Basically MS camps on the best serving cell on the basis of C1 and C2. C1 is cell selection criteria which is already mentioned by manu. if “enabled” C2 criteria decides which cell to preferably camp on. C2 is defined as
C2 = C1 + CRO – TO * H ( PT – T )
here
CRO = Cell Reselect Offset
TO = Temporary Offset
PT = Penality time
T is initiated from
zero when the MS places the neighbouring cell on the list of the six
strongest carriers.
In this manner we can camp the MS on the cell which may not be the best server. This practise is often used for traffic balancing.
So we may say that MS is NOT “always camping within the cell offering the best coverage”.