information. For this purpose a 'dead reckoning' system can be fitted to the car, which basically connects to the pulses generated by the vehicle odometer. Special testing software can be programmed to generate calls of a fixed duration and fixed repetition to a certain test number. The laptop then records all the measurements made by the phone, which are usually signal strength, neighbour lists, call quality and mobile output power. Most drive test equipments are also able to record the signalling messages between the mobile and the network. Most of the KPIs mentioned above can be measured using such drive test equipment. In the initial stages of the network, especially before commercial launch, the drive test equipment is the only way to test the network since there are no other users on the network. Drive test equipment is able to pinpoint the geographical location of any problem. The data collected can then be analysed to find out the cause and correct the problem. A second drive test can confirm whether the problem is corrected. For indoor measurement the same set-up can be used. As GPS-based positioning does not work inside buildings, there is also available a complete test equipment in a single handset. This can be used to collect information about calls and the radio environment, but the user has to separately record position information based on markers than can be inserted while performing the test. NETWORK STATISTICS The advantage of drive testing is that precise geographical information is available and the testing does not depend on the vendor supplying the equipment. Further, some tests like MOS tests can be performed only with drive test equipment. Disadvantages are that drive testing is expensive and is limited to the roads, or in the case of indoor testing to accessible areas. D.5 NETWORK STATISTICS Most network vendors have counters to count the events occurring on the network. These counters are then collected by the network management system (NMS) for the particular sub- system. In a typical m