Call drop caused by reverse interference

Typical case:
As MS moves, its Rx power and pilot Ec/Io keeps in normal level;
As MS moves, MS Tx power increases and tends to the maximum 23dBm, until call drop;
As MS moves, MS Tx_Adj increases and it will be positive value, until call drop;
MS re-initializes after call drop and will stay in previous pilot. There is signal in MS, but origination call is difficult or call drop is very easy to happen after successful origination.

Analyzing:
In the above case, MS Rx power and pilot Ec/Io are all good, and this means the forward link is good. But in MS origination procedure MS is increasing transmitting power until maximum, and this means the reverse link is bad. That is there is reverse interference. Tx_Adj>0 also means forward is better than reverse. As MS moves continuously, MS R-FER will increase higher and higher. BTS can not receive the signal from MS correctly and BTS call drop mechanism is triggered, and then call drop will happen.

Note:
Call drop caused by reverse interference is very similar to forward and reverse imbalance, in fact reverse interference is just one of reasons that lead to forward and reverse imbalance. For the reverse interference source, there are two kinds: external interference; internal interference. External interference: other system radio signal may drop into BTS received
bandwidth; Internal interference: there may be illegal MS which try to access continuously. Because MS Tx power is limited, the number of illegal MS must be very large.

Optimization method:
External interference: Inform customer and they connect with government to clear; Internal interference: Usually this case seldom happens, but there is possibility, for example like repeaters with MS module, which repeaters use MS module for
background observation. But sometimes, if MS is not assigned number, its origination will be illegal, and then this will become strong interference. The solution is to close them or assign numbers to them.