A proof-of-concept superregenerative QPSK transceiver

In this paper we present a description and experimental verification of an HF-band proof-of-concept superregenerative transceiver for QPSK signals. We describe a simple implementation of an all-digital, FPGA-based, QPSK transmitter section. On the receiver side, the quench signal is generated in the same FPGA with a minimum of analog circuitry. As the main novelty, we present a simple synchronization scheme suitable for packetized transmissions.Peer ReviewedPostprint (author’s final draft

Wireless sensors and IoT platform for intelligent HVAC control

Energy consumption of buildings (residential and non-residential) represents approximately 40% of total world electricity consumption, with half of this energy consumed by HVAC systems. Model-Based Predictive Control (MBPC) is perhaps the technique most often proposed for HVAC control, since it offers an enormous potential for energy savings. Despite the large number of papers on this topic during the last few years, there are only a few reported applications of the use of MBPC for existing buildings, under normal occupancy conditions and, to the best of our knowledge, no commercial solution yet. A marketable solution has been recently presented by the authors, coined the IMBPC HVAC system. This paper describes the design, prototyping and validation of two components of this integrated system, the Self-Powered Wireless Sensors and the IOT platform developed. Results for the use of IMBPC in a real building under normal occupation demonstrate savings in the electricity bill while maintaining thermal comfort during the whole occupation schedule.QREN SIDT [38798]; Portuguese Foundation for Science & Technology, through IDMEC, under LAETA [ID/EMS/50022/2013

Field test of multi-hop image sensing network prototype on a city-wide scale

Open Access funded by Chongqing University of Posts and Telecommuniocations Under a Creative Commons license, https://creativecommons.org/licenses/by-nc-nd/4.0/Wireless multimedia sensor network drastically stretches the horizon of traditional monitoring and surveillance systems, of which most existing research have utilised Zigbee or WiFi as the communication technology. Both technologies use ultra high frequencies (mainly 2.4 GHz) and suffer from relatively short transmission range (i.e. 100 m line-of-sight). The objective of this paper is to assess the feasibility and potential of transmitting image information using RF modules with lower frequencies (e.g. 433 MHz) in order to achieve a larger scale deployment such as a city scenario. Arduino platform is used for its low cost and simplicity. The details of hardware properties are elaborated in the article, followed by an investigation of optimum configurations for the system. Upon an initial range testing outcome of over 2000 m line-of-sight transmission distance, the prototype network has been installed in a real life city plot for further examination of performance. A range of suitable applications has been proposed along with suggestions for future research.Peer reviewe

Channel Sounding for the Masses: Low Complexity GNU 802.11b Channel Impulse Response Estimation

New techniques in cross-layer wireless networks are building demand for ubiquitous channel sounding, that is, the capability to measure channel impulse response (CIR) with any standard wireless network and node. Towards that goal, we present a software-defined IEEE 802.11b receiver and CIR estimation system with little additional computational complexity compared to 802.11b reception alone. The system implementation, using the universal software radio peripheral (USRP) and GNU Radio, is described and compared to previous work. By overcoming computational limitations and performing direct-sequence spread-spectrum (DS-SS) matched filtering on the USRP, we enable high-quality yet inexpensive CIR estimation. We validate the channel sounder and present a drive test campaign which measures hundreds of channels between WiFi access points and an in-vehicle receiver in urban and suburban areas

Digitally-Assisted RF-Analog Self Interference Cancellation for Wideband Full-Duplex Radios

The ever-increasing demand for more data from users is pushing the development of alternative wireless technologies to improve upon network capacity. Full-Duplex radios provide an exciting opportunity to theoretically double the available spectral efficiency of wireless networks by simultaneously transmitting and receiving signals in the same frequency band. The main challenge that is presented in the implementation of a full-duplex radio is the high power transmitter leaking to the sensitive receiver chain and masking the desired receive signal to be decoded. This transmitter leakage is referred to as self interference and it is required that this self interference signal be cancelled below the receiver noise floor to achieve the full benefits of a full-duplex radio. Cancellation of the self interference signal is realized through several techniques, categorized as passive suppression, digital cancellation, and analog cancellation. These methods all have their challenges in achieving the full amount of cancellation necessary and therefore all three techniques are typically employed in the system. In this thesis, a novel digitally assisted radio frequency (RF) analog self interference canceller is proposed to suppress the self interference signal before the receiver chain for wide modulation bandwidth signals. This canceller augments minimum complexity RF-analog interference cancellation hardware that uses an RF vector multiplier in combination with a flexible digital rational function finite impulse response filter. The simple topology reduces the number of impairments added to the system through the analog components and identifies the parameters of the proposed filter in a deterministic and single iteration algorithm. The hardware proof-of-concept prototype is built using off-the-shelf RF-analog components and demonstrates excellent cancellation performance. Using four TX test signals with modulation bandwidths of 20~MHz, 40~MHz, 80~MHz, and 120~MHz, the self interference canceller achieves a minimum of 50~dB, 47~dB, 42~dB, and 40~dB of cancellation respectively. This thesis reviews the previously proposed self interference cancellation topologies, system non-idealities that provide challenges for full-duplex implementation, and the realization of the proposed RF-analog self interference canceller