International Telecommunication Union Radiocommunication Research Articles

Sixth Generation 6G to the Waying Seventh 7G Wireless Communication Visions and Standards, Challenges, Applications

The increasing need for next-generation wireless networks becomes apparent as the Internet of Everything (IoE) gains prominence in smart services, projecting widespread popularity in the future. While sixth generation (6G) networks have the capability to support a diverse range of IoE services, their potential limitations in meeting the demands of innovative applications prompt consideration for seventh generation (7G) wireless systems. This article seeks to compare the characteristics of 6G and the planned 7G wireless systems. The commercial development of fifth generation (5G) mobile communication systems is currently underway, introducing new services and enhancing user experiences. Despite these advancements, 5G encounters challenges that require on-going improvements. With the International Telecommunication Union Radio communication Sector (ITU-R) actively envisioning 6G and anticipating a consensus on 7G by October 2024, numerous unresolved questions persist in global discussions. This paper delivers a comprehensive overview of the current understanding of 7G, exploring the vision, technical requirements, and application possibilities. It presents a critical evaluation of the 7G network architecture and essential technologies. Furthermore, the article provides an in-depth examination of advanced 7G verification platforms and existing test beds, unveiling these aspects for the first time. Future research directions and lingering issues are emphasized to contribute to the on-going global discourse on 7G networks. Discussions on lessons learned from 7G networks culminate in the suggestion that 7G systems signify the pinnacle of mobile communication technology. The ongoing research on 7G, an intelligent cellular technology, holds promise for the future of wireless communication.

Co-regulation strategy dominated by double short molecules permitting the regrowth of quantum dots for efficient deep-blue perovskite light-emitting diodes

Recently, blue perovskite quantum dots (PeQDs) have garnered considerable attention for use in full-color optoelectronic displays. However, the large specific surface area caused by the small particle size of blue PeQDs results in high defect state density, which severely limits their optical pursuit. To address this issue, a co-regulation strategy using double short-chain molecules of tetraoctylammonium fluoride and tetraethylammonium perfluorooctanesulfonate is proposed to enhance the regrowth of blue CsxRb1−xPb(ClyBr1−y)3 PeQDs. Long-chain insulated oleylamine and oleic acid ligands, which restrict the growth of PeQDs, are substantially replaced using short-chain ligands with higher adsorption energy. This replacement promotes PeQDs to regrow considerably from ∼8 to ∼18 nm, and the defect-state density decreases by 3–5 times. Consequently, highly efficient blue PeQDs with a photoluminescent quantum yield of unity are obtained. Moreover, the PeQDs exhibit lower insulating ligand density and improved charge injection property. As a result, the synthesized deep-blue PeQD light-emitting diodes (PeQLEDs) exhibit a maximum external quantum efficiency of 5.7% at the CIE coordinate of (0.148, 0.032). According to the International Telecommunication Union Radiocommunication Sector television standard (Rec. 2100), the obtained PeQLEDs are state-of-the-art among colloidal deep-blue PeQDs. This study provides a novel strategy to improve the optical performance of deep-blue PeQLEDs and paves the way for developing high-end wide color-gamut displays.

On the Study of Interference Scenario on TV Broadcast and Wireless Systems for Emergency Communication Networks in TVWS

This paper investigated frequency sharing between primary TV systems (channels 32 and 49) and Emergency Communication Networks (ECNs). The networks to be implemented in the Osogbo axis of Osun State function on a secondary geographical basis, creating no harm to the original licensed primary TV viewers. A minimum separation distance of 41 dB was suggested as the protected contour for the UHF spectrum to oversee the protection of primary TV users for the UHF bands under consideration. The effects of changing the secondary systems' transmitting power, transmission frequency, and antenna height on the service coverage distance were also explored. The performance of the UHF band was evaluated when it was utilized for secondary transmission at both low and high transmitting powers, with the performance criterion being percentage coverage distance. This work complies with the International Telecommunication Union-Radio sector (ITU-R) recommendations of 16 dB for signal-to-noise ratio and 41 dB for signal strength. It can also be deduced from the result that when the transmission power of ECN devices is raised from 40 mW to 4 W, Effective Isotropic Radiated Power (EIRP) is used; it caused a 76.19% reduction in the coverage spacing for TV channels of ECN Network secondary devices. For the White Space Device (WSD) to operate in Temporal mode, the maximum allowable power (4 W) used in spatial mode should be replaced by a 76.19 per cent reduction. Additional sensing margins of 3.76 dB and 4.04 dB for channels 33 and 43 must be added to the FCC threshold limit of -114 dBm criterion for TV white spaces to assure ECN deployment without causing severe interference to TV customers.

Rain Attenuations Based on Drop Size Distribution (DSD) Model and Empirical Model at Low THz Frequencies

Rain attenuation based on the drop size distribution (DSD) with different rainfall rates (R) at low THz frequencies is investigated in this paper. The rain attenuation is calculated using the DSD measured for one year and the extinction cross-section (ECS) by the Mie scattering theory. Moreover, the obtained specific rain attenuation is verified by the empirical model using the measurement system consisting of a transmitter, a receiver, and weather measurement units. We measured the received power against the uniform transmitted power at 240, 270, and 300 GHz on the rooftop of the National Radio Research Agency (RRA) in Korea during the same period as the DSD measurement period. After curve fitting by regression analysis, we compared both rain attenuations obtained in two methods with the recommendation International Telecommunication Union Radiocommunication Sector (ITU-R) P.838-3. The root mean square errors (RMSEs) of the DSD model are 2.8977, 2.8646, and 2.8331 at 240, 270, and 300 GHz, respectively. The calculated result using the Mie scattering and the measured DSD methods shows the best fit to the data of the ITU-R recommendation for a rainfall rate of up to 5 mm/h. On the other hand, the empirical results using the T/Rx antenna system are slightly higher compared to the data of the ITU-R recommendation. As the rainfall rate increases, the difference between our results and ITU-R recommendation increases. This study will be useful for predicting rain attenuation for terrestrial wireless links operating at low THz frequencies.

Cascading Energy Transfer for Highly Efficient Deep-Red OLED Emission with Cyclometalated [3+2+1] Iridium Complexes.

The promising cyclometalated iridium (III) complexes have been proved to possess great potential in vacuum-deposited organic light-emitting diodes (OLEDs) applications for full-color displays and white solid-state lighting sources. Herein, based on the unique bidentate ligand of dibenzo[a,c]phenazine (dbpz) group with strong conjugated effect of aromatic rings for red emission, four novel [3+2+1] coordinated iridium (III) emissive materials have been rationally designed and synthesized. The monodentate ligands of -CN and -OCN have been effectively employed to tune the deep-red emission of 628-675nm with high photoluminescence quantum yields up to 98%. Moreover, all devices displayed deep-red color coordinates ranging from (0.675, 0.325) to (0.716, 0.284), which is close to the standard-red color coordinates of (0.708, 0.292), as recommended by International Telecommunication Union Radiocommunication (ITU-R) BT.2020. The device based on nBuIr(dbpz)CN with an exciplex cohost has exhibited maximum external quantum efficiencies of 20.7% and good stability. With nBuIr(dbpz)CN as an effective sensitizer, the nBuIr(dbpz)OCN based phosphorescent OLED devices have successfully demonstrated cascading energy transfer processes, contributing to pure red emission with maximum luminance as high as 6471cd m-2. Therefore, this work has been successfully demonstrated rational molecular design strategy of [3+2+1] iridium complexes to obtain highly efficient deep-red electrophosphorescent emission.

23.1-Gb/s 135-GHz Wireless Transmission Over 4.6-Km and Effect of Rain Attenuation

In this article, we have experimentally demonstrated a fiber-wireless-integration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$</tex-math> </inline-formula> -band (110–170 GHz) transmission system. To extend the wireless transmission distance while maintaining the wireless bit rate as high as possible, we designed high-gain lens horn antenna modules consisting of a pair of dielectric plano-convex lenses and horn antennas for long-haul wireless links. In addition, we employ the Volterra nonlinear equalization (VNE) algorithm based on the multiple-input–multiple-output (MIMO) structure to precisely compensate for the in-phase/quadrature (I/Q) imbalance and nonlinear impairment of quadrature amplitude modulation (QAM) signals mainly caused by photoelectric (O-E) conversion and electric-photo (E-O) conversion. Meanwhile, one of the methods adopted in our experiment to decrease the influence of nonlinearity on high-order QAM signals is coupling the high-order modulation format with the probabilistic shaping (PS) technology. As a result of outdoor field experimental verification, the demonstration at 135 GHz carrier with a net rate of 23.1 Gb/s over 10 km optic-fiber and 4.6 km wireless transmission distance has been successfully carried out. It is, as we know, the first time that a record-breaking product of net bit rate and wireless transmission distance, i.e., 23.1 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4.6 km <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 106.3 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot$</tex-math> </inline-formula> km, has been accomplished based on a fiber-wireless-integration system. Also, for the first time, we have measured the effect of rain attenuation for the 135 GHz millimeter-wave (mm-wave) wireless link and established more accurate rainfall models for the Shanghai region of China by comparing them with multiple rainfall models. This work can be used as a complement to the International Telecommunication Union-Radiocommunication sector (ITU-R) recommendations.

Radio Refractivity Impact on Signal Strength of Mobile Communication

This research investigated radio refractivity impact on signal strength of mobile communication. The mobile communication signal strengths of two popular networks in Nigeria, 9Mobile and MTN, were considered. In the 2100 MHz-3 G band, 9Mobile transmits in the downlink spectrum of 2130.00–2140.00 MHz, while MTN transmits in the downlink spectrum of 2110.00–2120.00 MHz. Also, 9Mobile transmits in the downlink spectrum of 791–821 MHz in the 800 MHz band and 1805–1880 MHz in the 1800 MHz, while MTN transmits in the downlink spectrums of 2620–2690 MHz in the 2600 MHz band; all in the 4 G band. Using the instrument of a mobile station in each station (location) in some selected cities in southern Nigeria, the signal strengths were measured. A cell signal monitor (version 5.1.1) mobile application installed in an Android (transceiver) device (having two SIM slots) constituted the mobile station. To achieve high accuracy, there was a restriction in measuring transmission from specific cells. Hourly measurement of signal strengths was carried out and instantaneously corresponding weather parameters were recorded. Weather parameters for this investigation; atmospheric temperature and pressure; and relative humidity were excerpted online from the Nigeria Meteorological Agency (NIMET) hourly weather report for the various cities where the stations were situated. The hourly radio refractivity was computed using the 2015 International Telecommunication Union–Radio-communication sector (ITU-R) recommended model. Overall, the results indicate that there was no established linear relationship between signal strength and radio refractivity since the overall average R value is 0.0123691 and the overall average standard deviation of R values is 0.1112165. The inconsistencies in the linear relationships obtained from different locations and cells could be due to variations in topography, antenna properties, seasonal variations, wind and position, and distance of the receiver from the transmitter.

Co-Channel Compatibility Analysis of IMT Networks and Digital Terrestrial Television Broadcasting in the Frequency Range 470-694 MHz Based on Monte Carlo Simulation.

According to Resolution 235 adopted during the World Radiocommunication Conference 2015 (WRC-15) and the preliminary agenda item 1.5 of WRC-2023, the International Telecommunication Union Radiocommunication Sector (ITU-R) has been entrusted to carry out sharing and compatibility studies between broadcasting and mobile services in the frequency range 470-694 MHz in Region 1. This study specifically focuses on evaluating electromagnetic compatibility in potential co-channel sharing scenarios between Digital Terrestrial Television Broadcasting (DTTB) and International Mobile Telecommunications (IMT) systems within the 470-694 MHz frequency band that may arise in the foreseeable future. To assess the conditions for coexistence, a Monte Carlo simulation method implemented through the SEAMCAT software version 5.4.2 is employed, examining six potential interference scenarios. The simulation results yield the minimum coordination distance required between IMT and DTTB services in the 470-694 MHz band based on the protection criteria to ensure harmonious coexistence while maintaining satisfactory performance. Furthermore, the study investigates the impact of various factors such as transmitter power, antenna heights, coverage radius, antenna discrimination, and antenna tilt angle on the separation distances. The focus lies primarily on critical interference scenarios across neighboring countries' borders. The simulation outcomes confirm that sharing the same frequency band between IMT and DTTB networks would result in significant mutual interference. Nevertheless, carefully analyzing diverse parameters and assumptions helped provide recommendations to reduce the required separation distances. These findings are valuable for broadcasters, mobile operators, and regulators in establishing the technical coexistence conditions for DTTB and IMT in the new band.

A Breakthrough in Solution-Processed Ultra-Deep-Blue HLCT OLEDs: A Record External Quantum Efficiency Exceeding 10% Based on Novel V-Shaped Emitters.

It is always a great challenge to achieve high-efficiency solution-processed ultra-deep-blue organic light-emitting diodes (OLEDs) with the Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates matching the blue primary of Rec. International Telecommunication Union-Radiocommunication BT.2100, which specifies high dynamic range television image parameters. Inspired by hybrid local and charge transfer (HLCT) excited state emitters improving exciton utilization through high-lying reverse intersystem crossing, here, a series of high-performance blue emitters by a V-shaped symmetric donor (D)-π-acceptor (A)-π-D design strategy are developed. Here, the large torsions and unstable bonds of D-A structures can be improved through π bridges, and also the conjugation length and donor groups can be easily adjusted. The obtained emitters merit excellent photophysical and electrochemical properties, thermal stability, solution processibility, and HLCT excited state excellence. Results suggest that the OLEDs based on the obtained blue emitters all achieve high maximum external quantum efficiency (EQEmax ) of more than 8% with very low efficiency roll-off. In particular, the device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[fluorene-9,2'-imidazole] exhibits a satisfactory ultra-deep-blue emission (CIEx , y = 0.1579, 0.0387) and a record-high EQEmax (10.40%) among solution-processed HLCT OLEDs, which is very close to the record EQEmax of devices by vacuum vapor deposition technology.

Influence of wind speed on rain-based attenuation at Ku-band for earth-satellite links in Nigeria

The peculiarity of the tropical climate shows that when the quality of service (QoS) on Satellite-Earth propagation links is to be determined, the statistics of rain-based attenuation (RbA), storm speed, and their impacts are the important parameters to be considered, especially at frequencies above 10 GHz. This paper assesses the influence of storm speed in estimating RbA at Ku-band, based on 2-year rain rate data obtained using automatic weather station (AWS) and RbA beacon measurements in Nigeria. The rain rates based on the time series were employed to deduce the time series RbA based on the synthetic storm technique (SST) algorithm. The results show a seasonal pattern of rain rate that correlates with the SST-based RbA. The RbA generated closely follows suit with the beacon measurement, especially under low wind speed, and outperforms the international telecommunications union–radiocommunication sector (ITU-R) model based on the lowest metric measures. However, at a higher storm speed, the RbA generated deviated widely from the measured RbA values by about 16%. These results are crucial for figuring out what needs to be done to protect QoS in a tropical area where wind and rain are common.

Adoption of Deep Neural Network Model for the Prediction of Rain Attenuation

Weather, rain, and atmospheric forces cause attenuation in communication satellites and devices, which affects the quality of calls and internet access. Communication signals can seriously be affected by rainfall and various research has entailed developing adequate rainfall prediction models that can accurately predict rain attenuation. Predicting rainfall attenuation from measured data is a challenging process and several rainfall attenuation models exist, but their estimates are not close to actual measured rainfall attenuation data. This paper predicts rain attenuation using a Deep Neural Network (DNN) and modelling process to propose a probabilistic model that gives better results. The proposed model was built using information from the International Telecommunications Union Radiocommunication for propagation statistics and prediction techniques needed for the construction of Earth-space telecommunication systems. Rainfall data spanning a period of seven years (January 2014 to December 2020) in Oyo State were collected from Nigerian Meteorological Agency (NIMET). Results showed that the proposed model was able to predict well even with new data (2021) and this was used to show how well the DNN model can perform using rainfall features and elimination complex mathematical models to describe the mappings between rainfall attenuation and rainfall data. This is also evident from the performance graph which shows an RMSE of 0.21 and a Loss of 0.021 at the 100 epochs. The results also reveal that the proposed model results observed against predicted, performed relatively well. From the performance metrics, it shows a value of 0.7172 for Pearson’s linear correlation, showing a strong similarity of predicted versus observed. The mode efficiency index nt on the other hand, shows a value of 0.1744 and gives near acceptable results. In conclusion, the research showed that the Deep Neural Network model was able to predict well compared to the ITU-R model.

Millimeter Wave Attenuation Due to Wind and Heavy Rain in a Tropical Region.

Millimeter wave fixed wireless systems in future backhaul and access network applications can be affected by weather conditions. The losses caused by rain attenuation and antenna misalignment due to wind-induced vibrations have greater impacts on the link budget reduction at E-band frequencies and higher. The current International Telecommunications Union Radiocommunication Sector (ITU-R) recommendation has been widely used to estimate rain attenuation, and the recent Asia Pacific Telecommunity (APT) report provides the model to estimate the wind-induced attenuation. This article provides the first experimental study of the combined rain and wind effects in a tropical location using both models at a frequency in the E band (74.625 GHz) and a short distance of 150 m. In addition to using wind speeds for attenuation estimation, the setup also provides direct antenna inclination angle measurements using the accelerometer data. This solves the limitation of relying on the wind speed since the wind-induced loss is dependent on the inclination direction. The results show that the current ITU-R model can be used to estimate the attenuation of a short fixed wireless link under heavy rain, and the addition of wind attenuation via the APT model can estimate the worst-case link budget during high wind speeds.

An Optimized Planning Tool for Microwave Terrestrial and Satellite Link Design

Today, the internet is fundamental to social inclusion. There are many people that live in remote areas, and the only way to supply internet services is through the use of microwave terrestrial and satellite systems. Thus, it is important to have efficient tools to design and optimize these systems. In this paper, a tool with the objective to shorten the time spent in the design process of microwave terrestrial and satellite point-to-point links is presented. This tool can be applied in academia by engineering students, providing an extended analysis of many sections of a link project design, as well as in professional practice by telecommunication engineering departments, presenting a concise step-by-step interactive design process. This tool uses three-dimensional world visualization, with the Cesium Application Programming Interface (API), to display and analyze site-specific characteristics that can disrupt the link’s quality of service (QoS). Using this visualization, two ray-tracing algorithms were developed to analyze signal diffraction and reflection mainly throughout terrestrial links. Using this new algorithm, an innovative process for signal diffraction and reflection calculations was created. Using updated standards provided by the International Telecommunication Union Radiocommunication Sector (ITU-R), the characteristics of the defined simulated links could be predicted, thus providing the user with the metrics of signal quality and system link budget.

On the applicability of some existing tropospheric scintillation prediction models for Ikeja and Abuja, Nigeria

Tropospheric scintillation which causes rapid fluctuation of signal due to the turbulence in the atmosphere is of significance in satellite link budget design. Existing models that predict the intensity of scintillation such as Karasawa, International Telecommunication Union Radiocommunication (ITU-R) Sector, Otung, Van de Kamp and Ortgies are not appropriate for predicting scintillation intensity (SI) in Nigeria due to localization of the models to particular regions. The monthly average air temperature and relative humidity for Ikeja and Abuja, Nigeria, retrieved from the Nigerian Meteorological Centre data bank were used for the investigation. An elevation angle of 5° was used as look angle, antenna diameter of 0.3 m, 40 GHz and 45 GHz frequencies were considered in this study. The existing scintillation model values were then compared with the measured values for the two locations to determine the best performance model. The SI results at 40 GHz and 45 GHz were obtained for each of the existing models. It could be deduced from the results obtained that orgies model values were the most closet to the measured values. Therefore, Orgies-N model was the most appropriate for SI prediction in Ikeja and Abuja.

Ku-band specific attenuation coefficients for high-throughput satellites in equatorial region

Ku-band have a larger attenuation during heavy rain in the equatorial region. Despite that, Ku-band has been identified as a frequency band in high-throughput satellite systems (HTS) for broadband satellite communication. The available rain fade prediction models are still not able to accurately predict rain attenuation in the equatorial region. The models depend on the specific attenuation parameters produced based on the international telecommunication union radiocommunication sector (ITU-R) instead of the measured value. Direct measurement of specific attenuation is more accurate but difficult to obtain because the correlation of rainfall rate and satellite signal loss due to rain must be obtained simultaneously. This paper aims to derive new specific attenuation frequency-dependent coefficients for Ku-band using the semi-empirical method. The Malaysia East Asia Satellite 3 (MEASAT-3) satellite data was collected using a 13 m antenna located at Cyberjaya, Selangor while the rainfall data was collected by the nearby hydrological station. The specific attenuation was obtained from correlations of the direct measurement of rain attenuation and rainfall rate. The new frequency-dependent coefficients for Ku-band specific attenuation values are k = 4.6690 and α = 0.1941. The newly acquired specific attenuation coefficients have improved the rain attenuation model prediction for the equatorial region.

Mixed-Numerology Channel Division for Wireless Avionics Intracommunications

Increasing attention has been paid to the wireless avionics intracommunications (WAIC) on aircraft. The frequency band of 4200-4400 MHz is recommended to WAIC by the International Telecommunication Union Radio Communication Sector (ITU-R), which thereby comes with a new challenge of using the available frequency band effectively to cater for the massive communication needs in aircraft. To address this challenge, we propose the first channel design framework named mixed-numerology channel division (MNCD) specifically for WAIC. Furthermore, a general interference model has been proposed to better utilize the recommended frequency band. Extensive evaluations show that the proposed framework can be a promising solution for massive wireless communications in aircraft.

Realistic Prognostic Modeling of Specific Attenuation due to Rain at Microwave Frequency for Tropical Climate Region

Absorption and scattering of propagated microwave radio signals by atmospheric variables, particularly rainfall, remained a major cause of propagation attenuation losses and service quality degradation over terrestrial communication links. The International Telecommunications Union Radio (ITU-R) reports and other related works in the literature provided information on attenuation due to rain and microwave propagation data. Such propagation attenuation information in the tropical region of Nigeria is destitute, especially at lower radio waves transmission frequencies. Therefore, this study addresses this problem by employing 12-year rainfall datasets to conduct realistic prognostic modeling of rain rate intensity levels. A classification of the rainfall data into three subgroups based on the depth of rainfall in the region is presented. Additionally, an in-depth estimation of specific rain attenuation intensities based on the 12-year rainfall data at 3.5 GHz is demonstrated. On average, the three rainfall classes produced rain rates of about 29.27 mm/hr, 73.71 mm/hr, and 105.39 mm/hr. The respective attenuation values are 0.89 dB, 1.71 dB, and 2.13 dB for the vertical polarisation and 1.09 dB, 1.20 dB, and 2.78 dB for the horizontal polarisation at 0.01% time percentage computation. Generally, results indicate that higher rain attenuation of 12% is observed for the horizontal polarisation compared to the vertical polarisation. These results can provide valuable first-hand information for microwave radio frequency planning in making appropriate decisions on attenuation levels due to different rainfall depths, especially for lower frequency arrays.

Water vapor estimation based on 1-year data of E-band millimeter wave link in North China

Abstract. The amount of water vapor in the atmosphere is very small, but its content varies greatly in different humidity areas. The change in water vapor will affect the transmission of microwave link signals, and most of the water vapor is concentrated in the lower layer, so the water vapor density can be measured by the change in the near-ground microwave link transmission signal. This study collected 1-year data of the E-band millimeter wave link in Hebei, China, and used a model based on the International Telecommunication Union Radiocommunication Sector (ITU-R) to estimate the water vapor density. An improved method of extracting the water-vapor-induced attenuation value is also introduced. It has a higher time resolution, and the estimation error is lower than the previous method. In addition, this paper conducts the seasonal analysis of water vapor inversion for the first time. The monthly and seasonal evaluation index results show a high correlation between the retrieved water vapor density and the actual water vapor density value measured by the local weather station. The correlation value for the whole year is up to 0.95, the root mean square error is as low as 0.35 g m−3, and the average relative error is as low as 5.00 %. Compared with European Center for Medium-Range Weather Forecast (ECMWF) reanalysis, the correlation of the daily water vapor density estimation of the link has increased by 0.17, the root mean square error has been reduced by 3.14 g m−3, and the mean relative error has been reduced by 34.00 %. This research shows that millimeter wave backhaul link provides high-precision data for the measurement of water vapor density and has a positive effect on future weather forecast research.

A Medium-Sized Monitor Loudspeaker for Multichannel Audio Environments Conforming to ITU-R Recommendation

A medium-sized monitor loudspeaker is proposed and developed for multichannel audio environments conforming to the requirements of International Telecommunication Union Radiocommunication Sector (ITU-R): Recommendation (Rec.) ITU-R BS.1116-3. Moderate monitor loudspeakers are currently required in dubbing studios and experimental rooms in which multiple loudspeakers need to be installed. Such a loudspeaker requires a sufficient maximum sound pressure level, a flat frequency response, and an appropriate directivity providing a practical coverage; a size acceptable for multichannel audio environments is also essential. The proposed loudspeaker is developed realizing the directivity index within the specified target range by combining multiple loudspeaker units and controlling the cross-over frequencies. An integrally powered structure is adopted for convenience of installation, and a switching amplifier is selected for downsizing. As a result, the size of the developed loudspeaker gets suitable for the existing multichannel audio environments. The acoustic characteristics of the developed loudspeaker is investigated both in static and dynamic conditions. The measurement results verify that the developed loudspeaker conforms to almost all specifications of Rec. ITU-R BS.1116-3.

Rain Attenuation Scaling in South Korea: Experimental Results and Artificial Neural Network

Scaling rain attenuation parameters will significantly benefit the quick monitoring of rain attenuation in a particular channel with previously known results or in situ setup attenuation measurements. Most of the rain attenuation scaling techniques have been derived for slant links. In this study, we also applied frequency and polarization scaling techniques for terrestrial link applications. We collected real measured datasets from research paper publications and examined those datasets using International Telecommunication Union-Radiocommunication sector (ITU-R) models (P.530-17, P.618-13). Our analyzed results show that existing long-term frequency and polarization scaling rain attenuation models (ITU-R P.618-13 for slant links and ITU-R P.530-17 for terrestrial links) show reduced performance for frequency and polarization scaling measured locations in South Korea. Hence, we proposed a new scaling technique using artificial neural networks from the measured rain attenuation data of slant and terrestrial links in South Korea. The experimental results confirm that the proposed Artificial Neural Network (ANN)-based scaling model shows satisfactory performance to predict attenuation for frequency and vertical polarization scaling.