In the first of a new series focussed on academic research on spectrum-related issues, we look at whether radar and communication systems could share spectrum to help relieve spectrum scarcity.
With wireless spectrum prices on the rise, and frequencies becoming increasingly congested, mobile network providers looking for ways to reuse spectrum are turning their attention to the possibility of sharing with radar bands. That’s according to Fan Liu of University College London (UCL), who is part of a research group investigating the issue under a Marie Curie Fellowship.
Radar spectrum is increasingly seen as being able to co-exist with wireless communications systems such as 5G New Radio and Wi-Fi. Radar and communication platforms are also expected to be able to co-exist in the higher frequencies, including mmWave, for 5G and other services. As these bands are being allocated to wireless technologies, however, interference in the radar bands is growing, sparking concerns from governmental and military organisations, and prompting research on the issue of communications and radar spectrum sharing (CRSS).
CRSS research currently follows two paths: radar-communications coexistence and dual-functional radar-communication systems. The former aims to develop effective interference management techniques to allow the two systems to operate harmoniously; the latter focuses on designing joint systems that can deal with wireless communications and remote sensing simultaneously.
The research group proposes a dual-functional radar-communication system, operated in the mmWave band, that uses a massive MIMO antenna array and hybrid analogue-digital beamforming, along with a TDD frame structure that can unify radar and communications operations.
Why does coexistence matter?
Among other things, allowing radar and communications to operate in the same spectrum could improve sensing capabilities in the vehicle-to-everything (V2X) network needed for next-generation autonomous cars. CRSS could also enable Wi-Fi-based indoor positioning technologies that would act as a kind of passive radar to locate a particular target based on the received signals sent by user equipment. Potential applications here might include healthcare for elderly people and anti-terrorism activities. CRSS-based techniques could also play a role in amplifying and forwarding weak communications signals to remote users.
On the military side, CRSS could help create multi-function radio frequency systems that could simultaneously support, for example, integrated RF systems including radar, communications and electronic warfare. Or it could use existing communications systems such as cellular base stations to monitor unauthorised unmanned aerial vehicles while offering wireless services to authorised end users. The principal investigator of this research, Christos Masouros, is part of a research project with the University Defence Research Collaboration focusing on such applications.
Although research is ongoing into radar-communications coexistence and joint radar-communication systems, there’s much more to do, the academics say.
One key challenge for CRSS is to distinguish between the echoes from targets and communication signals from users in the presence of noise and interference. Another is to resolve security and privacy issues arising from military radar sharing spectrum with communications systems.
The research group investigating this issue includes Christos Masouros and Hugh Griffiths, also of the UCL Department of Electronic and Electrical Engineering; Athina Petropulu of the State University of New Jersey Department of Electrical and Computer Engineering; and Lajos Hanzo of the University of Southampton School of Electronics and Computer Science.
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