Network slicing (NS) is one of the key techniques to manage logical and functionally separated networks on a common infrastructure, in a dynamic manner. As the complexity of virtualizing a full infrastructure required unprecedented effort, the initial idea of combining satellite and terrestrial networks has not been fully implemented in 5G yet. 6G networks are expected to further bring NS to a substrate network that is more heterogeneous, due to the full integration between terrestrial and satellite networks. NS describes the process of accommodating virtual networks, typically composed of nodes and links with the respective requirements, into the main infrastructure. This is an NP-Hard problem, typically also known as Virtual Network Embedding (VNE). Existing VNE solutions are designed per use-case and lack flexibility, adaptation and traffic-awareness, especially in such dynamic satellite environment. In this work, we investigate the VNE implementation to integrated satellite-terrestrial networks and propose a novel flexible framework, named Slice-Aware VNE for Satellite-Terrestrial (SAST-VNE), which 1) operates based on traffic prioritization; 2) jointly optimizes the load-balancing and the migration cost when network congestion occurs; and 3) provides a near-optimal solution. We compare SAST-VNE to existing well-known near-optimal VNE algorithms such as VINEYard and CEVNE and the shortest-path SN-VNE solution for satellite networks. The simulations showed that SAST-VNE reduces the migration costs between 10% and 40% during satellite handovers while maintaining the network load under control. Furthermore, when congestion occurs, SAST-VNE proved to be flexible in matching the priority of the slice, i.e., tolerated latency, with the time complexity and optimality of the solution.

Non-Geostationary Orbit satellite (NGSO) is an essential element in 5G Non-Terrestrial Networks (NTNs), which can operate either independently or as complementary parts to terrestrial systems to boost the network capacity, coverage and resilience. Due to the highly dynamic topologies, one of the challenges in NGSO is how to harmonize the network virtualized resources to satisfy diverse quality of service requirements in an efficient manner. In this paper, we investigate Virtual Network Embedding (VNE) for integrated NGSO-terrestrial systems while considering dynamic topologies. We propose a Dynamic Topology-Aware VNE (DTA-VNE) algorithm which, given priori information about the network’s evolution over time, can plan the embedding for each Virtual Network Request (VNR) over its lifetime. In a highly dynamic environment, the VNE decision can be varying for different VNRs at the expense of a considerable cost of migrating traffic and reconfiguring resources. The proposed DTA-VNE aims at minimizing this migration cost and thus avoids unnecessary re-mappings. In numerical results, the effectiveness of the proposed DTA-VNE is demonstrated with much lower migration cost than the conventional implementations. We show the benefit of planning for more time slots, in terms of migration cost, and the impact on the computation time, due to the increasing problem complexity. The trade-off between these two performance metrics is studied. Furthermore, we verify the efficiency of DTA-VNE in a MultI-layer awaRe SDN-based testbed for SAtellite-Terrestrial networks (MIRSAT). Finally, the application of DTA-VNE to novel scenarios such as mega LEO constellations is discussed, highlighting the challenges and possible solutions.

Before the advent of High-Throughput Satellites (HTSs), the satellite capacity was not enough to accommodate a large amount of data. Thanks to HTS, beyond 5G networks will boost the cooperation between space, air and terrestrial networks. The coexistence of heterogeneous QoS traffic demands, (e.g., emergency services, In-Flight Connectivity (IFC), Earth Observation Missions (EOMs)), over a dynamic environment, such as Multi-layer satellite-terrestrial networks, made the routing complex to handle. Additionally, due to numerous Inter-Satellite Links (ISLs) and their frequent changes, a testbed with real network emulation is challenging to develop.It is relevant not only to optimize the dynamic routing, but also to emulate the network in a testbed. This allows to consider systems constraints such as communication and technology delays in the most realistic manner. This paper investigates the future coexistence of the mentioned use cases for integrated Non-Terrestrial Networks (NTN)-terrestrial networks. We use Software Defined Networking (SDN) to monitor the substrate network with traffic statistics and apply routing decisions, via traffic handovers, during unexpected situations (congestion, link unavailability), in a reactive manner. Furthermore, we show that, for traditional handovers due to loss of Line of Sight (LoS), the SDN controller manages the procedure proactively to minimize traffic losses.

Non-Geostationary Orbit satellite (NGSO) is an essential element in 5G Non-Terrestrial Networks (NTNs), which can operate either independently or as complementary parts to terrestrial systems to boost the network capacity, coverage and resilience. Due to the highly dynamic topologies, one of the challenges in NGSO is how to harmonize the network virtualized resources to satisfy diverse quality of service requirements in an efficient manner. In this paper, we investigate Virtual Network Embedding (VNE) for integrated NGSO-terrestrial systems while considering dynamic topologies. We propose a Mixed Binary Linear Programming (MBLP) formulation for a Dynamic Topology-Aware VNE (DTA-VNE) algorithm. Given priori information about the network’s evolution over time, DTA-VNE plans the embedding for each Virtual Network Request (VNR) over its lifetime. In a highly dynamic environment, the VNE decision can be varying for different VNRs at the expense of a considerable cost of migrating traffic and reconfiguring resources. DTA-VNE aims at minimizing this migration cost to avoid unnecessary re-mappings. To tackle the exponential complexity of the MBLP, we propose an efficient algorithm based on relaxation approaches (DTA-R) to solve large-scale problems. In numerical results, the effectiveness of the proposed DTA-R is demonstrated with much lower migration cost than the conventional implementations. The trade-off between the computation time and migration cost of DTA-R is studied. Finally, we test DTA-R and the baselines in our developed MultI-layer awaRe SDN-based testbed for SAtellite-Terrestrial networks (MIRSAT) to precisely quantify the packet lost for each migration. DTA-R proved to reduce the packet lost by ~2.5-5% compared to baselines.

In this paper, we address the virtual network embedding (VNE) problem in non-terrestrial networks (NTNs) enabling dynamic changes in the virtual network function (VNF) deployment to maximize the service acceptance rate and service revenue. NTNs such as satellite networks involve highly dynamic topology and limited resources in terms of rate and power. VNE in NTNs is a challenge because a static strategy under-performs when new service requests arrive or the network topology changes unexpectedly due to failures or other events. Existing solutions do not consider the power constraint of satellites and rate limitation of inter-satellite links (ISLs) which are essential parameters for dynamic adjustment of existing VNE strategy in NTNs. In this work, we propose a dynamic VNE algorithm that selects a suitable VNE strategy for new and existing services considering the time-varying network topology. The proposed scheme, D-ViNE, increases the service acceptance ratio by 8.51% compared to the benchmark scheme TS-MAPSCH.

This paper studies the Gateway Diversity concept in a satellite scenario, using ONOS, Mininet and OpenSAND. ONOS is used as SDN controller, while Mininet and OpenSAND are used for network emulation and satellite network emulation, respectively. The ability and efficiency of ONOS SDN controller to switch the traffic, for example due to weather conditions, in real-time between two Gateways is presented. Furthermore, a method for allowing automatic instantiation of Gateway and restart of the OpenSAND simulation process promptly is analyzed. Finally, simulation results are shown for the evaluation of these technologies.