasing, but the pilot Ec/Io is decreasing, this means there is forward interference. When MS moves to interference continuously, the pilot Ec/Io will decrease continuously, until F-FER increases very fast and MS fading timer expires, MS will initialize again, that is call drop.

Note:
For the forward interference source, there are two kinds: external interference; internal interference.
External inherence: the radio signal from other system drops into MS receive bandwidth, MS will re-initialize after call drop and stay in previous pilot. Call drop is very easy to happen again, even if origination call is successful. Internal interference: usually it is handoff which causes call drop. When MS moves to a new cell, for some reasons (wrong neighbor list setting; too narrow search window) handoff is failed, and the objective cell pilot will be a strong pilot interference. This kind of interference belongs to internal interference. The difference from external interference is: MS will re-initialize after call drop and stay in one new pilot (the objective handoff cell pilot) very well.

Optimization method:
External interference: Inform customer and they connect with government to clear; Internal interference: Check background configuration and adjust the related parameters.