Personal computing paradigm flourished faster than any other domain and with its marriage with the networking world, it gave birth to a new era of computing called ubiquitous computing. 4G is not the name of a single technology, rather it is a cooperative platform where a large range of heterogeneous wireless networks and services coexist. The diverse devices, network and service elements find their way into the life of the end-user and this integration of 4G elements into the end-user environment should ideally go unnoticed to the user; so that the technology eventually focuses over the user and not the user focuses on the diversity of technology around him. Calm 4G technology integrated into user's world is only possible with the essence of cooperation, sharing, openness and trust, within the user's own devices and among the users. The notion of cooperation in personal/group services may take various dimensions ranging from technology and services to socio-physiological aspects.
There is a large array of actors in 4G service arena such as user, service/content provider, network operator, regulatory bodies, and so on, who bind their own proper stakes with 4G's success. However, economically speaking, user is a major player; a center of the entire 4G globe, whereas the other actors join hands to meet the expectations of the end-user. Taking the technological dimension, in the last few years, number of heterogeneous devices emerged and networked, ranging from mobile communication equipments to home electronics. This proliferation results into the availability of large range of choices to the user to communicate in highly diverse environments. As a result, in a 4G system, the user is surrounded by a variety of devices offering a multiplicity of different services, as shown in Figure 1. Moreover, the utilization of these devices and services dramatically changes with the change in user's environment. Therefore, the devices and services in the 4G world should have a high deal of adaptation capabilities. "Personalization" is a key word in this context. Since every user is unique in his roles, taste and likings; the 4G systems should be intelligent enough to fully understand the user and adapt the network and service elements according to user's preferences.
In a user-centric model, the user is the focus of the whole system. The cooperation among his heterogeneous devices and his environment is vital for the seamless working of the entire 4G system. Here, we refer to the cooperation in two dimensions. At first, the devices themselves need to cooperate, for instance, while the user is busy working on his laptop and he receives an important voice message on his mobile phone, the mobile phone should track the activity of the user in order to notify him about the voice message. To this end, irrespective of their specifications, the user's devices should be able to cooperate in order to help the user in his daily life. And second, the devices should cooperate with the user's environment. Since the user preferences vary with the change in his environment therefore the devices should be capable to dynamically adjust themselves accordingly. For instance, if the user receives a video call while at home sitting in his TV lounge, the mobile phone should intelligently detect the activity/mood of the user and should propose to transfer the video flow on the higher resolution screen placed in front of the user. These both dimensions of cooperation are only possible when the 4G systems encircling the distinct end-user, fully understand the socio-physiological and the technological potentials and limitations of cooperation.
In 4G, towards personalization and user-centric cooperation, we generalize the concept of Personal Computers (PCs) and extend it towards Personal Networks (PN). It is a system/network owned and operated by one person i.e. the PN owner. The PN owner is the sole authority in his personal interconnected devices and can use the PN in a way he wants. The personal devices may be located, both in his close vicinity (forming a PAN) and at remote locations. Figure 2 presents the PN of Bob, which is composed of his home, office and car clusters. The owner of the PN can add new devices or personalized services in his personal network according to his will. The PN for its owner is a heaven of personalized services in the cyberspace and appears as a black box to the outside world.
Group-centric cooperation is also referred as cooperation among the end-users who are organized in groups. This is somehow fundamentally opposite to the user-centric cooperation, where only the user's devices and environments cooperate, and this cooperation appears as a dark cloud for the outside world (for other users). In fact, the 4G services which can be made available to a single user (with user-centric cooperation) are limited and the users need to cooperate with the each other to extend their global services repository. In addition, many service-oriented patterns need to extend the boundaries of "user-centric cooperation" and involve the secure interaction of multiple users having common interests for various professional and private services. Moreover, in this federated users environment towards group-centric cooperative model, the distinct users can offer services to each other promoting the concept of "give and take".
In order to promote the group-centric cooperation in 4G systems, the concept of Personal Network Federations (PN-F) has been recently introduced in the European MAGNET Beyond project. PN-F addresses the interactions between multiple PN users with common interests for a range of diverse services. A PN federation can be defined as a secure impromptu, situation-aware or beforehand agreed cooperation between a subset of relevant devices belonging to different PNs for the purpose of achieving a common goal or service by forming an efficient collaboration. Consider the PN-F B in Figure 3, a simple example of PN-F is the federation of PNs belonging to a group of students in a classroom, sharing lecture notes.
Based on how cooperation between devices in different PNs is realized in order to establish the federation, we can differentiate between infrastructure and spontaneous PN federations. In an infrastructure based federation, PN-F is established between devices in PN clusters that are all connected to an infrastructure network. As shown in Figure 3, the infrastructure PN-F i.e. PN-F A is formed between the user 1 and user 2, who are located across the infrastructure network. On the other hand, in a spontaneous/ad-hoc PN-F, the federation is formed in the absence of a fixed infrastructure. This type of federation mostly occurs when nearby users collaborate within a federation.
The cooperation among the users, their devices and environments results into the development of a "Personal Ubiquitous Environment" around the user, which permits the "ubiquitous global access" to a vast number and variety of information resources. This uniform and comprehensive sense of cooperation results into a vast base of services for all the users who are part of this personal ubiquitous environment village. In the language of Personal Networking, we can collectively define PN and PN-F as a Personal Ubiquitous Environment. As shown in Figure 4, three users come closer to share devices, services and environments to form the cooperative group (PUE/PN-F). In PUE environment, the users believe in the essence of openness and sharing not only for their self-centric goals but also for the global benefits of the entire cooperative community. Those users, who are satisfied with their own proper resources and do not have any intention to cooperate; stays in their own user-centric environments i.e. PN, as shown in Figure 4.
