RSCP is more or less similar to RX level of 2G,
Ec/Io to C/I
The range of RSCP is similar to RX level but the range of Ec/Io is from 0 to -30. Greater the Value better is the quality. The value is -ve as the Io includes Iown, I others and noise.(I=interferece).
Note: Unlike in GSM if u miss defining any neighbor site as neighbor there will be a call drop. This is because we are operating the whole Network on one single frequency and missing neighbor of that same frequency is considered as interfernce and the Ec/Io value becomes poor and thus leads to a call drop.