Effects of Imperfect Reference Signal Recovery on Performance of SC and SSC Receivers over Generalized Fading Channels

This paper presents the study of the effects of imperfect reference signal recovery on the bit error rate (BER) performance of dual-branch switch-and-stay combining (SSC) and multibranch selection combining (SC) receivers in a generalized - fading channel. The average BER of binary and quaternary phase shift keying (BPSK and QPSK) is derived under the assumption that the reference carrier signal is extracted from the received modulated signal. For SSC receiver the optimal switching threshold (in a minimum BER sense) is numerically evaluated. Hereby we determine and discuss the simultaneous influence of the average signal-to-noise ratio (SNR) per bit, fading severity, product phase-locked loop (PLL) bandwidthbit duration (B_LT_b), switching threshold of SSC and diversity order of SC on BER performance. The influence of B_LT_b in different channel conditions and modulation formats is pointed out. The numerical results are confirmed by computer simulations

Analysis of Selective-Decode and Forward Relaying Protocol over κ-µ Fading Channel Distribution, Journal of Telecommunications and Information Technology, 2020, nr 1

In this work, the performance of selective-decode and forward (S-DF) relay systems over κ-µ fading channel conditions is examined in terms of probability density function (PDF), system model and cumulative distribution function (CDF) of the κ-µ distributed envelope, signal-to-noise ratio and the techniques used to generate samples that rely on κ-µ distribution. Specifically, we consider a case where the sourceto-relay, relay-to-destination and source-to-destination link is subject to independent and identically distributed κ-µ fading. From the simulation results, the enhancement in the symbol error rate (SER) with a stronger line of sight (LOS) component is observed. This shows that S-DF relaying systems may perform well even in non-fading or LOS conditions. Monte Carlo simulations are conducted for various fading parameter values and the outcomes turn out to be a close match for theoretical results, which validates the derivations mad

Performance Analysis, Resource Allocation and Optimization of Cooperative Communication Systems under Generalized Fading Channels

The increasing demands for high-speed data transmission, efficient wireless access, high quality of service (QoS) and reliable network coverage with reduced power consumption impose demanding intensive research efforts on the design of novel wireless communication system architectures. A notable development in the area of communication theory is the introduction of cooperative communication systems. These technologies become promising solution for the next-generation wireless transmission systems due to their applicability in size, power, hardware and price constrained devices, such as cellular mobile devices, wireless sensors, ad-hoc networks and military communications, being able to provide, e.g., diversity gain against fading channels without the need for installing multiple antennas in a single terminal. The performance of the cooperative systems can in general be significantly increased by allocating the limited power efficiently. In this thesis, we address in detail the performance analysis, resource allocation and optimization of such cooperative communication systems under generalized fading channels. We focus first on energy-efficiency (EE) optimization and optimal power allocation (OPA) of regenerative cooperative network with spatial correlation effects under given power constraint and QoS requirement. The thesis also investigates the end-to-end performance and power allocation of a regenerative multi-relay cooperative network over non-homogeneous scattering environment, which is realistic case in practical wireless communication scenarios. Furthermore, the study investigates the end-to-end performance, OPA and energy optimization analysis under total power constraint and performance requirement of full-duplex (FD) relaying transmission scheme over asymmetric generalized fading models with relay self-interference (SI) effects.The study first focuses on exact error analysis and EE optimization of regenerative relay systems under spatial correlation effects. It first derives novel exact and asymptotic expressions for the symbol-error-rates (SERs) of M -ary quadrature amplitude and M -ary phase-shift keying (M -QAM) and (M -PSK) modulations, respectively, assuming a dual-hop decode-and-forward relay system, spatial correlation, path-loss effects and maximum-ratio-combing (MRC) at the destination. Based on this, EEoptimization and OPA are carried out under certain QoS requirement and transmit power constraints.Furthermore, the second part of the study investigates the end-to-end performance and power allocation of MRC based regenerative multi-relay cooperative system over non-homogeneous scattering environment. Novel exact and asymptotic expressions are derived for the end-to-end average SER for M -QAM and M -PSK modulations.The offered results are employed in performance investigations and power allocation formulations under total transmit power constraints.Finally, the thesis investigates outage performance, OPA and energy optimization analysis under certain system constraints for the FD and half-duplex (HD) relaying systems. Unlike the previous studies that considered the scenario of information transmission over symmetric fading conditions, in this study we considered the scenario of information transmission over the most generalized asymmetric fading environments.The obtained results indicate that depending on the severity of multipath fading, the spatial correlation between the direct and relayed paths and the relay location, the direct transmission is more energy-efficient only for rather short transmission distances and until a certain threshold. Beyond this, the system benefits substantially from the cooperative transmission approach where the cooperation gain increases as the transmission distance increases. Furthermore, the investigations on the power allocation for the multi-relay system over the generalized small-scale fading model show that substantial performance gain can be achieved by the proposed power allocation scheme over the conventional equal power allocation (EPA) scheme when the source-relay and relay-destination paths are highly unbalanced. Extensive studies on the FD relay system also show that OPA provides significant performance gain over the EPA scheme when the relay SI level is relatively strong. In addition, it is shown that the FD relaying scheme is more energy-efficient than the reference HD relaying scheme at long transmission distances and for moderate relay SI levels.In general, the investigations in this thesis provide tools, results and useful insights for implementing space-efficient, low-cost and energy-efficient cooperative networks, specifically, towards the future green communication era where the optimization of the scarce resources is critical

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Optical Communication

Optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components, systems, networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries

Exponentiated weibull fading channel model in free-space optical communications under atmospheric turbulence

Free-space optical (FSO) communications is drawing increasing attention as a promising technology to overcome bandwidth shortage, of an evermore crowded wireless marketplace. Currently radio-frequency (RF) technology struggles to cope with the ever increasing demand for high-bandwidth data. Moreover, as the number of users increases, the RF spectrum is getting so crowded that there is virtually no room for new wireless services, with the additional inconvenient of limited bandwidth restriction for using a RF band and the license fees that have to be paid for such bands. FSO communications offer clear advantages over other alternatives such as narrower and more secure beams, virtually limitless bandwidth and no regulatory policies for using optical frequencies and bandwidth. Moreover, in the space sector FSO technology is becoming more attractive for satellite communication systems due to the less mass and power requirements --compared to RF. The major drawback for deploying wireless links based on FSO technology is the perturbation of the optical wave as it propagates through the turbulent atmosphere. Many effects are produced, of which the most noticeable is the random fluctuations of the signal-carrying laser beam irradiance (intensity), phenomenon known as scintillation and quantified by the scintillation index (SI). The statistical analysis of the random irradiance fluctuations in FSO links is conducted through the probability density function (PDF), from which one can obtain other statistical tools to measure link performance such as the probability of fade and the bit error-rate (BER). Nowadays, the most widespread models for the irradiance data are, by far, the Lognormal (LN) and Gamma-Gamma (GG) distributions. Although both models comply with actual data in most scenarios neither of them is capable of fitting the irradiance data under all conditions of atmospheric turbulence for finite receiving aperture sizes, i.e. in the presence of aperture averaging. Furthermore, there are several cases where neither the LN or the GG model seem to accurately fit the irradiance data, specially in the left tail of the PDF. The work presented in this thesis is devoted to propose a new model for the irradiance fluctuations in FSO links under atmospheric turbulence, in the presence of aperture averaging; resulting in the exponentiated Weibull (EW) distribution. A physical justification for the appearance of the new model is provided along with numerous test scenarios in the weak-to-strong turbulence regime --including numerical simulations and experimental data-- to assess its suitability to model the irradiance data in terms of the PDF and probability of fade. Here, a semi-heuristic approach is used to find a set of equations relating the EW parameters directly to the SI. Such expressions were tested offering a fairly good fitting the actual PDF of irradiance data. Furthermore, for all the scenarios tested a best fit version of the EW PDF is obtained and always presents itself as an excellent fit to the PDF data. The new model has been compared to the LN and GG distributions proving to cope to the predictions made by those and, in some cases, even outperforming their predictions. Additionally, a new closed-form expression has been derived for estimating the BER performance under EW turbulence, for intensity-modulation/direct-detection (IM/DD) systems using on-off keying (OOK) modulation. Moreover, this expression has been extended to include pointing errors. Finally, the exponentiated Weibull PDF has been proved to be valid with fully and partially coherent beams. The results presented here suggest that the EW distribution presents the better fit for data under different scenarios, thus, the exponentiated Weibull distribution becomes an excellent alternative to model the PDF of irradiance data under all conditions of atmospheric turbulence in the presence of aperture averaging

Uticaj nesavršene ekstrakcije referentnog nosioca na performanse diverziti prijemnika digitalno fazno modulisanih signala u kanalu sa fedingom

The results of the research, presented in this dissertation, refer to the analysis of imperfect reference signal recovery influence on performance of digital systems with BPSK and QPSK modulation and diversity at the reception applied. In order to make the content easy for understanding, the theoretical basics, necessary for calculations performed in the following chapters, has been presented at the beginning. In the analysis of the imperfect reference signalrecovery influence on the performance of single channel systems for BPSK and QPSK signal detection two cases have been considered. The analysis has been performed for Hoyt and composite Kg fading channel. ..

Publications of the Jet Propulsion Laboratory, 1985

This bibliography describes and indexes by primary author the externally distributed technical reporting, released during calender year 1985, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: JPL publications in which the information is complete for a specific accomplisment; Articles from the quarterly Telecommunications and Data Acquisition (TDA) Progress Report; and article published in the open literature