Based on a thorough analysis of the DVB-S2 and the DVB-RCS2 normative documents, we have analyzed (1) how the control functions are currently implemented in satellite gateways, (2) how they can be virtualized and (3) how their management can be enhanced. This analysis has been used to identify the aspects that have to be carefully considered in the virtualization process of a satellite gateway and its softwarized control.

This brief article quickly present a novel framework named Satellite Cloud Radio Access Network (SatCloudRAN) that leverages cloud-based infrastructure and SDN-enabled network virtualization to deliver cost efficient, high-level resources availability and flexible resources sharing.

• A satellite core network

In the context of satellite broadband access for fixed communications, a general reference model for a multigateway satellite ground segment is structured in several main subsystems, as depicted in Figure 1.

Figure 1 : Satellite network architecture

The “satellite access network” includes the satellite gateways and the satellite terminals, which are interconnected through the resource of one or several satellite channels.

The “satellite core network” is an aggregation network that interconnects different satellite gateways and includes the network nodes located at international Point of Presence (PoP)s to interconnect with other operators, corporations and Internet Service Provider (ISP).

The “control and management subsystems” is composed of Network Control Centre (NCC) and Network Management Center (NMC). NCC is used for real-time control of the connections and associated resources allocated to terminals that constitute one satellite network. NMC is used for non-real-time management functions related to a single satellite network. 

• Focus on a typical satellite gateway

Figure 2 : Satellite gateway reference architecture

The reference architecture of a satellite gateway is depicted on Figure 2, which shows the following main elements that compose a typical satellite gateway: (1) an OutDoor Unit (ODU), composed of an antenna and its radio components (Block Up Converter (BUC) to transmit to the satellite and Low Noise Block-converter (LNB) to receive from the satellite), we define here the satellite hub as the place where the ODU is located; (2) a physical gateway, dealing with physical layer related processes; (3) an access gateway, dealing with

Media Access Control (MAC) layer related processes; (4) network connectivity block, dealing with the interface for aggregation network access (IP router, Ethernet switch).

• The SatCloudRAN framework

SatCloudRAN platform implements the separated baseband functionalities in a centralized cloud-based processing platform. This separation between the virtualized and the physical components can be achieved at various layers of the satellite architecture model such as the network layer, the MAC layer, the physical layer or up to the Radio Frequency (RF) front-end of out-door unit as shown in Figure 3.

Figure 3: Variants for the functional split

In the light of our analysis, an interesting trade-off for the centralization of the gateway, in terms of performance, cost effectiveness and feasibility, would be to isolate the network functions and the access gateway from the hub, where the physical gateway shall remain. Also, in this case we recommend to let the access gateway close to the hub, or to adapt its exchanges with the physical gateway. The processes of the network functions and access gateway are subject to virtualization.

• The SatCloudRAN : a framework that allows the SDN control of a satellite core network

Figure 4:  Multiple SDN-based control architecture for SVNO support

Figure 4 details the architecture for the SDN control of the virtualized environment. It is composed of a high level controller in charge of controlling and managing the entire network resources whereas low-level controller in charge of controlling and managing specific network element or domain-specific resources.

Using a SatCloudRAN approach, network operators will be able to provide: (1) optimized dynamic QoS, (2) resilient management of multiple satellite gateways, and (3) dynamic bandwidth on demand.

• Conclusion

The role that satellite communications can play in the forthcoming 5G ecosystem is being revisited. The concepts of SDN and NFV are seen as key facilitators to make satellite communications to become a constituent part well integrated within an anticipated heterogeneous 5G network architecture. With the introduction of SDN and NFV, greater flexibility is expected to be achieved by satellite network operators, in addition to the much-anticipated reduction of both operational and capital expenses in deploying and managing SDN and NFV compatible networking equipment within the satellite networks. This proposed concept, namely satellite cloud RAN, exploits cloud based infrastructure and data-center virtualization to deliver cost efficient, high level resources availability and flexible resources sharing. This concept shed light on better interaction and integration of the satellite network with terrestrial functionalities while supporting advance features such as traffic engineering and load balancing.

Article contributed by Nicolas Kuhn, CNES

The VITAL project participated at the 14th session of the ETSI Satellite Communication and Navigation Working Group which took place at Sophia Antipolis/France on 26th January 2016. As part of this event, the 5G and SatCom workshop was organized which was a gathering point of several H2020 5G projects and relevant ESA/H2020 projects related to SatComs. 

The main objectives of the workshop was to discuss about

• possible re use of 5G network elements, protocols and/or technologies in future satellite systems
• novel integration scenarios of satellite systems in the 5G architecture in relation with the “5G Connectivity Using Satellites” use case of 3GPP TR 22.891 on 5G-SMARTER 

The VITAL project presentation was well received and the project was invited by the SCN WG to contribute to the on-going WI on integration of satellite in 5G, but taking into account the architecture approach defined by 5G projects such as 5GNORMA.

Tinku and Ramon represented the VITAL project at the event. The presentation can be accessed at the link provided below.

The workshop minutes can be accessed here [you need to be an ETSI member to access the files].

CNES, the VITAL project partner, release the OpenSAND 4.0.0 version this week.

OpenSAND is an user-friendly and efficient tool to emulate satellite communication systems, mainly DVB-RCS - DVB-S2. It provides a suitable and simple means for performance evaluation and innovative access and network techniques validation. Its ability to interconnect real equipments with real applications provides excellent demonstration means and is of particular importance for the VITAL hybid emulation environment to validate virutalized SatCom modules.

The new release is available within the Net4Sat [1] forge platform, owned by the CNES and dedicated to network research on satellite communications. The OpenSAND website [2] has been updated consequently, and the sources and report bugs on the Net4Sat gitlab [3] is available, with possibility to join the mailing list or to install the last version. Also, there is a new repository now available [4].

This version contains mainly these updates:

• add SCPC access on return link
• add multi-spot support
• add multi-GW support
• add support for Ubuntu 14.04 LTS
• add a new interface for resources management
• rework MODCOD handling

OpenSAND will be enhanced during the VITAL project to add new features for the virtualization platform and to integrate the emulation platform into an OpenStack VIM to enable the necessary configuration platform for validating the SatCloudRAN approaches in VITAL. Furthermore, OpenSAND will be integrated as the key SatCom emulation link to perform final end-to-end validation of different VITAL use cases, both in conjuction with physical testbeds and hybrid emulation environments from the project. Stay tuned to our blogspace for new updates.

[1] The Net4Sat forge website
[2] The OpenSAND website
[3] The OpenSAND gitlab on Net4Sat
[4] The OpenSAND repository
[5] The OpenSAND mailing list
[6] The OpenSAND bugtracker