## 3 Use Case: UMTS Networks
### Data Selection  
In this step, variables for each one of the categories established in the previous step are selected. Note that this selection should seek to maximize the quality of the final result. The variables should be determined following the quality dimensions of relevance (qualitative assessment of the value contributed by the data), interpretability (simplicity of understanding, using and analyzing the data), coherence (consistency of the data; data can be combined in different ways), timeliness (length of time between data availability and the related event), accessibility (conditions in which data are accessed), credibility (confidence in the data), and accuracy (closeness between the values provided and the unknown true values), according to [25]. In this case, basic KPIs that are defined by the 3 GPP are determined as variables. In each category, the most representative ones are selected and, in the specific cases of accessibility and retention categories, KPIs that discriminate by service are accounted for in order to evaluate the performance in both voice circuit switched (CS) and packet switched (PS) data. Next, a description of the KPIs established for each category is provided:  
* **Accessibility** Two KPIs are selected with the aim of breaking down the service between data or voice services. There will be a loss of generality, since this selection does not take into account where accessibility problems remain, nor does it distinguish whether accessibility will be good or bad in the radio resource allocation phase or at the stages of establishment of the radio bearer, congestion, or use of resources. The call setup success rate (CSSR) is the considered KPI, which indicates the percentage of calls that require access from a service, and this is satisfactorily provided. The PS and CS versions are included. * **Retainability** The KPIs that were selected in this category aim to quantify the falls according to the service. Three KPIs are considered, covering the data services (DROP HSPA and DROP R99) and the voice service (DROP CS). The difference between High Speed Packet Access (HSPA) [33] and R99 (Release 99 [34]) is the underlying technology, since R99 was the first 3G version of the standard and HSPA offers better throughput values. With these KPIs, the performance of the network is covered and, in addition, it is possible to differentiate by users (voice services, low data speed, and high data speed). * **Integrity** In this category, throughput is the selected KPI, since it indicates the performance that is achieved by the network. This KPI collects the average throughput of each of the connections that are established in the network. It is defined as the number of bits per second that the user perceives in the network. * **Mobility** Three KPIs that differentiate three different types of mobility are selected: mobility in the same frequency (intra-freq), mobility to a different frequency (inter-freq), and handovers (HO) or transfers to 2G. The corresponding KPIs are INTRA-HO (percentage of HOs in the same frequency between different cells), INTER-HO (percentage of HOs in different frequencies between different cells), and inter-radio access technology (INTER-RAT) HO (percentage of HOs to 2G technology), respectively. With these KPIs, a global vision of network mobility is achieved, although the vision of mobility by service is lost. This choice is justified, because bad retention values can lead to bad values in mobility, so there is more weight, in that sense, to the other statistical dimension. * **Quality** Two KPIs are considered here. The first one is the ratio between the received energy from the pilot signal chip (Ec) to the noise density (N0), which is, Ec/N0. This KPI provides a measurement of the interference that was measured by the user at a cell level. The secondKPI is the received signal code power (RSCP), which indicates whether the average receive signal level is adequate or not. Both of the KPIs are measured in dBm.