Improvement of wireless telecommunication system perfomances in the presence of fading with a dominant electromagnetic wave component : doctoral dissertation

[D. A. Aleksić]

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Predmet istraživanja ove doktorske disertacije su bežični telekomunikacioni sistemi i poboljšanje njihovih performansi kada su prisutni brzi feding, spori feding i međukanalna interferencija. Pri tome, cilj istraživanja je da se odrede diverziti tehnike pomoću kojih mogu da se smanje uticaji brzog i sporog fedinga na performanse navedenog sistema. U prvom delu disertacije razmatrani su statistički modeli kanala u prisustvu Rajsovog fedinga i Gama sporog fedinga, a zatim i k-µ slučajni proces. Pored toga, razmatran je slučaj kada je u bežičnim kanalima prisutan spori Gama feding i brzi k-μ feding. Pri tome, analitički i grafički su određene gustina verovatnoće (PDF) i kumulativna verovatnoća (CDF). U drugom delu disertacije razmatrani su modeli makrodiverziti sistema sa dva mikrodiverziti SC kombinera i jednog makrodiverziti SC kombinera, u prisustvu brzog k-μ fedinga i sporog Gama fedinga, odnosno u prisustvu k-μ brzog fedinga, Gama sporog fedinga i k-μ međukanalne interferencije, respektivno. Analitički su određeni PDF i CDF, a zatim dati grafički prikazi za sve proračunate formule PDF i CDF, kao i grafički prikazi za verovatnoću otkaza u zavisnosti od zadatog praga. Primenom razmatranog makrodiverziti sistema pokazano je da se smanjenjem korelacionog koeficijenta Gama sporog fedinga ρ, a bez povećanja širine frekvencijskog opsega i bez povećanja snage na predaji, povećava dobitak makro kombinovanja. Na kraju, data su merenja realnog scenarija kanala koja su pokazala veoma dobro poklapanje sa teorijskim rezultatima. Naime, dobijeni rezultati za verovatnoću otkaza pokazali su opravdanost primene diverziti tehnike, koja može biti korisna u projektovanju bežičnih sistema u okruženju sa ograničenom interferencijom u smislu predviđanja performansi sistema i otkaza sistema.

This doctoral dissertation analyzes wireless communication systems and proposes methods to enhance their performance in the presence of long-term fading, short-term fading, and co-channel interference (CCI). The aim of the research is to identify diversity schemes capable of mitigating the effects of long-term fading and short-term fading on system performance. In the first part of the dissertation, statistical channel models are considered in the presence of Rician fading, Gamma long-term fading, and a к-µ random process. In addition, scenarios involving short-term Gamma fading and long-term к-µ fading in wireless channels are analyzed. Consequently, the probability density function (PDF) and cumulative density function (CDF) are derived analytically and through graphical representations. In the second part of the dissertation, models are considered for macro-diversity systems with two micro-diversity SC combiners, and one macro-diversity SC combiner in the presence of long-term к-µ fading, short-term Gamma fading, that is, in the presence of long-term к-µ fading, short-term Gamma fading, and к-µ co-channel interference, respectively. Analytical expressions for the PDF and CDF are presented, accompanied by graphical representations of these functions and outage probability plots for varying thresholds. Using the discussed macrodiversity system, it has been shown that by reducing the correlation coefficient of Gamma shortterm fading, ρ, without increasing the frequency range bandwidth, and without increasing transmission power, an increase in macro-combining gain is achieved. Finally, measurements of real channel scenarios are given, demonstrating a very good match with the theoretical results. Namely, the obtained results for the outage probability have revealed the justification for using the diversity technique, which can be useful in designing wireless systems in settings with limited interference, particularly for system performance prediction and outage assessment.

Rajsov feding, k-µ brzi feding, gustina verovatnoće (PDF), kumulativna verovatnoća (CDF), verovatnoća otkaza, SC kombiner, makrodiverziti sistem, merenje.

Rician fading, к-µ long-term fading, probability density function (PDF), cumulative density function (CDF), outage probability, selective combining, macro-diversity system, measurement.

621.396:537.876 537.876

Bežični telekomunikacioni sistemi - Feding

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