Povećanje informacionog kapaciteta i pouzdanosti u bežičnim optičkim komunikacijama primenom algoritama adaptivnog prenosa

This dissertation considers adaptive transmission algorithms and their influence towards increasing information capacity and system reliability. Theses algorithms are applied to optical wireless communications, as well as to radio-frequency system with diversity receiver. System of adaptive transmission is described in detail, and different algorithms of adaptation are applied: ORA, OPRA, CIFR, and TIFR. Derived probability density function combines influence of atmospheric turbulence, atmospheric losses and positioning errors that consist of laser pointing precision and jitter. FSO system without adaptation is also considered. For this case, bit-error rate and outage probability are determined when signal is exposed to different strengths of atmospheric turbulence, when there is atmospheric attenuation and positioning errors due to both main causes, when IM/DD and heterodyne detection are used. Power penalty is also determined for such system. Bit-error rate is also determined for the case when SIM is used in combination with binary modulation and quadrature amplitude modulation. Capacity analysis is given for the use of ORA, OPRA, CIFR and TIFR adaptive transmission algorithms, and for IM/DD and heterodyne detection cases. Algorithms used for transmitter power adaptation are additionally analyzed and improved with an aim to obtain realistic and functional systems. Based on analytical expression, simulation model is developed for adaptive transmission systems, which is used to validate numerical results. Approximate expressions are also given for used adaptive algorithms. Finally, adaptive transmission is considered also for a class of wireless RF systems. Fading model used is based on α-κ-μ distribution. Outage probability and amount of fading are given as representative performance measures. Besides adaptive transmission algorithms used in FSO systems, analysis of space diversity reception is also presented for the general case of using L antennas

LEVEL CROSSING RATE OF MACRODIVERSITY SYSTEM OVER COMPOSITE GAMMA SHADOWED ALPHA-KAPPA-MU MULTIPATH FADING CHANNEL

In this paper macrodiversity system with macrodiversity selection combining (SC) receiver and two microdiversity SC receivers operating over composite shadowed multipath fading environment is considered. Received signal is subjected simultaneously to gamma long term fading and α-κ-μ short term fading resulting in system performance degradation. Macrodiversity SC receiver reduces gamma long term fading effects and microdiversity SC receivers mitigate α-κ-μ short term fading effects. Analitical expression for average level crossing rate of proposed wireless mobile system represented as an infinite series is evaluated. Mathematical and numerical analysis are shown influences of gamma fading severity, α-κ-μ multipath fading severity, and Rician factor on average level crossing rate

OUTAGE PERFORMANCE OF MULTI-BRANCH SC RECEIVER OVER CORRELATED WEIBULL CHANNEL IN THE PRESENCE OF CORRELATED RAYLEIGH CO-CHANNEL INTERFERENCE

The aim of this paper is to consider the performance of wireless communication system with signal-to interference ratio (SIR) based multiple-branches selection combining (SC) receiver. The proposed system operates over correlated Weibull multipath environment, in the presence of co-channel interference (CCI) subjected to correlated Rayleigh multipath fading. SC diversity technique is used to reduce the effects of multipath fading and CCI on the system performance. Infinite-series expression for outage probability (OP) in terms of Meijer G functions is derived. Further, numerical results are graphically presented and discussed to show the influence of fading parameters on outage probability

Povećanje informacionog kapaciteta i pouzdanosti u bežičnim optičkim komunikacijama primenom algoritama adaptivnog prenosa

This dissertation considers adaptive transmission algorithms and their influence towards increasing information capacity and system reliability. Theses algorithms are applied to optical wireless communications, as well as to radio-frequency system with diversity receiver. System of adaptive transmission is described in detail, and different algorithms of adaptation are applied: ORA, OPRA, CIFR, and TIFR. Derived probability density function combines influence of atmospheric turbulence, atmospheric losses and positioning errors that consist of laser pointing precision and jitter. FSO system without adaptation is also considered. For this case, bit-error rate and outage probability are determined when signal is exposed to different strengths of atmospheric turbulence, when there is atmospheric attenuation and positioning errors due to both main causes, when IM/DD and heterodyne detection are used. Power penalty is also determined for such system. Bit-error rate is also determined for the case when SIM is used in combination with binary modulation and quadrature amplitude modulation. Capacity analysis is given for the use of ORA, OPRA, CIFR and TIFR adaptive transmission algorithms, and for IM/DD and heterodyne detection cases. Algorithms used for transmitter power adaptation are additionally analyzed and improved with an aim to obtain realistic and functional systems. Based on analytical expression, simulation model is developed for adaptive transmission systems, which is used to validate numerical results. Approximate expressions are also given for used adaptive algorithms. Finally, adaptive transmission is considered also for a class of wireless RF systems. Fading model used is based on α-κ-μ distribution. Outage probability and amount of fading are given as representative performance measures. Besides adaptive transmission algorithms used in FSO systems, analysis of space diversity reception is also presented for the general case of using L antennas

HK distribution model for atmospheric turbulence channel under the influence of pointing errors

In this paper, HK statistical model is considered. The application of HK distribution in modeling atmospheric turbulence channel under the influence of strong and weak turbulences and all irradiance fluctuations are discussed. Expression for atmospherics turbulence channel model, pointing error models and path loss are given. Probability density functions (PDF) for both pointing error models (zero boresight and nonzero boresight) are calculated and graphically represented. Also, average bit-error-rate (BER) for zero boresight pointing error and nonzero boresight pointing error are calculated and graphically represented. Closed form expression for PDF and BER are given. Impact of zero boresight pointing error and nonzero boresight pointing error on transmission over atmospheric turbulence channel in FSO system is explained

Wireless Communication System Performance in M2M Nakagami-m Fading Channel

In this paper, we investigate a wireless mobile communication system with a cooperative network operating over a mobile-to-mobile (M2M) fading channel in the presence of co-channel interference. Since there is no direct line of sight between the source (S) and the destination (D) due to various obstacles, the signal transmission takes place by using a relay (R). We modeled and represented the desired signal and co-channel interference by using the Nakagami-m fading distribution from the source (S) to the relay (R), as well as from the relay (R) to the destination (D). As the popularity of M2M communication has increased in 5G cellular networks, the performance analysis of the proposed system is of great importance. We derived closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-interference ratio (SIR) at the input of the destination station. Based on the cumulative distribution function (CDF), we also evaluated the outage probability (Pout) of the proposed communication system. In addition, we derived a closed-form approximate expression for the level crossing rate (LCR) by using the Laplace approximation formula for the three-fold integral. Validity of the derived theoretical results we approved by Monte Carlo simulations

Analysis of the influence of communication parameters of FSO channels on the reception quality

In this paper, the signal transmission in the Free -Space Optics (FSO) communication system using the software package OptiSystem 7.0 is analyzed. The influence of parameters FSO (Free -Space-Optics) channels (Range, Attenuation, Beam Divergence, Transmitter Loss, Receiver Loss, and Additional Losses) on the reception quality is considered. The reception quality is analyzed according to the values of BER (Bit Error Ratio) and Q factor. Graphics and tables of the changes of BER and Q factor depending on the parameters of FSO are given. Also, the eye diagrams for the characteristic parameter values are given