Patrick Gelard

Software defined networking and virtualization for broadband satellite networks

Satellite networks have traditionally been considered for specific purposes. Recently, new satellite technologies have been pushed to the market enabling high-performance satellite access networks. On the other hand, network architectures are taking advantage of emerging technologies such as software-defined networking (SDN), network virtualization and network functions virtualization (NFV). Therefore, benefiting communications services over satellite networks from these new technologies at first, and their seamless integration with terrestrial networks at second, are of great interest and importance. In this paper, and through comprehensive use cases, the advantages of introducing network programmability and virtualization using SDN and/or NFV in satellite networks are investigated. The requirements to be fulfilled in each use case are also discussed.

SDN/NFV-enabled satellite communications networks

In the context of next generation 5G networks, the satellite industry is clearly committed to revisit and revamp the role of satellite communications. As major drivers in the evolution of (terrestrial) fixed and mobile networks, Software Defined Networking (SDN) and Network Function Virtualisation (NFV) technologies are also being positioned as central technology enablers towards improved and more flexible integration of satellite and terrestrial segments, providing satellite network further service innovation and business agility by advanced network resources management techniques. Through the analysis of scenarios and use cases, this paper provides a description of the benefits that SDN/NFV technologies can bring into satellite communications towards 5G. Three scenarios are presented and analysed to delineate different potential improvement areas pursued through the introduction of SDN/NFV technologies in the satellite ground segment domain. Within each scenario, a number of use cases are developed to gain further insight into specific capabilities and to identify the technical challenges stemming from them.

Software-defined satellite cloud RAN

This is the peer reviewed version of the following article: Ahmed, T., Dubois, E., Dupe, J.-B., Ferrus, R., Gelard, P., and Kuhn, N. (2018) Software-defined satellite cloud RAN. Int. J. Satell. Commun. Network., 36: 108–133, which has been published in final form at 10.1002/sat.1206. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

A DTN Routing Scheme for Quasi-Deterministic Networks with Application to LEO Satellites Topology

We propose a novel DTN routing algorithm, called DQN, specifically designed for quasi-deterministic networks with an application to satellite constellations. We demonstrate that our proposal efficiently forwards the information over a satellite network derived from the Orbcomm topology while keeping a low replication overhead. We compare our algorithm against other well-known DTN routing schemes and show that we obtain the lowest replication ratio without the knowledge of the topology and with a delivery ratio of the same order of magnitude than a reference theoretical optimal routing.

On the existence of optimal LEDBAT parameters

The Low Extra Delay Background Transport (LEDBAT) protocol is a recently standardized protocol that aims to offer a scavenger service (i.e. the goal is to exploit the remaining and unused capacity of a link). LEDBAT is a delay-based protocol mainly defined by two parameters: a target queuing delay and a gain. The RFC 6817 provides guidelines to configure both parameters that strongly impact on the LEDBAT behavior in terms of fairness with other protocols. However, these guidelines are questioned by several studies as they might lead to the generation of a non-LBE (Less-than-Best-Effort) traffic. This paper explores the set of optimal parameters allowing LEDBAT protocol to effectively perform as an LBE traffic. We conclude that the optimal couple of target and decrease gain is (5 ms; 10). However, we observe that the aggregated use of optimized LEDBAT sources still disturb the overall traffic performance and that the exponential backoff is not an answer to this issue. As a result, we believe that additional strategies to limit the number of LEDBAT flows are required for integrating this protocol at a large scale.

DTN routing for quasi‐deterministic networks with application to LEO constellations

We propose a novel DTN routing algorithm, called DQN, specifically designed for quasi-deterministic networks with an application to satellite constellations. We demonstrate that our proposal efficiently forwards the information over a satellite network derived from the Orbcomm topology while keeping a low replication overhead. We compare our algorithm against other well-known DTN routing schemes and show that we obtain the lowest replication ratio with a delivery ratio of the same order of magnitude than a reference theoretical optimal routing. We also analyze the impact of terrestrial gateways density and analyze DQN performances in heterogeneous cases.

Handover Management for Hybrid Satellite/Terrestrial Networks

Initially envisaged to support handover between different wireless 802.x network technologies, the IEEE 802.21 standard also appears as the good candidate for handover management in future integrated satellite / terrestrial systems. This paper presents an analysis of how this standard could be implemented in the frame of a realistic scenario and taking into account the current trends in wireless network and mobility architectures. Our solution is then evaluated by means of emulation over a DVB-RCS representative testbed, and based on an experimental MIH implementation. We finally show that seamless handover can nearly be achieved with very short service outages.

Reliable multicast transport of BGP for geostationary satellite networks

Initially deployed for TV broadcasting, geostationary satellite networks and DVB standards have become mature technologies for IP communications. Also used to interconnect wide IP networks, dynamic IP routing is required in geostationary mesh satellite networks. Nevertheless, terrestrial IP routing protocols are not optimized for satellite networks. Especially, as far as BGP operates over TCP at transport layer, it does not provide any multicast support and is not optimized for natural broadcast properties of satellite systems (e.g. DVB-S2), involving a significant amount of overhead and important complexity at the satellite terminal side. To integrate and interconnect satellite systems to the IP world, the use of BGP (as EGP) is required. Therefore, this paper analyzes the different ways to deploy BGP in DVB-S2/RCS networks and the opportunity to take advantage of a reliable multicast transport layer. A light, multicast and reliable mechanism to transport BGP4 is proposed and compared to the existing solutions.

Optimized handover and resource management: an 802.21-based scheme to optimize handover and resource management in hybrid satellite-terrestrial networks

Satellite communications can provide fourth generation (4G) networks with large-scale coverage. However, their integration to 4G is challenging because satellite networks have not been designed with handover in mind. The setup of satellite links takes time, and so, handovers must be anticipated long before. This paper proposes a generic scheme based on the Institute of Electrical and Electronics Engineers 802.21 standard to optimize handover and resource management in hybrid satellite-terrestrial networks. Our solution, namely optimized handover and resource management (OHRM), uses the terrestrial interface to prepare handover, which greatly speeds up the establishment of the satellite link. We propose two mechanisms to minimize the waste of bandwidth due to wrong handover predictions. First, we leverage the support of 802.21 in the terrestrial access network to shorten the path of the signaling messages towards the satellite resource manager. Second, we cancel the restoration of the satellite resources when the terrestrial link rolls back. We use OHRM to interconnect a digital video broadcasting and a wireless 4G terrestrial network. However for the simulation tool, we use a WiMAX as the terrestrial technology to illustrate the schemes. The simulation results show that OHRM minimizes the handover delay and the signaling overhead in the terrestrial and satellite networks.

Carreau: CARrier REsource Access for mUle, DTN Applied to Hybrid WSN / Satellite System

Both WSNs (Wireless Sensor Networks) and observation satellites are able to get measurements from a geographic area. To interconnect these technologies, we propose to use a store-carry-and-forward architecture relying on the DTN (Disruption and Delay Tolerant Networking) Bundle Protocol. This architecture aims at being generic, so it is application-agnostic and suits a wide range of scenarios. WSN may collect sporadically large data volume while terrestrial stations communicating with Low Earth Orbit (LEO) satellites have to endure long link disruptions when the satellite is not in the line of sight. These sporadic growths within the WSN coupled with the large latency on satellite links require to schedule data to provide quality of service to several flows. We propose a scheduling policy based on deadline of Bundles and compare it with classical DTN solutions.