Cognitive Radio Technology Optimises Use Of Spectrum In Wireless Networks

EU-funded researchers developed smart wireless technology that efficiently manages radio-frequency spectrum resources and avoids transmission bottlenecks. The new system, which also prevents selfish attacks by secondary users, could be used in military and commercial wireless applications.

The growing popularity of wireless networks has highlighted the need to increase network capacity and efficiency. Cognitive radio-based networks have attracted increased attention and have been studied in depth to overcome the problem of spectrum scarcity in next-generation wireless communication systems.

Within the EU-funded project CORPA, researchers successfully developed cognitive radio technologies to optimise radio spectrum usage i.e., accessing and sharing unused parts of the spectrum. Drawing on fundamental elements of, amongst others, hardware design, network theory, and optimisation and signal processing, the team unveiled a disruptive radio system design that efficiently allocates unused bands to secondary spectrum users whenever possible.

Choosing non ‘crowded’ frequencies
The idea of sharing non-utilised portions of the spectrum may seem fairly obvious, raising the question of why it has not yet been implemented. “Although the subject of cognitive radio networks spans some years of intense research and has led to a number of interesting results, hardware design and system development are progressing at a much slower pace. The technologies required for spectrum sharing have only recently matured,” notes Dr Van Tam Nguyen.

The radio spectrum is a valuable resource in wireless communications. “The current static spectrum allocation to spectrum management that divides the spectrum into licensed bands allocated over large geographic areas is not adaptive any more to supply-and-demand dynamics. This imbalance of supply and demand leads to many allocated bands being under-utilised, while others are overwhelmed, thereby squandering the spectrum’s enormous capacity and unnecessarily creating conditions of scarcity,” explains Dr Nguyen.

Future wireless networks will need to use greater intelligence to avoid interference, while optimising the spectrum by collaborating with other systems that occupy the same spectrum bands.” Unlicensed bands or shared spectrum provide more flexibility and efficiency in spectrum usage,” Dr Nguyen concludes.

Breakthrough radio technology
CORPA researchers conducted pioneering work on radio technologies to meet future demands in terms of spectral efficiency, energy efficiency and application performance. “A key bottleneck in cognitive radio systems has always been and continues to be the development of a flexible radio-frequency transceiver that consumes very low power and has the ability to convert the analogue radio input into a digital output that is compatible with digital processing,” points out Dr Nguyen.

Researchers successfully addressed this key issue by designing advanced receiver architecture that facilitates the realisation of radio-frequency functions for military and commercial communications systems. Compared to state-of-the-art solutions, the new cognitive-radio receiver prototype consumes power much more efficiently and spans an extended range of frequencies from 400 MHz to 6 GHz – this makes it ideal for use in 5G networks.

The system also boasts low noise figures, low distortion, and a signal-to-noise ratio that is 10 times better than current solutions. The Schreier factor of merit, which is often used to compare the analogue-to-digital conversion, is also better in the specified frequency range, reaching 149 dB.

Combating selfish behaviour
There are many network functions that can be compromised because of the presence of bad users. “Regarding the network availability, an unused spectrum band that can be accessed by licenced users should always be available to them; however, a selfish behaviour can compromise that,” says Dr Nguyen.

Determining proper surveillance strategies is necessary to ensure fairness in network operation. Researchers demonstrated that the conventional behavioural game theory algorithms used to describe the interaction between a defender and an attacker are not optimal when the latter has the capacity to learn. Instead, the team designed a new algorithm that reinforces network surveillance, based on the so-called strong Stackelberg equilibrium.

The rapid increase in wireless data traffic highlights the importance of the intensive dynamic use of the available spectrum. With its disruptive new system, CORPA will aid in the development of new wireless services with improved quality.