Stochastic Approach to a Rain Attenuation Time Series Synthesizer for Heavy Rain Regions

In this work, a new rain attenuation time series synthesizer based on the stochastic approach is presented. The model combines a well-known interest-rate prediction model in finance namely the Cox-Ingersoll-Ross (CIR) model, and a stochastic differential equation approach to generate a long-term gamma distributed rain attenuation time series, particularly appropriate for heavy rain regions. The model parameters were derived from maximum-likelihood estimation (MLE) and Ordinary Least Square (OLS) methods. The predicted statistics from the CIR model with the OLS method are in good agreement with the measurement data collected in equatorial Malaysia while the MLE method overestimated the result. The proposed stochastic model could provide radio engineers an alternative solution for the design of propagation impairment mitigation techniques (PIMTs) to improve the Quality of Service (QoS) of wireless communication systems such as 5G propagation channel, in particular in heavy rain regions

Atmospheric Impairments and Mitigation Techniques for High-Frequency Earth-Space Communication System in Heavy Rain Region: A Brief Review

This work surveys the atmospheric impairments that affect a satellite link operating in a high-frequency band, such as Ka and Q/V bands, particularly in heavy rain regions. The impacts of hydrometeors and cloud attenuation are emphasised and discussed along with the contribution of gases and scintillation to signal fade. Also, propagation impairment mitigation techniques are reviewed from the perspective of satellite operators in heavy rain areas

Frequency diversity wideband digital receiver and signal processor for solid-state dual-polarimetric weather radars

2012 Summer.Includes bibliographical references.The recent spate in the use of solid-state transmitters for weather radar systems has unexceptionably revolutionized the research in meteorology. The solid-state transmitters allow transmission of low peak powers without losing the radar range resolution by allowing the use of pulse compression waveforms. In this research, a novel frequency-diversity wideband waveform is proposed and realized to extenuate the low sensitivity of solid-state radars and mitigate the blind range problem tied with the longer pulse compression waveforms. The latest developments in the computing landscape have permitted the design of wideband digital receivers which can process this novel waveform on Field Programmable Gate Array (FPGA) chips. In terms of signal processing, wideband systems are generally characterized by the fact that the bandwidth of the signal of interest is comparable to the sampled bandwidth; that is, a band of frequencies must be selected and filtered out from a comparable spectral window in which the signal might occur. The development of such a wideband digital receiver opens a window for exciting research opportunities for improved estimation of precipitation measurements for higher frequency systems such as X, Ku and Ka bands, satellite-borne radars and other solid-state ground-based radars. This research describes various unique challenges associated with the design of a multi-channel wideband receiver. The receiver consists of twelve channels which simultaneously downconvert and filter the digitized intermediate-frequency (IF) signal for radar data processing. The product processing for the multi-channel digital receiver mandates a software and network architecture which provides for generating and archiving a single meteorological product profile culled from multi-pulse profiles at an increased data date. The multi-channel digital receiver also continuously samples the transmit pulse for calibration of radar receiver gain and transmit power. The multi-channel digital receiver has been successfully deployed as a key component in the recently developed National Aeronautical and Space Administration (NASA) Global Precipitation Measurement (GPM) Dual-Frequency Dual-Polarization Doppler Radar (D3R). The D3R is the principal ground validation instrument for the precipitation measurements of the Dual Precipitation Radar (DPR) onboard the GPM Core Observatory satellite scheduled for launch in 2014. The D3R system employs two broadly separated frequencies at Ku- and Ka-bands that together make measurements for precipitation types which need higher sensitivity such as light rain, drizzle and snow. This research describes unique design space to configure the digital receiver for D3R at several processing levels. At length, this research presents analysis and results obtained by employing the multi-carrier waveforms for D3R during the 2012 GPM Cold-Season Precipitation Experiment (GCPEx) campaign in Canada

Channel Modeling and Tropospheric Effects on Millimeter Wave Communications for Aviation Applications

Next generation communication systems will be designed to be faster, more secure and easier to connect with than current systems. Along with the concept of internet of things (IoT), many more devices will be required to communicate with each other. In the case of aeronautical vehicles and systems, in addition to current navigation and surveillance systems, more data links will be required for multiple applications, such as photography, inspections, and entertainment. Current aviation frequency bands will likely be unable to support all proposed services. Apart from air-to-ground (AG) communication links, airport surface terrestrial links and satellite-to-air links (SA) are also of research interest. Most AG communication systems operate in L-band (960-1164 MHz) and below, with a few operating in C-band (5030-5150 MHz). Bandwidth provided by these frequency bands is limited, and will be unable to meet demands for future applications. Hence higher frequency bands in the millimeter wave range (30-300 GHz) are being actively investigated, aiming to fully utilize the much larger available bandwidths. Since millimeter wave (mmWave) signals behave somewhat different from lower frequency signals in AG, SA and terrestrial links, more work is needed to characterize mmWave channels in terms of tropospheric attenuation, path loss, obstacle attenuation, and wideband multipath fading and Doppler effects. In this dissertation, we investigate and model the tropospheric attenuation for AG and SA links, and model path loss and obstacle attenuation for terrestrial channels, with focus on aviation applications. Some wideband terrestrial channel measurement and modeling is also included. We utilize the tropospheric attenuation empirical model developed by the International Telecommunications Union (ITU) and quantify the effect of the type of precipitation data input on mmWave channel attenuation. Variability of tropospheric attenuation over the long term is also investigated for rain and cloud attenuation in particular, i.e., we investigate extreme rainy and foggy cases, since mmWave signals are so susceptible to these attenuations. Our findings quantify the differences in tropospheric attenuation model outputs with different precipitation data inputs: we find that differences can be substantial in terms of the percentage of time a given attenuation value is exceeded. Frequencies of 30, 60 and 90 GHz are investigated for terrestrial and short AG links, and frequencies 30 and 45 GHz for AS links, for four different climate types: temperate, subtropical, tropical, and rainforest. Results show that in 1 km terrestrial or AG links, local measured rain data input increases mean rain attenuation by 0.5-2 dB over results when ITU’s regional empirical rain data is input. Fog attenuation may increase by 8 dB at 90 GHz in the same comparison. In AS links, mean rain attenuation increases by 0.8 and 1.1 dB at 30 and 45 GHz, respectively, using local measured data input. Rain attenuation has a larger probability of occurrence at moderate-to-significant rain attenuation values: for example, at 90 GHz, 20 dB rain attenuation occurs at most 0.02% of time with ITU’s input data, but occurs an order of magnitude more often (0.2% of the time) with local measured input data. For path loss, we employ measurements in several settings, including a small airport building, and compare with ray tracing simulations. Multipath components are simulated via ray tracing software Wireless Insite, to obtain channel impulse responses, from which path loss and delay dispersion (e.g., root-mean-square delay spread (RMS-DS) were estimated. We compare the ray-tracing results with measurements for both narrowband signals and wideband signals of bandwidth 500 MHz. The characterization includes path loss and delay spread, and the mmWave results employ directional antennas. We provide preliminary channel characterization for several indoor channels and an outdoor channel at frequencies of 5, 30 and 90 GHz. Comparing our measured path loss results with free space path loss, mean path loss difference are 2.47, 2.72 and 0.31 dB for 5, 30 and 90 GHz, respectively, in indoor channels. For the widely used “close-in” reference distance path loss model, comparing simulation and measurement in 90 GHz channels, differences in model slope versus distance for simulation and measurement are less than 0.2, and standard deviation of large scale fading is less than 1.8 dB. These differences are less than 0.2 and 2 dB at 30 GHz, and less than 0.4 and 1.8 dB at 5 GHz. For large scale fading, the Generalized Extreme Value (GEV) distribution appears to describe excess path loss the best, instead of the commonly used Gaussian distribution. The Kolmogorov-Smirnov (KS) goodness of fit test statistic for GEV is 3% less than that for the Gaussian, for an example 90 GHz indoor channel. Small scale fading was also investigated for a densely sampled 5 GHz line of sight indoor office channel. The Lognormal distribution was found as the most accurate fit among tested distributions

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments

Proceedings of the Fourteenth NASA Propagation Experimenters Meeting (NAPEX 14) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX XIV was held on May 11, 1990, at the Balcones Research Centers, University of Texas, Austin, Texas. The meeting was organized into two technical sessions: Satellite (ACTS) and the Olympus Spacecraft, while the second focused on the fixed and mobile satellite propagation studies and experiments. Following NAPEX XIV, the ACTS Miniworkshop was held at the Hotel Driskill, Austin, Texas, on May 12, 1990, to review ACTS propagation activities since the First ACTS Propagation Studies Workshop was held in Santa Monica, California, on November 28 and 29, 1989

Study of advanced communications satellite systems based on SS-FDMA

A satellite communication system based on the use of a multiple, contiguous beam satellite antenna and frequency division multiple access (FDMA) is studied. Emphasis is on the evaluation of the feasibility of SS (satellite switching) FDMA technology, particularly the multiple, contiguous beam antenna, the onboard switch and channelization, and on methods to overcome the effects of severe Ka band fading caused by precipitation. This technology is evaluated and plans for technology development and evaluation are given. The application of SS-FDMA to domestic satellite communications is also evaluated. Due to the potentially low cost Earth stations, SS-FDMA is particularly attractive for thin route applications up to several hundred kilobits per second, and offers the potential for competing with terrestrial facilities at low data rates and over short routes. The onboard switch also provides added route flexibility for heavy route systems. The key beneficial SS-FDMA strategy is to simplify and thus reduce the cost of the direct access Earth station at the expense of increased satellite complexity

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications