Kevin S. Paulson

Diversity improvement estimation from rain Radar databases using maximum likelihood estimation

This research examines route diversity as a fade mitigation technique in the presence of rain, for terrestrial microwave links. The improvement in availability due to diversity depends upon the complex spatio-temporal properties of rainfall. To produce a general model to predict the advantage due to route diversity it is necessary to be able to predict the correlation of rain attenuation on arbitrary pairs of microwave links. This is achieved by examination of a database of radar derived rain rate fields. Given a representative sample of rain field images, the joint rain attenuation statistics of arbitrary configurations of terrestrial links can be estimated. Existing rain field databases often yield very small numbers of high joint attenuation events. Consequently, estimates of the probability of joint high attenuation events derived from ratios of the number of occurrences can be highly inaccurate. This paper assumes that pairs of terrestrial microwave links have joint rain attenuation distributions that are bi-lognormally distributed. Four of the five distribution parameters can be estimated from ITU-R models. A maximum likelihood estimation (MLE) method is used to estimate the fifth parameter, i.e., the covariance or correlation. The predicted diversity statistics vary smoothly and yield plausible extrapolations into low probability situations.

A phase modulation-based ultrasonic communication system using Variable Structure Control

Narrow bandwidth transducers used in existing ultrasonic data communication systems are known to be devices with a high Q resonant response and low coupling to both the electrical drive and acoustic output interfaces. These features limit the speed of phase change when phase modulation (PM) is used. This paper studies the design of a Variable Structure Controller (VSC)-based transmitter with the aim of increasing the capacity of a PM-based communications system. Simulation results are presented to demonstrate the potential of this approach.

Simulation of rain fade on arbitrary microwave link networks by the downscaling and interpolation of rain radar data

To predict the Quality of Service at a node in heterogeneous networks of line-of-sight, terrestrial, microwave links requires knowledge of the spatial and temporal statistics of rain over scales of a few meters to tens or hundreds of kilometers, and over temporal periods as short as 1 s. Meteorological radar databases provide rain rate maps over areas with a spatial resolution as fine as a few hundred meters and a sampling period of 2 to 15 min. Such two-dimensional, rain rate map time series would have wide application in the simulation of rain scatter and attenuation of arbitrary millimeter-wave radio networks, if the sampling period were considerably shorter, i.e., of the order of 10 s or less, and the integration volumes smaller. This paper investigates a stochastic-numerical method to interpolate and downscale rain rate field time series to shorter sampling periods and smaller spatial integration areas, while conserving the measured and expected statistics. A series of radar derived rain maps, with a 10 min sample period, are interpolated to 10 s. The statistics of the interpolated-downscaled data are compared to fine-scale rain data, i.e., 10 s rain gauge data and radar data with a 300-m resolution. The interpolated rain map time series is used to predict the fade duration statistics of a microwave link, and these are compared to a published and ITU-R model.

A Review of Channel Simulators for Heterogeneous Microwave Networks

A review is performed of the current simulation tools able to produce simultaneous dynamic fading, due to a range of mechanisms, experienced by heterogeneous networks of SHF and EHF radio links. The primary focus is fading due to rain. A taxonomy of tools is proposed, based on the methods used to generate fields of meteorological parameters. The capabilities, deficiencies, and futures of these tools are discussed, and a series of research questions are proposed.

A systems framework for national assessment of climate risks to infrastructure

Extreme weather causes substantial adverse socio-economic impacts by damaging and disrupting the infrastructure services that underpin modern society. Globally,

Evidence of trends in rain event size effecting trends in rain fade

2.5tn a year is spent on infrastructure which is typically designed to last decades, over which period projected changes in the climate will modify infrastructure performance. A systems approach has been developed to assess risks across all infrastructure sectors to guide national policy making and adaptation investment. The method analyses diverse evidence of climate risks and adaptation actions, to assess the urgency and extent of adaptation required. Application to the UK shows that despite recent adaptation efforts, risks to infrastructure outweigh opportunities. Flooding is the greatest risk to all infrastructure sectors: even if the Paris Agreement to limit global warming to 2°C is achieved, the number of users reliant on electricity infrastructure at risk of flooding would double, while a 4°C rise could triple UK flood damage. Other risks are significant, for example 5% and 20% of river catchments would be unable to meet water demand with 2°C and 4°C global warming respectively. Increased interdependence between infrastructure systems, especially from energy and information and communication technology (ICT), are amplifying risks, but adaptation action is limited by lack of clear responsibilities. A programme to build national capability is urgently required to improve infrastructure risk assessment. This article is part of the theme issue ‘Advances in risk assessment for climate change adaptation policy’.

A method to estimate trends in distributions of 1 min rain rates from numerical weather prediction data

Rain gauge studies have shown that the incidence of rain at rates associated with outage on terrestrial links, has shown an increasing trend in several countries, over the last 30 years. However, no evidence is available from microwave links to show whether outage rates, or the incidence of fade, is similarly increasing. This paper presents evidence of fade trends, derived from a decade of rain radar data. Although a decade is too short a period to observe rain rate trends, evidence is presented that trends in the size of rain events is leading to changes in the relationship between point rain rates and rain fade. Furthermore, these trends are shown to vary significantly across the UK. Temporal trends in both rain rates and their link to rain fade, make it more difficult to adapt ITU-R Recommendation to a changing climate.

Performance measurements for full wave inversion (FWI) based multistatic handheld ground penetrating radar (GPR) for landmine detection

It is known that the rain rate exceeded 0.01% of the time in the UK has experienced an increasing trend over the last 20 years. It is very likely that rain fade and outage experience a similar trend. This paper presents a globally applicable method to estimate these trends, based on the widely accepted Salonen-Poiares Baptista model. The input data are parameters easily extracted from numerical weather prediction reanalysis data. The method is verified using rain gauge data from the UK, and the predicted trend slopes of 0.01% exceeded rain rate are presented on a global grid.

A comparison of bistatic and multistatic handheld ground penetrating radar (GPR) antenna performance for landmine detection

This paper reports the results of a study to investigate the impact of antenna configuration and rough ground surface on the performance of multistatic handheld ground penetrating radar (GPR) systems for anti-personnel (AP) landmine detection. The work is a follow on to the conclusions presented in [1] which include the fact that enhanced imaging through full wave inversion (FWI) is achieved with multiple receivers in comparison to typical bistatic systems in handheld GPR. This paper seeks to address a couple of aspects of future work outlined in the aforementioned work. Specifically, the study aims to quantitatively characterise the effect of different antenna configurations and rough ground surface on the performance of small multistatic GPR systems used for FWI based subsurface imaging for demining operations. The 3D electromagnetic (EM) software CST STUDIO SUITE is used to model and simulate the GPR system and singular value decomposition (SVD) analysis is used to estimate parameter sensitivity based on the assumption of prior FWI.

Performance analysis of a phase modulation-based ultrasonic receiver using Variable Structure Control

This paper reports the results of a study comparing the performance of bi-static and multi-static antennas systems for handheld ground penetrating radar (GPR), applied to humanitarian anti-personnel (AP) landmine detection. The investigation is focused on mine detection using handheld multi-sensor systems that combine metal detection and GPR. Single A-scan, 1 dimensional data from 3D time domain models of each system are considered. The modelling and simulations were performed using the Computer Simulation Technology (CST) Microwave Studio (MWS). Principal Component Analysis (PCA) is used to identify the features of the landmine that most strongly effect the measured GPR data. A comparison of the principal components and Eigen-values quantifies the advantage gained from using multi-static over bi-statics systems for landmine detection.