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Successful field trials for multicarrier system

French research insitute Leti and CloudNet IT-Solutions, a Scottish SME that specialises in TV white space (TVWS) communications, have held field trials and published results for a new flexible multicarrier system.

The trial, carried out in the Orkney Islands, was designed to demonstrate a post-OFDM (orthogonal frequency-division multiplexing) multicarrier waveform.

The trial showed the waveform – a block filtered-OFDM (BF-OFDM) – can overcome all shortcomings inherent in OFDM waveforms (WiFi/LTE) and is backward compatible with existing receivers.

“The results of these field trials enhance Leti’s technology-to-system offer for its industrial partners in the context of telecom applications and ad-hoc proprietary radio solutions for vertical sectors,” explained Dimitri Ktenas, Leti's wireless lab manager. “Our patented technology unlocks the usage of spectrum sharing, such as License Shared Access in TVWS and Citizens Broadband Radio Service at 3.5GHz.”

Leti was granted in an 18-month license from Arcep, France’s telecommunications regulatory agency, in January this year, to run a field trial with multiservice transmission at 3.5 GHz TDD band, and is continuing to deploy its patented multicarrier technology on broadband wireless channels.

In the Orkney Islands field trial, Leti demonstrated the flexibility of the technology in terms of spectral efficiency in the 700MHz TVWS band for rural broadband and maritime broadband radio scenarios. The measurements were supported under the framework of the H2020 EU-funded GateOne project.

Leti’s post-OFDM multicarrier waveform is designed to achieve good frequency localisation and support simultaneous single-carrier and multicarrier modulations, along with classical multi-antenna systems, including MIMO solutions.

The duration of the elementary communication slot is configurable and can be adapted to the targeted latency and channel conditions. In addition, classical multi-user (MU) access can be used on top of it, and even combined with MIMO, leading to MU-MIMO technologies in fragmented spectrum scenarios.

The Orkney Islands deployment assessed performance of a broadband transmission in a 16MHz fragmented spectrum channel, while fitting with ETSI EN 301 598 TVWS regulation. The measurements performed at the beginning of November strongly validated the trial’s concepts in a real-life situation and rural broadband content delivery was demonstrated up to 20km, using non-contiguous channels.

Leti’s over-the-air portable test platform based on field-programmable gate arrays (FPGA), ARM processors and agile RF front-end was used to demonstrate a broadband transmission. The same set of equipment is also part of the 5G Leti testbed under evaluation in the future 5G 3.5GHz band.

Neil Tyler

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