Radio Conditions Research Articles

ADAPTIVE METHOD OF FORMING COMPLEX SIGNALS ENSEMBLES BASED ON MULTI-LEVEL RECURRENT TIME-FREQUENCY SEGMENT MODELING

The article investigates the implementation of an adaptive method for forming ensembles of complex signals based on multilevel recurrent time-frequency segmentation. It addresses the key challenges faced by cognitive wireless networks operating in dynamic radio frequency environments with high levels of interference, necessitating rapid adaptation to changes in the spectral characteristics of signals. The study substantiates the need for adaptive filters and specific transformations to enhance signal processing quality, particularly in environments with high variability in frequency characteristics and significant noise interference. The proposed method of multilevel recurrent time-frequency segmentation allows for the modification of time segment durations and the use of segments of varying lengths, providing flexibility in signal processing and adaptation to current conditions. This adaptability enables optimal signal processing for each individual case, taking into account short-term impulses, long-term fluctuations, and various types of noise and distortions. This approach effectively separates frequency components and reduces interference between them, which is crucial for maintaining high signal quality and communication stability in cognitive networks. It has been proven that the use of adaptive filters such as LMS (Least Mean Squares) and RLS (Recursive Least Squares), as well as fast Fourier Transform (STFT), wavelet, and Hilbert transforms at different stages of multilevel time-frequency segmentation, significantly enhances signal interference resistance and energy efficiency. Comparative analysis of signal metrics before and after filtering and transformation shows an increase in signal quality by 14,3–24,5% and a reduction in noise levels by 21,7–29,6%. The wavelet transform, in particular, proved to be highly effective, allowing for precise extraction of useful frequency components from the noise background and improving signal parameters through dynamic adjustment to specific radio environment conditions. Experimental results confirm the effectiveness of the proposed method, demonstrating its ability to ensure consistently high-quality processing of complex signal ensembles even in dynamic cognitive radio environments.

Mobile Data Network Performance Review – A Perspective of Zambia

High speed mobile internet results in better user experience and satisfied subscriber. However factors that affect the download speed include transfer technology, number of subscribers sharing the connection, device capability and radio conditions at the subscriber location. This research was conducted to review the mobile internet performance in Zambia and determine its conformity to the regulator, ZICTA, QoS regulation. Two sets of empirical data were collected in the capital city, first in 2021 during the covid pandemic period and second in 2024. The data was compared to check for network operator developments. The results reveal that two MNOs acquired new 2600MHz spectrum, however only one MNO drew maximum benefit resulting in improved 4G download speeds. This improvement was despite an increase in market share over the same period. The second operator that deployed the 2600MHz LTE TDD mode spectrum recorded a degradation in overall downloads speeds when compared to the initial data set in spite of a reduction in market share over the same period. Thus the steps to improve the LTE network are to add more spectrum to at least reach the 3GPP Rel 10 standard of 5 carrier configuration (5CC) to reach a total 100MHz and configure network features like Carrier Aggregation (CA) to provide for higher throughputs for capable devices. Other ways to expand LTE network include add more antennas to allow for higher spectral efficiency using 8 x 8 MIMO or more and thirdly deploy Small cells solution to enhance coverage and capacity in both indoor and outdoor environment.

Radio Contra Harmonic Mean Number of Graphs

Objectives: To explore the least upper bound of graphs by radio contra harmonic labeling. Methods: Contra harmonic mean function or , radio mean labeling condition and radio harmonic mean labeling are used. Findings: Here we introduce radio contra harmonic mean labeling and its least upper bound, designated as radio contra harmonic mean number, by formulating the constraints. Novelty: Based on radio mean labeling and contra harmonic mean labeling, the new concept of radio contra harmonic mean labeling was established. The bounds of some special graphs are encountered here. This kind of labeling is employed in secure communication networks and is also applicable in X-rays, crystallography, coding theory, computing etc. Keywords: Radio contra harmonic mean labeling, rchmn (G), Order, Diameter, Smallest span

The specific current action integral for conductors exploded by high-frequency currents

The explosive emission processes that occur at electrode surface microprotrusions may have harmful effects in a variety of electrodynamic and acceleration systems exposed to high-power radio frequency electromagnetic waves. This paper presents the results of a radiative magnetohydrodynamic simulation of the explosion of copper conductors that occur under conditions inherent in the explosion of electrode microprotrusions, i.e., at current densities of the order of 109 A/cm2. Explosions occurring under quasi-stationary and radio frequency conditions (hereinafter referred to as quasi-stationary and radio frequency explosions, respectively) were considered. It was shown that in all the considered cases, the explosion occurred at high temperatures, so that the energy deposited in the conductor by the time of explosion exceeded the sublimation energy of the conductor material. It turned out, however, that the energy deposited in the conductor under radio frequency conditions, regardless of the frequency of current oscillations, was more than two times less than that deposited under quasi-stationary conditions. The explosion time was also virtually independent of the frequency, and it was approximately three times longer than that calculated for quasi-stationary conditions. For a radio frequency explosion, the specific current action integral was somewhat less (by about 25%) than that for a quasi-stationary explosion, and its value was actually independent of frequency. At the same time, in the radio frequency regime, the radiation power coming out of the conductor substance drops strongly, and it is almost two orders of magnitude smaller compared to the radiation power in the quasistationary regime.

Evaluation of User-Centric Cell-Free Massive Multiple-Input Multiple-Output Networks Considering Realistic Channels and Frontend Nonlinear Distortion

Future 6G networks are expected to utilize Massive Multiple-Input Multiple-Output (M-MIMO) and follow a user-centric cell-free (UCCF) architecture. In a UCCF M-MIMO network, the user can be potentially served by multiple surrounding Radio Units (RUs) and Distributed Units (DUs) controlled and coordinated by a single virtualized Centralized Unit (CU). Moreover, in an M-MIMO network, each transmit frontend is equipped with a Power Amplifier (PA), typically with nonlinear characteristics, that can have a significant impact on the throughput achieved by network users. This work evaluates a UCCF M-MIMO network within an advanced system-level simulator considering multicarrier transmission, using Orthogonal Frequency-Division Multiplexing (OFDM), realistic signal-processing steps, e.g., per resource block scheduling, and a nonlinear radio frontend. Moreover, both idealistic independent and identically distributed (i.i.d.) Rayleigh and 3D ray-tracing-based radio channels are evaluated. The results show that under the realistic radio channel, the novel user-centric network architecture can lead to an almost uniform distribution of user throughput and improve the rate of the users characterized by the worst radio conditions by over 3 times in comparison to a classical, network-centric design. At the same time, the nonlinear characteristics of the PA can cause significant degradation of the UCCF M-MIMO network’s performance when operating close to its saturation power.

Cross-Layer Methods for Ad Hoc Networks—Review and Classification

The OSI model used to be a common network model for years. In the case of ad hoc networks with dynamic topology and difficult radio communications conditions, gradual departure is happening from the classical kind of OSI network model with a clear delineation of layers (physical, channel, network, transport, application) to the cross-layer approach. The layers of the network model in ad hoc networks strongly influence each other. Thus, the cross-layer approach can improve the performance of an ad hoc network by jointly developing protocols using interaction and collaborative optimization of multiple layers. The existing cross-layer methods classification is too complicated because it is based on the whole manifold of network model layer combinations, regardless of their importance. In this work, we review ad hoc network cross-layer methods, propose a new useful classification of cross-layer methods, and show future research directions in the development of ad hoc network cross-layer methods. The proposed classification can help to simplify the goal-oriented cross-layer protocol development.

Enabling Extremely Energy-Efficient End-to-End Secure Communications for Smart Metering Internet of Things Applications Using Static Context Header Compression

Smart metering IoT applications are among the most energy-critical in the current panorama. Metering sensors are battery-powered and are expected to have a lifetime exceeding ten years. In order to achieve such long operation duration, a generic header compression mechanism named Static Context Header Compression (SCHC) has been introduced and accepted as a standard by the Internet Engineering Task Force (IETF). This paper aims to demonstrate the energy savings enabled by the use of SCHC on a cellular IoT network by the means of real-life implementation and measurements. Experiments are conducted in a controlled environment for different scenarios and considering multiple parameters such as message size and radio conditions. Measurements show the high impact of this header compression mechanism, particularly when the radio conditions are bad and repetitions are used to improve the reliability of the transmission: a reduction of up to 40% in energy consumption is observed. Using SCHC over the non-IP transport mode (NIDD) of NB-IoT compared to the legacy IP mode also enables significant energy savings and allows the latency to be reduced while maintaining the interoperability provided by the IP layer.

UE Blocking Probability Model for Planning 5G Guaranteed Bit Rate (GBR) RAN Slices

Modeling the probability of blocking User Equipment (UE) sessions is key for planning in advance the amount of radio resources required by a Guaranteed Bit Rate (GBR) slice. This task is challenging since the amount of these resources depends on factors such as the channel quality of each UE, the packet scheduler discipline, and the GBR requirements. Under this context, we propose an analytical model to evaluate the UE blocking probability for a GBR slice. A key aspect of the proposed model is considering as input the distribution of the average Signal-to-Interference-plus-Noise Ratio (SINR) experienced by the UE, therefore allowing to capture the radio conditions in the cell. Our model builds a multi-dimensional Erlang-B system which meets the reversibility property. This involves our model is insensitive to the holding time distribution for the UE sessions. The reversibility property also involves the state transition probabilities have product form, so that the computational complexity of our model is low. Furthermore, the proposed model captures the SINR gain provided when the base station implements a channel-aware packet scheduler to allocate radio resources to the UE sessions. We validate the proposed model, demonstrating an estimation error for the UE blocking probability below 1.5%.

Dispelling Revisionist Myths Regarding Spectrum Property Rights in the 1920s

ABSTRACT Failures to understand the constraints and incentives facing decisionmakers have resulted in the creation of the myth that property rights and spectrum markets would have been superior to the regulatory system of the Radio Act of 1927. Discussions of hypothetical spectrum property rights in the 1920s fail to take account of (1) the vast differences between the radio propagation conditions in the radio spectrum in use then and propagation in the bulk of the radio spectrum today and (2) the technical limitations of equipment at that time. The author concludes that spectrum property rights would have resulted in more radio service in urban areas, a substantial loss of rural service, and diminished consumer welfare.

Reinforcement-Learning-Based Robust Resource Management for Multi-Radio Systems

The advent of the Internet of Things (IoT) has triggered an increased demand for sensing devices with multiple integrated wireless transceivers. These platforms often support the advantageous use of multiple radio technologies to exploit their differing characteristics. Intelligent radio selection techniques allow these systems to become highly adaptive, ensuring more robust and reliable communications under dynamic channel conditions. In this paper, we focus on the wireless links between devices equipped by deployed operating personnel and intermediary access-point infrastructure. We use multi-radio platforms and wireless devices with multiple and diverse transceiver technologies to produce robust and reliable links through the adaptive control of available transceivers. In this work, the term ‘robust’ refers to communications that can be maintained despite changes in the environmental and radio conditions, i.e., during periods of interference caused by non-cooperative actors or multi-path or fading conditions in the physical environment. In this paper, a multi-objective reinforcement learning (MORL) framework is applied to address a multi-radio selection and power control problem. We propose independent reward functions to manage the trade-off between the conflicting objectives of minimised power consumption and maximised bit rate. We also adopt an adaptive exploration strategy for learning a robust behaviour policy and compare its online performance to conventional methods. An extension to the multi-objective state–action–reward–state–action (SARSA) algorithm is proposed to implement this adaptive exploration strategy. When applying adaptive exploration to the extended multi-objective SARSA algorithm, we achieve a 20% increase in the F1 score in comparison to one with decayed exploration policies.

On the Feasibility of Out-of-Band Spatial Channel Information for Millimeter-Wave Beam Search

Prolonged beam alignment is the main source of overhead in mobile wireless communications at millimeter-wave (mm-wave) frequencies due to narrow beams following the requirement of high antenna gains. Out-of-band spatial information may be used in initial beam search when lower frequency band radios are operating in conjunction with mm-wave radios. The feasibility of using low-band channel information for coarse estimation of high-band beam directions strongly depends on the spatial congruence between the two frequency bands. In this work, we try to answer two related questions. First, how similar is the power angular spectrum (PAS) of propagation channels between two widely separated frequency bands? Then, what is the impact of practical antenna configurations on spatial channel similarity? We propose a beam directions based metric to assess the power loss and number of false directions if out-of-band spatial information is used instead of in-band information. This metric is more practical and useful than comparing the PASs directly. Point cloud ray tracing and propagation measurement results across multiple frequency bands and environments are used to show that the degree of spatial similarity of beamformed channels is related to antenna beam widths, frequency gap, and radio link conditions.

Secure Real-Time Multimedia Data Transmission from Low-Cost UAVs with A Lightweight AES Encryption

In the context of real-time wireless multimedia transmission from Unmanned Aerial Vehicles (UAVs), equipped with microphone arrays and cameras, data security is crucial. Data security should be guaranteed from the acquisition onboard the drones to its delivery to the destination node or ground station. A real-time light-weight application-level Advanced Encryption Standard (AES) encryption algorithm has been considered to be applied to multimedia data and supported by the single-board-computers mounted onboard the drones, with low computational power. The study shows that the main advances are related to the design of a streaming application in a transmission architecture for military counter-UAV scenarios that is effective, secure, quick, and trustworthy for audio and video data. A multiple synchronous key management is also newly experimented. The thorough experiments have confirmed the effective validity of the encryption and decryption processes, even in the presence of adverse radio spectrum conditions.

Inpatient stroke survivors with low gait functioning benefit from music interventions during cardiorespiratory exercise: A randomized cross-over trial

ABSTRACT Introduction Stroke survivors struggle to meet clinical recommendations for physical exercise duration and intensity. During the past two decades, emerging evidence has shown effectiveness of music interventions for several motor tasks in stroke rehabilitation. Additionally, music has been found effective for increasing exercise performance in athletes and clinical populations. It is postulated that the therapeutic effects of music in physical exercise are modulated by preference and task-specificity of the music. Methods We tested this hypothesis in a pilot study using a three-arm randomized cross-over design comprising the following auditory conditions during cycle ergometry cardiorespiratory exercise sessions: (a) a group-tailored music playlist, (b) radio music, and (c) a non-music control condition. Participants (n = 19) were inpatient stroke survivors undergoing rehabilitation between 2 and 12 weeks post infarct. Results Our results demonstrate that clinical characteristics are an important determinant for identifying patients who can benefit from music. Specifically, participants with a higher level of gait functioning experienced no benefit, whereas participants with a low level of gait functioning showed an increase in both exercise duration (M = 4.46 minutes) and time spent in the recommended heart rate intensity (M = 6.39 and M = 2.49 minutes for the playlist and radio condition, respectively). Discussion The findings suggest a beneficial role of music in rehabilitation of stroke patients with low gait functioning. Future studies should ultimately disentangle which musical parameters are more likely to induce the putative ergogenic effects. Trial registry number: NCT05398575.

Bounds on radio mean number of graphs

A radio mean labeling l of G maps distinct vertices of G to distinct elements of ℤ + satisfying the radio mean condition that diam ( G ) + 1 - d G ( w , w ′ ) ≤ ⌈ l ( w ) + l ( w ′ ) 2 ⌉ , ∀ w , w ′ ∈ V ( G ) where dG (w, w′) is the smallest length of a w, w′- path in G and diam (G) = max {dG (w, w′) : w, w′ ∈ V (G)} is the diameter of G. The radio mean number of graph G is defined as rmn (G) = min {span (l) : l isaradiomeanlabelingof G} where span(l) is given by max {l (w) : w ∈ V (G)}. It has been proved in literature that |V (G) | ≤ rmn (G) ≤ |V (G) | + diam (G) -2. Cryptographic algorithms can exploit the unique radio mean number associated with a graph to generate keys. An exhaustive listing of all feasible radio mean labelings and their span is essential to obtain the radio mean number of a given graph. Since the radio mean condition depends on the distance between vertices and the graph’s diameter, as the order and diameter increase, finding a radio mean labeling itself is quite difficult and, so is obtaining the radio mean number of a given graph. Here we discuss the extreme values of the radio mean number of a given graph of order n. In this article we obtained bounds on the radio mean number of a graph G of order n and diameter d in terms of the radio mean number of its induced subgraph H where diam (H) = d and dH (w, w′) = dG (w, w′) for any w, w′ ∈ V (H). The diametral path Pd+1 is one such induced subgraph of G and hence we have deduced the limits of rmn (G) in terms of rmn (Pd+1). It is known that if d = 1, 2 or 3, then rmn (G) = n. Here, we have given alternative proof for the same. The authors of this article have studied radio mean labeling of paths in another article. Using those results, we have improved the bounds on the radio mean number of a graph of order n and diameter d ≥ 4. It is also shown that among all connected graphs on n vertices, the path Pn of order n possesses the maximum radio mean number. This is the first article that has completely solved the question of maximum and minimum attainable radio mean numbers of graphs of order n.

Modern Solutions to Improve the Energy Efficiency of Radio Lines for the Technical Renewal of Radio Stations of Integrated Communication Systems

Promising tasks for improving radio equipment with increased energy efficiency, related to in-depth preliminary study and efficiency research using the stand of the chief designer, are considered. Initially, a theoretical factor analysis of the interference radio terminal energy efficiency with respect to evenly distributed over the spectrum is given. The problem of choosing a variant of digital modulation and parameters of a noise-resistant code from the condition of obtaining the least energy for the transmission of one bit of information at a given error probability per bit and the level of spectral noise density is examined. With regard to broadband signals, energy-efficient linearly frequency-modulated signals are allocated. In the case of narrowband signals, cognitive technologies for improving energy efficiency for radio paths with partially filled spectrum, tuning radio lines to the 'windows of the best transparency' of the spectrum, are studied. Their importance for VHF radio lines and HF radio systems with tuning to the optimal frequency by regular ionosphere sounding is noted. The features of cognitive radio networks development to improve the energy efficiency of radio facilities are considered. The ways of algorithms design for modem and noise-resistant encoder energy effective tuning to a given radio line conditions for testing in the stand of the Chief Designer are discussed. Priority tasks for improving radio equipment with increased energy efficiency have been specified. Urgent specific subtasks for elaboration at the stand of the Chief Designer are highlighted.

Performance Assessment of Reinforcement Learning Policies for Battery Lifetime Extension in Mobile Multi-RAT LPWAN Scenarios

Considering the dynamically changing nature of the radio propagation environment, the envisioned battery lifetime of the end device (ED) for massive machine-type communication (mMTC) stands for a critical challenge. As the selected radio technology bounds the battery lifetime, the possibility of choosing among several low-power wide-area network (LPWAN) technologies integrated at a single ED may dramatically improve its lifetime. In this article, we propose a novel approach of battery lifetime extension utilizing reinforcement learning (RL) policies. Notably, the system assesses the radio environment conditions and assigns the appropriate rewards to minimize the overall power consumption and increase reliability. To this aim, we carry out extensive propagation and power measurements campaigns at the city-scale level and then utilize these results for composing real-life use cases for static and mobile deployments. Our numerical results show that RL-based techniques allow for a noticeable increase in EDs’ battery lifetime when operating in the multi-RAT mode. Furthermore, out of all considered schemes, the performance of the weighted average policy shows the most consistent results for both considered deployments. Specifically, all RL policies can achieve 90% of their maximum gain during the initialization phase for the stationary EDs while utilizing less than 50 messages. Considering the mobile deployment, the improvements in battery lifetime could reach 200%.

Метод оцінки зв’язності вузлів бездротових епізодичних мереж за умови застосування безпілотних літальних апаратів

The paper considers a method for assessing the connectivity of nodes of wireless episodic networks (WEN) under the condition of using unmanned aerial vehicles (UAVs). It is proposed to perform an evaluation of the connectivity of a pair of nodes according to a method, which is based on: an evaluation of geometric connectivity, which is limited to the maximum range of radio visibility at the physical level and the vulnerability interval of a given multiple access protocol at the channel level; assessment of information connectivity, which takes into account the presence of not only a physical connection of a given reliability, but also the presence of a free channel resource, a given amount of transmission delay at a given traffic limit value; assessment of the duration of connectivity taking into account the mobility of network nodes. On the basis of analytical mathematical models, the duration of connectivity of mobile subscribers (nodes) (MS) of the WEN consisting of MS and UAVs in direct radio visibility conditions and taking into account relaying was investigated. The connectivity of a pair of nodes is determined by the characteristics of different levels of OSI information interaction, such as radio range, channel bandwidth, information transmission delay, etc. It is shown that the duration of connectivity is directly proportional to the size of the coverage zone and inversely proportional to the speed of movement of nodes. The nature (scenario) of node mobility also affects the duration of connectivity. The simulation of the movement of nodes was carried out under 4 scenarios: «march», «skirmish», «random wandering in the field» and «random wandering in the city». The largest values of the duration of connectivity correspond to the third scenario, and the smallest to the second (with a fixed radius of the coverage area and the speed of movement of nodes). Thus, the average connection duration of the UAV-pedestrian connection in the event of a «difference» will be of the order of 36 minutes, and the UAV-car connection of the order of 5 minutes. The obtained results can be used in the UAV network topology control method.

Determination of radio wave propagation conditions in the atmosphere of Hanoi using the radiosonde data of balloons

This article uses radiosonde data of balloons in Hanoi to determine the radio refractive index and the conditions of radio wave propagation in the atmosphere. The research results in the three years 2016–2018 show the highest average radio refractivity, the maximum radio refractivity difference between the years. Secondly, radiosonde data are used to estimate the accuracy of global ITU models, and showed that the radio refractivity’s difference between the ITU-R model and the observed value by radiosonde method is up to 60 N-units at a lower altitude of atmosphere. In conclusion, it is recommended to use radiosonde data instead of the ITU model (where available) to obtain refractive index when studying wave propagation conditions in the atmosphere.

Mesoscale Variability of Surface Ducts During Santa Ana Wind Episodes

AbstractMesoscale variability of the marine boundary layer characteristics and the corresponding radio wave ducting conditions over the Southern California Bight (SCB) during three Santa Ana wind events have been examined based on the analysis of field observations and diagnosis of mesoscale model simulations. Under the influence of a dry and the stably stratified airflow from inland, a shallow moist internal boundary layer (MIBL) develops over the coastal waters. The MIBL consists of a thin well‐mixed moist layer capped by an inversion layer where the specific humidity decreases with height sharply. Accordingly, a surface duct (SD) is virtually ubiquitous with its depth compared with the MIBL depth. The wind direction and the SD characteristics exhibit diurnal variations over the SCB area associated with land and sea breezes. In addition, the MIBL interacts with the coastal topography, Channel Islands, and sea surface temperature gradients, resulting in spatial mesoscale variabilities in SD characteristics. Specifically, the SD height and strength grow with the offshore distance owing to the surface latent heat flux over sea, and in the meantime, exhibit substantial along‐shore variations. The shallow MIBL tends to split and flow around the higher elevation of the islands, leading to the formation of wakes with reduced modified refractivity. These island wakes may extend dozens of kilometers downstream with the SD height and strength growing accordingly.

Investigation of Optimum Deposition Conditions of Radio Frequency Reactive Magnetron Sputtering of Al0.7Sc0.3N Film with Thickness down to 20 nm

AbstractFerroelectric aluminum scandium nitride (Al0.7Sc0.3N) has attracted increasing interest due to its high remanent polarization (Pr, >100 µC cm−2) and coercive field (Ec, >5 MV cm−1). The four radio frequency reactive magnetron sputtering conditions (sputtering power, N2 flow ratio, pressure, and temperature) influence the ferroelectric and material properties of 45 nm‐thick Al0.7Sc0.3N deposited on the TiN/SiO2/Si substrate. Crystallinity is enhanced under the deposition conditions with higher adatom energy but deteriorates when the growth condition increases over the optimum. The well‐crystallized films have (002)‐preferred orientation with the in‐plane compressive stress imposed by the peening effect and thermal stress. The imposed compressive stress increases the c0/a0 value, where c0 and a0 mean the c‐ and a–axis lattice parameters, which eventually increases the Ec of the film. Pr increases with the c0/a0 value, but other factors also influence the change. The films with high oxygen concentration show the wake‐up properties due to the large percentage of domain walls and their depinning. Finally, ferroelectricity is confirmed with films down to a thickness of 20 nm. However, the thinnest film shows a higher Ec and lower Pr. These findings imply the presence of non‐ferroelectric interfacial layers, which induce the depolarization effect.