Influence of Wind and Rain on a Foliage Radio-wave Propagation Channel
Chapter One
Aim and Objectives of the Thesis Work
The aim of this thesis work is to determine the additional power attenuations, statistically model and characterize the temporal variations caused by wind and rain on a short-range, short-height foliage radio-wave propagation channel.
The objectives of this investigation are as follows:
-To create the required rain (artificially).
-To determine the relationship between rain intensity and rotations of the stop cock of water sprinkler (i.e. to calibrate the valve or faucet which controls the rate of water flow and hence the rain intensity).
-To create the required wind (artificially).
-To determine the relationship between wind speeds and currents into the fan (i.e. to calibrate the current transformer which controls the current flow into the fan and hence the wind speed).
-To group each weather condition into three and combine them to form nine combinations so that the resulting weather model represents that of Katsina metropolis where the investigation was conducted.
-To apply the created weather conditions (at different ranges of rain intensities and wind speeds) on the short-height foliage environment in which the microwave transmitter and receiver are situated.
-To carry out EM wave measurements in the foliage channel under the influence of these applied weather conditions.
-Finally, to carry out statistical analysis of the results.
CHAPTER TWO
LITERATURE REVIEW AND THEORETICAL BACKGROUND
Introduction
In this chapter available documents (both published and unpublished) on the topic, which contains information, ideas, data and evidence written from particular point of view are selected. The chapter expresses certain views on the nature of the topic and how it was investigated. It also presents an effective evaluation of the literatures in relation to the thesis.
The chapter also explains the theory of EM wave attenuation and scattering by vegetation and by rain drops. In addition to these, it explains briefly the reasons why rain drops scatter EM waves and the essential features of rain scatter.
Literature Review
- Meng, Y.S., et al, (2007): investigated the effect of tropical weather on foliage radio wave propagation channel at UHF and VHF
- James S.T., (1998): carried out a research work and wrote a paper titled “RF Propagation and system design technique for broadband wireless application from 5 to 40GHz”.
- Perras S., et al (2002) investigated the various temporal characteristics of radio channels for a broad range of frequencies (from 2 to 60 GHz), in various foliage environments and weather conditions.
- Joshi G.G. et al (2005) investigated the effect of rain on near-ground propagation at 1900 MHz in a forest
- Chua T.H., et al (2010) investigated the combined effects of wind and wind direction on received signal strength (RSS) in foliated broad band fixed wireless
- Mike W. (2011), investigated extensively, the impact of clutter (including vegetation under the influence of wind) on radio wave propagation
Comparison of the literature in Relation to the Thesis Work
The idea of this thesis was derived from the IEEE journal paper by Meng Y. S. In that research work, the experimental site was a large-tree plantation investigated using VHF and UHF (240 MHz) and (700 MHz) frequencies at a foliage depth of 400 meters. While in this thesis work, young eucalyptus tree plantation was investigated using microwave frequency at a foliage depth of just three (3) meters due to the limit of the transmitter range and the length of the water sprinkler. This mean that there is a well pronounced difference in tree- trunk diameters, the wave lengths of the propagated signals and the length of the foliage depths.
In the referred paper, natural rainfall and wind were used while in this thesis work, artificially created wind and rainfall were used. This implies that there is an advantage in this thesis work, because parameters of the artificially created weather conditions (wind speed and rain intensity) can be controlled at will, by controlling the independent variable (i.e. current into the fan and angle of rotation of the stopcock of the sprinkler respectively).
Although created weather conditions (wind and rain) were used, the result is believed to be reliable because such created conditions are widely used for commercial and scientific applications with high degree of success. Popular examples include:- 1) Space explorations,
where astronauts are subjected to artificially created weightlessness conditions similar to that of free space in order to acclimatize before embarking on space travels. 2) The second popular example is artificial avian egg incubation practice in which eggs are subjected to artificially created temperature and humidity conditions similar to that provided by the mother-birds. 3) In film making industries artificially created wind and rain are used in place of natural ones.
CHAPTER THREE
METHODOLOGY
Introduction
This chapter explains, in details, how various equipments were used to create the artificial rain and wind and how the relationships between these two dependent variables and the independent ones were established. It also explains the experimental set up for EM wave measurements in the foliage channel under the influence of the applied parameters (rain intensity and wind speed). The procedures for data recording as well as the recoded data are also presented in this chapter.
Experiment site
The experiment site is a naturally grown vegetation of young eucalyptus trees of heights ranging from 1.5m to 4m, located directly opposite Hassan Usman Katsina Polytechnic, Katsina; and adjacent to Federal College of Education, Katsina. It is an irregular- shaped site with approximate area of 5000m2. The experiment was conducted in the dry season as such the tree- leaves were scanty and their water contents considered being very low. The young trees are nearly equally spaced at a distance of about 0.3m apart. The average tree trunk diameter at antenna height is about 3cm and the leaves of the trees measure approximately 2cm by 6cm.
Creation of the artificial rain
The maximum amount of rainfall recorded in a single day in Katsina city was 71.50mm on 24th April, 2010 from 16.32 GMT to 17.48 GMT (UMYA, 2010). That is the duration of the rainfall was 1 hour and 16 minutes (or 1.267 hours).
CHAPTER FOUR
RESULTS ANALYSIS
Introduction
In this chapter, the additional power attenuation imposed by each weather phenomenon is determined from the results. The same experimentally obtained data or result (i.e. the set of values of the received signal in the foliage channel under the influence of wind and/or rain) is then normalized to its mean (using Microsoft Excel) to extract the temporal variations (Meng, et al, 2007). These temporal variations are characterized through the statistical modeling of the signal envelop (amplitude) using the commonly known probability distributions usually associated with radio-wave propagation channels. Before the data analysis, the four distribution functions and the software program used for the analysis are briefly discussed in the following sections.
CHAPTER FIVE
SUMMARY, CONCLUSION AND RECOMMENDATIONS
Introduction
In chapter one it was stated that the study of combined effects of wind and rain on foliage radio channels has not been fully developed, because there is still no mathematical model for calculating power loss in forest environments under the influence of the above mentioned weather conditions. This is so despite the importance of the area and the considerable amount of development in telecommunication engineering. It was this situation that prompted this study, the aim of which was to find, experimentally, the additional power attenuations imposed on the channel, characterize the variations and determine a statistical model which compares very well with the experimental results. This could serve as a step towards solving the above mentioned problem.
Summary
Foliage radio propagation channels, under the influence of wind and rain are very difficult to investigate in the above mentioned region or Katsina metropolis in particular where rainfall is seasonal, which means that long term measurements are required in order to get meaningful results. Furthermore, there is no radar system to provide the required full set of volumetric reflectivity and velocity data of weather information during the measurements (Meng, et al, 2007) around the city, periodically.
Notwithstanding these problems, this work has produced some useful results and ideas that will go a long way in contributing to the study of foliage channels under the influence of wind and rain. The achievements could be summarized as follows:
- Wind and rain have been systematically created using the combination of both standard and improvised equipment so that the required weather information (wind speed and rain intensity) is easily derived.
- Using the maximum wind speed and maximum average rain intensity of Katsina metropolis (UMYA, 2010), a weather model with nine combinations was developed to represent the actual weather conditions of the
- EM wave measurements in the channel under the influence of the artificially created weather conditions were successfully carried out and the raw data/corresponding graphical representations have been presented.
- Additional power attenuations imposed by the different weather phenomena have been determined and compared.
- After normalization of data about its mean, the temporal variations have been statistically modeled and found to be Rician distributed.
- Based on the Rician model, the variations have also been characterized by calculating the K- factor for each weather phenomenon. It was found that the K-factor decreases as the weather conditions become stronger. This indicates that variability of the propagation channel increases when the strength of wind or rain intensity
Conclusion
The effects of artificially created weather conditions (wind and rain) on a short-range foliated microwave channel have been studied in this thesis. The experimental results show that wind and rain, even though created, can impose additional attenuation on propagating signals in foliage environments. The imposed attenuation, as well as variability, increases when wind speed or rain intensity increases.
In the final conclusion, it is the humble view of the author that the aim and objectives of the thesis have been achieved. The work can be useful for design of a fade margin for microwave communication systems to be used in foliage environments having a weather condition similar to that of Katsina city which is located in the Savanna region of Northern Nigeria.
Limitations
There are imitations in the accuracy of the results in this thesis due to the following reasons:
- The applied weather conditions were artificially created; as such the coverage area is
- The pipe-borne water used for creation of the rain contains dissolved compounds for water purification. This could affect the attenuation and scattering effects of the rain drops and hence the accuracy of the data.
- The microwave transmitter used was of low power, as such there was a limit to the range of the propagation channel.
Recommendations for further work
The following suggestions are hereby given for further work
- Development of a mathematical model for power loss in foliage environments taking into account the effects of wind and rain. This can be achieved through long term measurements in different forest environments using standard and sophisticated measuring
- Investigation of foliage channels to find attenuations and variability in relation to the size and water contents of the leaves, tree-trunk diameter, height of the trees, and their average separation distance, under the influence of weather
References
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- Bryc, W. (1995). Normal Distribution, Characterization with Application. Retrieved June 2, 2011 from http://booksxyz.com/publishers.php
- Chua, T.H., Wassel, L.T., & Abd.Rahman T. (2010). Combined Effects of Wind and Wind Speed on Received Signal Strength in Foliated Broadband Fixed Wireless Links. Retrieved April 12, 2011 from http://www.cl.cam.ac.uk/research/dtg/www/files/publications/public/thc33/1841779.pdf
- Electromagnetic spectrum. (2011). Retrieved June 2, 2011 from http://hosting.soonet.ca/eliris/remotesensing/bl130lec3.html
- Farlex. (2011). Definition of Wind. Retrieved January 2, 2011 from http:www.thefreedictionary.com/wind
- Harry, F. (1994), Statistics, Concept and Applications, Cambridge University Press, New York. Hoang P. (2008). Springer Handbook of Engineering Statistics.
- http://books.google.com.ng/books
- James, S.T. (1998). RF Propagation and system design technique for broadbandwirelessapplication from 5 to 40 GHz. Retrieved November 7, 2010 from www.mprg.org/publications/presentations/bellcore 093098.pdf
- Jean-Paul M.G. (2009). Distribution of Amplitude and Power for Rcian Fading. Retrieved May 12, 2011 from www.wirelesscommunication.NL
