Wi-Fi Backscatter System with Tag Sensors Using Multi-Antennas for Increased Data Rate and Reliability

Abstract

In this paper, we propose tag sensor using multi-antennas in a Wi-Fi backscatter system, which results in an improved data rate or reliability of the signal transmitted from a tag sensor to a reader. The existing power level modulation method, which is proposed to improve data rate in a Wi-Fi backscatter system, has low reliability due to the reduced distance between symbols. To address this problem, we propose a Wi-Fi backscatter system that obtains channel diversity by applying multiple antennas. Two backscatter methods are described for improving the data rate or reliability in the proposed system. In addition, we propose three low complexity demodulation methods to address the high computational complexity problem caused by multiple antennas: (1) SET (subcarrier energy-based threshold) method, (2) TCST (tag’s channel state-based threshold) method, and (3) SED (similar Euclidean distance) method. In order to verify the performance of the proposed backscatter method and low complexity demodulation schemes, the 802.11 TGn (task group n) channel model was utilized in simulation. In this paper, the proposed tag sensor structure was compared with existing methods using only sub-channels with a large difference in received CSI (channel state information) values or adopting power-level modulation. The proposed scheme showed about 10 dB better bit error rate (BER) performance and throughput. Also, proposed low complexity demodulation schemes were similar in BER performance with a difference of up to 1 dB and the computational complexity was reduced by up to 60% compared to the existing Euclidean distance method.

Scalable Wi-Fi Backscatter Uplink Multiple Access for Battery-Free Internet of Things

“…Backscatter communications harvests energy from ambient radio frequency (RF) sources, such as TV towers, frequency modulation (FM) radio towers, cellular base stations, and Wi-Fi access points (APs), enabling ultralow-power or even battery-free operation of Internet of Things (IoT) devices and significantly mitigating the deployment hurdles of many IoT applications [1][2][3]. Wi-Fi backscatter has recently been considered a promising solution for achieving a battery-free IoT paradigm because commodity Wi-Fi APs and Wi-Fi devices are immediately deployable as the transmitter and receiver of the backscatter communications architecture, significantly reducing its deployment costs [4][5][6][7]. The Wi-Fi backscatter has a bistatic backscatter system architecture composed of a Wi-Fi helper (as an RF source), Wi-Fi reader (as a receiver), and Wi-Fi backscatter tag (as a transmitter), where the Wi-Fi backscatter tag reflects or absorbs the packets sent from the Wi-Fi helper to enable the Wi-Fi reader to detect the tag information [8][9][10].…”

Data Downlink System in the Vast IOT Node Condition Assisted by UAV, Large Intelligent Surface, and Power and Data Beacon

“…This is beneficial as it allows for the miniaturization of the IOT system. Depending on whether a system relies on energy-receiving devices storing energy or directly reflecting it, RFET systems can be categorized into twotypes: energy-harvesting systems and backscattering systems [ 5 , 6 ]. Energy harvesting systems can be used for both downlink and uplink communication, while backscattering systems are often used for uplink communication [ 7 ].Thus, by using RFET technology and building an energy-harvesting system, IOT nodes can acquire enough energy to complete the downlink data receiving procedure.…”