Pusan National University proposes backscatter comms for low-power IoT

Researchers from Pusan National University have designed a low-power backscatter communication system that they claim achieves a high spectral efficiency and enhanced energy efficiency when compared with traditional methods.

Also known as BackCom, backscatter communication is regarded as a promising low-power method for the widespread adoption of internet of things (IoT) technologies, where connected devices reflect and modulate existing signals by altering their load impedance, rather than generating signals themselves.

To achieve low bit error rates and high data rates, higher-order modulation schemes such as Quadrature Amplitude Modulation (QAM) are selected based on accurately modelled reflection coefficients.

However, the research team at Pusan noted that discrepancies between simulations and real-world measurements make it challenging to accurately predict the optimal reflection coefficient.

Looking to address these issues, and highlighted in a publication regarding their work, a research team led by professor Sangkil Kim from the Department of Electronics Engineering at Pusan National University used transfer learning to accurately model the in-phase/quadrature or I/Q load modulators. Additionally, the team introduced polarisation diversity to design a BackCom system that utilises multiple antennas for simultaneous signal transmission and reception.

The researchers designed a 2 × 2 × 2 MIMO transceiver system for BackCom, featuring two transmit and two receive antennas with different polarisations, such as vertical and horizontal. The setup enhanced signal reception, throughput, and efficiency in BackCom. Using a dual-polarised Vivaldi antenna, the team achieved a gain exceeding 11.5 dBi and effective cross-polarisation suppression of 18 dB.

The topline finding of the work was that overall, the proposed system lays the groundwork for a highly reliable and efficient backscatter system for multiple applications, including consumer electronics, healthcare monitoring, smart infrastructure for urban management, environmental sensing, and even radar communication. 

The new system is said to be 40% more energy-efficient than conventional backscattering systems and enables integrated sensing and communication technology. In addition to marking a significant step forward in efficient IoT communications and will be of great value in IoT use cases such as smart homes, wearable technology and industrial automation.

In addition, the team tested their algorithm and MIMO BackCom system in the 5.725 GHz to 5.875 GHz C-band of the Industrial, Scientific, and Medical band, offering a 150 MHz bandwidth. Their approach achieved a spectral efficiency of 2.0 bps/Hz using 4-QAM modulation, demonstrating effective bandwidth utilisation. They also attained an error vector magnitude of 9.35%, indicating said the team high reliability and efficiency in data transmission.

“As the technology for more efficient and reliable backscatter communication improves, it lowers the barrier for IoT adoption across numerous industries,” said Kim.

“This could lead to a proliferation of IoT devices and integrated sensing and communication [ISC], facilitating smart cities, more efficient industries, and enhanced personal and public services.

“The combination of accurate circuit modelling, advanced modulation techniques, and polarisation diversity, all tested in over-the-air environments, presents a holistic approach to tackling the challenges in ISC and IoT,” he added.