PS) is also needed to localise the position of quality degradation precisely. The overall system is mounted on a vehicle. The first installation of the equipment requires some operations like calibration of the GPS. In fact, manually calibrated GPSs contain an odometer and a gyroscope, which may require going through specific routes with various distances and various speeds. In some cases, an attenuator is used on the antenna chain in order to cancel antenna gain and have a 0 dBm chain. The performance of the tool depends on the ability of the handset to report or not some specific data. Each mobile can be in one of three modes: idle, call generator or frequency scan. The same set can also be used for benchmarking several networks. As shown in Figure 2.46 (laptop screen), a lot of information can be displayed online. Some tools bring additional features such as channel lock, layer 3 message decoding and online sound warnings for events and GPS signal loss. Log files of the measurements can then be recorded and reviewed later. They can also be used to plot some data on maps or graphs. Generally each tool has a specific software application to anal- yse the measurements further. Drive testing is necessary in many phases of network evolution. Be- fore sites are installed and after BTS roll-out, frequency plan implementation, etc., every time that a change is performed on the network in terms of site engineering and/or parameters, drive tests should be performed. To draw a drive test route, field knowledge is very important. The route should be drawn both by the measurements technician and radio planning engineer. The direction where a certain road will be driven is also important to identify, especially when interested in a certain handover sequence. KPIs used during drive testing are how given. Radio Network Optimisation Table 2.19 BER to RXQUAL conversion table RXQUAL BER < 0.2% 0.2% < BER < 0.4% 0.4% < BER < 0.8% 0.8% < BER < 1.6% 1.6% < BER < 3.2% 3.2% < BER < 6.4% 6.4% < BER < 12.8% 12.8% < BER The BER is an es