Numerous experts have pointed at the incapacity of current backhaul networks to support the 5G networks that should, as of 2020, enable the Internet of Things. Commonly called the 5G backhaul challenge, this issue arose from the use of the ultra-dense and heavy traffic cells necessary to support the propagation of 5G millimetre wave (mmW) networks. These densified networks have very high requirements related to capacity, latency, availability and energy/cost efficiency, and current backhaul systems are nowhere near fit for purpose. As SANSA project coordinator Prof Ana Pérez-Nera points out, “If we want people to have proper access to 5G networks, the backhauling paradigm must completely change to become much more agile and dynamic, as well as be able to use the different infrastructures that 5G embraces such as radio, fibre and satellite.” Besides, 5G envisions service continuity from the densest to the most sparsely populated area or during transit. So how exactly do we make that happen? “The integration of satellite communications in 5G will play a major role”, says Prof Pérez. Specifically, Prof Pérez and the rest of the SANSA consortium led by CTTC have been developing a novel hybrid terrestrial-satellite backhaul network relying on two core components. The first component is a set of smart antennas with advanced mmW beamforming capabilities. These antennas are deployed in terrestrial backhaul nodes to enable network topology reconfiguration, frequency reuse and spatial interference mitigation. The second component is a hybrid network manager (HNM) which enables the efficient and dynamic use of all network resources, be it from terrestrial or satellite segments, to improve capacity and energy efficiency. “Together, these components can execute network alert detection (such as link failures or congestion), network topology reconfiguration, distributed routing, load balancing, traffic classification as well as energy management and off-line caching functions,” Prof Pérez explains. “Smart antenna techniques provide self-pointing solutions, whilst the reconfigurable network reduces the need for network planning and the overdimensioning of resources to deal with link failures or congestion.” SANSA also proposes a hybrid terrestrial-satellite caching scheme that will contribute to important bandwidth savings in backhaul networks. Remarkably, satellites play a major role in this scheme by providing an efficient placement of content in edge caches, thanks to their wide coverage and inherent multicast capabilities. Simulations demonstrated significant improvements in performance metrics such as aggregated network spectral efficiency (9x), aggregated throughput (50 %), packed delivery rates, delay (35 %), and energy efficiency by up to 37 %. A proof-of-concept of the two components has also shown the capability of SANSA to efficiently react to changes in traffic profiles. Before SANSA, making terrestrial and satellite communications compatible with each other had already become a very sensitive matter. Both 5G and satellite communications are required to work at high frequencies, making coexistence within the same spectrum very difficult to achieve. “Thanks to SANSA, we are now confident that satellites will play a key role in several 5G use cases. But the success of SatComs inside 5G will largely depend on their capability to provide cost/bit comparable to terrestrial systems, and enough throughput to support wide range of 5G services, including offloading and backup. This is precisely why we will keep improving satellite capabilities through the exploitation of the new opportunities that a satellite segment, characterised by the large overlapping between GEO and non-GEO satellites, will offer in the near future,” Prof Pérez concludes.
SANSA, satellite, backhaul challenge, 5G, networks, mmWave, performance