WCA May/July 2020

Telecom news

UK research could bring ultra-fast data transmission a little closer Researchers from the UK universities of Leeds and Nottingham could be paving the way to delivering ultra-fast modulation, using a combination of acoustic and light waves. The team’s breakthrough is in the control of terahertz quantum cascade lasers, which could lead to a transmission rate of 100Gbps – a thousand times faster than “fast” Ethernet of 100Mbps. Terahertz quantum cascade lasers emit light in the terahertz range of the electromagnetic spectrum, and are used in spectroscopy. They could also, potentially, provide ultra-fast, short-hop wireless links where data is transferred across campuses or between facilities, or even in satellite communications. To send data at such high speeds the lasers need to modulate very quickly, pulsing at around 100 billion times every second. John Cunningham, professor of nanoelectronics at Leeds, said, “At the moment, the system for modulating a quantum cascade laser is electrically driven, but that system has limitations. Ironically, the same electronics that deliver the modulation usually puts a brake on the speed of the modulation. The mechanism we are developing relies instead on acoustic waves.” In a quantum cascade laser an electron passes through the optical component, through a series of “quantum wells” where the electron’s energy level drops and a photon, or pulse of light energy, is emitted. One electron can emit many photons. Researchers used acoustic waves to vibrate the quantum wells inside the quantum cascade laser. Acoustic waves were generated by the impact of a pulse from another laser onto an aluminium film, causing the film to expand and contract and, so, sending a mechanical wave through the quantum cascade laser. Tony Kent, professor of physics at Nottingham University, said, “Essentially, what we did was use the acoustic wave to shake the intricate electronic states inside the quantum cascade laser.

We could then see that its terahertz light output was being altered by the acoustic wave.” Although, Prof Cunningham added, “We did not reach a situation where we could stop and start the flow completely, … we were able to control the light output by a few per cent, which is a great start. We believe … we will be able to develop a new mechanism for complete control of the photon emissions from the laser, and perhaps even integrate structures generating sound with the terahertz laser, so that no external sound source is needed.” Prof Kent concluded, “This result opens a new area for physics and engineering … in the interaction of terahertz sound and light waves, which could have real technological applications.” The team’s findings were published in the journal Nature Communications . Speculative look at 6G A recent paper from researchers at Saudi Arabia’s King Abdullah University of Science and Technology, published in Nature Electronics , has offered a possible vision for the development of 6G communications, based on speculations about the future of telecommunications. “Our speculations are summarised from our … research activities in recent years, related to terahertz radios, terrestrial-aerial-space integrated net- working, novel modulation schemes, and artificial intelligence-aided communications,” said researcher Shuping Dang. “The main objectives of this perspective paper were to define the key potential features of 6G, discuss the required communication technologies, and explore issues beyond communication technologies that could hamper future research and the deployment of 6G.” As is already the case for 5G, human-centric mobile communi- cations will most likely be the prominent application for the 6G network, so believe Mr Dang and his colleagues. As a result, developers of the new network are expected to pay particular attention to aspects such as security, secrecy and privacy.

In their paper, the researchers also suggest that artificial intelligence could play a particularly important role. “Artificial intelligence and machine learning could bring unprecedented communication services and experiences to users,” Mr Dang enthused. “However, we should always be aware of the accompanying challenge of privacy protection, as well as the risk of potentially creating a horrific world watched and controlled by a technocratic Big Brother.” Mr Dang and his colleagues believe it will be vital that 6G communications are easily available to all regions and populations as this will, ultimately, promote and enable faster worldwide connectivity. And, he believes, “Most importantly, we must admit that the advancement of wireless communications is highly restricted by basic sciences, especially mathematics and physics, as well as information theory and electronics. Without breakthroughs in these subjects, the essential improvement in the capacity- and delay-related performance metrics of communication systems would be impossible.” The predictions made by Mr Dang and his colleagues are mainly based on speculation, but their ideas could serve as a general guideline for other 6G-related research activities. “We now plan to explore ways to enhance security, secrecy and privacy for 6G communications,” Mr Dang added. “We are currently studying a decentralised, high-performance network architecture enabled by terahertz spectra and federated learning techniques.” FCC plans to take action over wireless real-time location data disclosures Ajit Pai, chairman of the US Federal Communications Commission (FCC), has confirmed plans to take action against one or more unnamed wireless carriers over the alleged unauthorised sale of users’ real-time location data. In May 2018, the FCC’s enforcement bureau began investigations into whether a website flaw could have

Illustrations: BigStockPhoto.com • Artist: Asmati

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Wire & Cable ASIA – May/July 2020

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