Information and Communication Technologies (ICT) is not only an important sector of economic activity in its own; it is the essential engine for innovation within all knowledge-intensive domains of the European society. ICT is widely recognized as one of the driving forces in innovation. In the past decade, the growth of productivity in Europe has lagged behind the growth in competing economic zones to a large extent because of insufficient use of ICT. A quarter of the EU GDP growth, and 40% of its productivity growth, are due to ICT. Differences in economic performance between industrialized countries can be largely explained by the level of ICT investment, research, and adoption, and by the competitiveness of their information society and media industries. A clear increase in the use of ICT is necessary for this gap to be bridged.

One of the key milestones in ICT is the emergence of modern communication systems. In fact, large communication networks are among the most complex of all man-made artifacts and the proliferation of new services and communicating devices constantly places tremendous demands on their design. The evolution of contemporary communication systems, specifically, is defined by the increasing availability of broadband connections, a variety of mobile access networks, and an abundance of heterogeneous communicating and sensing devices that range from RFID chips to mobile phones, portable computers, household appliances, servers, and even classic mainframe computers. As a result, communication networks are rapidly changing in three fundamental aspects:

 Very diverse computing, communicating and sensing devices are emerging, driven by the decreasing costs and growing interconnection capabilities. System adaptation to the capabilities of every individual device will be a major requirement for widespread intelligent applications and services. Heterogeneous and densely deployed wireless networks, which integrate sensors, processors and controllers of different nature (collectively referred to as Sensor Networks) provide the clearest example of this revolution.

 New functionalities and interactive services emerge as systems become progressively networked and mobile access possibilities become abundant. Personalized and multimodal human-computer interaction technologies are needed in these highly connected environments.

 Modern society relies on communication networks to an ever-increasing extent. This buttresses the importance of providing the technology needed to offer secure, robust and seamlessly integrated services and of providing users with a transparent interface irrespective of the actual physical connection. Enabling the convergence of heterogeneous networks and designing reliable and secure infrastructures, tolerant to subsystem failures and various attacks, is critical.

The fundamental question is then, what are the critical research challenges for the ICT sector in the 21st century? We strongly believe that the answer to this question resides in the following two main themes:

 Communication Networks. There is an urgent need to completely rethink the architecture of wireless communication networks. Ubiquitous connectivity with wireline-like quality of service (QoS) requires transmission rates as high as two orders of magnitude above current 3G cellular networks. There is a general agreement in the engineering community that such requirements cannot be attained, in an economically sustainable way, by simply scaling up existing architectures because they would become very inefficient. Indeed, the development of more flexible, robust and efficient wireless network configurations seems possible only if radically new schemes, such as those based on the idea of cooperative communication, are devised. Thus, we are moving towards a new paradigm for wireless networking in which the relationship among nodes will be inherently collaborative, adaptive, and aimed at optimizing the flow of information. This ambitious goal demands establishing and thoroughly understanding the theoretical foundations and methodological tools involved.

 Sensor Networks. It is critical to develop the fundamental theory behind wireless sensor networks. Wireless sensor networks are demanded to sense the environment, detect and react to events, predict physical phenomena, self-heal, organize, and isolate faulting nodes. However, the fundamental theory needed to both understand and optimally build these systems is still far from developed. There is an imperative need to advance the theoretical characterization of sensor networks, and this can only be attained via a continued cross-fertilization among several disciplines that have traditionally been studied separately. This includes networking, information theory, and statistical learning, all of them combined with proper algorithmic development and implementation assessments in order to impact important practical applications of both societal and scientific interest.