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Shared Access Terrestrial-Satellite Backhaul Network enabled by Smart Antennas

Periodic Reporting for period 2 - SANSA (Shared Access Terrestrial-Satellite Backhaul Network enabled by Smart Antennas)

Reporting period: 2016-08-01 to 2018-01-31

The aim of SANSA project was to boost the performance of mobile wireless backhaul networks in terms of coverage, capacity and resilience while assuring an efficient use of the spectrum and a reduction of the power consumption. Unprecedented global mobile traffic increases were recently predicted. The industry and research communities are proposing novel access technologies such as millimeter wave access or dense small cell deployments for facing these traffic requirements. However, these technologies impose new challenging requirements to backhaul networks, so novel solutions are required to avoid backhaul becoming the bottle neck of future mobile networks. In this sense, SANSA proposed a spectrum efficient self-organizing hybrid terrestrial-satellite backhaul network based on three key principles: (i) a seamless integration of the satellite segment into terrestrial backhaul networks; (ii) a terrestrial wireless network capable of reconfiguring its topology according to traffic demands; (iii) a shared spectrum between satellite and terrestrial segments. SANSA solution is enabled by two key components. On the one side, low-cost smart antennas deployed in terrestrial nodes allowing the network topology reconfiguration and spatial interference mitigation. On the other side, a hybrid network management scheme for an efficient use of all the network resources, either terrestrial or satellite. This scheme is based on a centralized component, i.e. Hybrid Network Manager (HNM), and distributed components deployed at the terrestrial nodes, i.e. Intelligent Backhaul Nodes (IBN). SANSA project succeeded in the design, development and experimental validation of both key enabling components.
The technical activities of SANSA were focused, on the on hand, on the specification of the network architecture, the development of the main functionalities of the HNM and IBN entities and their evaluation with NS3 simulations. In particular, SANSA developed: (i) a novel backpressure hybrid algorithm and evaluated it in rural and dense urban scenarios against state-of-the-art solutions; (ii) a novel topology manager capable of providing alternative topologies in the presence of congestion or link failure events; (iii) an energy saving agent based on a distributed q-learning solution for dense scenarios based on small cells equipped with energy harvesters; and (iv) a new algorithm enabling to combine link selection capabilities with traffic classification techniques enabling an efficient offloading of terrestrial traffic. The combination and smart orchestration of these functionalities provided noticeable performance improvements to backhaul networks. Specifically, aggregated throughput gains up to 35% and latency improvements for delay non-tolerant traffic of 150%, as well as energy saving up to 37% were demonstrated in a realistic scenario based on a real network deployment close to Helsinki. In addition, SANSA also explored a hybrid terrestrial/satellite caching scheme for content delivery networks, which enable drastic bandwidth savings in terrestrial backhaul networks.
On the other hand, SANSA developed interference mitigation techniques enabling an efficient use of the spectrum. SANSA explored multi-antenna beamforming and nulling solutions with the focus on low cost/low complexity schemes. Hence, SANSA studied low cost antenna technologies such as hybrid analog-digital arrays, reflectarrays, metasurface antennas and parasitic arrays, as well as an extensive range of beamforming strategies covering point-to-point, point-to-multipoint and multipoint-to-multipoint situations. Beamforming algorithms were evaluated in the realistic Helsinki scenario providing network spectral efficiency (NSE) gains up to 3.5x which could be extended to 9x in the case the channel characteristics permit multi-stream transmissions. These gains were upper bounded by the original number of carriers used in the benchmark scenario and reused thanks to SANSA solutions. NSE gains above 10x could be envisaged in future dense deployments. SANSA complemented the multi-antenna techniques with the development of dynamic and hybrid resource management solutions.
After the promising results obtained at simulation level, SANSA proceeded to the experimental validation of its two main enabling components. To this end, a hybrid analog-digital array prototype was developed and used in the over-the-air demonstration of the spectrum coexistence of a satellite and a terrestrial link. The antenna prototype in combination with the developed beamforming algorithms successfully protected a closely located satellite receiver, which was able to reproduce a received video with high quality. In addition, a HNM and IBN prototypes were evaluated in a pure virtual network emulation at IP level. It permitted demonstrating the improved resilience of SANSA networks thanks to the capabilities of the HNM/IBN to adapt the network topology to the traffic status and demands, thus solving congestion and link failure events.
These technical activities were disseminated in 4 SANSA events, 16 scientific journals, 58 conference/workshop papers and in 2 book chapters. In addition, spectrum sharing results were disseminated to regulatory bodies such as CEPT FM 44 group or the Hellenic Telecommunications and Post Commission (EETT). SANSA also contributed to two working groups in ETSI SES SCN and in 3GPP SA1 related to the integration of satellites in 5G. On the exploitation side, the project produced two patent fillings, analysed a successful business case for the SANSA solution and detailed a roadmap for bringing SANSA to the market in the next future.
As can be derived from the large list of publications, SANSA technical activities represented a noticeable advance over the state-of the art in many research topics. Moreover, SANSA explored for the first time the seamless integration of the satellite segment in terrestrial backhaul networks, as well as terrestrial backhaul networks with self-organizing capabilities that include the possibility of changing the network topology. In SANSA, both concepts are enabled by the novel management scheme based on the HNM and IBNs, which again represent an important step beyond the state-of-the art.
The interest for integration of satellite communications in 5G has grown up during the project execution. Currently, there are many activities in the standardization (ETSI and 3GPP working groups) and research fields (H2020 and ESA initiatives) devoted to this integration. Remarkably, SANSA is not only a pioneer on these topics but SANSA use cases and results are benefiting and will keep on benefiting all these recently started activities. In addition, the work relative to the self-organization and terrestrial topology configuration and to beamforming solutions for interference mitigation is very relevant to future 5G deployments in dense scenarios.
In the long term, SANSA project will also have a strong indirect impact over the European society. On one side, SANSA hybrid terrestrial-satellite technology will contribute to the appearance of new applications and user trends providing fast internet connection every time and everywhere. On the other side, SANSA will contribute to the economic growth of the European satellite and terrestrial telecommunications industries, which will be translated in new job openings, and thus it will strengthen the welfare state of the European citizens.
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