Information harvesting: Leveraging wireless power transfer for next-generation communication frameworks

As wireless information transmission (WIT) progresses into its sixth generation (6G), the challenge of sustaining terminal operations with limited batteries for Internet-of-things (IoT) platforms arises. Wireless power transfer (WPT) emerges as a solution, empowering battery-less infrastructures and enabling nodes to harvest energy for sustainable operations. The integration of WPT with WIT mechanisms becomes crucial to mitigate the need for battery replacements while ensuring secure and reliable communication. A novel protocol, Information Harvesting (IH), amalgamates WIT and WPT through index modulation (IM) techniques atop the existing far-field WPT mechanism to address challenges in wireless information and power transfer (WIPT). Moreover, innovative modes of information and power transfer are explored to meet the rising demand for energy and spectrum resources in next-generation IoT systems. One potential solution involves harnessing the active transmission capability of devices to facilitate data transmission and wireless energy harvesting (WEH) for backscatter communication (BC), forming a symbiotic radio (SR) environment. Furthermore, incorporating reconfigurable intelligent surfaces (RISs) into the SR environment enhances the reliability of backscatter communication, reinforcing symbiotic relationships between active and passive devices. This thesis explores novel and synergistic methods for coordinating WPT and WIT in next-generation communication systems through state-of-the-art technologies. In Chapter 3, a unified framework for index modulation (IM)-based IH mechanisms is presented, evaluating their energy harvesting capability, bit error rate (BER), and ergodic secrecy rate (ESR) performance for diverse IM schemes. The findings indicate significant potential in facilitating reliable data communication within existing far-field WPT systems, underscoring promising refinements in green and secure communication paradigms for next-generation IoT wireless networks. Chapter 4 introduces a new IH mechanism atop the orthogonal frequency-division multiplexing (OFDM)-based far-field WPT mechanism, investigating its benefits in terms of harvested energy, achievable rates, and reliability. Finally, Chapter 5 presents a novel SR system, where a standalone RIS sustains its functions through WEH based on a low-power RIS structure. Mutualistic symbiosis is established by utilizing a signal conveyed by the primary transmitter (PTx) to assist ongoing transmissions and convey information to the primary receiver (PRx). The PTx employs time index modulation (TIM) to transmit information to the PRx and power to the RIS and energy harvester (EH). A log-likelihood ratio (LLR)-based detector is presented to address challenges in the TIM scheme. The performance of the proposed scheme is investigated in terms of harvested direct current (DC) power at the RIS and EH, as well as the BER at the PRx.