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One of the aims of the SatNEx (Satellite Network of Excellence, http://www.satnex.de) European project is to provide the scientific community that operates on satellite communications with measurement campaign results and evaluation tools, in order to support research activities that investigate problems in satellite communications at different levels of the OSI stack. In fact, the research activities developed in SatNEx address the most relevant aspects of satellite communications, such as channel modulation and coding schemes, access strategies, advanced networking, end-to-end quality of service, transport performance, delay tolerant networks, and new applications. Even if SatNEx is mainly devoted to satellite communications, integration of satellite and terrestrial wireless segments has also been taken into account. This paper presents the results obtained in the specific research activity devoted to trials and testbeds developed during the SatNEx project. The high number of authors of this paper is an indication of the strong collaborative work sustained, the numerous measurement campaigns, and the complexity in developing integrated testbeds.

One of the aims of the SatNEx (Satellite Network of Excellence) European project is to provide the scientific community that operates on satellite communications with simulation/emulation tools and real measurement campaigns, in order to support various research activities that investigate problems in satellite communications at different levels of the OSI stack. In particular, one among the various joint activities (JAs) in SatNEx is devoted to "Research tools, trials and testbeds", and, within this, one group of activities concentrates on "Access, network, and transport layer trials" (JA 2410). This paper addresses the results obtained just within this joint activity, thus presenting both the real experiments carried out on a satellite platform, and describing the specific testbeds developed for this aim. The high number of authors of this paper is an indication of the strong collaborative work sustained, the large measurement campaigns, and the complexity in setting up some tests. In the SatNEx project we envisaged a quite complex reference scenario, where particular research aspects needed to be sustained by measurements and adequate tools of investigation. The research activity developed in SatNEx addresses the most relevant aspects of satellite communications, such as access schemes, advanced networking, end-to-end quality of service, transport performance, and deployment of new applications. In this view, specific integration issues among heterogeneous networks, encompassing satellite and wireless segments, were taken into account. The testbeds developed allowed the study of interplanetary environments, as well. In this specific case, attention was put in the communication and networking challenges arising in the design of a telecommunication infrastructure suitable to convey data derived from remote stations, located on planets, and addressed to Earth data gathering centres.

The importance of DiffServ technique, based on cellular neural network (CNN), for satellite communication systems is discussed. In satellite communication systems, DiffServ policy computational capabilities are placed at the edge points. A CNN has been designed to maximize a cost functional, related to the on-board switch throughput and QoS constraints. The CNN make feasible to take the best decision for the packet to be delivered to each output satellite beam, in order to meet specific QoS constraints. The system is based on the Internet Engineering Task Force (IETE) recommendations.

The network emulation support in ns-3 enables the interaction with real devices allowing the integration of a simulated node or network in an emulated scenario. Also, the network emulation support in a simulator is fundamental to validate its models. For both purposes, the emulation capabilities in ns-3 must reproduce the real host incoming and outgoing networking paths to increase the emulation credibility. In this work, we present our effort to introduce kernel bypass techniques in ns-3 to improve the network emulation support. We used netmap, a fast packets processing framework, to bypass the host networking stack and gain direct access to network device. We designed and introduced in ns-3 a new device to perform emulation that uses the netmap primitives to read and write packets on a real device. We carried out a preliminary benchmark of our device in an ethernet back-to-back scenario. The results show a more accurate performance in terms of delay and more realistic distributions of packets backlog in traffic-control of ns-3 and of packets inflight.

Quality of Service (QoS) has become an important topic in modern telecommunication network in order to guarantee multimedia traffic. In IP networks, diffServ seems to be the best approach to satisfy QoS constraints, due to its end-to-end philosophy. Actual trend is to consider satellite on-board switching capabilities for managing multibeam input and output. In this paper, for reducing computational complexity, a cellular neural network (CNN) has been proposed for the on-board switching problem; several traffic classes have been considered and switching algorithm has been implemented within a CNN taking into account their priority, queue length and time spent inside queues. Numerical results shows performance similar to optimal switching solution, but with a higher flexibility due to neural techniques. Simulation results have been driven with memoryless distribution and heavy-tailed distribution for several input buffer size and switch dimension.