Principle of Statistics Extraction Process In a macroscopic view, the collection mechanism of statistics is described in Figure 2.56. To proceed first with collecting statistics, measurement tables for the BSC should be configured and activated. Otherwise, no values are reported. Tables are organised by categories to allow the operator to reduce load on NMS processors and download only wanted measurements (traffic, resource availability, handover, power control, etc.). Mobile subscribers report the active wanted measurements to the BTS while in idle or connected modes. The BTS sends those measurements to the internal database of the BSC. According to the operator's settings, the BSC can either store the statistics or redirect them to the NMS. Via a specific tool installed at the NMS level, pure counters are computed into predefined formulas. The output KPIs are then grouped into generic reports and sent to the office. Then, some other specific tools, generally internally made, allow archives and visualising statistics to be stored in a friendlier interface than text reports. Statistics are reported regularly during the day to allow the operator to monitor the network in a very reactive way. Reports Generation A KPI is the result of a formula that is applied to counters (called performance indicators). Using a specific tool, KPIs are extracted in the format of predefined reports. These reports are addressed to specific target groups who may use them for various purposes. This is why the content of the report is customised according to the needs. This mechanism is illustrated in Figure 2.57. In the following subsections, key components of statistics processing are detailed. General Notions Here the basic notions used in statistics management are presented. Radio Network Optimisation Measurements Abis Interface Air Interface BSC Database Brut counters Mobile subscribers Reports Specific Tool Graphics, Archive Office Figure 2.56 Architecture of KPI extraction Formula Reports Process Target group Figure 2.57 KPI extra