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 improvements in wireless CDMA communications utilizing adaptive antenna arrays

This dissertation studies applications of adaptive antenna arrays and space-time adaptive processing (STAP) in wireless code-division multiple-access (CDMA) communications. The work addresses three aspects of the CDMA communications problems: (I) near-far resistance, (2) reverse link, (3) forward link. In each case, adaptive arrays are applied and their performance is investigated. The near-far effect is a well known problem which affects the reverse link of CDMA communication systems. The near-far resistance of STAP is analyzed for two processing methods: maximal ratio combining and optimum combining. It. is shown that while maximal ratio combining is not near-far resistant, optimum combining is near-far resistant when the number of cochannel interferences is less than the system dimensionality. The near-far effect can be mitigated by accurate power control at the mobile station. With practical limitations, the received signal power at a base station from a power-controlled user is a random variable clue to power control error. The statistical model of signal-to-interference ratio at the antenna array output of a base station is presented, and the outage probability of the CDMA reverse link is analyzed while considering Rayleigh fading, voice activity and power control error. New analytical expressions are obtained and demonstrated by computer simulations. For the application of an adaptive antenna. array at the forward link, a receiver architecture is suggested for the mobile station that utilizes a small two-antenna array For interference suppression. Such a receiver works well only when the channel vector of the desired signal is known. The identifying spreading codes (as in IS-95A for example) are used to provide an adaptive channel vector estimate, and control the beam steering weight, hence improve the receiver performance. Numerical results are presented to illustrate the operation of the proposed receiver model and the improvement in performance and capacity

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

Performanse bežičnog telekomunikacionog sistema u prisustvu n-m fedinga

In this thesis characteristics of wireless communication system operating over η-μ fading channel are considered together with diversity reception techniques which reduce the influence of η-μ fading on the system’s outage probability, average bit error rate, channel capacity, level crossing rate and average fade duration. Performance improvement is very significant within radio systems operating into cell network configuration. Cell network configuration realization could be used for increasing capacity of wireless communication system. With the increase of number of cells, i.e. with reducing the surface area of each cell, channel capacity increases. With the increase of number of cells, co-channel interference level increase, which degrades system performance values. In this work the compromise between the system capacity and reception quality is inquired. By applying diversity reception techniques, system performance values, degraded by the influences of slow fading, multipath fading and co-channel interference, are improved, so it is possible to reduce the cell area and to increase system capacity. In the second part of Phd thesis, various distributions for modeling the envelope variations in fading channels have been presented, cases in which these models are used have been pointed out, and advantages and imperfections of corresponding models for corresponding propagation scenarios have been presented. In third chapter, statistical characteristics of the first order of η-μ random variable, α-η-μ random variable and squared η-μ random variable are considered. For each mentioned variables, expressions for probability density function, cumulative distributive function, characteristic function and moments have been derived. Also for each observed case sum of two random variables, product of two random variables, ratio of two random variables, maximal value of two random variables and minimum value of two random variables have been determined. Obtained results are used for determining performances of wirelles reception with applied diversity technique for mitigation fading influence on system performances. Based on obtained expressions, graphs are depicted for probability density functions and cumulative distribution functions for the various values of propagation environment parameters. Probability density function and cumulative distribution function values are also graphically presented for α-η-μ random variable in the function of α and μ parameter change. For the purpose of performance analysis in η-μ fading environment, in the fourth chapter have been considered transformations of three η-μ random variables. Based on presented transformations of η-μ random variables, transmission performances estimation has been conducted, for the η-μ fading channel. Estimation of signal performances for the cases when diversity techniques are applied are carried out based on standard signal performance measures, i.e. outage probability (OP), average bit error probability (ABER), for observed modulation format and channel capacity. Graphically are presented ABER values for various values of system parameters when transmission is carried out with different modulation formats. By comparing obtained values it can be seen received signal performance improvement for the cases when diversity techniques are apliied over the reception case when there is no diversity technique applied. In the fifth chapter statistical characteristics of the second order of η-μ radnom proccess, and random proccesses which represent various variations of η-μ radnom proccess, are considered. Brand new random proccesses, for describing fading in special channel conditions are fromed. For all this cases level crossing rates are determined. In the sixth chapter of this Phd thesis are considered wireless communication systems with reception with applied diversity techniques for mitigating the influence of η-μ fading on system performances. Space diveristy technique has been used. Useful signals are accepted at the antennas, envelopes of these signals are combined and decision is made based on the signal values at the combiner outputs. System performances are determined for the cases of SC and MRC combining. For bouth cases probability density function and cumulative distribution function of the signal at the combiners outouts are derived, as well as the average bit error rate for the various used modualtion formats and level crossing rate. Results for ABER for various modulation formats are graphically presented as well as the improvement of the outage probability at the reception obtained by applying SC with two reception branches. In this part it has also been considered the case when bouth desired and interferring signal are described with η-μ distribution, as well as the case when desired signal has been described with η-μ distribution while interference has been described with κ-μ distribution. In the seventh chapter macrodiversity sistem with SC reception and two MRC microdiversity combiners has been considered. At the inputs at the microdiversity combiners η-μ fading is present, while at the inputs as macrodiversity combiners slow Gamma fading is present. For this model of system it has been calculated probability density function, cumulative distribution function, characteristic function, moments, variance, outage probability and level crossing rate for the signal at the macrodiversity combiner output. Results obtained for level croosing rate at the macrodiversity combiner output are graphically presented

Role of Interference and Computational Complexity in Modern Wireless Networks: Analysis, Optimization, and Design

Owing to the popularity of smartphones, the recent widespread adoption of wireless broadband has resulted in a tremendous growth in the volume of mobile data traffic, and this growth is projected to continue unabated. In order to meet the needs of future systems, several novel technologies have been proposed, including cooperative communications, cloud radio access networks (RANs) and very densely deployed small-cell networks. For these novel networks, both interference and the limited availability of computational resources play a very important role. Therefore, the accurate modeling and analysis of interference and computation is essential to the understanding of these networks, and an enabler for more efficient design.;This dissertation focuses on four aspects of modern wireless networks: (1) Modeling and analysis of interference in single-hop wireless networks, (2) Characterizing the tradeoffs between the communication performance of wireless transmission and the computational load on the systems used to process such transmissions, (3) The optimization of wireless multiple-access networks when using cost functions that are based on the analytical findings in this dissertation, and (4) The analysis and optimization of multi-hop networks, which may optionally employ forms of cooperative communication.;The study of interference in single-hop wireless networks proceeds by assuming that the random locations of the interferers are drawn from a point process and possibly constrained to a finite area. Both the information-bearing and interfering signals propagate over channels that are subject to path loss, shadowing, and fading. A flexible model for fading, based on the Nakagami distribution, is used, though specific examples are provided for Rayleigh fading. The analysis is broken down into multiple steps, involving subsequent averaging of the performance metrics over the fading, the shadowing, and the location of the interferers with the aim to distinguish the effect of these mechanisms that operate over different time scales. The analysis is extended to accommodate diversity reception, which is important for the understanding of cooperative systems that combine transmissions that originate from different locations. Furthermore, the role of spatial correlation is considered, which provides insight into how the performance in one location is related to the performance in another location.;While it is now generally understood how to communicate close to the fundamental limits implied by information theory, operating close to the fundamental performance bounds is costly in terms of the computational complexity required to receive the signal. This dissertation provides a framework for understanding the tradeoffs between communication performance and the imposed complexity based on how close a system operates to the performance bounds, and it allows to accurately estimate the required data processing resources of a network under a given performance constraint. The framework is applied to Cloud-RAN, which is a new cellular architecture that moves the bulk of the signal processing away from the base stations (BSs) and towards a centralized computing cloud. The analysis developed in this part of the dissertation helps to illuminate the benefits of pooling computing assets when decoding multiple uplink signals in the cloud. Building upon these results, new approaches for wireless resource allocation are proposed, which unlike previous approaches, are aware of the computing limitations of the network.;By leveraging the accurate expressions that characterize performance in the presence of interference and fading, a methodology is described for optimizing wireless multiple-access networks. The focus is on frequency hopping (FH) systems, which are already widely used in military systems, and are becoming more common in commercial systems. The optimization determines the best combination of modulation parameters (such as the modulation index for continuous-phase frequency-shift keying), number of hopping channels, and code rate. In addition, it accounts for the adjacent-channel interference (ACI) and determines how much of the signal spectrum should lie within the operating band of each channel, and how much can be allowed to splatter into adjacent channels.;The last part of this dissertation contemplates networks that involve multi-hop communications. Building on the analytical framework developed in early parts of this dissertation, the performance of such networks is analyzed in the presence of interference and fading, and it is introduced a novel paradigm for a rapid performance assessment of routing protocols. Such networks may involve cooperative communications, and the particular cooperative protocol studied here allows the same packet to be transmitted simultaneously by multiple transmitters and diversity combined at the receiver. The dynamics of how the cooperative protocol evolves over time is described through an absorbing Markov chain, and the analysis is able to efficiently capture the interference that arises as packets are periodically injected into the network by a common source, the temporal correlation among these packets and their interdependence

Hybrid satellite–terrestrial networks toward 6G : key technologies and open issues

Future wireless networks will be required to provide more wireless services at higher data rates and with global coverage. However, existing homogeneous wireless networks, such as cellular and satellite networks, may not be able to meet such requirements individually, especially in remote terrain, including seas and mountains. One possible solution is to use diversified wireless networks that can exploit the inter-connectivity between satellites, aerial base stations (BSs), and terrestrial BSs over inter-connected space, ground, and aerial networks. Hence, enabling wireless communication in one integrated network has attracted both the industry and the research fraternities. In this work, we provide a comprehensive survey of the most recent work on hybrid satellite–terrestrial networks (HSTNs), focusing on system architecture, performance analysis, design optimization, and secure communication schemes for different cooperative and cognitive HSTN network architectures. Different key technologies are compared. Based on this comparison, several open issues for future research are discussed

Komunikace na milimetrových vlnách v 5G a dalších sítích: Nové systémové modely a analýza výkonnosti

The dissertation investigates different network models, focusing on three important features for next generation cellular networks with respect to millimeter waves (mmWave) communications: the impact of fading and co-channel interference (CCI), energy efficiency, and spectrum efficiency. To address the first aim, the dissertation contains a study of a non-orthogonal multiple access (NOMA) technique in a multi-hop relay network which uses relays that harvest energy from power beacons (PB). This part derives the exact throughput expressions for NOMA and provides a performance analysis of three different NOMA schemes to determine the optimal parameters for the proposed system’s throughput. A self-learning clustering protocol (SLCP) in which a node learns its neighbor’s information is also proposed for determining the node density and the residual energy used to cluster head (CH) selection and improve energy efficiency, thereby prolonging sensor network lifetime and gaining higher throughput. Second, NOMA provides many opportunities for massive connectivity at lower latencies, but it may also cause co-channel interference by reusing frequencies. CCI and fading play a major role in deciding the quality of the received signal. The dissertation takes into account the presence of η and µ fading channels in a network using NOMA. The closed-form expressions of outage probability (OP) and throughput were derived with perfect successive interference cancellation (SIC) and imperfect SIC. The dissertation also addresses the integration of NOMA into a satellite communications network and evaluates its system performance under the effects of imperfect channel state information (CSI) and CCI. Finally, the dissertation presents a new model for a NOMA-based hybrid satellite-terrestrial relay network (HSTRN) using mmWave communications. The satellite deploys the NOMA scheme, whereas the ground relays are equipped with multiple antennas and employ the amplify and forward (AF) protocol. The rain attenuation coefficient is considered as the fading factor of the mmWave band to choose the best relay, and the widely applied hybrid shadowed-Rician and Nakagami-m channels characterize the transmission environment of HSTRN. The closed-form formulas for OP and ergodic capacity (EC) were derived to evaluate the system performance of the proposed model and then verified with Monte Carlo simulations.Dizertační práce zkoumala různé modely sítí a zaměřila se na tři důležité vlastnosti pro buňkové sítě příští generace s ohledem na mmW komunikace, kterými jsou: vliv útlumu a mezikanálového rušení (CCI), energetická účinnost a účinnost spektra. Co se týče prvního cíle, dizertace obsahuje studii techniky neortogonálního vícenásobného přístupu (NOMA) v bezdrátové multiskokové relay síti využívající získávání energie, kde relay uzly sbírají energii z energetických majáků (PB). Tato část přináší přesné výrazy propustnosti pro NOMA a analýzu výkonnosti se třemi různými schématy NOMA s cílem určit optimální parametry pro propustnost navrženého systému. Dále byl navržen samoučící se shlukovací protokol (SLCP), ve kterém se uzel učí informace o sousedech, aby určil hustotu uzlů a zbytkovou energii použitou k výběru hlavy shluku CH pro zlepšení energetické účinnosti, čímž může prodloužit životnost sensorové sítě a zvýšit propustnost. Za druhé, přístup NOMA poskytl mnoho příležitostí pro masivní připojení s nižší latencí, NOMA však může způsobovat mezikanálové rušení v důsledku opětovného využívání kmitočtů. CCI a útlum hrají klíčovou roli při rozhodování o kvalitě přijímaného signálu. V této dizertace je brána v úvahu přítomnost η a µ útlumových kanálů v síti užívající NOMA. Odvozeny jsou výrazy v uzavřené formě pro pravděpodobnost výpadku (OP) a propustnost s dokonalým postupným rušením rušení (SIC) a nedokonalým SIC. Dále se dizertace zabývá integrací přístupu NOMA do satelitní komunikační sítě a vyhodnocuje výkonnost systému při dopadech nedokonalé informace o stavu kanálu (CSI) a CCI. Závěrem disertační práce představuje nový model pro hybridní družicově-terestriální přenosovou síť (HSTRN) založenou na NOMA vícenásobném přístupu využívající mmWave komunikaci. Satelit využívá NOMA schéma, zatímco pozemní relay uzly jsou vybaveny více anténami a aplikují protokol zesilování a předávání (AF). Je zaveden srážkový koeficient, který je uvažován jako útlumový faktor mmWave pásma při výběru nejlepšího relay uzlu. Samotné přenosové prostředí HSTRN je charakterizováno pomocí hybridních Rician a Nakagami-m kanálů. Vztahy pro vyhodnocení výkonnosti systému navrženého modelu vyjadřující ergodickou kapacitu (EC) a pravděpodobnost ztrát (OP) byly odvozeny v uzavřené formě a následně ověřeny pomocí simulační numerické metody Monte Carlo.440 - Katedra telekomunikační technikyvyhově

Razvoj metoda i algoritama za procenu performansi komunikacionih sistema primenom aproksimacija specijalnih funkcija

The intensive development of wireless communication systems has been accompanied by the need to develop methods and algorithms for implementing appropriate approximations of special functions in order to efficiently estimate the corresponding performance of these services through their application. In order to evaluate the behavior of digital communications systems, it is necessary to estimate standard performance measures for the observed wireless communications systems, various modulation types application, detection types, as well as channel models, and observe relations between performance and key values of system parameters. The analysis of the average bit error rate at reception for the applied modulation format is one of the tools for assessing service performance, that describes the nature of the wireless communication system in the best manner. In order to analytically evaluate the average bit error rate for the applied modulation format, it is necessary to perform the most accurate implementation of the approximation of special functions erfc(x), erf (x), Marcum Q, in the widest input range values. The dissertation will present composite methods of the special functions’ approximations. In addition to the simplicity of realization in approximating the observed functions, the aspect of robustness of approximations absolute and relative error values in a wide range of input parameters values will be considered. The advantages of the proposed solutions will be highlighted by direct comparison with the absolute and relative errors obtained by using the known special functions’ approximations from the literature. Furthermore, when transferring information through fading communication channels, for cases of application of proposed special functions’ approximations, it will be proved that system performance can be determined more easily by applying solutions proposed in the dissertation. In this way, it would be easier to determine the probability of the error of communication systems due to different types of fading existance in the channel. By comparing predicted values of the average bit error rate at reception, when transmitting signals through various communication channels medias, for cases of application of existing, previously proposed special functions’ approximations, with the average bit error rate at reception obtained by calculation based on the proposed approximation solutions, it will be shown that communication performances can be calculated more precisely. Proposed approximations could also be used in the source coding of the signal and could simplify design and realization of the quantizers

Application of diverse techniques to reduce the impact of α-k-μ-g and k-μ-g feding on wireless performance

U ovoj tezi izvršena je analiza performansi bežičnog prenosa_signala_u_prisustvu α-k-μ-g i k-μ-g fedinga_u_kanalu. Izvedeni_su_izrazi u zatvorenom obliku za funkcije_gustine verovatnoće_raspodele i kumulativnu_funkciju_raspodele odnosa signal-šum (SNR) na prijemu kada se bežični prenos vrši kroz kanale sa fedingom. Primenjene_su_standardne_mere_kvaliteta odnosno_performansi_primljenog_signala, kao što su verovatnoća otkaza (OP - Outage probability) i srednji broj osnih preseka (LCR- Level Crossing Rate), koje su_dobijene za_slučajeve_prenosa u funkciji različitih vrednosti parametara sistema. Poboljšanje ovih mera performansi analizirano je za slučaj kada su kada su na prijemnoj_strani_korišćene_prostorne diverziti tehnike_kombinovanja. U tezi je razmatrano nekoliko tehnika_kombinovanja_signala na prijemu. Korišćene_su_tehnika selektivnog_kombinovanja_signala (SC-Selection Combining) i tehnika_kombinacija_signala_sa_maksimalnim_odnosom (MRC-Maximal Ratio Combining), u cilju_procene_mogućnosti_slabljenja_uticaja fedinga pri prenosu signala u kanalu. Izvršena je i analiza_istovremenog_uticaja pojavljive_fedinga i efekta_senke pri bežičnom_prenosu_signala, a razmatrane su mogućnosti_istovremene_primene tehnika makro-diverziti_kombinovanja gore navedenih prostornih diverziti tehnika, kako_bi_se_smanjili ovi štetni efekti uticaja smetnji i poboljšao_kvalitet_signala_na_prijemnoj_strani. Rezultati_dobijeni u_ovoj_tezi, pokazuju da se primenom_pristupa_predloženih u disertaciji_može postići smanjenje štetnih efekata α-k-μ-g i k-μ-g fedinga u kanalu pri_različitim_scenarijima_bežičnog prenosa