Table 2.

Example of call detail records (CDRs)

Timestamp	Tower	Caller	Callee
(a)
2007/09/10 23:34	36	4F80460	4F80331
2007/10/10 01:12	36	2B01359	9H80125
2007/10/10 01:43	38	2B19935	6W1199
$⋮$	$⋮$	$⋮$	$⋮$

Tower	Latitude	Longitude
(b)
36	49.54	3.64
37	48.28	1.258
38	48.22	− 1.52
$⋮$	$⋮$	$⋮$

Every time a user makes a call, a record is created with timestamp, the phone tower serving the call, the caller identifier and the callee identifier (a). For each tower, the latitude and longitude coordinates are available to map the tower on the territory (b)