The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. ...The total phenolic content, determined according to the Folin−Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the β-carotene bleaching method expressed as AOX (Δ log A 470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products
Nowadays, cities and towns all over the world are dotted with high-rise buildings, and floor positioning technology has gradually become the focus of indoor positioning research. Multi-level ...buildings with an atrium space structure mainly consist of shopping malls and hospital outpatient buildings. This kind of building is widely spread, and they usually have a lot of people and a high demand for location-based services. The specific spatial structure of the indoor atrium makes the propagation of wireless signals different, which leads to most of the wireless signal-based floor positioning methods not working well in such an environment. Aiming at this atrium structure environment, this paper proposes a high-precision multi-method adaptive weighted fusion algorithm based on Bluetooth Low Energy signals. In experiments, the real-time dynamic floor positioning accuracy reached 92.7%, while the floor positioning accuracy in the 5-s static state was as high as 100%. Besides, when using 3 s of test data rolled back, real-time effects could also be achieved, with an accuracy of 98.3%. This method can be used alone for real-time floor positioning, it is suitable for wireless fidelity signals, and it can provide a highly accurate initial floor reference for barometric or inertial methods. It could also be integrated with other methods to provide highly accurate floor locations for long periods of time. The fingerprint library acquisition in this method saves time and effort. The database volume is small and generalizable to a wide range of applications.
Communication networks are a key element in the development of Smart Cities. This field is a constantly evolving environment, for which new protocols are constantly appearing. Due to the ...heterogeneous nature of the technologies, the most appropriate candidate must be selected in order to get the best performance to satisfy the application requirements. One of these protocols is Bluetooth Low Energy (BLE), particularly with the upgrades introduced in version 5.x. Its new features are focused on providing increased range, improving robustness, and expanding beaconing capabilities. Connectionless applications such as information broadcasting in Smart Cities could take advantage of this protocol. Furthermore, the wide availability on common devices (mobile phones, car infotainment, etc.), the deployment of these applications can be carried out easily and at low cost. This paper presents an experimental evaluation of the new robust, long-range radio mode of BLE over a set of Smart Cities scenarios, taking into account different conditions such as wireless interference, distances, dynamicity, etc. The results show a promising performance of the protocol even with these constraints.
Due to the popularity of short-range communications and the ultra-dense deployment of the Internet of Things (IoT), the occurrence of severe signal collision in crowded nodes is becoming increasingly ...critical. We propose a scheme called anti-collision voting based on Bluetooth low energy improvement for the ultra-dense edge, in which one topic can be identified and separated from the others to enable intensive voting. The scheme alleviates the exponential growth of advertising collisions and achieves efficient consensus between the devices and humans by localized the message advertising. The previous proposals focused on enhancing the hardware and optimizing the parameters to establish a connection for interaction. Considering the limitation of connective devices, our scheme adopts a novel advertising model in which the nodes can promptly exit the advertising state by actively responding. In addition, the scheme merges active responses into a group to notify the advertising nodes and randomly chooses a channel to reduce redundancy and save energy. The simulations demonstrate that the scheme can reduce the collisions by more than 90% and channel occupancy by half, while doubling the capacity and efficiently supporting intensive voting within edge networks.
The 2.4 GHz spectrum is home to several Radio Access Technologies (RATs), including ZigBee, Bluetooth Low Energy (BLE), and Wi-Fi. Accordingly, the technologies' spectrum-sharing qualities have been ...extensively studied in literature. License-Assisted Access (LAA) Listen-Before-Talk (LBT) has been identified in technical reports as the foundation for the channel access mechanism for 5G New Radio-Unlicensed (NR-U) operating in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. The introduction of NR-U into this band raises new concerns regarding coexistence of the newcomer with traditional incumbents. This article reports an investigation of BLE 5 and cellular LBT coexisting systems by means of empirical evaluation. The importance of this study stems from that the studied LBT mechanism is indicative of how 5G NR-U would perform in the 2.4 GHz band. Tests were performed in conformity with the American National Standards Institute (ANSI) C63.27 standard for evaluation of wireless coexistence, and results were reported in terms of throughput and interframe delays. In accordance with the standard and under different BLE physical layers (PHYs) and LBT priority classes, three setups were investigated. These pertain to the three tiers of evaluation, which correspond to the criticality of the device under test. Results demonstrated how BLE throughput dropped as the intended-to-unintended signal ratio decreased, and LBT classes exhibited a diminishing effect as the class priority descended. Long Range BLE PHY was found to sustain longer gap times (i.e., delay) than the other two PHYs; however, it showed less susceptibility to interference. Results also demonstrated that low data rate BLE PHYs hindered the LBT throughput performance since they correspond to longer airtime durations.
Purpose
The purpose of this paper is to introduce a new linearization technique known as the passive linearizer technique which does not affect the power added efficiency (PAE) while maintaining a ...power gain of more than 20 dB for complementary metal oxide semiconductor (CMOS) power amplifier (PA).
Design/methodology/approach
The linearization mechanism is executed with an aid of a passive linearizer implemented at the gate of the main amplifier to minimize the effect of Cgs capacitance through the generation of opposite phase response at the main amplifier. The inductor-less output matching network presents an almost lossless output matching network which contributes to high gain, PAE and output power. The linearity performance is improved without the penalty of power consumption, power gain and stability.
Findings
With this topology, the PA delivers more than 20 dB gain for the Bluetooth Low Energy (BLE) Band from 2.4 GHz to 2.5 GHz with a supply headroom of 1.8 V. At the center frequency of 2.45 GHz, the PA exhibits a gain of 23.3 dB with corresponding peak PAE of 40.11% at a maximum output power of 14.3 dBm. At a maximum linear output power of 12.7 dBm, a PAE of 37.3% has been achieved with a peak third order intermodulation product of 28.04 dBm with a power consumption of 50.58 mW. This corresponds to ACLR of – 20 dBc, thus qualifying the PA to operate for BLE operation.
Practical implications
The proposed technique is able to boost up the efficiency and output power, as well as linearize the PA closer to 1 dB compression point. This reduces the trade-off between linear output power and PAE in CMOS PA design.
Originality/value
The proposed CMOS PA can be integrated comfortably to a BLE transmitter, allowing it to reduce the transceiver’s overall power consumption.
Device-free occupancy detection is very important for certain Internet of Things applications that do not require the user to carry a receiver. This paper achieves the device-free occupancy detection ...with RF fingerprinting, which labels each zone with a 2M-dimensional fingerprint vector. Specifically, the fingerprint vector consists of received signal strength (RSS) values measured from M Bluetooth low energy (BLE) beacons and also their corresponding temporal RSS variations. However, the unreliable RSS values caused two common issues with the fingerprint vector: 1) noise and 2) sparsity. To this end, we propose denoising-contractive autoencoder (DCAE) to jointly deal with these two issues, by learning a robust fingerprint prior to device-free occupancy detection. We validate the performance of our proposed DCAE with large-scale real-world datasets. The experimental results indicate the substantial performance gain of our proposed DCAE in comparison with state-of-the-art autoencoders. In particular, the classifier trained using the fingerprints learned by our proposed DCAE is able to maintain at least 90% accuracy when the noise factor or sparsity ratio increases to 0.6 and 0.5, respectively.
In this paper, an autonomous wearable sensor node is developed for long-term continuous healthcare monitoring. This node is used to monitor the body temperature and heart rate of a human through a ...mobile application. Thus, it includes a temperature sensor, a heart pulse sensor, a low-power microcontroller, and a Bluetooth low energy (BLE) module. The power supply of the node is a lithium-ion rechargeable battery, but this battery has a limited lifetime. Therefore, a photovoltaic (PV) energy harvesting system is proposed to prolong the battery lifetime of the sensor node. The PV energy harvesting system consists of a flexible photovoltaic panel, and a charging controller. This PV energy harvesting system is practically tested outdoor under lighting intensity of 1000 W/m2. Experimentally, the overall power consumption of the node is 4.97 mW and its lifetime about 246 hours in active-sleep mode. Finally, the experimental results demonstrate long-term and sustainable operation for the wearable sensor node.
•A low-cost generic measurement setup applied to test BLE procedures and devices.•New test setups to enhance and measure the real behavior of IoT devices.•Experimental characterization combining ...current measurement and upper layer response.•Hardware design and software configuration of the proposed measurement system.
The methodology presented in this paper aims to characterize impairments shown by real devices which are usually neglected on standardized tests but that become very important in massive IoT scenarios.
For instance, we have measured that real BLE scanners are not able to scan continuously even though they are configured to do so. Besides, we have also found and demonstrated that some manufacturers seem not to apply any backoff mechanism although it is mandatory. These two unexpected behaviors have a significant impact on the performance of massive wireless sensor networks based on BLE. So, it becomes necessary to characterize these and other impairments.
The proposed tests are based on device current consumption measurements and their association with the information obtained from upper layers.
We describe a new low-cost generic measurement setup and provide all the necessary data (configuration parameters, scripts, etc.) for applying the proposed methodology. As an example, we use it to profile the behavior of Bluetooth Low Energy devices. Furthermore, the proposed setup can also inspire researchers to characterize other wireless technology devices, like Wi-Fi, Zigbee, LoRa, etc.
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