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Golubović, Aleksandra D.

Primena tehnika kombinovanja kod bežičnih telekomunikacionih sistema u prisustvu smetnje

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Academic metadata

Doktorska disertacija

Tehničko-tehnološke nauke

Univerzitet u Nišu

Elektronski fakultet

Katedra za telekomunikacije

Other Theses Metadata

Application of combining techniques in wireless telecommunication systems in presence of interference

[A. D. Golubović]

XV, 135 listova

Datum odbrane: 16.10.2017.

Telecommunications

Milić, Dejan (mentor)

Perić, Zoran 1964- (član komisije)

Milović, Danijela (član komisije)

Đorđević, Goran T. 1970- (član komisije)

Petrović, Mile (član komisije)

Research results shown in this thesis consider selection combining space diversity
systems. Weibull fading model is used to describe a desired signal and interference in a
wireless telecommunication channel. In an interference-limited environment, like a cellular
communication system, the level of cochannel interference is sufficiently high compared to
noise so that it can be neglected. In that case, a selection combining receiver can employ
different combining algorithms, that can be used to forward the chosen signal to the output of
the receiver.
After the theoretical basis, which is given at the beginning of the thesis, a detailed
analysis of space diversity systems that use different selection algorithms is presented. The
system performance is analyzed using one of the proposed criteria: maximal signal-tointerference
ratio, maximal desired signal, maximal total signal, and minimal interference.
For a system employing each of these algorithms, a detailed analysis of statistical
characteristics of first and second order is given using the expressions derived in this thesis.
The first focus is on deriving the expressions for probability density function of instantaneous
signal-to-interference ratio at the output of selection combining receiver employing each of
the previously mentioned algorithms. Based on the derived expressions, numerical results are
presented for statistical characteristics of the first order, namely outage probability, average
bit error probability, average signal-to-interference ratio and channel capacity. Additionally,
for the statistical characteristics of the second order, which are level crossing rate and average
fade duration, expressions for joint probability density function of instantaneous signal-tointerference
ratio and its time derivative are derived.
A new mathematical approach for obtaining analytical expression for probability
density function of instantaneous signal-to-interference ratio at the output of selection
combining receiver with two branches that uses maximal signal-to-noise ratio algorithm is
presented.
Considering that mobile terminals are relatively small, the distance between receiving
antennas is not large enough to be neglected. Therefore, the correlation between the branches
is included in the analysis of statistical characteristics of the first order. Due to easier
mathematical manipulation, statistical characteristics of second order do not consider
correlation between receiving branches.
Numerical results obtained using the expressions derived in this thesis for different
decision algorithms are presented graphically. The illustrations show the influence of fading
severity, correlation between the desired signals, as well as the interfering ones and balanced
and unbalanced inputs for each of mentioned algorithms on outage probability, average bit
error probability, average signal-to-interference ratio and channel capacity.
The results for second order statistics for dual branch selection diversity system
operating in Weibull fading environment were compared for a system that employs two
selection algorithms, algorithm based on maximal signal-to-interference ratio, as most
frequently used one, and algorithm based on minimal interference, the algorithm that was not
exploited in literature.
The main contribution of this thesis lies in obtained results for statistical
characteristics and performance of the system that uses four proposed algorithms at receiver
side. The presented analysis of selection diversity system for given channel conditions can be
applied to achieve optimized solutions of wireless system design.

algoritmi za odabir signala, bežične telekomunikacije, diverziti sistemi sa selektivnim kombinovanjem, kanal sa Vejbulovim fedingom, interferencija

Research results shown in this thesis consider selection combining space diversity
systems. Weibull fading model is used to describe a desired signal and interference in a
wireless telecommunication channel. In an interference-limited environment, like a cellular
communication system, the level of cochannel interference is sufficiently high compared to
noise so that it can be neglected. In that case, a selection combining receiver can employ
different combining algorithms, that can be used to forward the chosen signal to the output of
the receiver.
After the theoretical basis, which is given at the beginning of the thesis, a detailed
analysis of space diversity systems that use different selection algorithms is presented. The
system performance is analyzed using one of the proposed criteria: maximal signal-tointerference
ratio, maximal desired signal, maximal total signal, and minimal interference.
For a system employing each of these algorithms, a detailed analysis of statistical
characteristics of first and second order is given using the expressions derived in this thesis.
The first focus is on deriving the expressions for probability density function of instantaneous
signal-to-interference ratio at the output of selection combining receiver employing each of
the previously mentioned algorithms. Based on the derived expressions, numerical results are
presented for statistical characteristics of the first order, namely outage probability, average
bit error probability, average signal-to-interference ratio and channel capacity. Additionally,
for the statistical characteristics of the second order, which are level crossing rate and average
fade duration, expressions for joint probability density function of instantaneous signal-tointerference
ratio and its time derivative are derived.
A new mathematical approach for obtaining analytical expression for probability
density function of instantaneous signal-to-interference ratio at the output of selection
combining receiver with two branches that uses maximal signal-to-noise ratio algorithm is
presented.
Considering that mobile terminals are relatively small, the distance between receiving
antennas is not large enough to be neglected. Therefore, the correlation between the branches
is included in the analysis of statistical characteristics of the first order. Due to easier
mathematical manipulation, statistical characteristics of second order do not consider
correlation between receiving branches.
Numerical results obtained using the expressions derived in this thesis for different
decision algorithms are presented graphically. The illustrations show the influence of fading
severity, correlation between the desired signals, as well as the interfering ones and balanced
and unbalanced inputs for each of mentioned algorithms on outage probability, average bit
error probability, average signal-to-interference ratio and channel capacity.
The results for second order statistics for dual branch selection diversity system
operating in Weibull fading environment were compared for a system that employs two
selection algorithms, algorithm based on maximal signal-to-interference ratio, as most
frequently used one, and algorithm based on minimal interference, the algorithm that was not
exploited in literature.
The main contribution of this thesis lies in obtained results for statistical
characteristics and performance of the system that uses four proposed algorithms at receiver
side. The presented analysis of selection diversity system for given channel conditions can be
applied to achieve optimized solutions of wireless system design.