Simultaneous wireless information and power transfer (SWIPT)-aided nonorthogonal multiple access (NOMA) systems, which is used for communication in the Industrial Internet of Things (IIoTs), suffers from energy loss with transmission distance. Now, researchers from Korea have developed an energy-efficient framework by applying SWIPT-NOMA to a distributed antenna system. The technology is expected to pave the way for more efficient and optimized IoT environments.
IIoTs refers to a technology that combines wireless sensors, controllers, and mobile communication technologies to make every aspect of industrial production processes intelligent and efficient.
Since IIoTs can involve several small battery-driven devices and sensors, a growing need exists to develop a robust network for data transmission and power transfer to monitor the IIoT environment.
In this regard, wireless power transfer is a promising technology. It uses radio frequency signals to power small devices that consume minimal power. Simultaneous wireless information and power transfer (SWIPT), which use a single radio frequency signal to perform energy harvesting and information decoding, has attracted interest for IIoTs.
Additionally, with smart devices growing, SWIPT has combined with nonorthogonal multiple access (NOMA) systems – a promising candidate for IIoTs because of their ability to extend the battery life of sensors and other devices.
However, the energy efficiency of this kind of system diminishes with transmission distance from the central controller.
To overcome this limitation, South Korean researchers, led by Associate Professor Dong-Wook Seo from the Division of Electronics and Electrical Information Engineering at Korea Maritime and Ocean University, have developed a framework by applying SWIPT-aided NOMA to a distributed antenna system (DAS), and the result has been improving the energy and spectral efficiencies of IIoTs.
“By applying a DAS with supporting antennas relatively close to edge users alongside a central base station, SWIPT-NOMA’s loss with growing distance can be reduced efficiently. This improves information decoding and energy harvesting performance,” Seo explained.
The study is available at published in Volume 19, Issue 7 of the journal IEEE Transactions on Industrial Informatics.
The researchers formulated a three-step iterative algorithm to maximize the energy efficiency of the SWIPT-NOMA-DAS system. They first optimized the power allocation for the central IoT controller.
After that, the power allocation for NOMA signaling and power splitting (PS) assignment for SWIPT were optimized, while minimizing the data rates and harvested energy requirements. Finally, the team analyzed an outage event in which the system cannot provide sufficient energy and data rates, thereby extending the joint power allocation and PS assignment optimization method to the multi-cluster scenario.
They validated their algorithm through extensive numerical simulations, finding the proposed SWIPT-NOMA-DAS system is five times more energy efficient than SWIPT-NOMA without DAS.
Also, it shows a more than 10 percent improvement in performance over SWIPT-OMA-DAS.
Highlighting the significance of their study, Seo said, “This technology ensures very efficient energy consumption and offers various advantages such as convenience, low power, and battery life extension. Thus, it can be applied to smartphones, laptops, wearable devices, and electric vehicles. Most importantly, the SWIPT-NOMA-DAS system can optimize resource allocation and efficiently perform wireless charging and information transmission for users in an IoT environment.”
