Initiation, Formation and Usage of Spontaneous PN-F

Since in the spontaneous PN-F, the federation is formed in the absence of a fixed infrastructure; therefore we extend our proposal for PN cluster formation i.e. PNRP, for the initiation, formation and usage of spontaneous PN-Fs. The Personal Network Routing Protocol (PNRP) extension for PN-F is a variant of on-demand multi-hop routing protocol such as AODV and DSR, which adapts to the personal networking environments for communication among PNs. The PN-F creator decides the PN-F members and sends them, the PN-F profile. On the reception of PN-F profile, if the initially proposed members decide to be the part of PN-F, they exchange their PN-F participation profile with the PN-F creator.

Therefore, PN-F initiation becomes an intrinsic capability of PN-F formation owed by PNRP. Moreover, PN-F routing mechanisms assist to determine the routes towards the desired PN-F members and provide means to form and to use PN Federations.

PN-F Topology Discovery, Initiation and Formation

PN-F routing builds routes using a join request/reply query cycle. When a PN desires to create a PN-F with certain defined PN-F members, it creates a PN-F profile and sends to its FMs, piggybacked with a Join-Request (JR) message, leveraging the inter-cluster routes; thanks to PNRP's PN-cluster formation capability. As show in Figure 1, in order to create a PN-F with PN2, PN3 and PN4, the PN1 (i.e. PN-F creator) sends the JR message to its FMs. The Join-Request (JR) message contains two lists of PN-IDs such as "destination-list", which stores the potential PN-F participants and "destination-attained-list", which represents the PNs already attained by the JR message. As FMs receive the JR, they investigate whether the PN-ID of their neighbouring PN is mentioned in JR message destination-list. In case of positive response, the JR is forwarded to the FM of the neighbouring PN. In contrast, if the FM does not find the adjacent PN in the destination-list and the potential participant PNs are not accessible through other FMs of the same PN, a "Connectivity PN-F" can be formed with the adjacent PN in order to relay the PN-F information towards the potential PN-F members.

 
Figure 1: PN-F topology discovery in PNRP

On the reception of JR message, the neighbouring PN's FM first removes its PN-ID from JR's destination-list and then put it in the destination-attained-list. Moreover it also sets up backward pointers in PN-F routing table, towards the PN which sent the JR, as a next-hop to reach all the PNs mentioned in the destination-attained-list. PN1's FM (i.e. A) forwards the JR to PN2's FM (i.e. B), which sets the entries in its PN-F routing table that PN1 is reachable through its FM B.

The above presented mechanisms are repeated at each next PN until all the PNs mentioned in the JR destination-list are reached. Finally, on the reception of JR if the PN finds the JR's destination-list is empty, it will send a Joint-Request-Ack (JRA) message (by replacing the entries of destination-attained-list with destination-list) backwards to the PN which forwarded the JR message. As shown in Figure 1, the JRA is initiated by PN4, which receives the empty destination-list. The mechanisms of setting backward pointers to the PNs declared in destination-attained-list and moving the PN-IDs from destination-list to destination-attained-list at every next PN is also repeated for JRA message until it reaches the PN-F creator, who triggered the PN-F formation. The exchange of JR and JRA messages facilitate the establishment of PN-F routing tables at the Federation Managers of PNs, which are participating in the PN-F.

Data Forwarding and PN-F Use

During the integrated PN-F topology discovery process, the entire participant PNs learns the routes not only towards the PN-F creator but also towards each other. These routes are stored in the PN-F routing table and are leveraged to exchange, initially the PN-F profiles and then the PN-F participation profiles in order to form the PN-F. To this end, the data packets destined to any other PN are first forwarded to the FMs, which further routes the data with the help of PN-F routing table. The profiles are stored at the FMs (the entry points of PNs), which are used to enforce PN-F policies on the PN-F routing in order to ensure secure PN-F overlay concept.

PN Cluster Formation and Personal Network Routing Protocol (PNRP)

The initial step towards the PN formation is the formation of PN clusters i.e. all the personal nodes that are in the close vicinity of each other discover the routes towards each other. Subsequently, the different geographically separated clusters of a PN are glued together to form a PN with the help of PN Agent. To this end, we propose the Personal Network Routing Protocol (PNRP) which helps in determining the routes among all the personal nodes in a PN cluster.

PNRP is a variant of link-state multi-hop routing protocol that adapts to the personal networking environments. It maintains the proactive topology of nodes which lie within the PN cluster boundary, at every personal node of the PN cluster. Moreover, the information on functionalities of the personal nodes such as Gateway Node and/or Federation Manager is also exchanged within the PN topology in order to facilitate PN's access to the outside world. In the following subsections, we discuss different steps that PNRP performs towards the formation of a PN cluster.

Integrated Topology Discovery

The role of Integrated Topology Discovery mechanism is to determine how the personal nodes are connected (using which interfaces in single/multi hop) in order to provide routes for any source/destination pair in the PN cluster. It first determines the direct connectivity among nodes and further exchanges this information to form a unified cluster topology.

Neighbor discovery is incorporated into PNRP by allowing every personal node to periodically transmit "Hello" packets on all of its interfaces. "Hello" packet contains the PN-ID and the Node-ID of the source node which is processed at the destination node to identify the source of the "Hello" packet. It is possible that the personal nodes may discover the non-personal nodes; therefore PN level authentication is indispensable. Every node maintains a 1-hop neighbour table and associated costs to each link with its direct neighbours and their PN identification. For the current implementation of PNRP, we have considered number-of-hops as a cost metric.

Once the 1-hop topology is formed, it is exchanged with other personal nodes in order to form a complete snapshot (table) of the PN cluster on its every single node. The topology information is only exchanged with the personal nodes i.e. among the nodes which belong to the same PN. To this end, every personal node periodically transmits the "Cluster topology (Ctopo)" message towards all its personal nodes (neighbours). On the reception of "Ctopo", the PN cluster routing tables are formed/updated and further exchanged with the other neighbouring nodes. Figure 1 shows the PN routing table at a personal node constructed after the exchange of "Hello" and "Ctopo" messages.

 
Figure 1: PNRP for PN routing

Gateway and Neighboring PN's Discovery

In PNRP, each Gateway Node (GN) advertises in the "Hello" message, whether it has connectivity with the infrastructure network or not. As can be seen in Figure 1, the exchange of integrated PN cluster topology with the help of "Ctopo" message permits each node to maintain routes to all the existing GNs and the cost to reach them, in the PN routing table.

Discovery of the neighbouring PNs is also intrinsic to Integrated Topology Discovery mechanism. During the exchange of "Hello" messages, if the destination node finds out that it's not the part of the source node's PN (with the help of PN-ID), the destination node sets itself as a Federation Manager (FM) to the source node's PN. The connectivity among the PNs is realised with the help of FMs. Once the integrated topology information is exchanged among all the nodes of the PN, every node knows the exit points (FMs) to communicate with other neighbouring PNs, which further helps in PN to PN (PN-F) routing. In case of multiple GNs or FMs, the minimum cost option is selected.

Route Discovery

PNRP differentiates the route discovery procedure when the destination is the part of same PN as the source and/or from the case when the destination is the part of different PN. In latter case, "PNRP for PN-F" mechanisms are triggered. In former case, since a proactive PN cluster-level topology is maintained at each PN node, the route to all the destinations in the PN will be known before time.

TECHNICAL DIMENSION: ROUTING, A PRACTICAL ENABLER OF COOPERATION IN 4G

The key to successful realization of user-centric (Personal Network (PN)) and group-centric (PN Federation) cooperation is the general connectivity architecture which can seamlessly bridge heterogeneous personal devices, placed both in the close vicinity and at remote locations. The development, implementation and integration of global Personal Network architecture for connecting the devices geographically separated across the interconnection structures (intranet or Internet, for instance) has been explored recently in Hoebeke (2006). However, the ad-hoc seamless connectivity among the heterogeneous PN devices present in the close vicinity of each other, is still open to research. Moreover, the extension of PN concept to realize the group-centric Personal Network Federation (PN-F) i.e. connecting multiple PNs, towards PUE is a research theme that emerged recently. In this section, we present general connectivity architecture i.e. a routing protocol, which enables cooperation in PUE. At first, it facilitates the cooperation between the user's heterogeneous devices in order to form a Personal Network (PN). Moreover, at second, our cooperative routing protocol enables multiple PNs to join hands to form a PN Federation. In order to summarize, the routing solution enables the cooperation not only within the devices of a distinct user, but also among the devices of different users, making the vision of PUE, a reality.

Preliminaries

1 Terminology

As described previously, we define a "personal node (pn)" to be the node that belongs to the owner of a PN. Each node is identified by its Personal Network Identification (PN-ID) and Node Identification (NID). All personal nodes of a PN owner share the same PN-ID. A "Gateway Node (GN)" is a personal node that enables the connectivity to the infrastructure network such as Internet or corporate LAN. A personal node is defined to be "Federation Manager (FM)", if it enables connectivity to the personal nodes of the other PN(s). A "PN Cluster" is a network of personal nodes located within a limited geographical area (such as house, office or car). One or more than one "PN cluster" of a single owner contributes his PN.

2 Cooperative PN Federation Profiles

In order to interact among the PNs and to create trustable PN Federations (PN-Fs), rules and polices are needed to determine for instance, who is or can become member of the federation and how and which resources are made available to the PN-F members. Based on this, two different types of profiles have been identified to realise the concept of PN-F (PN to PN interaction), such as "PN-F profile" and "PN-F participation profile". As shown in Figure 1, the PN-F profile is common to the federation, created by the PN-F creator, which reflects the global information about the PN-F. Whereas, the "participation profile" is bound to the individual PN-F member and it reflects his local view regarding the PN-F. The PN-F is initiated by the PN-F profile, which is further updated with the help of participation profiles during the course of PN-F's existence.

Figure 1: Personal network federation (PN-F)

COOPERATIVE PERSONAL/GROUP SERVICES IN 4G

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.

 
Figure 1: User-centric cooperation

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.

 
Figure 2: Bob ‘s personal network

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.

 
Figure 3: Personal network federation architectures

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.

 
Figure 4: Personal ubiquitous environment