IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 15, NO. 12, DECEMBER 2016 8477 QoS Support in SGD-Based High Throughput Satellite Networks Muhammad Muhammad, Student Member, IEEE, Giovanni Giambene, Senior Member, IEEE , and Tomaso de Cola, Member, IEEE Abstract—This paper proposes a quality of service (QoS) management framework for high throughput satellite (HTS) systems using extremely high frequency (EHF) frequency bands, which can achieve high capacity provided that feeder link outage events caused by severe weather conditions can be properly counteracted. To this regard, smart gateway diversity archi- tectures implementing advanced gateway handover procedures are certainly attractive, although they can only partly mitigate the negative effects of adverse weather conditions in terms of packet losses, delays, and jitters, which significantly degrade the performance of delay-sensitive and delay-insensitive traffic flows. To cope with these technical challenges, we propose an incremental rerouting scheme to control congestion events because of capacity reduction during the transient phase, con- sisting of offloading high-priority QoS traffic flows from the affected gateway towards gateways operating in more favorable conditions. Moreover, we apply inter-flow network coding at the gateways to protect delay-insensitive flows from packet losses occurring during feeder link outage. Finally, extra capacity is reserved at the gateways to handle the additional traffic resulting from gateway handover. The theoretical analysis (validated by simulation campaigns) allowed characterizing network coding performance and confirming the potentialities of our QoS man- agement framework for HTS systems. Index Terms— QoS management, inter-flow network coding, terabit satellite systems, smart gateway diversity. I. I NTRODUCTION The availability of large spectrum portions in Extremely High Frequency (EHF) bands (Q, V, and W, i.e., greater than 40 [GHz]) has paved the way to the design of High Throughput Satellite (HTS) systems [1], [2], able to meet users’ demands in terms of high-quality and high data-rate services for emerging applications such as 3D, 4K and Ultra High Definition TV (UHDTV), just to cite a few examples. The exploitation of EHF frequency bands, however, intro- duces formidable technical challenges due to severe propaga- Manuscript received September 16, 2015; revised March 24, 2016 and August 20, 2016; accepted September 22, 2016. Date of publication October 6, 2016; date of current version December 8, 2016. This work has been supported by CNIT within the framework of the SatNEx III Project with ESA. The associate editor coordinating the review of this paper and approving it for publication was M. Li. M. Muhammad and G. Giambene are with the Department of Informa- tion Engineering and Mathematical Sciences, CNIT–University of Siena, 53100 Siena, Italy (e-mail: muhammad.muhammad@unisi.it; giambene@ unisi.it). T. de Cola is with the German Aerospace Center, Department of Satellite Networks, Institute of Communications and Navigation, 82234 Oberpfaffenhofen, Germany (e-mail: tomaso.decola@dlr.de). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TWC.2016.2615618 tion impairments (gateway feeder link outage), thus requiring a careful design of the overall system from both communica- tion and networking standpoints. In this respect, the satellite communications research community mostly focused on prop- agation countermeasures and satellite capacity investigations, proposing techniques to improve the service availability, based on the Smart Gateway Diversity (SGD) concept [3]. The SGD technique takes advantage of the spatial diversity existing between gateways, using a gateway handover scheme so that the traffic flows transported by the feeder link going to suffer from outage are rerouted towards a more favorable gateway in terms of channel conditions and available satellite capacity. On the other hand, to the best of authors’ knowledge, only few studies addressed the design of handover schemes and routing- related implications, but none of them has actually provided any insights in terms of Quality of Service (QoS) management. For instance, [3] and [4] investigate the technical challenges that gateway handover can introduce and survey the possible solutions based on mobile Internet Protocol (IP), without however proposing any specific routing design. Our previous papers [5], [6] provide some new insights into specific rout- ing strategies and overall handover management. Moreover, they consider network coding combined with smart rerouting techniques to protect traffic flows from severe losses occurring during handover and link disconnection phases. Nevertheless, these preliminary studies focused only on packet losses and disregarded other QoS figures, like, delay and jitter that can degrade the overall applications performance. This paper attempts to fill these research gaps by propos- ing a QoS management framework for gateway handover procedures in SGD systems. Inspired by the ITU-T Y.1541 Recommendation for IP-based services [7], we adopt two broad QoS classes for data traffic: 1) QoS-1 class for real- time and streaming applications (e.g., VoIP, VoD, IPTV in both HD and UHD), 2) QoS-2 class for best-effort traffic (e.g., gaming, e-mail, Internet browsing, and generic signaling transported over HTTP). QoS-1 class has requirements for Packet Loss Rate (PLR) measured at the layer 3 of the protocol stack (i.e., network layer), packet transfer delay and packet delay variation (jitter), whereas QoS-2 class has “unspecified” QoS requirements. In order to introduce QoS support in SGD systems, this paper proposes a combined scheme that adopts Incremental Rerouting (IR) to offload QoS-1 sensitive traffic flows from the impaired gateway towards another gateway, operating in clear sky conditions and offering spare satellite capacity by means of the Extra Reserved Capacity (ERC) concept. Moreover, network coding is applied at the impaired 1536-1276 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.