  The growing awareness that human communications and social interactions are
assuming a stratified structure, due to the availability of multiple
techno-communication channels, including online social networks, mobile phone
calls, short messages (SMS) and e-mails, has recently led to the study of
multidimensional networks, as a step further the classical Social Network
Analysis. A few papers have been dedicated to develop the theoretical framework
to deal with such multiplex networks and to analyze some example of
multidimensional social networks. In this context we perform the first study of
the multiplex mobile social network, gathered from the records of both call and
text message activities of millions of users of a large mobile phone operator
over a period of 12 weeks. While social networks constructed from mobile phone
datasets have drawn great attention in recent years, so far studies have dealt
with text message and call data, separately, providing a very partial view of
people sociality expressed on phone. Here we analyze how the call and the text
message dimensions overlap showing how many information about links and nodes
could be lost only accounting for a single layer and how users adopt different
media channels to interact with their neighborhood.
