Fade Margin Research Articles

Slant Path Ka-Band rain attenuation statistics in equatorial Malaysia obtained using stratiform convective-synthetic storm technique

In the design of satellite communication link, rain attenuation statistics is essential information for system designer to realistically determine link availability and provide means to combat system degradation. Due to the limitation of available measured data in equatorial regions especially for high frequencies (Ka-band and above), the prediction model is the best way to obtain rain attenuation statistics. This paper presents statistical analysis of rain attenuation at Ka-band by applying the Stratiform Convective-Synthetic Storm Technique (SC-SST) model taking advantage from local weather features from rain rate time series. The study on seasonal and diurnal variability is also presented in this paper to provide good insight in the design and implementation of fade margin.

Fading Characteristics in Evaporation Duct: Fade Margin for a Wireless Link in the South China Sea

Evaporation ducts (ED), which are caused by a rapid decrease in the refractive index of the lower atmosphere, are known to trap radio waves between the evaporation duct layer and the sea surface. Although signal propagation and refractivity estimation in evaporation ducts have been well studied, the fading characteristics of ED must be accurately established to help determine fade margin, required for a reliable wireless communication link. In this paper, based on the percentage of occurrences of evaporation ducts, that have been measured and reported in the literature, the statistical distribution of path loss in the South China Sea is calculated for varying distances. These path loss distributions are weather-dependent and time-varying and define several slow time-varying fading characteristics. These slow fading characteristics are, what can be termed as log-lognormal in nature. Propagation in ED, being non-line-of-sight, also has a fast-fading component that is Rayleigh in nature. Once, the complete fading characteristics are known, the overall fade margin due in part; to both slow fading and fast fading can be obtained. For a distance of 100 km, approximately 99% availability can be obtained with an 88-dB fade margin while for a shorter distance of 50 km, the required total margin for 99% availability is only 50-dB.

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.

IoT‐Based Management Platform for Real‐Time Spectrum and Energy Optimization of Broadcasting Networks

We investigate the feasibility of Internet of Things (IoT) technology to monitor and improve the energy efficiency and spectrum usage efficiency of broadcasting networks in the Ultra‐High Frequency (UHF) band. Traditional broadcasting networks are designed with a fixed radiated power to guarantee a certain service availability. However, excessive fading margins often lead to inefficient spectrum usage, higher interference, and power consumption. We present an IoT‐based management platform capable of dynamically adjusting the broadcasting network radiated power according to the current propagation conditions. We assess the performance and benchmark two IoT solutions (i.e., LoRa and NB‐IoT). By means of the IoT management platform the broadcasting network with adaptive radiated power reduces the power consumption by 15% to 16.3% and increases the spectrum usage efficiency by 32% to 35% (depending on the IoT platform). The IoT feedback loop power consumption represents less than 2% of the system power consumption. In addition, white space spectrum availability for secondary wireless telecommunications services is increased by 34% during 90% of the time.

Performance analysis of rain attenuation on earth-to-satellite microwave links design in Libya

Performances of earth-to-satellite microwave links operating in Ku, Ka, and V-bands are degraded by the environment and strongly attenuated by rain. Rain attenuation is the most significant consideration and challenge to design a reliable earth-to-satellite microwave links for these frequency bands. Hence, it is essential for satellite link designer to take into account rain fade margin accurately before system implementation. Rain rate is the main measured parameter to predict of rain attenuation. Rainfall statistical data measured and recorded in Libya for the period of 30 years are collected from 5 locations. The prediction methods require one minute integration time rain intensity. Therefore, collected data were analyzed and processed to convert into one–minute rain rate cumulative distribution in Libya. The model proposed by ITU-R is used to predict and investigate rain fade based on converted 1-minute rain rate data. Rain fade predicted at two locations are used for performance analysis in terms of link spectral efficiency and throughput. V-band downlink shows that 99.99% availability is possible in all the Southern part stations in Libya at 0.29 bps/Hz spectral efficiency and 20.74 Mbps throughput when 72 MHz transponder band width is used which is not feasible in Northern part. Results of this paper will be a very useful resource to design highly reliable earth-to-satellite communication links in Libya.

Path Loss Measurements of Indoor LTE System for the Internet of Things

The Internet of Things (IoT) provides communication service for future smart manufacturing, which is capable of independently exchanging and responding to information to manage industrial production processes. For the purpose of connecting machines, devices, sensors, and people with each other in a factory, reliable and scalable communication networks used in the cellular IoT are of great importance. This paper aims at channel parameter measurements of indoor Long Term Evolution systems in order to achieve good coverage and service reliability (SR) for the IoT. For the purpose of determining the path loss exponent and the standard deviation of the received shadow fading signal, we use software defined radio techniques to build a small cell experimental platform which contains an evolved node B and user equipment. Received power measurements were performed on this platform. Finally, based on the experimental results, the modified path loss model and the calculated fade margin (FM) for 90% SR are exploited to predict the coverage range of the small cell base station deployed in the factory. The measured path loss channel models are compared with International Telecommunication Union (ITU) path loss channel model.

Mitigation of Ionospheric Scintillation Effects on GNSS Signals Using Variational Mode Decomposition

This letter addresses the problem of ionospheric scintillation effects on the global navigation satellite system (GNSS) signals. Severe scintillations degrade the signal intensity below the fade margin of the GNSS receiver, resulting in failure of the positioning and navigational services. A robust methodology is needed for the estimation and mitigation of such ionospheric scintillation effects. Hence, in this letter, the application of an adaptive signal decomposition technique based on variational mode decomposition (VMD), in combination with the detrended fluctuation analysis (DFA) method, is reported. VMD-DFA effectively decomposes the GNSS signal affected by ionospheric scintillations into a number of intrinsic mode functions and provides a threshold for the detection and mitigation of scintillations noise. Monte Carlo simulation results demonstrate that the proposed algorithm is superior and reliable for eliminating the amplitude scintillation effects compared to the complementary ensemble empirical mode decomposition method. The application of the proposed algorithm on both synthetic (Cornell scintillation model) and real-time measured GNSS data obtained from GNSS software navigation receiver at Rio de Janeiro, Brazil, has shown its potentiality in mitigating the ionospheric amplitude scintillation effects.

DESIGN AND IMPLEMENTATION OF MICROWAVE PLANNING TOOL WITH STUDYING THE EFFECT OF VARIOUS ASPECTS

Microwave Line-of-sight radio is one of most important and common transmission methods in telecommunications networks. As the microwave radio signals are propagated through the lower atmosphere, they are sensitive to terrain, atmospheric, and climatic conditions. The planning and design of a reliable microwave links is very difficult and require a lot of complex computations. Therefore, not only software implementation is required, but studding the effect of all the different design aspects is very crucial for the telecommunication systems. The software then estimates the path profile, link budget, fade margin, and all other parameters at any place. This paper presents the microwave software planning tool design and implementation with study of all of the design parameters. This software is an engineering tool to aid in the design and planning of the microwave transmission links considering the geography, distance, antenna height, transmit power, frequency, temperature, atmospheric effect, pressure, losses, and other factors which affects on the microwave line-of-sight radio link

Derivation of Z-γ (Reflectivity-Specific Attenuation) Relation for Satellite Link in Tropical Region

The investigation of deriving the Z-γ (reflectivity-specific attenuation) relation is critical in the development of a novel rain attenuation prediction for a satellite link using radar information. Comparison between S-band radar derived reflectivity data and measured received power signals of X-band RazakSAT’s Malaysian remote satellite link is presented. RazakSAT’s satellite link received power during clear sky and rainy conditions are compared to extract the rain attenuation values. The specific attenuation of the link can be derived from the rain attenuation values. The S-band radar with horizontal polarization reflectivity information was used to compare the likely rain attenuation along the same RazakSAT satellite propagation paths. Both reflectivity information and specific attenuation data are tabulated during the RazakSAT operation in 2009 to derive the relationship. Later, the radar reflectivity values, Z are converted into specific attenuation, γ using the derived relationship of the Z-γ to calculate the rain attenuation and fade margin for a slant path link. The current rain attenuation prediction is using point rainfall but in this technique the reflectivity values is being explored. The relationship is derived using similar path length, elevation angle, time and date from the RazakSAT link and the radar information for both stratiform and convective events. Therefore, the relationship can be a good landmark for the future engineers and researchers to estimate the rain attenuation using radar information.

An Analysis Framework for Buffer-Aided Relaying Under Time-Correlated Fading Channels

In this paper, we propose a framework to analyze the performance of buffer-aided (BA) relaying under time-correlated fading channels in terms of the queueing behavior of packets at the relay's buffer. Unlike independent and identically distributed (i.i.d.) fading, correlated fading brings challenges in performance analysis since the state transition probabilities of buffer occupancy become time variant. To overcome this issue, we first establish an aggregate quasi-birth-death (QBD) Markov chain integrating both the buffer occupancy process and the channel fading process, then analyze the stationary distribution of the aggregate chain, and finally extract the stationary distribution of buffer occupancy from it. Using the stationary distribution of buffer occupancy, system throughput, end-to-end delay, and outage probability are derived. Numerical results verify our analyses and show that the throughput of BA relaying under correlated fading channels can approach the one under i.i.d. fading only for loose delay constraints or high fading margins. For stringent delay constraints and low fading margins, correlated fading causes great degradation of throughput. In particular, a throughput loss of about 16% under an infinite buffer (28% under a finite buffer) is observed for the requirement of an average delay of 20 slots and a fading margin of 5 dB. This means that the designs based on i.i.d. fading are not always feasible for correlated fading. According to these observations, some insights on performance degradation and guidelines on redesigning improved policies under correlated fading are provided.

Intelligent Weather Awareness Technique for Mitigating Propagation Impairment at SHF and EHF Satellite Network System in a Tropical Climate

This paper presents an Intelligent Weather Awareness Technique (IWT) based on fuzzy logic to achieve optimum signal quality when the impact of weather attenuations become manifest in Earth-satellite link. An adaptive measure of a decision support system is adopted using the point rainfall rate to predict rain-induced attenuation over three locations in the tropical region of Nigeria based on Moupfouma rain rate and attenuation model. In order to impact good Quality of Service (QoS) in the overall design of satellite communication networks, considerable efforts have to be made, such as the use of appropriate forward error correction codes, the choice of modulations and the range of uplink/downlink power controls. The IWT interacts with the input parameters to optimise the Signal to Noise Ratio (SNR) values while the input parameters are varying. The results show that in all three locations considered, a minimum fade margin of about 12 dB on the uplink and ~ 8 dB on the downlink may be allowed at the 99.5% availability for a worst case scenario at Ka-band. Analysis based on SNR and consumed power at the same weather conditions confirms the suitability of introduction of fuzzy logic for optimum availability of good QoS in a weather impaired satellite system. The overall results would provide tolerance margins needed for better QoS, especially during bad weather in the study locations.

Refining Ku-Band Rain Attenuation Prediction using Local Parameters in Tropics

Background/Objectives: Researches disclosed rain attenuation prediction models offered by ITU-R severely underestimate the signal attenuation in tropical region. Improvement can be accomplished by incorporating three in-situ parameters of prediction models. Methods/Statistical Analysis: The locally derived components are rainfall rate, rain height and specific attenuation coefficients. Beacon signal data for MEASAT-I satellite were sampled for one year. Sampling time of 1 minute was chosen for rainfall rate. Both attenuation and rainfall rate were represented in terms of annual cumulative distribution. Rain height data were gathered from related researches and visually compared with radar data of 10 convective and 30 stratiform rain events. Findings: In previous works, these components were treated separately. By combining all three components, rain attenuation prediction model with distinctive accuracy can be acquired compared to the previous results. All previous and current works exhibited significant improvement from the latest ITU-R P.618 revision 12 model. The new result closely fitted in with measured attenuation which was not present in any previous work. This was shown by RMS error of 2.02 dB at availability of 99.9% to 99.999% (0.1% to 0.001% exceedance). Application/ Improvements: Accurate representation of fade margin can be included in link budget analysis by designers for satellite deployment in tropical region.

A Power-Efficient Clustering Protocol for Coal Mine Face Monitoring with Wireless Sensor Networks Under Channel Fading Conditions.

This study proposes a novel power-efficient and anti-fading clustering based on a cross-layer that is specific to the time-varying fading characteristics of channels in the monitoring of coal mine faces with wireless sensor networks. The number of active sensor nodes and a sliding window are set up such that the optimal number of cluster heads (CHs) is selected in each round. Based on a stable expected number of CHs, we explore the channel efficiency between nodes and the base station by using a probe frame and the joint surplus energy in assessing the CH selection. Moreover, the sending power of a node in different periods is regulated by the signal fade margin method. The simulation results demonstrate that compared with several common algorithms, the power-efficient and fading-aware clustering with a cross-layer (PEAFC-CL) protocol features a stable network topology and adaptability under signal time-varying fading, which effectively prolongs the lifetime of the network and reduces network packet loss, thus making it more applicable to the complex and variable environment characteristic of a coal mine face.

Predicting Atmospheric Attenuation Under Pristine Conditions Between 0.1 and 100 THz

This multidisciplinary paper reports on a research application-led study for predicting atmospheric attenuation, and tries to bridge the knowledge gap between applied engineering and atmospheric sciences. As a useful comparative baseline, this paper focuses specifically on atmospheric attenuation under pristine conditions, over the extended terahertz spectrum. Three well-known simulation software packages (`HITRAN on the Web', MODTRAN ® 4, and LBLRTM) are compared and contrasted. Techniques used for modeling atmospheric attenuation have been applied to investigate the resilience of (ultra-)wide fractional bandwidth applications to the effects of molecular absorption. Two extreme modeling scenarios are investigated: horizontal path links at sea level and Earth-space path links. It is shown by example that a basic software package (`HITRAN on the Web') can give good predictions with the former, whereas sophisticated simulation software (LBLRTM) is required for the latter. Finally, with molecular emission included, carrier-to-noise ratio fade margins can be calculated for the effects of line broadening due to changes in macroscopic atmospheric conditions with sub-1-THz ultra-narrow fractional bandwidth applications. Outdoors can be far from pristine, with additional atmospheric contributions only briefly introduced here; further discussion is beyond the scope of this paper, but relevant references have been cited.

Effect of partially coherent laser source on the performance of fiber-coupling DPSK receiver for optical communication

In practice, due to the reasons related to the laser device and the inevitable error of the processing technique, a laser source emitted from a communication terminal is represented by partially coherent laser source. The fiber-coupling efficiency and the incident optical power at the receiver aperture are affected by the source coherent parameter ζ through atmospheric turbulence. In this paper, the statistical distribution of both the fiber-coupling efficiency and the incident optical power are given, based on which the effect of the source coherent parameter ζ on the performance of fiber-coupling differential phase-shift keying (DPSK) receiver is systematically analyzed. The system fade margin, the average bit error rate (BER) and the power penalty are obtained in the presence of the degradation of the source coherent degree. The results manifest that the performance of fiber-coupling DPSK receiver system degrades drastically with increasing source coherent parameter ζ. The hope of this work is to improve the redundancy design of fiber-coupling DPSK receiver system.

장거리 무선 링크의 가용도 보장을 위한 적응전송 기법

In Microwave Radio Link, it is necessary to consider the radio fading to consistently assure the radio link of the high quality as the distance. If the fixed modulation is used for the microwave radio link, it is difficult to keep the high availability of link for the case of the long distance. Adaptive Modulation(AM) provide good quality on microwave link, but the application of the only-AM is not enough to provide the availability assurance due to the fluctuating characteristics of link capacity. Our previous study has proposed the improvement method of transmission in association with the distance, however the previous method needed to make up for the common application. There was no suggestion of a mathematical formula with a variable. In this paper, we propose an optimized Adaptive Transmission Techniques with calculating formula of the priority traffic transmission capacity based on AM in consideration of the fade margin for the availability assurance as the distance and the comparison of the channel bandwidth for Long-distance Radio Link.

Variation of slant path Ka/V-band rain attenuation over seven tropical locations in Nigeria using synthetic storm techniques

In this paper, rain characteristics and slant path rain attenuation at 30 and 40 GHz using synthetic storm techniques over seven tropical locations in Nigeria have been presented. The technique can be used to predict the local first-order statistical rain attenuation to mitigate the severe fade experienced at higher frequency bands by employing local rainfall rate statistics. Three years rain rate data at seven tropical and equatorial locations in Nigeria were utilized for the purpose of this work. The predicted statistics are in good agreement with those obtained from the propagation beacon measurement (EUTELSAT W4/W7 satellite-12.245 GHz) It could be observed that at 99.99 % link availability over these locations, the fade margin of higher dB (74 and 81 dB) are required at 30 and 40 GHz frequency bands, respectively. When diurnal variation was observed for four time intervals: 00:00–06:00, 06:00–12:00, 12:00–18:00, and 18:00–24:00, there is a variation of the fade margin over the hours of the day. The overall results will be needed for an acceptable planning that can effectively reduce the fade margin to a very low value for an optimum data communication over the studied locations.

Achievable Gains of Directional Antennas in Outdoor-Indoor Propagation Environments

We present an empirically based model for the gain of an indoor antenna array. This corresponds to the re-parametrization of the Greenstein-Erceg model, as applied to 5 m-50 m narrowband outdoor-indoor links. Our model is applicable to a few adjacent tones in an OFDM femtocell system such as LTE. We find that as much as 14 out of 16 dB of antenna-gain are attainable even in rich indoor scattering conditions. At the same time, no larger fade margin is required when using the array vs. the omnidirectional antenna. To provide a reference for the observed results we consider a simple propagation model, which is analyzed theoretically and via simulation. This model is found to match our empirical results very well.

Channel estimation and transmit power control in wireless body area networks

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on-body to on-body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature.

Dependence of the bit error rate on the signal power and length of a single-channel coherent single-span communication line with polarisation division multiplexing

We have studied experimentally and using numerical simulations and a phenomenological analytical model the dependences of the bit error rate (BER) on the signal power and length of a coherent single-span communication line with transponders employing polarisation division multiplexing and four-level phase modulation ( DP-QPSK format). In comparing the data of the experiment, numerical simulations and theoretical analysis, we have found two optimal powers: the power at which the BER is minimal and the power at which the fade margin in the line is maximal. We have derived and analysed the dependences of the BER on the optical signal power at the fibre line input and the dependence of the admissible input signal power range for implementation of the communication lines with a length from up to a maximum length of .