The 3GPP Release 10 standard contains an interesting feature under the rather unexciting title of “Minimization of Drive Testing” (MDT). Drive Testing is the process often used by operators to measure their network coverage. Special measuring equipment is installed in a car and it is driven round different locations to take measurements. The upside of traditional drive testing is that is provides a nice summer job for students. The downside is that even with students doing the work it is slow and expensive.

MDT exploits the fact that all mobile phone routinely measure signal quality information and use it to make decisions about how best to connect to the network. Once MDT is enabled (which in theory should require user permission for privacy reasons) then the network can request a phone that supports MDT to log its coverage measurements and report them to the network. The logging process can take place even if the phone isn’t in an active session with the network. MDT thus give the network operator a view of the coverage as measured by the phone actually in users’ bags, pockets and glove boxes.

The idea of MDT is simply to reduce the amount of drive testing a network operator has to perform (dur!) but in fact MDT may reveal facts about coverage that could be surprising or even uncomfortable for the operators. When the BBC used a mobile app to measure UK 3G coverage the results were significantly worse than the operators’ official coverage predictions (http://www.bbc.co.uk/news/business-14574816). What’s the difference between coverage as measured by a drive test and coverage as measured by a mobile? A drive test measures the available signal in an outdoor location. Mobiles measure the signal that actually reaches them – this could be limited by many factors including screening when inside cars or buildings, antenna orientation, proximity of other objects and interference by other devices. All in all signal quality as measured by the mobile could be very different (and more representative of user experience) that than seen in a drive test.