Introduction - Social Group Utility Maximization - page 1

Chapter 1
Introduction

1.1 Mobile Social Networks

Mobile networks have been growing rapidly in the past few years and this trend will
continue in the foreseeable future. Indeed, mobile phone shipments are projected to
reach 1.9 billion units in 2014, which is about 7 times that of desktop and laptop com-
bined [ 1 ]. Mobile data traffic is predicted to increase by over 100 times in the next
ten years [ 2 ]. The widespread popularity of mobile networks has been driven by con-
tinuing advances of technologies. On one hand, advanced wireless communication
technologies (e.g., MIMO, OFDM) have drastically improved the communication
efficiency in existing wireless networks (e.g., cellular networks, WLANs). On the
other hand, advanced mobile devices (e.g. smartphones) equipped with powerful
sensors (e.g., cameras) and high computing capability have enabled a wide range
of applications on mobile platforms. As a result, mobile networks have nowadays
become an indispensable infrastructure in people's everyday life.
Different from other networks (e.g., sensor networks), a distinctive characteristic
of mobile networks is that mobile devices are carried and operated by human beings.
As a result, mobile users' interactions hinge heavily on human behavior. It is then
natural to ask “How would mobile users' social ties influence their behaviors in
mobile networks?” Social ties are built upon human social relationships (e.g., kinship,
friendship, colleague relationship). Indeed, social ties play an unprecedented role in
people's interactions with each other, mainly due to the explosive growth of online
social networking services (e.g., Facebook, Twitter) in the past few years. In 2013,
the number of online social network users worldwide has crossed 1.73 billion, nearly
one quarter of the world's population [ 3 ]. With pervasive connectivity to the Internet
via mobile devices, mobile users can interact with each other much more readily
than ever before via online social networking services.
The social aspect of mobile networking is an emerging paradigm for network
design and optimization. A survey of mobile social networking can be found in [ 5 ].
There has been some work using the social aspect of mobile users to enable user
cooperation (e.g. cooperative forwarding [ 4 , 6 ], cooperative relaying [ 7 ]). However,
most of them do not consider that a user's cooperative behavior can affect multiple
users, and affect different users to different extents. Furthermore, as a user's social