ted by the engineer for optimisation purposes. Different check and control mechanisms help to localise and clear possible eventual incoherence in handover settings. Some specific warning alarms in the Operations and Maintenance System (OMS) may help engineers to identify adjacent cell configuration errors. Possible examples of this are: Same BCCH used in source and target cells. In fact, when measuring this frequency an MS cannot tell the difference between the cell it is camping on and the adjacent cell. In this case, one of the frequencies should be changed. Duplicate BCCH + BCC + NCC in adjacencies. If a cell has two adjacents carrying the same frequency and BSIC, the MS camping on this cell cannot differentiate between the two target cells and then cannot perform any handover towards them. There may be many handover failures because the MS may measure the first cell and the network may initiate handover towards the second one. One possible solution could be changing only the NCC or BCC. In the end, correct neighbour topology saves a lot of optimisation time. Parameter Management The base station subsystem (BSS) along with the network switching subsystem (NSS) play a fundamental role in setting up calls to and from different users. Thousands of parameters exist that drive the GSM network functioning. From the BSS perspective it is possible to talk about parameters and from an NSS point of view to signify that more timers are related to the radio resource, mobility and call managements. Parameters and timers are of different types and concern many algorithms. This is why tuning is the trickiest part in the optimisation process. As the number of parameters is huge and as performance targets are not fixed, a great number of combinations is possible. This complicates the tuning task. Operators usually start at the beginning of the site roll-out by implementing standard templates of parameters and then apply fine-tunings to specific sites/areas. It is important to understand first the parameter classification and t