he algorithms they are involved in and afterwards to deal with their handling. BSS Parameters Classification The network architecture shows that a BTS is the entry point for an MS to the GSM network and that the BTS is linked to the BSC. However, from the NMS perspective a BTS site is recognised in a certain hierarchy reflecting the hardware structure. Figure 2.71 illustrates the BSS hierarchy. One BSC ID identifies each BSC on the network. The BCF ID is unique per BSC and identifies one site. One site may contain more than one sector; these sectors are recognised through the BTS ID. The BTS ID should also be unique per BSC. Finally, each sector transmits on several frequencies; one transmission/reception unit commonly called TRX carries each of the frequencies. The TRX ID is unique per BCF. As explained before, parameters concern several algorithms and depending on these they may belong to one of the layers in the hardware hierarchy. Radio Network Planning and Optimisation BSC ID V BCF BCF ID Sectors BTS ID TRX ID Frequencies Figure 2.71 BSS hierarchy from the NMS perspective Concerned Algorithms Parameters can generally take one value among a range of possible values. Different values for one parameter generate different behaviours of the system towards a certain event. More explicitely, param- eters are involved in determining the logic behind algorithms. The most important algorithms related to optimisation issues are power control, handover control and adjacency control. Power Control Power control parameters handle the thresholds for activating the algorithm, the steps for varying the power and the averaging mechanisms. It is interesting to note that power control parameters can be classified into four groups. Enablability Such a parameter indicates whether uplink and downlink power control mechanisms are allowed or not. Generally this type of parameter is Boolean; they take either 'yes' or 'no' values. Interval This group of parameters defines first the interval of the control range specifying the minimum 