32 research outputs found
Performance of generalized selection combining for mobile radio communications with mixed cochannel interferers
The performance of generalized selection combining (GSC) space diversity for mobile radio systems in the presence of multiple cochannel interferers is studied. Two cochannel interference models are considered: 1) L cochannel interferers consisting of L-N Nakagami-m interferers and N Rayleigh interferers and 2) L cochannel interferers in which each interferer follows Nakagami-m distribution for a fraction of time and Rayleigh distribution for the remaining of time. The fading parameters of the Nakagami-m interferers are limited to integer values only. The desired signal is assumed to be Rayleigh faded. Also, all the desired signals and the cochannel interferers received on each branch are independent of each other. Closed-form expressions are derived for the probability density functions (pdfs) of the instantaneous signal-to-interference power ratio (SIR) at the output of the GSC for the two cochannel interference models. Using these SIR pdfs, closed-form expression for evaluating the outage probability and the average bit error probability (BEP) are subsequently derived. A differential phase-shift keying scheme is considered in the derivation. Numerical results showing the influences of various system parameters on the outage probability and the average BEP are then presented.published_or_final_versio
Vjerojatnost ispada koreliranih SIR prijemnika sa SSC raznolikosti putem kanala s kompozitnim K_G slabljenjem/zasjenjivanjem signala
In this paper, the effects of multipath fading and shadowing over the propagation channel are observed through the performance analysis of switch and stay selection combining (SSC) technique. The short term fading (multipath fading) in conjunction with the long term fading (shadowing) are both modeled by Generalized-K (K_G) distribution. The proposed system is considered as interference-limited system in correlated fading environment. The probability density function (PDF) of signal-to-interference ratio (SIR) at the output of SSC receiver is derived in form of Meijer G functions. According to this new expression, the outage probability is considered and the effects of fading and shadowing parameters and correlation coefficients on the performance gain are analyzed.U radu su razmatrana djelovanja višeputnog slabljenja i zasjenjivanja signala u propagacijskom kanalu pomoću analize SSC prijemnika raznolikosti (prekidački prostorni kombinator raznolikosti). Kompozitni utjecaj brzog (višeputnog) i sporog slabljenja signala (zasjenjivanja) modeliran je poopćenom-K (K_G) razdiobom. Predloženi sustav razmatran je kao sustav s ko-kanalnom interferencijom kao dominantnom smetnjom i koreliranim slabljenjem signala. Funkcija gustoće razdiobe (PDF) odnosa signal/smetnja (SIR) SSC izlaza prijemnika izvedena je u obliku Meijer G funkcija. Na osnovu ovog izraza, razmatra se vjerojatnost ispada te analiziraju učinci parametara i korelacijskih koeficijenata slabljenja i zasjenjivanja signala na unaprijeđenje performansi sustava
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
Performance analysis of EGC combining over correlated Nakagami-m fading channels
In this paper, performance analysis of diversity technique with equal gain
combining method (EGC) with two branches for the detection of signals in
wireless communication systems is presented. In the following analysis, it is
assumed that the fading via channels is Nakagami-m correlated. The first
order statistical characteristics of the system are analysed. Useful formulae
for the probability density function (pdf) and cumulative distribution
function (CDF) of EGC output SIR are derived, and the effects of the fading
severity on the output signal are observed
Performance analysis of diversity techniques in wireless communication systems: Cooperative systems with CCI and MIMO-OFDM systems
This Dissertation analyzes the performance of ecient digital commu- nication systems, the performance analysis includes the bit error rate (BER) of dier- ent binary and M-ary modulation schemes, and the average channel capacity (ACC) under dierent adaptive transmission protocols, namely, the simultaneous power and rate adaptation protocol (OPRA), the optimal rate with xed power protocol (ORA), the channel inversion with xed rate protocol (CIFR), and the truncated channel in- version with xed transmit power protocol (CTIFR). In this dissertation, BER and ACC performance of interference-limited dual-hop decode-and-forward (DF) relay- ing cooperative systems with co-channel interference (CCI) at both the relay and destination nodes is analyzed in small-scale multipath Nakagami-m fading channels with arbitrary (integer as well as non-integer) values of m. This channel condition is assumed for both the desired signal as well as co-channel interfering signals. In addition, the practical case of unequal average fading powers between the two hops is assumed in the analysis. The analysis assumes an arbitrary number of indepen- dent and non-identically distributed (i.n.i.d.) interfering signals at both relay (R) and destination (D) nodes. Also, the work extended to the case when the receiver employs the maximum ratio combining (MRC) and the equal gain combining (EGC) schemes to exploit the diversity gain
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
Performance Analysis of Non-Ideal MIMO Systems in Fading Channels
En esta tesis se aborda el análisis de prestaciones de sistemas MIMO bajo ciertas condiciones no ideales. Se han considerado limitaciones realistas como son las interferencias co-canal, el canal de retorno con velocidad limitada, y la correlación espacial entre antenas. Bajo estas condiciones, se han analizado las probabilidades de error y de outage para sistemas MIMO que incluyen técnicas de conformación de haz en el transmisor y/o distintas técnicas de diversidad espacial en el receptor. Con el fin de obtener expresiones cerradas y exactas par los indicadores de rendimiento mencionados, se han desarrollo nuevos métodos o herramientas matemáticas que facilitan o, en algunos casos, hacen posible el análisis. En primer lugar, se han obtenido nuevas expresiones cerradas para las integrales del tipo Lipschitz-Hankel y para la distribución de los elementos de la diagonal de matrices Wishart complejas. Posteriormente, estos resultados han sido aplicados al análisis de prestaciones de distintos sistemas MIMO en condiciones no-ideales. Concretamente, se han obtenido nuevas expresiones cerrradas de la probabilidad de outage para: sistemas MRC con interferencia co-canal, sistemas MIMO con correlación espacial entre antenas, y sistemas MIMO MRC con un canal de retorno limitado en velocidad. Además, se han obtenido expresiones cerradas para la probabilidad de error en sistemas de diversidad en recepción que emplean modulaciones no coherentes y no ortogonales
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
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