Received Signal Level Research Articles

Robust Broadband Maritime Communications: Theoretical and Experimental Validation

AbstractAtmospheric ducts, which are caused by the rapid decrease in the refractive index of the lower atmosphere, have been recognized as the dominant propagation mechanism for long range maritime links. Recent advances in radio technology are making reliable high‐capacity overwater links a reality. A ray‐tracing simulation model was developed to obtain reliable prediction of maritime link performance beyond 30 km for realistic conditions. A series of static and mobile long range maritime multiple‐input multiple‐output links were tested with representative antenna heights at 1.39 (Band 3 or L‐Band) and 4.5 GHz (Band 4 or C‐Band) during periods with various levels of ducting activities, for example, sunset and sunrise times. Measured link performance and observed ducting occurrences are compared to predictions to validate the model ability to accurately predict and explain link performance for various ducting conditions. The test results agree with the model predictions and illustrate the various Received Signal Level degradation, enhancement, and fluctuations that can be expected in long range maritime links below 6 GHz. We also report on short‐term (few to several minutes) fluctuations of the received signal level at the two measurement frequency bands during high ducting activity periods. Measurements and theoretical analysis of the effect of ducting on the quality of maritime communication links indicate that both reflection‐induced and ducting‐induced disruptions are different and more frequent in higher‐frequency bands. This work opens interesting perspectives on providing more robust and more predictable communications in the presence of ducting.

Spectral coexistence between LEO and GEO satellites by optimizing direction normal of phased array antennas

This paper addresses the spectral coexistence between LEO constellation and GEO belt for global distributed earth stations. A specific method is introduced to mitigate the in-line interference by tilting the direction normal of phased array antennas of LEO satellites, and the optimal direction is found by solving a non-linear programming problem. The simulation results prove that the proposed approach leads to greater link availability while guaranteeing the desired received signal level especially for low-latitude earth stations.

WiFi-Friendly Building to Enable WiFi Signal Indoor

The 802.11 networks (wireless fidelity (WiFi) networks) have been the main wireless internet access infrastructure within houses and buildings. Besides access point placement, building architectures contribute to the WiFi signal spreading. Even dough WiFi installation in buildings becomes prevalent; the building architectures still do not take WiFi-friendliness into considerations. Current research on building and WiFi are on access point location, location based service and home automation. In fact, the more friendly the building to WiFi signal, the more efficient the 802.11 based wireless infrastructure. This paper introduces the term of WiFi-friendly building by considering signal propagations, the obstacle impact, as well as proposing an ornament-attaced reflector and a hole-in-the-wall structure to improve WiFi signal distribution. Experiment results show that obstacle materials made of concrete reducing WiFi signal the most, followed by metal and wood. Reflecting materials are able to improve the received signal level, for instance, the implemented ornament-attached reflector is able improving the received signal up to 6.56 dBm. Further, the hole-in-the-wall structure is successfully increasing WiFi signal up to 2.3 dBm.

Disparities in the Induced Rain Attenuation between Beacon (Narrowband) and Broadband Satellite Links in Tropical Zones

<span lang="EN-GB">The utilisation of higher frequency bands above 10 GHz by the satellite industries to provide the bandwidth (BW) required for broadband multimedia services, video conferencing, direct-to-home TV programmes and IP data requires the understanding of atmospheric losses and good link planning for satellite-to-earth links. The trade-off between the service availability, data rate and BW determine the type of modulation scheme and error corrections to be employed. These services also depend on the link performance under adverse atmospheric conditions, especially rain-induced attenuation. In this research, study measurements were conducted on space-to-earth satellite links using the beacon narrowband and broadband IP carrier signals of a Nigcomsat-1R satellite operating at 42.5°E. A VSAT receiving terminal at a latitude of 7.4°N, longitude of 9.04°E and altitude of 334 m above sea level was utilised to quantify the rain-induced attenuation of both the beacon and broadband signals during rain events. The measurements were then compared with the link performance under clear sky conditions. The performance revealed that, when compared with the broadband signal, the induced rain attenuation on beacon signal presented a disparity in the responses, resulting in significant variations of 10.14 dB in the carrier-to-noise ratio (C/N) and 17.42 dB in the received signal level at a Ku-band frequency of 12.518 GHz. These observations were also compared with the Crane global rain map and ITU-R P.618-12. Both models disagreed with the measurement values for Abuja, Nigeria.</span>

Measurements of the Received Signal Level and Service Coverage Area at the IEEE 802.11 Access Point in the Building

Access point (AP) is part of a Wireless Local Access Network (WLAN) with its communications using WiFi. AP is used to transmit and receive data to users/clients. The ability of AP to serve users/clients depends on many factors. Moreover, if AP is applied in conditions inside the building. In this study, AP is installed at two points inside the building and then measured in the form of the received signal level (RSL) and service coverage area. One AP measured its performance by 26 measurement points and the other AP measured its performance by 20 measurement points. When AP has measured its performance then another AP position is switched off. Based on the measurement result, the received signal level value is the highest value is about -47 dBm at a distance of 3.2 m, while the lowest is about -79 dBm at a 9.21 m because it is on barrier 2 walls. While based on service coverage area, the area which is far away from the AP then the quality of service becomes bad because the transmitted signal is weakening caused by the distance and the loss of the wall.

Resonance-Enhanced Coupling for Range Extension of Electromagnetic Tracking Systems

This paper investigates the use of resonance-enhanced coupling to increase the received signal level in a six-degree-of-freedom electromagnetic tracking system. Resonant coupling is found to increase the efficiency of the transmitter and increase the gain of the sensing coil, resulting in improved range. However, the measurement update rate is reduced due to the settling time of the transmitter circuit and the limited bandwidth of the sensing circuit. A resistive tuning approach is proposed to balance the tradeoff between a decreased measurement bandwidth and an improved signal level.

Artificial neural network based antenna sensitivity assignments for chaotic internet service provider network architecture

The connectivity and grade of service of an Internet Service Provider (ISP) in the Philippines is observed and analysed in this research. Traditionally, the sensitivity of the antennas for wireless access points are done manually by monitoring the signal levels onsite during the installation process. Ten subscriber locations are randomly selected as test points. The connectivity of these subscribers is observed given that their sensitivities are set manually. Finally, a proposed artificial neural network algorithm is presented to improve the availability of the internet link. The proposed algorithm incorporates the random variations of the received signal levels of the internet access points and possible degradation of signals from attenuation due to rain. Experiment results show that at least 75% increase in availability is observed using the proposed algorithm during rainy events.

Rainfall Estimation Based on the Intensity of the Received Signal in a LTE/4G Mobile Terminal by Using a Probabilistic Neural Network

Rainfall estimation based on the impact of rain on electromagnetic waves is a novel methodology that has had notable advancements during the last few years. Many studies conducted on this topic in the past considered only the electromagnetic waves with frequencies greater than 10 GHz since the rainfall impact on the electromagnetic wave attenuation is reduced at lower frequencies. Over the last few years, some authors have demonstrated that there can be a non-negligible attenuation even on the signals received on a global system for mobile communications mobile terminal in presence of rain. In this paper, we propose a new classification method based on a probabilistic neural network to obtain an accurate classification between four rainfall intensities (no rain, weak rain, moderate rain, and heavy rain). The innovative rainfall classification method is based on three received signal level (RSL) local features of the 4G/LTE: the instantaneous RSL, the average RSL value, and its variance calculated by using a sliding window. The proposed method exhibits good performance, obtaining an overall correct classification rate of 96.7%. Almost all papers on this topic present in the literature focus on electromagnetic waves with frequencies greater than 10 GHz, in which the rain impact is more relevant, according to the rain attenuation model. However, only the 4G/LTE signal has such widespread geographic coverage, so the proposed classification method can provide noticeable improvements in the creation of rainfall maps with higher spatial resolution.

Performance Evaluation of WCDMA Networks in Selected Geolocations Using Structured Questionnaire and Empirical Analysis Methods

High influx in the number of cellular subscribers is observed to be one of the constraints to incessant poor network  performance which results to increased congestion challenges. This work is attributed towards executing network performance evaluation to ascertain the levels of degradation on the WCDMA networks from selected geographical locations in Owerri, the capital city of Imo State, Nigeria. The methods adopted are structured questionnaire and empirical analysis. Structured questionnaires were administered to survey 250 customers from the two (2) major and dominant network providers in Owerri metropolis: MTN and AIRTEL, on their Quality of Service (QoS) delivery and to determine their network satisfactory performance rates. Empirical analyses were conducted on the two networks to evaluate their network performances using the selected Key Performance Indicators (KPIs). Aba road, FUTO road, Onitsha road, Orlu road and Wetheral road were selected for the analysis owing to the high density of the network subscribers within these regions. The Selected KPIs which include Call Drop Rate (CDR), Call Setup Success Rate (CSSR), Call Completion Success Rate (CCSR), network accessibility, network retainaibility and Receive Signal Level (RXLEV) were deployed to evaluate the various performance characteristics of the networks based on the QoS. From the result assessments, none of the networks met the Nigeria Communication Commission (NCC) thresholds based on the KPIs selected except for MTN network along FUTO, Wetheral and Onitsha roads marginally agreed with the NCC target value on CCSR. Also MTN network along Onitsha road slightly met the NCC target value on CSSR and network accessibility.

V2V Radio Channel Performance Based on Measurements in Ramp Scenarios at 5.9 GHz

This paper focuses on vehicle-to-vehicle (V2V) radio channel properties under ramp scenarios with different structures. Ramps are categorized according to different construction structures into: 1) viaduct ramp with soundproof walls in an urban area and 2) a general ramp without soundproof walls in a suburban region. Furthermore, considering whether the line of sight is available, the entire propagation process of the radio signal is divided into various propagation zones. Propagation characteristics, including the distribution of fading, fading depth (FD), level crossing rate, average fade duration, Root-Mean-Square (rms) delay spread, propagation path loss, and shadow fading, have been estimated and extracted. In particular, the radio channel properties in different types of ramp scenarios are compared and some interesting findings are obtained: 1) an abrupt fluctuation of the received signal level (RSL) in the urban viaduct ramp scenario indicates the nonignorable impact of soundproof walls on V2V radio channel and 2) continuous changes of RSL and different FD values in various propagation zones can be observed in suburban ramp scenarios. Furthermore, the statistical characteristics of RMS delay spread are fitted using a generalized extreme value model with a good fit. Furthermore, propagation path loss is modeled, demonstrating the difference of path loss values in the transition region owing to the impact of soundproof walls. Overall, the research results emphasize the significance of the V2V radio channel modeling under ramp scenarios.

The Wet-Antenna Effect—A Factor to be Considered in Future Communication Networks

An accurate design of the fading margin in wireless communication networks requires good modeling of the relationship between the rain rate and the attenuation. In this paper, we discuss the effect of the wet antenna (WA) on the fading margin. We claim that this effect is not negligible in commercial $E$ -band (i.e., 60–90 GHz) technologies, where the microwave links are relatively short and the sensitivity of the signal to attenuation induced by rain is significant. Consequently, we propose a method for estimating the WA-induced attenuation, so it can be incorporated in the current models. Different from previous studies, our proposed method can be implemented on received signal level measurements, which are standardly produced by commercial microwave links (CMLs) and a single rain gauge. We demonstrate our results using actual measurements taken by 73 GHz CMLs of about 1 km, provided by Ericsson.

Seasonal and Annual Analysis of Slant Path Attenuation Over a 12 GHz Earth-Satellite Link in Subtropical Africa

With a view to establish a measurement-based profile and prediction model of slant path attenuation due to subtropical rain, rainfall data as well as received signal level (RSL) over a 12 GHz satellite TV Receive Only (TVRO) link were monitored simultaneously over a period of about two years in Durban South Africa (28087’S, 30098’E). The rain rate (R0.01) exceeded at 0.01% of time at the location seasonally and over the period of measurement was obtained as 69 mmh-1. The variation pattern of the received signal in clear air over the period was investigated and its relationship with fluctuations of atmospheric parameters other than rain was established by multiple regression. Event-by-event correlation of the rain rate data with that of the RSL in the time domain was carried out, resulting in a reliable subtropical rain attenuation profile which was used to develop a model for slant path rain attenuation due to subtropical precipitation. The model was validated by comparison with the generalized ITU-R model. The latter was found to slightly overestimate path attenuation at rain rates higher than 30 mm/h. The path attenuation exceedance probability over the link is also presented.

Shore-to-Undersea Visible Light Communication

In this paper, a novel visible light based shore-to-undersea (S2US) communication is proposed. It considers various properties of both maritime and undersea environments such as wave height, wind speed, and absorption. A lighthouse transmits the signal using white light emitting diodes (LEDs) and this signal is received by a buoy that acts as a beacon to relay to the undersea receiver. The beacon employs the decode-and-forward (DF) method in such a way that green LEDs transmit the DF processed signal to the undersea receivers via the undersea optical channel. The performance of the proposed S2US system was first evaluated via simulations with the JONSWAP spectrum model representing the maritime optical channel and the Jerlov water type representing the undersea optical channel. The results show that the transmitted signal undergoes significant attenuation, particularly over the undersea optical channel. At the reference distance of 1.025 km with Jerlov water type I, a bit error rate performance of 10−4 is achieved with a data rate of 1 Mbps. The S2US was further verified with experiments in terms of received signal level on a laboratory scale. The comparative analysis demonstrates that the simulation and experiment results are in good agreement.

Changes of atmospheric properties over Belgrade, observed using remote sensing and in situ methods during the partial solar eclipse of 20 March 2015

Measurements of atmospheric parameters were carried out during the partial solar eclipse (51% coverage of solar disc) observed in Belgrade on 20 March 2015. The measured parameters included height of the planetary boundary layer (PBL), meteorological parameters, solar radiation, surface ozone and air ions, as well as Very Low Frequency (VLF, 3–30 kHz) and Low Frequency (LF, 30–300 kHz) signals to detect low-ionospheric plasma perturbations. The observed decrease of global solar and UV-B radiation was 48%, similar to the solar disc coverage. Meteorological parameters showed similar behavior at two measurement sites, with different elevations and different measurement heights. Air temperature change due to solar eclipse was more pronounced at the lower measurement height, showing a decrease of 2.6 °C, with 15-min time delay relative to the eclipse maximum. However, at the other site temperature did not decrease; its morning increase ceased with the start of the eclipse, and continued after the eclipse maximum. Relative humidity at both sites remained almost constant until the eclipse maximum and then decreased as the temperature increased. The wind speed decreased and reached minimum 35 min after the last contact. The eclipse-induced decrease of PBL height was about 200 m, with minimum reached 20 min after the eclipse maximum. Although dependent on UV radiation, surface ozone concentration did not show the expected decrease, possibly due to less significant influence of photochemical reactions at the measurement site and decline of PBL height. Air-ion concentration decreased during the solar eclipse, with minimum almost coinciding with the eclipse maximum. Additionally, the referential Line-of-Sight (LOS) radio link was set in the area of Belgrade, using the carrier frequency of 3 GHz. Perturbation of the receiving signal level (RSL) was observed on March 20, probably induced by the solar eclipse. Eclipse-related perturbations in ionospheric D-region were detected based on the VLF/LF signal variations, as a consequence of Lyα radiation decrease.

Small-aperture array processing for passive multi-target angle of arrival estimation.

Small aperture arrays (size less than a wavelength) can be used for passive angle of arrival (AOA) estimation of both broadband and narrowband signals in the frequency domain. Phase differences across the array are measured in the frequency domain and can be spectrally averaged if desired for stationary source AOA and frequencies. The array is capable of measuring multiple target AOAs so long as each target produces unique frequencies or radiates in unique frequency bandwidths. Broadband and narrowband signals from targets can be collected from the fast Fourier transform (FFT) bins and summed by arrival angle in elevation and azimuth using a bearing histogram where the amplitude is displayed in dB. This provides a very useful and intuitive display of received signal levels. The Cramer-Rao lower bound (CRLB) for bearing accuracy is presented as a function of frequency, aperture, and signal-to-noise ratio (SNR). The small aperture background noise includes any other coherent or incoherent signal other than the source of interest. Analysis of phase calibration requirements, nonstationary frequencies, and channel cross-talk are also presented, as well as a technique for generating broadband source signals with the fractional delays needed to simulate the correct AOA.

Stratospheric Winds and Rain Effect on HAPS Backhaul Link Performance


 today, fourth generation of mobile communication turn out to be in active mode for several countries and one of the most promisingtechnologies used for a backhaul service is High Altitude Platform Stations (HAPS). While HAPS still suffers from environment effects in stratospheric layer like rain and winds.In this research paper, a study of the effect of the positional instability of HAPS (aircraft category) on the link level performance of an International Mobile Telecommunications Advanced (IMT-Advanced) served by HAPS is presented. The analysis is performed in three different climatic conditions of Malaysia, which is a tropical country. Then two types of radio links have been analyzed – firstly, the end user link which connects aerial station and end user and then, backhaul link that establishes communication between HAPS and Ground Transmission Gateway (GTG). A Problem of fluctuations in the signal level and degrading the performance level had been solved by analyze the behavior of winds in stratospheric layer. Finally, the effect of instability was given in received signal level variation and link availability or percentage outage of the link. Obtained results showed that the link availability of the backhaul link meets the ITU-R recommendations. Lately, it can be said that the results of the service obtained can be used to design the communication network with a higher level of user satisfaction.

Improved ITU‐R model for digital terrestrial television propagation path loss prediction

The use of a suitable propagation model for coverage prediction is key during the planning and dimensioning process of a digital terrestrial television (DTT) system. This study optimises one of the most detailed models for this purpose, i.e. Recommendation ITU-R.P.1812-4, with the aim of improving its accuracy in propagation path loss prediction for DTT systems in outdoor environments of Caracas city, Venezuela. For model adjustment, it is used the bioinspired technique particle swarm optimisation (PSO) and received signal level measurements performed in DTT systems in Caracas city under fixed reception conditions. The results, quantitatively analysed by RMS error and grey relation grade and mean absolute percentage error, shows a significant increase of the accuracy of optimised model in comparison with the original version and even with others propagation models.

Increasing SDR Receiver Dynamic Range by ADC Diversity

Nowadays, most radio implementations are based on software-defined radio (SDR) technologies. The capabilities of digital signal processing enable new applications like low power wide area networks (LPWAN), which are expected to play a decisive role in the upcoming Internet of Things. Centralized gateways, usually realized in an SDR architecture, are used to connect many thousands of objects to the internet. Due to the high variance of the received signal level, a high dynamic range is required for the SDR receiver front-end. In current receiver architectures, the dynamic range is mainly limited by the analog-to-digital converter (ADC). Several techniques have been proposed to extend the dynamic range by stacking multiple ADCs and driving them with different gain factors. Correlation of quantization noise was identified as key parameter to determine the dynamic range enhancement. This paper compares the proposed techniques and extends existing analysis tools for the use of arbitrary gain factors. Additionally, the influence of further noise sources like thermal noise and jitter are taken into account. The theoretical considerations are supported by simulations and measurements using a real LPWAN SDR implementation.

Study of Indoor Path Loss Computational Models for Femtocell Based Mobile Network

Path loss minimization in next generation mobile network is a challenging research area. The signal transmitted by a base station degrades due to various obstacles in the environment. The received signal level at the mobile station is less than the transmitted signal level of the base station. This loss in the signal level is referred as path loss in mobile network. In this paper different path loss models are discussed for indoor environment covered by femtocell. It is assumed that the mobile users in that region exclusively access the services of femtocell. As only indoor area is considered, non-line of sight propagation is examined. Signal-to-interference-plus-noise-ratio for a femtocell base station is calculated. The performance of the path loss models are analyzed using vector signal generator and vector signal analyzer. A comparative analysis is carried out between the models. Based on the comparative analysis, a case study is performed to demonstrate how an appropriate path loss model will be selected depending on the frequency range, building type, walls and floors.

Dynamic Rain Attenuation Model for Millimeter Wave Network Analysis

In millimeter wave networks, a received signal level and interference dynamically vary due to rain attenuation. These physical layer variations have influence on upper communication layers, which yield to variable network capabilities to serve traffic demands. Standards and agreements between service providers and users usually specify performance objectives at annual level. In order to make realistic annual level performance analysis of such networks, a new computationally efficient dynamic rain attenuation model is proposed and analyzed. The model reproduces assumed rain statistics at annual level: cumulative distribution function (cdf) of rain intensity, number of rain events in which specified rain intensity threshold is exceeded, rain advection vector intensity, and rain advection vector azimuth. Derivation of model parameter tolerances is based on the experimental results from dense rain gauge network. As an example of model application, annual level cdfs of node-to-node connection capacity in a test network are calculated.