Channel Model Research Articles

Ionospheric Channel Impulse Response Measurement System for NVIS Propagation Mode Over Java Island Based on Low‐Cost SDR Platform

AbstractThe development of a digital high‐frequency (HF) radio communication system requires an ionospheric channel model from the channel impulse response (CIR) measurement. Although the Watterson ionosphere channel model has been available and used for a long time, several CIR measurements have been conducted in all regions of the Earth in an attempt to validate or replace the Watterson channel model with a suitable model for their region. However, only a few CIR measurements were conducted in low‐latitude regions, especially over Indonesia. In this study, we develop the CIR measurement system for the near vertical incidence skywave (NVIS) propagation mode over Java Island based on the software defined radio platform to meet low‐cost and simple operation requirements. The specification of the system is based on the International Telecommunication Union ionospheric channel characteristic document and increased in order to be able to capture higher values. Results from a 1‐week campaign measurement period show the ability of the system to measure the root mean square of time delay within the range of 0.2–1.3 ms and the Doppler shift within the range of 0.7–1.1 Hz in the quiet conditions of the ionosphere. Further measurements will be conducted to obtain a comprehensive ionosphere CIR that is useful for designing the NVIS‐HF digital communication in Indonesia, which is located beneath the crest region of an equatorial ionospheric anomaly.

Densifying MIMO: Channel Modeling, Physical Constraints, and Performance Evaluation for Holographic Communications

Densifying MIMO: Channel Modeling, Physical Constraints, and Performance Evaluation for Holographic Communications

Hybrid Beamforming for mm-Wave Massive MIMO Systems with Partially Connected RF Architecture

To satisfy the capacity requirements of future mobile systems, under-utilized millimeter wave frequencies can be efficiently exploited by employing massive multiple input-multiple output (MIMO) technology with highly directive beamforming. Hybrid analog-digital beamforming has been recognised as a promising approach for large-scale MIMO implementations with a reduced number of costly and power-hungry radio frequency (RF) chains. In comparison to fully connected architecture, hybrid beamforming (HBF) with partially connected RF architecture is particularly appealing for the practical implementation due to less complex RF power division and combining networks. In this paper, we first formulate single- and multi-user rate maximization problems as weighted minimum mean square error (WMMSE) and derive solutions for hybrid beamformers using alternating optimization. The algorithms are designed for the full-array- and sub-array-based processing strategies of partially connected HBF architecture. In addition, we propose lower complexity sub-array-based zero-forcing algorithms. The performance of the proposed algorithms is evaluated in two different channel models, a simple geometric model and a realistic statistical model. The performance results of the WMMSE HBF algorithms are meant to reveal the potential of partially connected HBF and serve as upper bounds for lower complexity methods. Numerical results imply that properly designed partially connected HBF has the potential to provide an good compromise between hardware complexity and system performance in comparison to fully digital beamforming.

Field Measurement and Channel Modeling Around Wailingding Island for Maritime Wireless Communication

Field Measurement and Channel Modeling Around Wailingding Island for Maritime Wireless Communication

Помехоустойчивость когерентного приема двоичных сигналов с огибающей вида приподнятый косинус в гидроакустическом канале связи

Goals: The main purpose of this work is to develop a methodology for determining the parameters of binary signals, at which the signals become relatively invariant to frequency distortions in the marine environment. The frequency distortion of the signals is caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. In accordance with this, the error probabilities of signal receivers with various types of manipulation are determined, which are optimal in the absence of distortion. Methods: The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content: The paper considered a model of a single-beam hydroacoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude -frequency response and a linear phase-frequency response. The error probabilities of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are determined. Coherent receivers optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment are considered as receivers. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters that are relatively invariant to frequency distortions in the marine environment are determined. Results: Expressions of the error probability of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of sending the signal, the carrier frequency and the initial phase of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, signal duration, for each type of signal, the boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed, a comparison is made with the case of signals with a sinusoidal envelope. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given. Expressions of the error probability of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of sending the signal, the carrier frequency and the initial phase of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, signal duration, for each type of signal, the boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed, a comparison is made with the case of signals with a sinusoidal envelope. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given.

Numerical simulation of fish damage in a bulb tubular turbine with different guide vane openings

Abstract Tubular turbines have advantages in developing low-head hydropower, however, the development of hydropower shouldn’t forget to maintain a balance with ecology. In this paper, a three-dimensional model of the flow channel of a low-head power plant bulb tubular turbine unit is established using Unigraphics NX, and the hydraulic characteristics and fish damage mechanisms of the turbine under different guide vane openings of 45∼85 mm in rated operating conditions are simulated and analyzed using STAR-CCM+, and it is found that the fish mainly suffers from impact damage and pressure damage in the downstream process with the highest probabilities of 15.73% and 15.72%, respectively. Furthermore, with the increase of the opening of the guide vane, the probability of shear damage to the fish first decreases and then increases, while the probability of pressure, pressure gradient, and impact damage all gradually increase, and the probability of all four types of damage reaches the highest when the opening of the guide vane is 85 mm. Although the unit will have a large output at large opening operating conditions, from the point of view of fish protection, it is better for such turbines not to be operated with large opening of the guide vane for a long time.

Multi-Scenario Broadband Channel Measurement and Modeling for Sub-6 GHz RIS-Assisted Wireless Communication Systems

Multi-Scenario Broadband Channel Measurement and Modeling for Sub-6 GHz RIS-Assisted Wireless Communication Systems

Channel Measurement, Characterization, and Modeling for Terahertz Indoor Communications Above 200 GHz

Channel Measurement, Characterization, and Modeling for Terahertz Indoor Communications Above 200 GHz

A Physics-Based and Data-Driven Approach for Localized Statistical Channel Modeling

A Physics-Based and Data-Driven Approach for Localized Statistical Channel Modeling

Holographic MIMO Communications With Arbitrary Surface Placements: Near-Field LoS Channel Model and Capacity Limit

Holographic MIMO Communications With Arbitrary Surface Placements: Near-Field LoS Channel Model and Capacity Limit

GPU‐Accelerated Urban Flood Modeling Using a Nonuniform Structured Grid and a Super Grid Scale River Channel

AbstractNew remote sensing technologies, and the meter‐scale geospatial data they create, now allow for detailed urban landscape characterization, thereby advancing grid‐based hydrodynamic models. However, using a uniform fine grid over urban catchments generally result in dense grids and can lead to prohibitive computational costs. Moreover, an inability to see below the water surface and measure river bathymetry in most terrain remote sensing can severely impact local‐scale river hydraulics calculations given the significant volume of water conveyed by the channel. This paper introduces a super grid channel model which allow river channels with any width above that of the grid resolution to be simulated in 1D manner. As an extension of a previous subgrid model, this integration facilitates a seamless transition between subgrid and super grid channels, accommodating situations where channel width may surpass or fall below the grid resolution. The key contribution is the integration of the novel 1D channel representation with a nonuniform structured 2D floodplain hydrodynamic model and then coding this for application on GPU. Compared with the previous pure 2D nonuniform structured approaches, the new model presents an efficient compromise for riverine urban flooding where we are less concerned about fine‐scale details of in‐channel flow. Three tests reveal that the proposed model maintains accuracy but with significantly reduced computational cost. By leveraging GPU architectures, a ∼10× speedup compared to CPU computations is achieved, and a typical 6‐day urban flooding problem (domain size 1.42 km2) at 1 m resolution can be achieved within 10 hr on a single 8 GB GPU.

Inertial Effect and Its Dependency on the Topographic Geometries in Barotropic Channel Models under the Weakly Nonlinear Regime

Abstract Recent studies have shown that the sensitivity of the circumpolar transport of channels to the westerlies is controlled by wind-driven gyre circulations. Although the form stress associated with the gyres has been shown to be controlled by eddies, bottom friction, and topographic width, the role of inertial effects has not been fully understood. In this study, we conduct a series of sensitivity analyses using the barotropic model with and without the advection term (hereinafter, the model without the advection term is denoted as linear model). Experiments showed that the sensitivity of the circumpolar transport decreased under the westerly winds compared to the linear model, while it increased under the easterly winds. We show that the inertial effect of western boundary currents generates anomalous anticyclonic circulations over the topography, producing the westward topographic form stress anomalies regardless of the wind directions. In addition, we discuss the sensitivity of the inertial effect mechanism to topographic height, width, and geometries. The inertial effect mechanism is robust as long as the gyre circulations dominate while its relative importance changes. We also found that the dynamics of the barotropic channel strongly depend on the geometries of geostrophic contours f/h. Therefore, we conclude that the dynamics of barotropic channel models might be interpreted with caution to understand the dynamics of the Southern Ocean. Significance Statement Previous studies have studied baroclinic and barotropic channel models as a benchmark of the Southern Ocean, but the nonlinear dynamics of channels have not been fully understood. In this paper, we show that the inertial effect by the mean flow works to decrease the sensitivity to the westerly winds in the barotropic channel models using numerical experiments. We also show that the inertial effect is robust as long as gyre circulations exist, while its relative importance differs.

Characteristics and Channel Capacity Studies of a Novel 6G Non-Stationary Massive MIMO Channel Model Considering Mutual Coupling

Characteristics and Channel Capacity Studies of a Novel 6G Non-Stationary Massive MIMO Channel Model Considering Mutual Coupling

Integrated Sensing and Communication Channel Modeling and Measurements: Requirements and Methodologies Toward 6G Standardization

Integrated Sensing and Communication Channel Modeling and Measurements: <i>Requirements and Methodologies Toward 6G Standardization</i>

Advancing reliability and efficiency of urban communication: Unmanned aerial vehicles, intelligent reflection surfaces, and deep learning techniques

Unmanned aerial vehicles (UAVs) have garnered attention for their potential to improve wireless communication networks by establishing line-of-sight (LoS) connections. However, urban environments pose challenges such as tall buildings and trees, impacting communication pathways. Intelligent reflection surfaces (IRSs) offer a solution by creating virtual LoS routes through signal reflection, enhancing reliability and coverage. This paper presents a three-dimensional dynamic channel model for UAV-assisted communication systems with IRSs. Additionally, it proposes a novel channel-tracking approach using deep learning and artificial intelligence techniques, comprising preliminary estimation with a deep neural network and continuous monitoring with a Stacked Bidirectional Long and Short-Term Memory (Bi-LSTM) model. Simulation results demonstrate faster convergence and superior performance compared to benchmarks, highlighting the effectiveness of integrating IRSs into UAV-enabled communication for enhanced reliability and efficiency.

Near-Field Channel Modeling for Holographic Mimo Communications

Near-Field Channel Modeling for Holographic Mimo Communications

Dependence of rain attenuation on rain rate and drop size distribution for Ka-band satellite communication over India

The Raindrop size distribution (DSD) is the most effective parameter to calculate rain-induced attenuation, which can be severe at Ka-band and higher frequencies. The authors have investigated the impact of rain rate and DSD on rain-induced specific attenuation over a tropical location Kolkata, India. DSD data from disdrometer has been used to calculate the specific rain attenuation with the help of Mie scattering theorem. Low to medium drop diameters (up to 3 mm) are the largest contributors to the various classes of rain rate and attenuation. Double peaks of drop sizes are significant for medium rain rate. The contribution of smaller drop diameters decrease, whereas the contribution of higher drop diameters increase with increasing rain attenuation. At lower rain attenuation, (up to 1.5 dB), complementary cumulative distribution function (CCDF) shows higher value for stratiform rain, with respect to convective rain. The higher attenuation occurrences are mostly observed during 12–18 Indian standard time (IST), i.e., in the afternoon. The results will be helpful for Ka-band (GSAT-14) and higher frequency satellite communication channel modeling over India.

A comparative study of deep learning and iterative algorithms for joint channel estimation and signal detection in OFDM systems

Joint channel estimation and signal detection (JCESD) is crucial in orthogonal frequency division multiplexing (OFDM) systems, but traditional algorithms perform poorly in low signal-to-noise ratio (SNR) scenarios. Deep learning (DL) methods have been investigated, but concerns regarding computational expense and lack of validation in low-SNR settings remain. Hence, the development of a robust and low-complexity model that can deliver excellent performance across a wide range of SNRs is highly desirable. In this paper, we aim to establish a benchmark where traditional algorithms and DL methods are validated on different channel models, Doppler, and SNR settings, particularly focusing on the semi-blind setting. In particular, we propose a new DL model where the backbone network is formed by unrolling the iterative algorithm, and the hyperparameters are estimated by hypernetworks. Additionally, we adapt a lightweight DenseNet to the task of JCESD for comparison. We evaluate different methods in three aspects: generalization in terms of bit error rate (BER), robustness, and complexity. Our results indicate that DL approaches outperform traditional algorithms in the challenging low-SNR setting, while the iterative algorithm performs better in high-SNR settings. Furthermore, the iterative algorithm is more robust in the presence of carrier frequency offset, whereas DL methods excel when signals are corrupted by asymmetric Gaussian noise.

Squaring Circuit Using 14nmFinFET Technology with Vedic Mathematics Approach

FinFET technology is an alternative to CMOS technology as in this technology device has higher drive current, speed, and low-power consumption. FinFET has better mobility and scaling than CMOS technology. A dedicated Squaring circuit is needed by many digital signal processors (DSP) and arithmetic and logical units (ALU). So fast, power-efficient, and compact squaring circuits can be designed with Vedic sutras. Vedic mathematics has 16 sutras and 13 sub-sutras that touch almost all different chapters of mathematics. Out of these sutras, Dwandwayoga has a duplex property that is used to find a square of an N-bit number. Also, Yavadunam is a special case for finding the square of a number that is closer to the base. This work targets a comparative analysis of these two square circuits having a Vedic approach with a conventional array multiplier. The proposed designs are implemented in micro-wind 3.9 electronic design automation tool (EDA) with 14 nm deep submicron technology post-layout. The values of model parameters are used from the current Berkeley 4 short channel model (BSIM4). It is observed that the proposed square architecture design using the Dwandwayog sutra and Yavadunam sutra achieves 185%, 272.45% delay depletion and a 122.22%, and 46.52% reduction in transistor requirements compared to the conventional array multiplier, respectively.

A Study on the Plugging Effect of Different Plugging Agent Combinations during CO2 Flooding in Heterogeneous Reservoirs

Gas channeling control is key to improving CO2-flooding efficiency. A traditional plugging system has disadvantages, such as poor adaptability and stability, leading to the poor plugging effect of CO2 channeling in heterogeneous reservoirs and difficulty in controlling the subsequent CO2 injection pressure. To achieve a significant plugging effect and effectively control the subsequent CO2 injection pressure, a heterogeneous physical model of gas channeling in a horizontal well was established, and plugging experiments were conducted using four different combinations of plugging agents during CO2 flooding. Three evaluation parameters were defined, including the temperature field variation coefficient (TFVC), medium-permeability diversion rate (MPDR), and subsequent injection pressure coefficient (SIPC). The plugging effect of different combinations of plugging agents during CO2 flooding in heterogeneous reservoirs was analyzed. The results show that the plugging effect after using a combination of plugging agents was significantly better than after using a single plugging agent, and different plugging agent combinations had distinct characteristics. The strong–medium–weak (S-M-W) combination had the best MPDR for subsequent CO2 flooding, but the SIPC was the highest. The strong–weak–strong–weak (S-W-S-W) and weak–strong–weak–strong (W-S-W-S) combinations could effectively control the SIPC. These results indicate that plugging using the S-W-S-W and W-S-W-S combinations can achieve an effective plugging effect and reasonably control the subsequent CO2 injection pressure. This work provides a personalized design scheme for effective gas channeling control and maintenance of appropriate injection pressure during CO2 flooding in heterogeneous reservoirs.