45 research outputs found
SECOND ORDER STATISTICS OF DUAL SELECTION DIVERSITY OVER CORRELATED WEIBULL FADING CHANNELS IN THE PRESENCE OF INTERFERENCE
In this paper, second order statistics of dual selection combining (SC) system applying desired signal decision algorithm are obtained for the case when that diversity system operates in Weibull interference-limited environment. Namely, a novel closed-form expression for outage probability (OP), necessary for an analysis of average fade duration (AFD), in the term of Meijer’s G-function is derived for general case in which desired signal and cochannel interference (CCI) are exposed to fading with different severities. Depending on fading environment, semi-analytical and analytical expressions for average lever crossing rate (LCR) are obtained, too. Numerical results are presented to accomplish proposed mathematical analysis and to examine the effects of system and channel parameters on concerned quantities
Primena tehnika kombinovanja kod bežičnih telekomunikacionih sistema u prisustvu smetnje
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
The LCR of wireless macrodiversity SSC receiver in the presence of gamma shadowed Kappa-Mu fading
Wireless mobile macrodiversity (MaD) radio system with switch and stay (SSC) receiver and two microdiversity (MiD) selection combining (SC) branches operating over Gamma shadowed Kappa-Mu (k-μ) multipath fading environment is considered. Novel, one-folded integral expression for average level crossing rate (LCR) of MaD SSC receiver output signal envelope is obtained. Numerical results of the proposed model are presented and discussed in relation to the system model parameters
Error performance analysis of cross QAM and space-time labeling diversity for cross QAM.
Doctoral Degrees. University of KwaZulu-Natal, Durban.Abstract available in the PD
LEVEL CROSSING RATE OF MACRODIVERSITY OUTPUT PROCESS IN THE PRESENCE OF η-μ SHORT TERM FADING AND GAMMA LONG TERM FADING
In this paper macrodiversity reception with macrodiversity selection combining (SC) receiver and two microdiversity MRC receivers operating over shadowed multipath fading channel is studied. Received signal experiences short term fading and correlated Gamma long term fading resulting in system performance degradation. Level crossing rate (LCR) of η-μ random process and level crossing rate of signals at outputs of microdiversity MRC receivers are efficiently calculated. By using these derived formulas, level crossing rate of macrodiversity SC receiver output signal process is calculated. By using this result, average fade duration (AFD) of the proposed wireless communication system can be calculated. The influence of η-μ short term fading severity parameter, Gamma long term fading severity parameter and Gamma long term correlation coefficient on level crossing rate is analysed and studied
Transmit antenna selection in fading wireless communication systems
Includes abstract.Includes bibliographical references (leaves 79-83).To address the drawbacks associated with multiple-input multiple-output (MIMO) systems, we propose the use of the transmit antenna selection technique. In transmit antenna selection, the best performing antenna(s) is selected from all the available transmit antennas for transmission. Transmit antenna selection reduces the number of radio frequency chains, and the system complexity while still achieving the goals of multiple antenna systems. In this thesis the performance of a MIMO system employing transmit antenna selection and maximal-ratiocombining is studied
Statističke karakteristike prvog i drugog reda signala u bežičnom telekomunikacionom sistemu sa selekcionim kombinovanjem
In doctoral dissertation, first and second order system performances of wireless
communication system in the presence of fading and interference are considered.
Theoretically, four cases are taken into consideration, and obtained numerical results are
graphically presented and analyzed.
Firstly, wireless mobile communication system with the receiver that contains
automatic frequency control (AFC) loop operating over fading channel in the presence of
single interference is considered. Performance measures, such as average switching rate
(ASR) and mean time lose of lock (MTTL), are defined. In this doctoral dissertation, ASR
and MTTL, for three different fading channels: Kg, α-μ and k-μ are obtained.
In the next chapter, wireless relay communication system with two sections in the
presence of multipath fading is considered. Signal envelope at the input of the receiver can
be expressed as product of the first section signal envelope and the second section signal
envelope. For such system model, average level crossing rate (LCR) for the case when
radio relay system of the first section operates over Nakagami-m fading environment and
second section operates over k-μ fading environment is obtained. Wireless relay system
with two sections in the presence of non-linear α-μ fading channel is than taken into
consideration. Moreover, radio relay system with two sections in the presence of multipath
fading and interference is also considered. LCR of the ratio of the product of two k-μ
random processes and k-μ random process is calculated. Finally, LCR of the ratio of
Rician random process and product of two Rician random processes is obtained.
Wireless communication system with two inputs SSC diversity receiver operating
over correlated multipath η-μ fading in the presence of interference is than considered.
Joint probability density function and joint distribution cumulative function of the ratios of
signal to interference at inputs of SSC receivers are calculated. By using obtained
expressions for probability density function (PDF), average bit error probability (ABER)
for different coherent and non-coherent modulation schemes is obtained while by using
derived cumulative distribution function (CDF), outage probability (OP) is obtained.
At the end of doctoral dissertation, macrodiversity system with macrodiversity
SSC receiver and two microdiversity SC receivers operating over Gamma shadowed
multipath fading channel is proposed. In one case Nakagami-m multipath fading channel is
considered while in the second case k-μ multipath fading is considered. System
performances of the proposed system are derived and numerical results are graphically
presented and discusse