Wireless RF power transmission from dedicated Energy Transmitters (ETs) is emerging as a promising approach to enable battery-less wireless networked sensor systems. However, when data communication and RF energy recharging occur in-band, sharing the RF medium and devoting separate access times for both operations raises architectural and protocol level challenges. This paper proposes a novel method of concurrent transmission of data and energy to solve this problem, allowing ETs to transmit energy and sensors to transmit data in the same band synchronously. Our key idea concerns devising a physical layer modulation scheme that allows the data transmitting node to introduce variations in the envelope of the energy signal at the intended recipient. We implemented a proof-of-concept receiver, modeled and validated through extensive experimentation. We then propose a new physical layer mechanism for guaranteed successful delivery of information in a point-to-point link. Quantitative results demonstrate the feasibility of joint energy-data transfer, along with its associated benefits and tradeoffs.

Simultaneous Wireless Information and Power Transmission (SWIPT) has been proposed as a feasible solution to enable joint power and data transfer for the nodes of a battery-less wireless networked sensor system. Different from existing approaches, where the incident energy is split between decoding and harvesting blocks at the receiver chain, this paper describes the design and implementation of an all-digital receiver circuit. We leverage the internal control signals of the circuit, targeting ultra-low power consumption, low bit-rate applications in SWIPT. A proof-of-concept receiver is modeled, implemented using off-the-shelf hardware, and validated through extensive experiments. Quantitative results demonstrate the benefits of this joint energy-data reception approach through a single receiver chain, offering bit-rates of 400 bps.

Multisource energy harvesters are a promising, robust alternative to power the future Internet of Nano Things (IoNT), since the network elements can maintain their operation regardless of the fact that one of its energy sources might be temporarily unavailable. Interestingly, and less explored, when the energy availability of the energy sources present large temporal variations, combining multiple energy sources reduce the overall sparsity. As a result, the performance of a multiple energy harvester powered device is significantly better compared to a single energy source even if they harvest the same amount of energy. In this context, a framework to model and characterize the area for multiple source energy harvesting (EH) powered systems is proposed. This framework takes advantage of this improvement in performance to provide the optimal amount of energy harvesters, the requirements of each energy harvester, and the required energy buffer capacity, such that the overall area or volume is minimized. On top of these results, self-tunable energy harvesters are explored as a solution and compared to multisource EH platforms. As the results show, by conducting a joint design of the energy harvesters and the energy buffer, the overall area or volume of an EH powered device can be significantly reduced.

Wireless RF power transmission promises battery-less, resilient, and perpetual wireless sensor networks. Through the action of controllable Energy Transmitters (ETs) that operate at-a- distance, the sensors can be re-charged by harvesting the radiated RF energy. However, both the charging rate and effective charging range of the ETs are limited, and thus multiple ETs are required to cover large areas. While this action increases the amount of wireless energy injected into the network, there are certain areas where the RF energy combines destructively. To address this problem, we propose a duty-cycled random- phase multiple access (DRAMA). Non-intuitively, our approach relies on deliberately generating random interferences, both destructive and constructive, at the destination nodes. We demonstrate that DRAMA optimizes the power conversion efficiency, and the total amount of energy harvested. Through real-testbed experiments, we prove that our proposed scheme provides significant advantages over the current state of the art in our considered scenario, as it requires up to 70% less input RF power to recharge the energy buffer of the sensor in the same time.

Multi-source energy harvesters are gaining interest as a robust alternative to power wireless sensors, since the sensor node can maintain its operation regardless of the fact that one of its energy sources might be temporarily unavailable. Interestingly, and less explored, when the energy availability of the energy sources present large temporal variations, combining multiple energy sources reduce the overall sparsity. As a result, the performance of a multiple energy harvester powered sensor node is significantly better compared to a single energy source which harvests the same amount of energy. In this context, a circuit area optimization framework for multiple source energy harvesting powered systems is proposed. This framework takes advantage of this improvement in performance to provide the optimal amount of energy harvesters, the requirements of each energy harvester and the required energy buffer capacity, such that the overall area or volume is minimized. As the results show, by conducting a joint design of the energy harvesters and the energy buffer, the overall area or volume of a sensor node can be significantly reduced.

Graphene-enabled wireless communications set the Terahertz Band as the frequency band of operation of future nanodevices (0.1-10 THz). Amongst others, femtosecond-long pulse-based modulation schemes have been recently proposed to enable the communication among nanodevices. Within this context, a receiver architecture suitable for nanodevices must be ultra compact, must have high sensitivity and must be ultra-low power. Unfortunately, common receiver architectures used in other communication schemes, such as IR-UWB, show a strong compromise between low complexity and performance. In this paper, a novel receiver architecture for pulse-based communication based on a Continuous-time Moving Average (CTMA) symbol detection scheme is presented. This scheme bases its symbol decision on the received signal power maximum peak after the CTMA, which is implemented with a single low-pass filter. Moreover, an analytical model for the symbol detection is provided and it is quantitatively shown that the proposed CTMA scheme outperforms previous symbol detection schemes for pulse-based modulations in terms of Symbol Error Rate (SER). The low complexity and relaxed synchronization needed for this symbol detector makes this structure specially suited for the development of future transceivers for nano-devices.

Wireless Sensor Networks (WSN) present a pending challenge for a complete deployability due to energy requirements. The Self-Powered WSN approach aims to extend the sensor node life by means of Energy Harvesting. The harvested energy presents an erratic behavior in both time and frequency. In this paper, a new concept of switch-mode electronically tunable band-pass filters is presented to adaptively follow the power source variations and to maximize the power transfer. To implement these switch-mode filters, three alternatives are presented. These filter topologies are modeled and evaluated. Additionally, some design guidelines are provided. The results show how these high efficiency topologies present a band-pass behavior whose center frequency can be electronically tuned over one decade. The results target the integration of these high-efficiency switch-mode band-pass filters into the future harvesting front-ends.