Changes In Signal Strength Research Articles

Wave Propagation Models for Optimization in Wireless Communication

To understand and build radio transmission systems, you need to know how waves travel. These models show how electromagnetic waves move through different settings, considering things like distance, obstacles, and the material the waves move through. A lot of what makes radio transmission work is being able to correctly guess how waves will spread in different situations. Wave propagation models come in many forms, such as open space, ground reflection (two-ray), and more complicated models such as the Hata, Okumura, and Rayleigh models. Each model is used for a different thing. For example, free space models are good at showing simple line-of-sight (LOS) situations, while empirical models like Hata are better at showing more complicated urban and residential settings. For example, the free space model believes that there are no hurdles between the sender and listener. This makes it perfect for situations like open fields or satellite communications. The Hata and Okumura models, on the other hand, are made for cities and suburbs, taking into account how buildings and geography affect signal power. Rayleigh and Rician models are scientific and are often used to describe situations where multipath transmission happens, like in crowded cities where signals bounce off many objects. These models help us understand things like fading, where the signal strength changes because of interference from different routes. Wave propagation models are important for making sure that wireless communication systems work well, whether they are simple field sets or complicated networks in cities. They help experts guess how signals will behave, find the best places to put antennas, and make the whole network work better. These models make sure that communication systems can stay connected and provide high-quality service in a wide range of settings by considering different transmission scenarios.

Received signal evaluation for Ultra High Frequency (UHF)terrestrial television; Case of Ekiti State, Nigeria

This paper presents the evaluation of the received signal for UHF channel 41, (transmitting frequency of 631.25 MHz) and Star-times (transmitting frequency of 618 MHz). Using a Digital Field Strength Meter, the signal strength from the two UHF Transmitting Stations was measured throughout the state along two routes. The elevation, geographic coordinates, and line of sight of the various data points from the base stations were determined using a global positioning system (GPS) receiver. Regression analysis and correlation were used in the signal assessment process. Analysis of the data collected from the field measurements indicated that as line of sight increases signal strength reduces along all the routes for Ekiti Television (EKTV) and Star-times except along Route B for Star-times. Line of Sight and Elevation have a strong negative connection in almost all routes except along route A for star-times. Elevation and Signal strength correlation indicated negatively very high except for that along route B for EKTV and route A for Star-times. Regression analysis revealed that variance in Line of Sight and Elevation accounted for high significant changes in signal strength for EKTV and consistently very high changes for Star-times. Generally, it was observed that distance from the base station, topography/elevation, power of the transmitter, nature of signal (Digital/Analog) as shown for regression analysis and other factors affected the quality of service of the propagated signal. Terrestrial Television stations should ensure they transmit with the standard parameters. To improve service quality, the transition from analog to digital should be accelerated in Nigeria such that most stations transmit via the standard Digital method of transmission.

Reduction of the received signal strength variation with distance using averaging over multiple heights and frequencies

As a simple and inexpensive channel characteristic, received signal strength (RSS) finds extensive usage in localization applications. However, the quick changes in signal strength impact the localization precision. By averaging over access points (APs) with multiple frequencies and/or heights, this article suggests a novel approach to lowering RSS fluctuation. Initially focused on the plane-earth loss model, the study was later extended to include a multipath indoor propagation scenario that was simulated. We used ray-tracing software to model the indoor propagation situation. This research takes into account the results of three distinct methods for averaging RSS: height averaging, frequency averaging, and hybrid frequency and height (FH) averaging, which combines the two. We discovered that the Height-only strategy considerably decreased the RSS variation with distance for both settings we looked at. Using the frequency-only method even further reduced the variation. Using the Hybrid FH technique greatly enhances the results. Root mean square error values of 4.427 dB, 3.70 dB, and 3.5 dB, respectively, are provided for the averaging approaches and the ideal scenario in which no variance occurs. Another finding is that averaging with APs that have double the height or frequency will not improve the RSS distance variation.

Electrochemiluminescent assay based on Co-MOF and TiO2 for determination of bisphenol A.

An electrochemiluminescence (ECL) sensor for determining bisphenol A (BPA) was prepared based on titanium dioxide (TiO2) and Co-MOF. TiO2 is a co-reaction promoter that amplifies the ECL signal in the Ru(bpy)32+-trinpropylamine (TPrA) system. When the electrode is modified with Co-MOF the ECL signal is significantly enhanced. This is because Co-MOF can not only be used as a co-reaction accelerator but also as a carrier to adsorb more luminescent substances. Possible mechanisms for amplifying the original signal through the synergistic action of the two substances are investigated. The ECL strength decreases with increasing concentrations of BPA, and the amount of BPA can be determined by the change in ECL signal strength (ΔI). Under optimal experimental conditions, the linear range of BPA was 2.0 × 10-10 to 2.0 × 10-5M, with a determination limit of 6.7 × 10-11M (3σ/m). The relative standard deviation (RSD) of the signal for ten consecutive measurements was 1.5%. The sensor can be used to detect BPA in bottled samples with recoveries of 96 to 105%.

A Study on the Correction Methods according to Change in Signal Strength due to Human Body Influence of the Wireless Communication-Based User Following Module

A Study on the Correction Methods according to Change in Signal Strength due to Human Body Influence of the Wireless Communication-Based User Following Module

LEO navigation augmentation constellation design and precise point positioning performance analysis based on BDS-3

Low Earth orbit (LEO) satellites have high signal strength and faster geometry changes over short periods, offering unique advantages in navigation augmentation. Integrating LEO satellites into the navigation system can help augment the performance of the global satellite navigation system and break the dilemma of the existing navigation system with limited services in challenging environments. Constellation design is the key before establishing a complete LEO navigation augmentation platform. Therefore, in this study, two LEO navigation augmentation constellations, Polar/Walker (S1) and Walker/Walker (S2) with different inclinations, are designed and optimized using the non-dominated sorting genetic algorithm III (NSGA-III). The global average geometric dilution of precision (GDOP) of BDS-3 is reduced from 1.56 to 0.92 and 0.95, and the average visible satellite number is improved from 11.74 to 27.83 and 25.72 with the navigation augmentation of the optimized constellations. To further validate the navigation augmentation effect of two LEO constellations on BDS-3 precision point positioning (PPP), nine stations at different latitudes were selected for LEO augmented BDS-3 PPP simulation experiments. The results show that after adding S1 and S2 constellations to BDS-3, respectively, the convergence times of the nine stations are reduced by 35.5%∼96.5% and 43.7%∼96.2%, and the positioning accuracy is improved by 5.7%∼71.9% and 24.2%∼69.5%, respectively. Overall, each S1 and S2 constellations can significantly improve the global service performance and PPP performance of BDS-3.

Continuous ground monitoring of vegetation optical depth and water content with GPS signals

Abstract. Satellite microwave remote sensing techniques can be used to monitor vegetation optical depth (VOD), a metric which is directly linked to vegetation biomass and water content. However, these large-scale measurements are still difficult to reference against either rare or not directly comparable field observations. So far, in situ estimates of canopy biomass or water status often rely on infrequent and time-consuming destructive samples, which are not necessarily representative of the canopy scale. Here, we present a simple technique based on Global Navigation Satellite Systems (GNSS) with the potential to bridge this persisting scale gap. Because GNSS microwave signals are attenuated and scattered by vegetation and liquid water, placing a GNSS sensor under a vegetated canopy and measuring changes in signal strength over time can provide continuous information about VOD and thus on vegetation biomass and water content. We test this technique at a forested site in southern California for a period of 8 months. We show that variations in GNSS signal-to-noise ratios reflect the overall distribution of biomass density in the canopy and can be monitored continuously. For the first time, we show that this technique can resolve diurnal variations in VOD and canopy water content at hourly to sub-hourly time steps. Using a model of canopy transmissivity to assess these diurnal signals, we find that temperature effects on the vegetation dielectric constant, and thus on VOD, may be non-negligible at the diurnal scale or during extreme events like heat waves. Sensitivity to rainfall and dew deposition events also suggests that canopy water interception can be monitored with this approach. The technique presented here has the potential to resolve two important knowledge gaps, namely the lack of ground truth observations for satellite-based VOD and the need for a reliable proxy to extrapolate isolated and labor-intensive in situ measurements of biomass, canopy water content, or leaf water potential. We provide recommendations for deploying such off-the-shelf and easy-to-use systems at existing ecohydrological monitoring networks such as FluxNet or SapfluxNet.

High‐Resolution Magnetic‐Geochemical Mapping of the Serpentinized and Carbonated Atlin Ophiolite, British Columbia: Toward Establishing Magnetometry as a Monitoring Tool for In Situ Mineral Carbonation

AbstractWe address in situ serpentinization and mineral carbonation processes in oceanic lithosphere using integrated field magnetic measurements, rock magnetic analyses, superconducting quantum interference device (SQUID) microscopy, microtextural observations, and energy dispersive spectroscopy phase mapping. A representative suite of ultramafic rock samples were collected, within the Atlin ophiolite, along a 100‐m long transect across a continuous outcrop of mantle harzburgite with several alteration fronts: serpentinite, soapstone (magnesite + talc), and listvenite (magnesite + quartz). Strong correlations between changes in magnetic signal strengths and amount of alteration are shown with distinctive contrasts between serpentinite, transitional soapstone, and listvenite that are linked to the formation and breakdown of magnetite. While previous observations of the Linnajavri ultramafic complex indicated that the breakdown of magnetite occurred during listvenite formation from the precursor soapstone (Tominaga et al., 2017, https://doi.org/10.1038/s41467-017-01610-4), results from our study suggest that magnetite destabilization already occurred during the replacement of serpentinite by soapstone (i.e., at lower fluid CO2 concentrations). This difference is attributed to fracture‐controlled flow of sulfur‐bearing alteration fluid at Atlin, causing reductive magnetite dissolution in thin soapstone zones separating serpentinite from sulfide‐mineralized listvenite. We argue that magnetite growth or breakdown in soapstone provides insight into the mode of fluid flow and the composition, which control the scale and extent of carbonation. This conclusion enables us to use magnetometry as a viable tool for monitoring the reaction progress from serpentinite to carbonate‐bearing assemblages in space and time with a caution that the three‐dimensionality of magnetic sources impacts the scalability of measurements.

Vehicle-to-vehicle communication channel measurements on a vertical curve road

Vehicle-to-Vehicle (V2V) communication channel measurements were carried out in different environments such as urban, suburban, rural, highway, tunnel, and overpass. The roads in these environments have generally flat terrain. However, there are horizontal or vertical curve roads that have been little focused in the literature. In this study, we performed two V2V measurements on a vertical-curve road in a rural environment to show how received signal strength changes with the distance between the transmitter and the receiver. The path loss exponent of log-distance path loss model was calculated by using the least-square method. According to the results, the path loss exponents were estimated as 7.53 and 7.61 with 78% and 83% fitting performances for two measurements. In literature, however, the path loss exponent for different propagation environments was obtained up to 6.13, especially in the straight road. Thus, our findings show that the vertical curve roads cause 15-20 dB more attenuation in the received signal strength than the straight roads. As a result, the vertical curve roads should be investigated and included in existing wireless communication simulators to better model real measurements. The authors contend that this study will aid in improving the channel modeling of V2V communication.

Research on Beidou Navigation Interference Monitoring Technology Based on CFAR

Satellite monitoring stations are often affected by strong clutter and interference when monitoring targets. When ground receivers receive target signals, they also receive noise, clutter, and interference signals. These signals have randomness and signal strength changes from time to time. Therefore, constant false alarm detection technology is used to detect interference signals. CFAR detectors construct different system functions in different clutter environments and maintain a constant false alarm rate by adaptively modifying the detection threshold. A comparison of CFAR algorithms shows that CA_ The CFAR algorithm has excellent monitoring performance in uniform environments_ CFAR is suitable for multi target environments, GO_ CFAR performs well in clutter edge environments, SO_ CFAR performs well under various conditions.

Analyzing Wireless Mesh Network Using Spectral Graph Theory

Wireless mesh networks (WMNs) are a type of wireless network that can be used for various applications, such as Internet access, disaster response, and military communication. These networks consist of mesh routers that can communicate with each other and form a mesh topology, allowing them to provide connectivity even if some of the routers fail or are out of range. In this study, we used spectral graph theory to analyze the performance of a WMN. For the analysis process, software was developed to calculate the topological characteristics of the graph representing the WMN. The correlation between the values of the parameters of spectral graph theory and the topological characteristics of the observed network is analyzed. First, an analysis of the influence of the change in signal strength, in the observed WMN, on the algebraic connectivity was performed, and then the change in the spectral radius was also analyzed. The analysis was performed using special software, which was developed for that purpose.

Target “turn on” electrochemical pseudocapacitive sensor for ultrasensitive detection of microRNA-141

In this study, an ultrasensitive electrochemical-detection system based on a target “turn-on” signal-enhancement pseudocapacitor was established for microRNA-141 (miRNA-141) detection. A three-dimensional porous film was constructed on the electrode surface in situ by chitosan, catechol and nanomaterials (gold nanoparticles and nitrogen-doped carbon nanotubes). When miRNA-141 hybridized with the probe on the electrode, ferrocene (Fc) was specifically introduced into the electrode surface, and then a pseudocapacitor containing Fc, ruthenium ion (Ru3+), catechol, and electrode formed (“turn on”). Fc and Ru3+ consumed in the electrode reaction can quickly recover to the original valence state on the surface of catechol/quinone and again participated in the electrode reaction. A "one to many" relationship existed between the target and the signal molecule Fc, which contributed to the improvement of the sensor sensitivity. The signal strength and stability of Fc improved and thus improved the sensitivity and stability of miRNA-141 detection. The concentration information of miRNA-141 was collected from the change in Fc signal strength. The linear detection range was 0.5 fM to 800 pM, and the detection limit can be calculated as 43.73 aM. This system overcame the problems of low reliability and weak signal of the traditional electroactive-ion labeling method, which relied on the change in electrostatic attraction/repulsion before and after probe–target hybridization.

Cell maximum life cycle based reliability analysis method for wireless mobile networks

The nodes of wireless mobile networks have mobility, which leads to the change of network topology and signal strength. Connectivity, a classical reliability index, calculated by existing methods based on graph theory often needs to find out all paths in fixed topology, which inevitably have combination explosion problems. With the changes of topological structure over time, a heavier calculation amount arises when the reliability of wireless mobile networks is calculated by existing methods to characterize the whole network as components of nodes and edges at every moment of a working phase. To solve the above problem, a new type of reliability analysis index for wireless mobile networks – the maximum life cycle of network cells, and its assessment model and algorithm are proposed, based on the concept of network cells and considered the network cells as components of wireless mobile networks. Through network cells, the reliability can be represented by cell maximum life cycle when it is relevant to the reliability of the whole network, and the focus is narrowed from whole network to the local part. Finally, the analysis and verification of a UAV(unmanned aerial vehicle) group network show that the proposed index has greatly improved the algorithm efficiency compared with the existing reliability analysis index.

Multi-wavelength pyrometry as an in situ diagnostic tool in metal additive manufacturing: Detecting sintering and liquid phase transitions in electron beam powder bed fusion

Radiation thermometry techniques have been implemented to measure thermal signatures in powder bed fusion (PBF) additive manufacturing (AM), including the use of imaging devices with a large field of view, to measure large areas of the powder bed with spatial discrimination, and those considered single spot devices that measure signatures from a small region. Traditionally, these techniques can be categorized as single-color (brightness) or two-color (ratio) pyrometry; imaging devices are single-color while spot devices can be either. Both techniques can be used to infer a target temperature using a priori knowledge of the emissivity or employing the graybody assumption of constant emissivity across the spectrum. However, the dynamics of PBF AM, where a concentrated heat source is employed to selectively melt powder material, lead to complex material phase transitions under non-equilibrium solidification conditions. This makes it challenging to measure accurate thermal signatures because the emissivity of the target is also constantly varying as the PBF process unfolds. In this work, we employed an established technique of multi-wavelength pyrometry in an electron beam powder bed fusion (PBF-EB) system to continuously measure temperatures and the thermal emissive behavior during sintering and melting of an Inconel 625 powder that was subjected to preheating by direct scanning with the electron beam. The measurements displayed distinctive changes in signal strength or emissivity (in the wavelength range between 1080 nm and 1640 nm) that indicated the material phase change from loose to sintered powder to molten material and finally to solidified material; these changes in signal strength/emissivity were correlated with electron microscopy observations. This work highlights the suitability of multi-wavelength (MW) pyrometry as an in situ diagnostic tool to identify thermal process signatures (i.e., absolute temperatures), and the radiative emissive behavior of the materials being processed. Several demonstrations of the use of this MW pyrometry technique as a diagnostic tool are provided, illustrating its ability to sense signal strength/emissivity differences as the material experiences changes due to its temperature, phase, morphology, and chemistry. Although spatial and temporal improvements in the technique can be pursued, the sensitivity of the approach is demonstrated, as an example, in the ability to capture the passing thermal wavefronts arising from the scanning electron beam. It is anticipated that this technique and the information it provides can be leveraged in the development of advanced techniques for thermal monitoring and process control in PBF.

Flexible Ring Sensor Array and Machine Learning Model for the Early Blood Leakage Detection during Dialysis

Severe blood leakage resulting from the detachment of dialysis tubing is often difficult to detect by nurses in busy clinics. This paper presents a flexible blood leakage detection system featuring a ring-light sensor array with an operating wavelength of 500–700 nm, which is held in place by the gauze covering the dialysis puncture site. A ring-light sensor is connected to a bidirectional hetero-associative memory network, which interprets detected changes in signal strength, the output signal of which is transmitted via WiFi to a server at the nursing station where a machine learning algorithm determines whether blood leakage has occurred. The compact design of this early warning system greatly enhances the comfort and mobility of patients undergoing dialysis. The efficacy of the proposed system was demonstrated in experiments involving artificial blood.

Loudness effect on pitch and timbre discrimination; a continuing study

Fine discrimination in pitch and timbre is a requisite skill for musicians and audio professionals. While several trade organizations have standardized electronic-acoustic calibration levels for equipment testing and operations, conflicting and often unfounded perceptual theories along with a lack of psychophysical evidence make it difficult to pinpoint the optimal presentation level for best pitch and timbre discrimination. Results from our previous study (Bulla & Chon, FDMC, 2021) revealed higher scores for lower listening levels in conditional 2-AFC pitch and timbre discrimination tasks (15 vs 83 dBA SPL). While outcomes there indicated a consistent negative influence of the larger signal strength on the accuracy of both pitch and timbre discrimination performance, this continuing study examined changes of signal strength in order to establish whether or not observations here may apply across a variety of listening levels. Data collection is ongoing and will provide insight through observed performance metrics and help determine if there is an optimal loudness range for engaging in listening tasks such as identifying differences of pitch, discriminating fine details in timbre, or the blending and balancing of musical instruments.

Age-related changes of deep-brain neurophysiological activity.

Cognitive decline with age is associated with brain atrophy and reduced brain activations, but the underlying neurophysiological mechanisms are unclear, especially in deeper brain structures primarily affected by healthy aging or neurodegenerative processes. Here, we characterize time-resolved, resting-state magnetoencephalography activity of the hippocampus and subcortical brain regions in a large cohort of healthy young (20-30years) and older (70-80years) volunteers from the Cam-CAN (Cambridge Centre for Ageing and Neuroscience) open repository. The data show age-related changes in both rhythmic and arrhythmic signal strength in multiple deeper brain regions, including the hippocampus, striatum, and thalamus. We observe a slowing of neural activity across deeper brain regions, with increased delta and reduced gamma activity, which echoes previous reports of cortical slowing. We also report reduced occipito-parietal alpha peak associated with increased theta-band activity in the hippocampus, an effect that may reflect compensatory processes as theta activity, and slope of arrhythmic activity were more strongly expressed when short-term memory performances were preserved. Overall, this study advances the understanding of the biological nature of inter-individual variability in aging. The data provide new insight into how hippocampus and subcortical neurophysiological activity evolve with biological age, and highlight frequency-specific effects associated with cognitive decline versus cognitive maintenance.

A comparison of activity data generated from cardiovascular telemetry studies - With quantitative open field locomotor studies in Wistar Han rats

Compound-mediated locomotion changes, conducted via open field infrared photobeam breaks, are an important common component of neurological assessments conducted in safety pharmacology studies. In addition to open field locomotor activity assessments, activity data (derived from changes in signal strength) from cardiovascular (CV) telemetry studies can also be an alternative method potentially used to assess locomotor effects. However, comparisons of these two methods have not been extensively characterized. The goal of this work was to compare these two methodologies to assess activity in rats using reference compounds known to have central nervous system (CNS)-stimulant (preladenant) or CNS-depressant (chlorpromazine) effects. Open field activity was conducted using the Kinder Scientific Motor Monitor system and data were collected for 30 min at each drug's expected time of maximum plasma exposure (Tmax). Telemetry-based CV assessment data were continuously acquired using DSI radiotelemetry instrumented animals for 24 h postdose (HPD). Drugs were administered during the lights-on period for both study types. Administration of preladenant caused increases in activity within 0.5–2 HPD for both methods. While administration of chlorpromazine caused decreases in activity in the infrared beam-based open field assessment (1.0–1.5 HPD), there was no effect on telemetry-derived activity during a similar time period. However, telemetry-derived decreases in activity were observed during the lights-off period (16–20 HPD), suggesting CNS-depressant compounds may be mischaracterized if the optimal dose administration time is not selected based on the light/dark cycle and pharmacokinetics. Overall, these results suggest that telemetry-based activity assessment is capable of detecting CNS-stimulant effects of compounds.

Prediction method of multi-frequency non-intermodulation electromagnetic radiation blocking effect of BeiDou navigation receiver

In the test of the electromagnetic radiation blocking effect of the navigation receiver, it is found that the sensitivity of the navigation receiver to single frequency continuous waves and sinusoidal amplitude modulation waves will change with the change in the satellite useful signal strength. This phenomenon reflects that the sensitivity of frequency equipment to multi-frequency electromagnetic radiation is not fixed to a certain extent. In order to make up for the deficiency that the existing multi-frequency electromagnetic radiation evaluation methods can only deal with a single situation, this paper uses the time delay characteristics of the circuit response, introduces the concepts of normalized interference levels and signal duty cycles, establishes the evaluation model of the multi-frequency non-intermodulation electromagnetic radiation blocking effect of frequency equipment, and puts forward the prediction method of the multi-frequency electromagnetic radiation blocking effect of frequency equipment. Taking a certain type of BeiDou navigation receiver as the test object, the single-frequency continuous wave and double-frequency continuous wave electromagnetic radiation blocking effect tests are carried out by using the full-level irradiation method. The test data are substituted into the model established in this paper for verification. The results show that the maximum evaluation error of the model is 2.23 dB. The model and the effect prediction method established in this paper are of great significance for the survival ability evaluation of frequency equipment in complex electromagnetic environments.

Dynamic Changes in Begging Signal Short-Term Information on Hunger and Need.

AbstractDynamic signals can convey distinct information to a receiver on different timescales, making assessment of how quickly signal strength changes important for understanding signal function. Here, we combine repeated measures of offspring begging behavior of western bluebirds with assessments of fitness as well as quantitative genetic analyses of cross-fostered offspring to investigate whether variation in begging behavior conveys information about hunger, need, or quality or has no signaling function. Begging intensity increased with food deprivation, supporting the signal-of-hunger hypothesis. However, after controlling for this variation, multiple lines of evidence showed that begging also signaled need but not quality. Specifically, begging intensity was repeatable only on short timescales, and nestlings that begged more intensely were in poorer condition. Moreover, variation in mean begging intensity was not strongly related to measures of fitness. In general, we found that begging behavior is a highly flexible trait that appears to be unconstrained by both genetic and early developmental influences, as indicated by the cross-fostering experiment that confirmed that the nest environment, not genetic relatedness, explained variation in begging behavior. Together, these results support the idea that begging dynamically signals shorter-term information: hunger and need. More generally, they show the importance of assessing the timescale of signal change to understand its function.