Clone of SEFDM: a bandwidth compressed technique shapes future 5G

The availability of frequencies in the electromagnetic spectrum to transmit to transmit wireless information over is limited. What happens when we reach the limit? 

Spectrally efficient frequency division multiplexing (SEFDM) a techique developed at UCL in 2003 by Dr Miguel Rodrigues and Professor Izzat Darwazeh could be the answer for future wireless communication.

A multicarrier communication technique, SEFDM splits up information and sends it over several frequencies, this, however, is not unique, the technique is special as it does this while significantly improving the spectral efficiency of communication systems.

The research of SEFDM has already contributed to the spectrally efficient systems designs ranging from cellular systems evolution (4G, 5G), optical systems, satellite (DVB-S2), radio over fibre and millimetre wave communications.

Within the UCL Communications and Information Systems Group practical systems have been developed covering new wireless air interface design, 60 GHz and E-band millimetre wave communications, massive IoT connections, enhanced DSL communications, optical access network design and long-haul optical fibre transmission. 

Demonstrations of SEFDM systems have shown the technique's advantages in potential data rate improvement, power efficiency and transmission distance extension.

Over the past 15 years, SEFDM research has achieved major success, both theoretically and practically. With over 100 cross-disciplinary papers within leading journals and conferences alongside several international invitations to speak on the topic and two chapters in key 5G systems books, SEFDM has become a serious contender for future networks.

The global impact of the work has seen academics worldwide independently reporting on SEFDM use in optical, wireless and satellite systems developments; in China (Fudan, BUPT and Jinan); The University of Luxembourg, Germany; McGill University in Canada and St. Petersburg Polytechnic University in Russia.

In 2015, the UCL group started a collaboration with Chalmers University of Technology in Sweden, to implement high-speed SEFDM signal transmission over the E-band spectrum, using millimeter wave circuits designed at Chalmers.

Further collaborative work is also occurring with the UK universities of Surrey, on sphere decoding and detection, and Southampton, on the use of optical modulators with SEFDM.

Significant interest from industry was raised following a 2014 paper on the first optical system implementation and a wireless system implementation first reported in 2015. The optical paper became the most downloaded paper of IEEE Photonics Technology Letters  in the month it was published, February 2014.

Following this industrial interest, Aeroflex UK, an aerospace company, donated equipment to support the design and implementation of the world's first fully running SEFDM wireless testbed. This testbed directly led to a 40% data rate improvement.

After this initial approach from industry in 2015, the UCL group collaborated with a major cable operator to request Engineering and Physical Research Council (EPSRC) funding which would support the translation of the wireless SEFDM signal format for implementation in legacy twisted copper DSL, enabling an increase of capacity in existing networks.

The researchers at UCL are now working with a major equipment manufacturer to implement SEFDM on optical fibre long-haul systems. In 2017, National Instruments (NI) supported the pre-commercialisation of a software-defined 5G transceiver with additional funding received from EPSRC supplemented by a donation of FPGAs from Xilinx in the USA through their Xilinx University Program (XUP).

At ICCS, research into SEFDM is still underway. Prof Darwazeh, Institute Director and leader of the SEFDM research hopes that its biggest impact will be in adopting SEFDM, or its successor,  in future wireless and optical transmission standards.

The opportunities for SEFDM have only just begun to be realised with new applications being identified every day in medical imaging and device design, cognitive radio, internet of things, machine learning and big data.

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Information on the SEFDM technique can be found in Signal Processing for 5G: Algorithms and Implementations (Wiley, 2016) and Key Enabling Technologies for 5G Mobile Communications (Springer, 2016).