Narrowband Wireless Research Articles

Dispersion effects in ionospheric radio channels Part 2. Types of time-frequency dispersion

In recent years, significant advancements have been made in technologies that enable reliable communication through wideband HF radio channels with bandwidths ranging from 3 to 48 kHz and adjacent channel steps of 3 kHz, achieving data transfer rates of up to 120 kbit/s. To support this, both software-defined radio (SDR) and cognitive radio (CR) technologies are now being implemented. However, a key challenge in ionospheric HF radio communication is the variability of its operating frequency range and the impact of factors such as intermode time-frequency dispersion and narrowband man-made interference, which negatively affect both narrowband (3 kHz) and wideband systems operating in composite narrowband subchannels. This paper examines the main types of time-frequency dispersion in single-mode dual-ray narrowband radio channels, as well as in single-mode and multiple-mode channels with diffuse multipath propagation. These are considered in the context of selecting a modem that ensures at least 80% availability, as well as modeling wave packet propagation through the ionosphere. Methods and techniques to mitigate these negative effects are discussed. The aim of the research was to analyze the negative effects of intermode time-frequency dispersion on HF communication systems and to explore methods and strategies for overcoming these challenges. The paper provides a scientific rationale for addressing the issue of ensuring that communication systems have data on the availability of channels affected by intermode time-frequency dispersion and man-made interference. The signal-to-noise ratio (SNR) was identified as the critical parameter that fluctuates most rapidly over geophysical time. Additionally, the paper presents an effective solution for channel diagnostics using active sensors in the 2–30 MHz range, employing SDR technology. Methods for diagnosing multiple channels and selecting those with at least 80% availability for a given modem are discussed. The paper proposes an approach and methods for mitigating the negative effects of intermode time-frequency dispersion and man-made interference through sensor diagnostics technology. It demonstrates the feasibility of adaptively selecting optimal channels from those tested, providing data on the required communication signal power and data transfer rates to enhance the overall efficiency of the communication system. Experimental results showed that the sensor diagnostics approach can yield a radiated power gain of 4–12 dB on mid-latitude paths and 5–6 dB on polar paths for a given modem or constant data rate. Furthermore, selecting channels with at least 80% availability for the modem with the highest possible data rate can increase throughput by up to 2 times during the day and night, and by 4–8 times during transition periods.

Quasi-likelihood estimation of the arrival time of an ultra-wideband quasi-radio signal with unknown amplitude and initial phase

The problem of estimating the time of arrival of a signal is relevant in the fields of radio and hydrolocation, radio astronomy, remote observation and sensing, etc. The useful signal is often described by a quasi-deterministic function of time, which can be regular or discontinuous. In recent years, problems of processing ultra-wideband signals have been of significant interest. Among the many UWB signals, it is customary to distinguish a separate class of ultra-wideband quasi-radio signals, the structure of which is similar to the structure of narrowband radio signals, but the condition of relative narrowband for which may not be met. Algorithms for estimating the arrival time of regular ultra-wideband quasi-radio signals have been studied in the existing literature. In this case, the synthesis and analysis of an algorithm for quasi-plausible estimation of the arrival time of a discontinuous signal of finite duration and arbitrary shape is of practical interest. The purpose of the work is to synthesize and analyze a quasi-likelihood algorithm for estimating the time of arrival of a discontinuous ultra-wideband quasi-radio signal with an unknown amplitude and initial phase against a background of white Gaussian noise. In this work, closed asymptotically exact expressions for the bias and scattering of the estimate are obtained, which make it possible to study the effectiveness of the synthesized algorithm, as well as compare its effectiveness with special cases of signal models - narrowband and wideband radio and video signals. The results of the study make it possible to determine losses in the accuracy of estimation the signal arrival time due to a priori ignorance of the initial phase and shape of the modulating function of the signal. Depending on the required accuracy of estimate the time of arrival of an ultra-wideband quasi-radio signal, it is possible to optimize the parameters of the transmitted signals and determine the limits of applicability of the designed radio system.

Design of Novel Filtenna for Wireless Applications

In this paper, a novel design based on a dual-mode ring resonator, the filtering balun, feeding the printed dipole antenna, the filter balun antenna (FBA), is presented. One port on the structure allows the signals to be phase-shifted 180 degrees from one unbalanced port to two balanced signals. The suggested designs use a single dual-mode ring resonator to operate as both a filter and a balun at the same time. Compact designs are achieved by applying feeding to the second layer. Another unique characteristic of the filtering balun is its ability to alter, based on perturbation size, the phase error and magnitude imbalance of the two balanced signals. With the use of the Advanced Design System (ADS) software, numerous structures have been developed, modeled, and evaluated. To achieve the highest performance, every section of the design is assessed and optimized. Because the substrate is a lossy type (FR4), the realized transmission coefficients, which are poorer than expected ideal values, make the suggested design a strong contender for narrow-band wireless applications. For S2,1 and S3,1, the signal is routed through two viasand fed into a dipole antenna in the opposite phase by employing the zero iteration for filtering the balun in the first layer to condense with the second layers. The antenna structure is a printed dipole antenna operating at 2.4 GHz

Design of Miniaturized Microwave Filtering-Balun Component for Wireless Applications

This research paper introduces a new design being Minkowski-like fractal filtering-balun MLFFB based on the dual-mode ring resonator. The structure has three ports, converting the signal from one unbalanced port to two balanced ports (i.e., 180° phase shift). The proposed design can act as a filter and balun simultaneously using one dual-mode ring resonator. The fractal curves are applied to have compact designs. The 0th, 1st, and 2nd iterations of the Minkowski-like fractal curves are applied to demonstrate the miniaturization ratio obtained in the proposed work. The miniaturization ratios are 47.8% and 73% of the 1st iteration and 2nd iteration of the Minkowski balun-filtering components, respectively, compared to the 0th iteration. Also, the filtering balun has a distinctive feature, which is the control of the phase error and magnitude imbalance of the two balanced ports, depending on the size of the perturbation part. Several structures have been designed, modeled, and analyzed utilizing the Advanced Design System (ADS) software. Each design iteration is evaluated and optimized to attain the best performance. The operating frequency is 2.4 GHz, and the realized transmission coefficients are S21 = -7 dB and S31 = -6.5 dB, which are less than expected ideal values because the substrate is a lossy type, being FR4. The S11 is less than -10 dB. The proposed design is a good candidate for narrow-band wireless applications.

A Solution to Continuous RFI in Narrowband Radio SETI with FAST: The MultiBeam Point-source Scanning Strategy

Narrowband radio search for extraterrestrial intelligence (SETI) in the 21st century suffers severely from radio frequency interference (RFI), resulting in a high number of false positives, and it could be the major reason why we have not yet received any messages from space. We thereby propose a novel observation strategy, called MultiBeam Point-source Scanning (MBPS), to revolutionize the way RFI is identified in narrowband radio SETI and provide a prominent solution to the current situation. The MBPS strategy is a simple yet powerful method that sequentially scans over the target star with different beams of a telescope, creating real-time references in the time domain for cross-verification and thus potentially identifying all continuous RFI with a level of certainty never achieved in any previous attempts. By applying the MBPS strategy during the observation of TRAPPIST-1 with the Five-hundred-meter Aperture Spherical radio Telescope, we successfully identified all 6972 received signals as RFI using the solid criteria introduced by the MBPS strategy. Therefore, we present the MBPS strategy as a promising tool that should bring us much closer to the first discovery of a genuine galactic greeting.

Phase-Based Ranging in Narrowband Systems With Missing/Interfered Tones

The growth in the number of low-cost narrow band radios such as Bluetooth low energy (BLE) enabled applications such as asset tracking, human behavior monitoring, and keyless entry. The accurate range estimation is a must in such applications. Phase-based ranging has recently gained momentum due to its high accuracy in multipath environment compared to traditional schemes such as ranging based on received signal strength. The phase-based ranging requires tone exchange on multiple frequencies on a uniformly sampled frequency grid. Such tone exchange may not be possible due to some missing tones, e.g., reserved advertisement channels. Furthermore, the IQ values at a given tone may be distorted by interference. In this paper, we proposed two phase-based ranging schemes which deal with the missing/interfered tones. We compare the performance and complexity of the proposed schemes using simulations, complexity analysis and measurement setups. In particular, we show that for small number of missing/interfered tones, the proposed system based on employing a trained neural network (NN) performs very close to a reference ranging system where there is no missing/interference tones. Interestingly, this high performance is at the cost of negligible additional computational complexity and up to 60.5 Kbytes of additional required memory compared to the reference system, making it an attractive solution for ranging using hardware-limited radios such as BLE.

Relating GPR system parameters to regulatory emissions limits

AbstractGround penetrating radar (GPR) is regulated regarding emission limits for ultra‐wideband in a number of jurisdictions. The definitions of these regulations employ concepts and terminology that are more suited to traditional narrow band radio transmitters. Further, the emissions limits were based on limited quantitative factual information and have resulted in stringent limitations on GPR technology advancement. Factual theoretical and experimental information on the emissions from actual GPR devices is not generally available, and the relationship with regulatory requirements is poorly understood by users. This information gap must be filled if a compelling argument for less stringent emissions levels is to be mounted in the future. Moreover, the current regulations have the potential to trigger further review of emission limits in the future which could be detrimental to the use of GPR. In this paper, we present the basic steps entailed in translating impulse time‐domain GPR instrument behaviour into ‘regulatory’ parameters. To achieve this, we also employ three‐dimensional finite‐difference time‐domain numerical modelling to simulate the transient electromagnetic field variation around dipole antennas placed on the surface of a half‐space or at a height over it to illustrate the dependency on sensor height and ground permittivity. The ultimate goal is to establish the foundation for more sensible rule making, if and when, the regulatory standards come under scrutiny for revision and further user understanding.

Квазиправдоподобный алгоритм оценки частоты сверхширокополосного квазирадиосигнала с неизвестной длительностью

The quasi-likelihood frequency estimation algorithm of an ultra-wideband quasi-radio signal with an unknown duration, observed with white Gaussian noise, is studied. When synthesizing the frequency estimation algorithm, instead of an unknown duration, some of its expected value was used. The dependence of the variance of the frequency estimate of an ultra-wideband quasi-radio signal on the signal-to-noise ratio for various values of the duration detuning and the dependence of the frequency estimate bias on the duration detuning for various values of the narrowband parameter are obtained. It has been established that the duration detuning has a significant effect on the efficiency of frequency estimation of an ultra-wideband quasi-radio signal, while at large values of the narrowband parameter, the obtained expressions coincide with the known expressions for the variance and bias of the frequency estimate of narrowband radio signal. Recommendations on the use of the synthesized algorithm in practical applications are formulated.

Self-Organized Low-Power Multihop Failover Protocol for a Cellular-Based Public Safety Device Network

This study proposes a network failover protocol for public safety devices, such as fire alarms and gas leak detectors using a cellular (i.e., 5G and LTE) Internet of Things (IoT) network, and evaluates its performance through experiments. The proposed protocol recovers communication functions by establishing a detour route through the secondary network (i.e., 447-MHz narrowband wireless network) when a problem occurs in the primary network (i.e., cellular network) in a disaster situation. All operations of the proposed protocol are performed autonomously by self-organization and collaboration of distributed nodes without centralized control. Thus, the communication function is maintained until all physically configurable routes are cut without any network reconfiguration process, even under adverse conditions, where nodes and communication paths status frequently change in real time due to a disaster. In addition, this failover protocol reduces power consumption by activating the secondary network only at the moment when network failover is necessary by using the novel self-organized low-power multihop relay wake-up scheme proposed in this study. Therefore, the proposed protocol can be easily applied to IoT devices that are often operated only by batteries. The proposed protocol also has the advantage of immediate use without any modification of the current cellular IoT network.

ILLOC

LoRaWAN is a narrowband wireless technology for ubiquitous connectivity. For various applications, it is desirable to localize LoRaWAN devices based on their uplink frames that convey application data. This localization service operates in an unobtrusive manner, in that it requires no special software instrumentation to the LoRaWAN devices. This paper investigates the feasibility of unobtrusive localization for LoRaWAN devices in hall-size indoor spaces like warehouses, airport terminals, sports centers, museum halls, etc. We study the TDoA-based approach, which needs to address two challenges of poor timing performance of LoRaWAN narrowband signal and nanosecond-level clock synchronization among anchors. We propose the ILLOC system featuring two LoRaWAN-specific techniques: (1) the cross-correlation among the differential phase sequences received by two anchors to estimate TDoA and (2) the just-in-time synchronization enabled by a specially deployed LoRaWAN end device providing time reference upon detecting a target device's transmission. In a long tunnel corridor, a 70 x 32 m2 sports hall, and a 110 x 70 m2 indoor plaza with extensive non-line-of-sight propagation paths, ILLOC achieves median localization errors of 6 m (with 2 anchors), 8.36 m (with 6 anchors), and 15.16 m (with 6 anchors and frame fusion), respectively. The achieved accuracy makes ILLOC useful for applications including zone-level asset tracking, misplacement detection, airport trolley management, and cybersecurity enforcement like detecting impersonation attacks launched by remote radios.

Narrow-Band Radio Propagation Prediction Based on a Highly Accurate Three-Dimensional Railway Environment Model

In this paper, radio propagation predictions were performed by a self-developed ray tracing simulator based on highly accurate three-dimensional (3D) environment models obtained by oblique aerial photography (OAP). In order to support ray tracing computations, the highly complex environment models were managed by three steps, including model separation, electromagnetic parameter assignment, and model lightweighting. Simulations and real-world experiments were conducted to test the proposed method. The results show that the root mean square errors (RMSE) in the predicted received signal strength curves were achieved 4 dB with comparably low computational complexity in the selected railway scenarios.

A Network Communication Frequency Routing Protocol of Coal Mine Safety Monitoring System Based on Wireless Narrowband Data Communication Network

In recent years, the coal industry has been expanding the scale and output of coal mining in China, yet the safety in production is faced with great challenge. Communication system in coal mines plays a significant role in production safety, and wireless narrowband data communication network technology is a new-type advantageous measure to construct wireless network security monitoring system for coal mining. Here, a coal mine monitoring signal transmission method based on bus technology and wireless data transmission technology suitable for coal mines is proposed. The corresponding monitoring system is designed, and the system is able to collect the gas concentration and mechanical operation status of the mines. Wireless sensor network nodes are used for the RF communication module. The communication performance of this system in coal and rock medium and the roadway along the goaf is simulated, and the quantitative relationship between the attenuation coefficient of different communication frequencies and the effective communication distance is obtained. Hence, the results show that the protocol has good performance in terms of route establishment, maintenance, and data transmission hop count for the positioning of coal mine employees.

No Redetections of blc1 in 39 hr of Reobservation Campaigns of Proxima Centauri

Abstract In 2019 April, radio observations of Proxima Centauri were performed with the Ultra-Wideband Low Receiver on the Parkes Telescope. A narrowband radio search of these data revealed a technosignature signal-of-interest reported as “blc1” at 982.002 MHz. After the initial discovery of blc1 in the data in 2020 October, we performed a series of reobservations over the next 6 months, totaling 39 hr of on-sky time. We do not redetect blc1, or find any other signals-of-interest, within ±1 MHz of 982.002 MHz in this data set. Taken in context, this null result implies that blc1 was transient radio frequency interference, makes it less consistent with a periodic transmission, and makes it less consistent with interstellar scintillation.

A low‐profile planar monopole antenna for ISM/IMT/Bluetooth/Zigbee/WiFi/WiMAX/WLAN wireless communication applications

SummaryRecently, there is a significant rise in the numbers of devices and systems that use industrial, scientific, and medical (ISM) frequency bands. The ISM band is not only used in ISM applications but also in telecommunication services including IMT, Zigbee, Bluetooth, WiFi, WiMAX, WLAN, RFID, military radars, and wireless sensor networks. To cover all these applications, in this paper, a low‐profile planar monopole antenna is suggested for 2.45‐GHz band communication applications. The anticipated antenna is composed of a vertical bar‐shaped radiator and a partial ground plane with two vertical slits. The inclusion of vertical slits in the ground plane forms a matching circuit by enlarging the current path, and hence, the studied design can achieve a measured operating band of 2.2 to 2.95 GHz. Moreover, the studied antenna achieved a maximum peak gain of 2.77 dBi and a maximum radiation efficiency of 82.45% and exhibited an omnidirectional radiation pattern that makes it appropriate for ISM and different narrowband wireless applications.

ВИМІРЮВАННЯ ОПОРНОЇ ЧАСТОТИ ВУЗЬКОСМУГОВОГО РАДІОСИГНАЛУ ОБМЕЖЕНОЇ ТРИВАЛОСТІ

The work concerns analog-digital systems that work with radio signals emitted and received by the antenna, and these signals have a limited duration, ie are pulsed. The propagation conditions of such signals and the processes of formation of echo signals affect their amplitude, frequency and phase characteristics in such a way that they form classical narrowband signals. The operation of the system involves the determination of certain parameters of echo signals, and taking into account their pulse nature for such a definition is given a limited time interval. This means that the procedure for determining the parameters must meet the criterion of high speed, and therefore differ from the traditional, built on the use of phase-locked loop. The article is devoted to solving the problem of measuring the reference frequency of a pulsed narrowband radio signal. By analyzing the results of experimental studies, two types of errors in measuring the reference frequency of a narrowband radio signal were identified and the causes of their occurrence were established. These errors are provoked by the peculiarities of the structure of the narrowband signal. The reason for the error of the 1st type, the absolute value of which correlates with the duration of the half-cycle of the reference frequency, is the so-called phase jumps at the point of change of the sign of the bypass. The frequency of such errors within the duration of the echo signal is generally low, although it increases with increasing signal spectrum width. Type 2 errors occur due to the appearance of zones with almost completely suppressed signal amplitude, which may be the result of intrapulse interference and / or signal attenuation. Such errors also occur more often if the spectrum width is larger. A method for measuring the reference frequency of a narrowband pulsed radio signal is proposed, which is based on counting the number of half-cycles of the reference frequency on a time-limited measurement interval and removing from this procedure areas with completely suppressed signal amplitude. An auxiliary highly stable reference frequency is used to establish the numerical value of the reference frequency. The block diagram of the frequency meter and the algorithm of its operation are given, the implementation of which avoids these errors.

High-precision time delay estimation of narrowband radio signal by PHAT-LSTM

In this article, a novel method for high-precision time-delay estimation (TDE) of narrow-band signals is proposed. It is based on a cross-correlation function, phase spectrum, long short-term memory (LSTM) artificial neural network to unwrap the phase transform (PHAT) spectrum of the cross-correlation function. The PHAT-LSTM architecture consists of three parts. The first part is a wrapping parameter estimator (WPE) used to estimate the wrapping parameter of the base-band phase spectrum. The second part, a wrapping classifier (WCF), is a single output network used to compensate the drawbacks of the WPE. The third part, a synthesize and fine estimator, synthesizes the information from the WPE and WCF to unwrap the phase and estimate the delay according to the phase-delay model. The input of the PHAT-LSTM are fast Fourier transforms of snapshot data from two receiving channels. In addition, the dimension of the input signals was dramatically decreased compared with other deep learning-based TDE methods. Simulation results show that the root mean square error (RMSE) of the PHAT-LSTM is decreased in low signal-to-noise ratio (SNR) compared with traditional TDE methods. When the SNR = 10 dB or 0 dB, the RMSE of TDE was about ten times smaller than that of traditional methods.

Low Noise Amplifier Design and Performance Analysis of RF Front-End for Narrow Band Receivers

This manuscript presents the low noise amplifier design and performance analysis of receiver RF front-end for narrowband wireless communications. The LNA is a central building block of the wireless receiver. A single-ended cascode CMOS LNA is purposeful for reconfigurable applications such as Wireless LAN. The scope of this manuscript is to design an LNA appropriate for wireless applications with improved performance metrics. The contributions of this paper are noise reduction and high gain using an inductive degeneration common source stage. The proposed LNA espouses the entire simulation results in the frequency band of 2.44GHz. The excellent Noise Figure obtained as 0.95dB; the preferable power gain (S21) is 17dB, also the results of P-1dB of -17.3dBm, IIP3 of -10.7dBm at 2.44GHz, respectively. However, the perfect input and output matching network is achieved with proper reverse shielding and excellent stability.

Estimation of electromagnetic compatibility of a narrow-band radio channel under the influence of unintended interference of the radar complicated pulse signals

The relevance of estimation of the electromagnetic compatibility (EMC) of narrow-band radio communication channels under the influence of unintended interference (UI) from radars with complex signals is due to the widespread use of both the first and second ones. At the same time, its equipment is often installed at the same carriers, which further complicates the task of providing EMC. The specificity of this situation is that narrow-band radio channels occupy a frequency band measured in few kilohertz, and the width of the spectrum of complicated signals used by radars is several and tens of megahertz. Under these conditions, during the preliminary estimation of the EMC, it is advisable to use the method of mathematical modeling and approximate a narrow-band radio receiving device (RRD) exposed to broadband UI with an equivalent circuit characterized with a given degree of accuracy by the parameters of this RRD. In this case, we used a chain approximation of the 4th order. This chain is represented by a system of differential equations that is solved in MATLAB. As a result of calculations, the dependence of the coefficient of suppression of unintended interference on the parameters of signals, interference and radio receivers was found. It was found that in the example under consideration, the suppression of unintended interference is at least 37 dB.

Low-Power Wireless Transceiver With 67-nW Differential Pulse-Position Modulation Transmitter

This article presents a low-power wireless narrowband (NB) transceiver consisting of a 434-MHz NB transmitter (NBTX) and a 434-MHz NB receiver (NBRX) implemented in 0.18 $\mu \text{m}$ CMOS. The NBTX utilizes differential pulse-position modulation (DPPM) to decrease consumed energy per bit (EPB) by up to 67% compared to on-off keying (OOK). The packet error performance of DPPM with a soft-decision decoding scheme is analyzed. According to the results, the packet error ratio (PER) does not deteriorate compared to OOK except at very low signal-to-noise levels. The lowest power consumption of the NBTX is 8.3 $\mu \text{W}$ when DPPM data is transmitted continuously. Utilizing packet-mode transmission, the average power consumption is 67 nW at a data rate of 4.8 kbps. The transmitted data was received with a PER of 0.1% by a receiver placed at a 30-meter distance from the NBTX. With a higher power consumption of 2.5 $\mu \text{W}$ at the same data rate, the estimated line-of-sight (LOS) uplink range is up to 200 meters. The NBRX is a mixer-first uncertain-IF receiver. A temperature-compensated ring oscillator (TCRO) is utilized as a local oscillator. Its measured deviation of frequency is from +0.1% to −1.2% over a temperature range from −40 to +85 °C. The NBRX utilizes Manchester encoding and the sensitivity is −87 to −82 dBm over the temperature range at a data rate of 40 kbps. The NBRX consumes 85 $\mu \text{W}$ .

Measurements to design a coverage area by using high altitude platform systems

This paper proposes the principles of how to design UMTS coverage area for Baghdad city the capital of Iraq country that occupy space about 204.2 km², by using new and promising technology for providing wireless narrowband and broadband telecommunication services as well as broadcasting services with either airships or airplanes which is named HAPs, Viewed from its altitude, HAPs floats within the stratosphere layer in the airspace, positioned between satellite and terrestrial platforms.this study also consider the affect of interference with the current broadband technology It will start with brief introduction for HAPS with its advantages, comparison between HAPS system and other services and specify requirements for design. Such as, enumerate the center of coverage area to find the coordinates. Then, supposed the coverage area for the city, and find the radius, elevation angle, and the location of earth stations which will connect HAPS with other networks and all other services location depending on latitude and longitude, finally the reduction of interference technique.