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This paper presents the main concepts of the IST Project FAIN "Future Active IP Networks" [10], a three-year collaborative research project, whose main task is to develop and validate an open, flexible, programmable and dependable network architecture based on a novel active node approach. This generic architecture for active networks is an innovative integration of active networking, distributed object and mobile agent technology.Starting from the definition of a business model that underlines the FAIN architecture, we identify three key working areas for contribution: the active node platform layer, the service programming environment and a build-in management system.The active node platform layer of the FAIN Active Node is comprised of the kernel OS, a node resource access control framework, and active components for management, security and service provision. These elements provide the foundations on which Execution Environments are deployed and operate in an independent manner.A novel service programming environment is envisaged enabling the dynamic creation or update and secure deployment and operation of protocols, and supports various role-specific ways of deployment, e.g. application-specific signalling or PNOgoverned network control signalling.The third aspect of FAIN is a management paradigm based on standardised API and autonomy of nodes. The paradigm enables the development of a fine-grained and more efficient management framework, which reduces needless traffic or information processing, e.g. by filtering and self-management of nodes which take care of the management of their own resources and states. Autonomous management of nodes enables the distribution of management intelligence. Loosely coupled management functions facilitates the traditional difficult tasks such as policy enforcement, and integration of new managing functions. Reusable components and interoperable operation can be achieved using the standard interface and an implementation using distributed objects and platforms.

A joint optimal power allocation and sensing threshold selection for capacity maximisation at the secondary user (SU) in spectrum sharing (SS) cognitive radio networks (CRNs) is proposed. Hence, both optimal power allocation and spectrum sensing is considered in the SS CRNs model. The obtained results show that such a joint optimal selection improves the performance of the SU by maximising its capacity.Introduction: In spectrum sharing (SS) cognitive radio networks (CRNs), optimal power allocation (OPA) and spectrum sensing (SpSe) are used for the protection of the primary user (PU) from harmful interference caused by the secondary user (SU). Furthermore, for capacity maximisation of the SU, the main parameters related to OPA, i.e. the SU's transmit power, P t , is adapted according to the received signalto-noise ratio (SNR), g s , and related to SpSe, i.e. sensing threshold, h, and sensing time, t, for a given sensed SNR, g, need to be also carefully selected [1]. Previous studies on SU's capacity maximisation include SS CRNs models with SpSe [2, 3] or without SpSe [4,5]. For the former and more general case, the optimisation presented in [2] is considered over P t and t assuming h to be constant. In [3], although the effects of h as a variable are studied, the research is focused on the interference caused to the PU rather than the optimisation of the SU's capacity. Thus, a more general approach is presented in this Letter where a jointly OPA and SpSe threshold selection is considered so that the SU's capacity is maximised over P t and h.

In opportunistic networks (OppNets), routing and data forwarding among mobile devices are facilitated by relays or next-hop forwarders. To guarantee end-to-end data delivery it is important to provide participation. However, in sparsely connected OppNets, it is extremely challenging to monitor the behaviour of the relays and identify selfish/malicious relays cooperating with each other in order to forge routing information or drop useful data. Cooperation enforcement schemes are seen as a lightweight alternative to conventional secure forwarding techniques that involve cryptographically signed certificate exchanges, providing a 'softer' security layer to protect basic networking operations. In general, cooperation enforcement schemes fall into two broad categories: trust establishment via a reputation system and pricing or credit-based schemes. This study offers a comprehensive survey of representative cooperation enforcement schemes that exploit a reputation system. The authors analyse their distinct features, identify and discuss critical challenges that should be efficiently addressed when designing such mechanisms, indicating at the same time potential solutions and provide an informative table to display the authors' findings. From this analysis, they examine issues and concerns surrounding the field of cooperation enforcement in OppNets, and provide guidelines and directions for future researchers.