Ning Wang, Chang Ge, Barry Evans, Yogaratnam Rahulan, and Michael Fitch, University of Surrey, UK
Published: 19 Apr 2019
CTN Issue: April 2019
A note from the editor:
5G will enable new types of applications and services in different domains, and satellite communications will be an essential part of the 5G infrastructure. However, is the technology ready?
In this article, Ning Wang from the University of Surrey 5G innovation center and his colleagues in the EU 5GPPP SAT5G project will present an overview of satellite communications in 5G, especially from content delivery point of view. As an integral part of 5G mobile networks, the fundamental pros and cons of satellite communications are analyzed, and technical issues that need to be addressed are highlighted.
On the Roles of Satellite Communications in 5G Content Delivery
Professor at 5G Innovation Centre
Senior Research Fellow at 5G Innovation Centre
Professor at 5G Innovation Centre
Chief 5G Network Architect at 5G Innovation Centre
SAT5G Project Technical Leader
Traditionally, satellite communication has remained standalone and separated from the technical domain of mobile networking. It hasn’t been until recently that efforts have been made to embed satellite communication as an integral part of the 5th generation (5G) mobile networks. One representative initiative in this respect is the Satellite and Terrestrial Networking for 5G (SAT5G) project  funded by the European Commission in the 5G Public and Private Partnership (5GPPP) Programme.
The fundamental pros and cons of satellite communication are more or less well-known – on one hand, satellite communication enables wide geographical connectivity coverage without necessarily deploying fixed infrastructures such as cable links, making it an efficient solution for rural and remote area coverage. Additional strengths include high bandwidth capacity and the capability of content broadcasting and multicasting on a large scale. Latency incurred by satellite links has remained an issue for some services, especially for geostationary (GEO) satellite systems. However, by caching at the edge this can be avoided and satellites can become an integrated part of future to fixed and mobile platforms in the 5G era.
As shown in Figure 1, a GEO satellite link connects the central 5G core network and multiple remote 5G mobile edges. In rural areas satellite may be the only backhaul option but also in other areas satellite can still be used in conjunction with terrestrial means. In content delivery networks the role of satellite can be to offline deliver (popular) content to the mobile edge and cache it at the local multi-access edge computing (MEC) servers. As such, local users will be able to access the pre-cached content at the attached MEC server, thus leading to the benefit of enhanced user experiences and reduced content traffic volume through the 5G core.
In a more adventurous challenge, the SaT5G project has further studied the feasibility of transmitting HLS (HTTP-based Live Streaming) based live streaming content with Ultra-high definition (UHD) 4K video at a bitrate of 20Mbps through the satellite-backhauled 5G network infrastructure. As can be expected, with a conventional end-to-end delivery scheme, it has been verified that the user experiences were extremely poor due to the limited TCP throughput incurred by the satellite link latency. However, the project team have designed and developed a MEC-enabled scheme to break the end-to-end connection with a transient video segment holding technique at the mobile edge ; the playback performance has been substantially improved with complete avoidance of streaming disruptions.
Now we further highlight specific technical issues pertaining to the integration of satellite communication into 5G that are being researched within SaT5G:
- Resource optimisation on parallel backhaul links. Given that satellite communication offers an additional channel for carrying traffic over the 5G backhaul, context-aware policies or mechanisms need to be in place to properly steer traffic through either the satellite or the terrestrial backhauls. We expect that this requirement will trigger research on backhaul research optimisation by taking into account a wide variety of contexts such as type of traffic, traffic load, location of destinations etc. It is also interesting to investigate multipath connections based on MP-TCP  or MP-QUIC  for performance optimality.
- Holistic orchestration of network functions: The orchestration architecture of a satellite network operator (SNO) when used as transport networks for 5G mobile network operator (MNO) networks partly depends on how the SNO networks support the MNO networks and partly on the virtualization architecture underlying the SNO networks. It can be envisaged that both SNO and MNO networks may encompass specific network functions, so how to orchestrate them in a holistic way while confirming to their respective operational objectives is a key technical issue.
- Further complexity in the business model. The business implication is that the SNO will become a new stakeholder in the evolved 5G ecosystem. One SNO can virtualise the satellite link capacity and provide backhaul services to multiple MNOs, and here the role of a broker would be interesting. Meanwhile, An MNO can slice the overall resources (including both terrestrial and “leased” satellite backhaul) to support different vertical applications, and the satellite backhaul may only be used in a subset of these slices. Concerning content delivery services as outlined above, how to holistically enable a win-win business relationship between MNO, SNO and CDN operator in future satellite-enabled 5G environments is yet to be explored.
- EU 5GPP SAT5G project: http://sat5g-project.eu/
- (2) C. Ge, N. Wang, I. Selinis, J. Cahill, M. Kavanagh, K. Liolis, C. Politis, J. Nunes, B. Evans, Y. Rahulan, N. Nouvel, M. Boutin, J. Desmauts, F. Arnal, S. Watts, G. Poziopoulou, QoE-Assured Live Streaming via Satellite Backhaul in 5G Networks, IEEE Transactions on Broadcasting, Accepted for publication, DOI: 10.1109/TBC.2019.2901397
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