circuit-switched mobile networks such as 2G (e.g. GSM) and the 3G CS part, while IAS requires IP connectivity over the mobile networks. Addi- tionally, one should note that even in covered areas, services (either voice or IAS) are not available at 100%. This is due to fluctuation in radio conditions (e.g. weather, peak hour which may result in attachments to a worse cell in the mobile network) and some- times equipment failure. In this regard, service availability is the KPI which can be added to mobile coverage to gain a complete notion about the accessibility of a given service, such as mobile voice or data (as the two most used over mobile networks). For example, for mobile IAS (i.e. mobile data) IP service access failure rate is in fact the opposite of IAS availability. IP access may fail for various reasons, including DHCP failures, DNS failures, congestion in the mobile network, packet errors (which may be caused by inter- ference, low SNR, etc.), long round trip delays in the mobile network (which may be the result of congestion), and SO forth. Generally speaking, service time availability refers to the availability of a given service (e.g. voice, data) during a defined time period (expressed in percentage of time when service is available). Also, it may be expressed as outage time (in minutes, hours) when the given service is not available within a given reference time period (e.g. day, month, or year). Although service availability is an important KPI, it is difficult to measure in many different locations through the mobile networks and at different time periods. Typically, measurements (by the NRA or the mobile operator) are done via drive tests or by using deployed probes; however, these can cover only limited numbers of locations (e.g. drive test can cover only roads, while probe stations can provide information only about the mobile networks regions where they are located). Another approach to obtain 9.6 KPIs and Measurement Methods for Fixed and Mobile Services information on service availability i