Guest editorial IJSCN special issue on ASMS/SPSC 2014

This special issue of the Wiley International Journal of Satellite Communications and Networking hosts a selection of papers from the seventh Advanced Satellite Multimedia Systems (ASMS) Conference and the 13th Signal Processing for Space Communications (SPSC) Workshop held in Livorno, Italy on 8 to 10 September 2014. The joint event was organized through a collaborative effort of the University of Bologna, the Institute of Communications and Navigation of DLR (German Aerospace Center), the European Space Agency (ESA), under the auspices of the Association ‘Toscana Spazio’ and the SatNEx III Network of Experts and in cooperation with the University of Pisa. The ASMS conference and SPSC workshop have become recognized events for industry and research institutions to exchange up-to-date information about recent advances and emerging technologies in the field of mobile satellite communication systems. The ESA's SPSC workshop dates back to 1988 when pioneering work in digital signal processing for satellite communications was first presented by worldwide authorities in the field. In addition, following the successful path opened by the 2006 edition of ASMS and continued with the 2008, 2010 and 2012 editions, the scope of the conference has been further widened, as the small though important change in its name by replacing the word ‘mobile’ with ‘multimedia’ testifies. This is remarkable not only because the major part of the SATCOM market belongs to broadcasting and broadband access operators but also fundamentally because the convergence of broadcast, mobile and fixed satellite communications is essential to offer seamless connectivity anywhere at any time, which is recognized as the key element for the successful deployment of future satellite systems. This issue collects the extended versions of six of the best papers presented at the last ASMS/SPSC joint event. The papers have been selected with the aim of providing an insight into the developments and findings in this exciting field. In the first paper, the authors investigate different techniques to improve the spectral efficiency of systems based on the DVB-S2 standard, whenever the transmitted signal bandwidth cannot be increased because it has already been optimized to the maximum value allowed by transponder filters. The second paper deals with the design of packet-level forward error correction (FEC) coding technique and pre-distortion adaptive optics technology for a digital transmission scheme to be employed in optical feeder links in a geostationary satellite communication system. Performances are evaluated in both up and downlink. The third paper proposes a new approach for blind feedforward and feedback recovery of the symbol timing, which needs just one or two samples per symbol. The method is characterized by a second filter operated in parallel to the receiver matched filter and allows avoiding the typical jitter floor irrespective of the selected modulation scheme. The fourth paper deals with the issue of boosting the capacity of xDSL networks in the presence of geographical gaps by exploiting the downlink of multibeam satellites for the delivering of packed-based traffic. To cope with time-varying channel and interference, the paper proposes a novel link resource adaptation scheme. The fifth paper addresses the problem of modulation and coding scheme selection in the return link of a mobile satellite system and proposes to use an affine combination of both open loop and closed loop signal quality indicators to perform this selection. The combination weights are dynamically adapted according to the ACK/NAK exchange between both ends, without making any assumptions on the channel distribution Last but not least, the sixth paper analyses the performance of two Contact Graph Routing (CGR) enhancements, namely CGR-ETO and Overbooking Management. These two enhancements have been recently included in the official CGR version as part of the Interplanetary Overlay Network DTN implementation maintained by NASA. In closing, the guest editors would like to thank all individuals and organizations that made this issue possible, including the European Commission, the Association ‘Toscana Spazio’, Wiley Interscience, the ASMS/SPSC 2014 Technical and Scientific Committees, all anonymous reviewers and all authors. In particular, we are grateful to Prof. Barry Evans, the Editor-in-Chief of the International Journal on Satellite Communications and Networking, for kindly inviting us once more to conduct this editorial process, as already done for past events. Given the great success of the join event, we are finally pleased to announce that the next ASMS/SPSC Conference is in fact supposed to take place in Palma de Mallorca (Spain) from 5 to 7 September 2016. More information is available at http://www.asmsconference.org/.