In a packet radio network, multiple terminals broadcast information over a shared communications medium. Messages are transmitted from a source terminal to a destination terminal over multiple relays or hops. The actions of one terminal in the network directly affect the actions of other terminals within its range. The analysis of packet radio networks is complex because system performance depends on the topology of the terminals in the network along with the random access protocol used. Researchers have been unable to model a packet radio network in its most general form. In this project, a model is developed for specific topologies of a packet radio network with a given random access protocol. The sponsor of this project has developed a packet radio network for an indoor wireless alarm system. At the start of the project, the effect of message collisions on system performance was unknown. As a result of this research, a collision model for the network has been developed for topologies of four, five, and six alarm units. The model has been validated with actual system testing. Furthermore, the effects of indoor propagation on system performance have been studied. The results of this work have led to the development of an installation plan for the indoor wireless alarm system. / Master of Science

It is important to investigate the threat posed to commercial aircraft by on board electronic transmitters in the passenger cabin and the cargo holds of large transport aircraft. These transmitters may be in the form of unintentional use of portable electronic devices or even intentional radio frequency (RF) threat sources from terrorists. Thus, it is of interest to determine the "interference path loss" (IPL) from a transmitting device inside the cabin of such aircraft to the antenna terminals of a potential victim system of the aircraft. Past studies have concentrated on measurements. These efforts to measure IPL directly have demonstrated that accurate and repeatible measurements are difficult to obtain. Very little modeling work has been done successfully to understand the IPL on aircraft. In this thesis, we propose a 3-step methodology to quantify the interference path loss (IPL). We then apply this methodology to a broad class of aircraft and show results. To validate our results, we compare our findings to known measurements and discuss possible sources of errors. Finally we suggest areas of improvement to our analysis and propose future work. / Master of Science

In this thesis it is investigated to what extent it is possible to accurately model path loss in indoor environments using a simple empirical approach. Two kinds of radio access antenna deployments are investigated: 1) standard dipole antennas and 2) leaky cables. For the case of standard dipole antenna deployment, a few well established empirical models are integrated in order to account for the main observed propagation mechanisms. One important propagation mechanism is wave guiding in corridors. It has been shown that a model designed for street microcells (“The recursive model”) combined with the power law model (combined model) well describes this wave guiding propagation. Some inaccuracies have, however, been observed when the direct pathway is dominating. In this master thesis it is therefore investigated if the model accuracy may be improved by integration of the Keenan-Motley and the Devasirvatham model (modified combined model) accounting for loss due to obstructions along the direct pathway. In this work, the primary models used for the case of leaky cable antenna deployments are the Keenan-Motley model (for short distances) and the modified combined model (for large distances). In order to improve and evaluate the modeling, propagation measurements have been carried out at the 2.44 GHz band in an indoor office environment. The measurement data, i.e., the calibrated frequency response of the channel, is obtained using the network analyzer measurement technique by sweeping the frequency over a range of 80 MHz around the center frequency. Hence, the path gain measured in dB-scale is obtained as the difference between the transmitted power and the received power. The combined model and the modified combined model are evaluated and parameterized based on the conducted measurements. The accuracy of the combined model is improved by the implemented modifications. In our case, the standard deviation error is reduced from 5-19 dB to 2-4 dB. Moreover, the measurements show that using leaky cables results in a better coverage in rooms alongside the corridor compared with using dipole antennas. Also the interference into adjacent cells is reduced using leaky cables compared with using dipole antennas.

Στην εποχή που ζούμε, η καθημερινότητα των πολιτών, από όλες σχεδόν τις πλευρές της, από την επαγγελματική και προσωπική της διάσταση έως τον τρόπο που επιλέγει πλέον κάποιος να διασκεδάζει και να κοινωνικοποιείται, είναι σε πολύ μεγάλο βαθμό εξαρτημένη από το νευραλγικό τομέα των επικοινωνιών. Διαπιστώνει κανείς πολύ εύκολα την ήδη εδώ και δεκαετίες, τεράστια διείσδυση των επικοινωνιών σε όλους τους παραγωγικούς τομείς της κοινωνίας, στους ίδιους τους μηχανισμούς της διακυβέρνησης και της ενημέρωσης. Το τεράστιο άλμα ωστόσο, πραγματοποιείται τα τελευταία χρόνια, με την ανάπτυξη των ασύρματων επικοινωνιών και διάφορων τεχνολογιών που προκύπτουν μέσα από επίπονη και πολύχρονη έρευνα. Κινητή τηλεφωνία, ασύρματα δίκτυα, πρόσβαση σε γρήγορο internet οπουδήποτε και οποτεδήποτε, είναι τεχνολογίες που έχουν αλλάξει δραματικά και ανεπιφύλακτα προς το καλύτερο, τις ζωές όλων μας. Στη παρούσα διπλωματική εργασία με τίτλο «Διερεύνηση τεχνικών παραμέτρων για βέλτιστη σχεδίαση συστημάτων τεχνολογίας Wi-Fi:», αφού πρώτα μελετήσουμε πλήρως το πρότυπο 802.11 ή κοινώς WiFi, όσο αφορά την αρχιτεκτονική του, τη δομή του και τις διάφορες εκδόσεις του, προχωράμε σε μια μελέτη γύρω από τα θεωρητικά μοντέλα διάδοσης της ηλεκτρομαγνητικής ακτινοβολίας σε εσωτερικούς χώρους με σκοπό να εξετάσουμε στη συνέχεια ένα τέτοιο πολύπλοκο περιβάλλον και τον τρόπο που συμπεριφέρεται το πρότυπο για μια συγκεκριμένη συχνότητα. Μέσω της μοντελοποίησης και της προσομοίωσης εκτιμάμε και αξιολογούμε τους παράγοντες που επηρεάζουν τη διάδοση αλλά και τυχόν καινούρια στοιχεία που μπορεί να προκύψουν. Στο πρώτο κεφάλαιο εισάγεται ο αναγνώστης στις ασύρματες επικοινωνίες με μια σύντομη ιστορική αναδρομή και την παρουσίαση των βασικών ασύρματων συσ τημάτων σήμερα. Στο κεφάλαιο δύο παρουσιάζεται πλήρως το πρότυπο 802.11. Αναπτύσσεται η αρχιτεκτονική του, η δομή του, το φυσικό του επίπεδο με τις τεχνικές μετάδοσης των διάφορων επικρατέστερων εκδόσεων του αλλά και οι λειτουργίες του επίπεδου MAC με τις παραμέτρους του. Προχωρώντας στο τρίτο κεφάλαιο, μελετάμε τους μηχανισμούς διάδοσης και τα φαινόμενα εξασθένισης του σήματος , κυρίως όμως γίνεται εκτενής αναφορά στα μοντέλα που περιγράφουν την ηλεκτρομαγνητική διάδοση σε περιβάλλον εσωτερικού χώρου, κάθως με βάση τα μοντέλα αυτά, γίνε ται η τελική αξιόγηση του πειραματικού μέρους της εργασίας. Στο τέταρτο κεφάλαιο παρουσιάζονται οι πειραματικές μας μετρήσεις, η τοπολογία και η διαδικασία με την οποία λήφθησαν. Πραγματοποιείται σύγκριση αυτών με τις προβλέψεις βασικών θεωρητικών μοντέλων, και μέσω προσομοίωσης που πραγματοποιήθηκε στο Matlab, εκτιμάται η απόκλιση των πειραματικών τιμών από τις θεωρητικές προβλέψεις. Στο τελευταίο κεφάλαιο παραθέτουμε τα γενικά συμπεράσματα που προέκυψαν από την πειραματική διαδικασία, αξιολογούμε τους παράγοντες που συνετέλεσαν στη λήψη των αποτελεσμάτων μας και αποφαινόμαστε για το καταλληλότερο μοντέλο στο περιβάλλον που εργαστήκαμε. / Nowadays, the citizen’s daily life from both the professional and personal point of view to the way somebody chooses to be socialized and get amused, is extremely dependent on the neuralgic field of communications. It becomes evident easily to anybody, the already for decades great penetration of communications to all the production sectors into society and the mechanisms of governess and mass media. However, the tremendous evolution is realized the very last years via the development of wireless communicat ions and the corresponding technologies that arise through arduous and extensive research. Mobile telephony, wireless networks, fast internet access anywhere and anytime, are technologies that has changed drastically and unreservedly our lives to the better. In this thesis, entitled “Investigation of Technical Parameters for Optimal design of WiFi Technology Systems”, after fully studying the 802.11 protocol, commonly referred as WiFi, regarding to its architecture, its structure, and its various versions, we proceed to a study of the theoretical indoor propagation models of electromagnetic radiation, in order to examine then such a complex environment and the behavior of the protocol for a specific frequency. Through modeling and simulation, we estimate and evaluate the factors that affect the propagation, but also any potential new information that may arise. The first chapter introduces to the reader the field of wireless communications and provides a historical overview of the basic wireless communication setups. In chapter two, protocol 802.11 is fully presented. Its architecture, its structure and its physical layer with the employed transmission techniques by its various predominant versions and also the functions of the MAC layer and its parameters are described. Chapter three discusses the transmission methods and the signal attenuation effect, with emphasis on the models that describe the electromagnetic transmission in enclosed spaces, as these models are used for the evaluation of the experimental part of this thesis. Chapter four contains the experimental part of this thesis and presents the topology and the exact procedure of the measurement setup. The obtained measurements are compared to the predicted ones using existing theoretical models via simulations that performed in Matlab and the prediction error is then computed and discussed. In the last chapter, we present the general conclusions derived from the measurement procedure, we evaluate the factors that contributed to the derivation of our results and we determine the most appropriate model for the environment in which we worked.

Οι ασύρµατες τοπολογίες εσωτερικού χώρου (Indoor propagation topologies) είναι πιο σύνθετες από τη φύση τους και απαιτούν µια πιο λεπτοµερή µαθηµατική περιγραφή, δεδοµένου ότι οι διαστάσεις των διαφόρων εµποδίων που παρεµβάλλονται µε το εκπεµπόµενο σήµα είναι συγκρίσιµες µε το µήκος κύµατος του σήµατος. Επιπλέον, οι µηχανισµοί διάδοσης (ανάκλαση-reflection, σκέδαση- scattering, περίθλαση-diffraction) έχουν ακόµα µεγαλύτερη επιρροή σε ένα εσωτερικό περιβάλλον όπου οι παράµετροι καναλιού είναι πολύ ευαίσθητοι και εξαρτώνται άµεσα µε τα ενδογενή χαρακτηριστικά της τοπολογίας. Ως αποτέλεσµα, στα µοντέλα εσωτερικού χώρου, πρέπει να λαµβάνονται υπόψη όλοι οι παράγοντες που συµβάλλουν στην παρεµπόδιση και εξασθένηση του σήµατος. Το µοντέλο εσωτερικών χώρων απώλειας διαδροµής της ITU (ITU indoor path loss model) κατατάσσει τους εσωτερικούς χώρους σε τρεις κύριες 7 κατηγορίες: Σπίτι, Γραφείο και Εµπορικές τοπολογίες. Η σπουδαιότητα που έχουν τα χαρακτηριστικά της τοπολογίας, όταν λαµβάνονται υπόψη στην επίδραση του ασύρµατου καναλιού, γίνεται εµφανής όταν εξετάζουµε τα Wi-Fi/WLAN συστήµατα. Τα τελευταία χρόνια, το ενδιαφέρον για µοντελοποίηση των απωλειών όδευσης έχει αυξηθεί σηµαντικά για τη συχνότητα 2,4 GHz, λόγω του γεγονότος ότι αυτή είναι η συχνότητα που λειτουργούν οι σύγχρονοι Wi-fi routers και άλλα ασύρµατα ηλεκτρονικά συστήµατα. Ο σκοπός της εργασίας αυτής είναι να παρουσιάσει µια µελέτη περίπτωσης µιας εµπορικής εσωτερική τοπολογία διάδοσης, τη ∆ηµόσια Βιβλιοθήκη του Πανεπιστηµίου Πατρών, καθώς και µιας ιδιωτικής οικίας και την επικύρωση της αξιοπιστίας των εσωτερικών µοντέλων RF. / Models for indoor propagation prediction at 2.4GHz frequency.

La facilité de déploiement et la flexibilité des technologies sans fil ont permis une évolution considérable des normes IEEE 802.11. L'arrivée de la fibre optique à la maison a également motivé des études de recherche pour accroître les débits et la capacité. Dans ce contexte, la dernière norme IEEE 802.11ac ratifiée en 2014 a normalisé de nouvelles technologies pour atteindre des débits maximaux au-dessus de 1Obit/s. En particulier, 802 llac propose le Multiple Input Multiple Output Multi-Utilisateurs (MIMO-MU) et le Transmit Beamforming (TxBF). Ces technologies d'antennes intelligentes supposent un diagramme d'antenne d'émission qui dépend de la position des utilisateurs et des caractéristiques du canal de propagation multi-trajets correspondant. Cependant, les outils d'ingénierie et de planification radio actuels simulent une carte de couverture fixe et indépendante de tout traitement d'antennes adaptatives côté émission. Cette thèse étudie l'impact de ces techniques MIMO-MU et TxBF et propose des solutions adaptées pour l'ingénierie radio et l'optimisation du système ainsi que pour les outils de planification radio. En effet, la première partie de cette thèse consiste à affiner les gains de capacité en identifiant les configurations et les paramètres système optimaux. La deuxième partie aborde les gains de beamforming en termes du gain sur le rapport signal à bruit (SNR) et sur la réduction du niveau d'interférence pour avoir une modélisation réaliste de la couverture radio. / The deployment facility and flexibility of wireless technologies have allowed considerable evolution of IEEE 802 .11 standards. The arrival of the optical fiber to the home has further motivated the research studies to increase data rates and capacity. ln this context, the latest IEEE 802.l lac standard ratified in 2014 proposes new technologies to achieve maximum data rates above 1 Gbit/s. ln particular, 802.l lac includes the Multi-User Multiple Input Multiple Output (MU-MIMO) and Transmit Beamforming (TxBF). These smart antenna technologies assume a variable transmit antenna pattern in function of the users' position and the corresponding multipath propagation channel characteristics. However, the actual radio planning tools give a fixed coverage map in dependent of any adaptive or smart antenna processing. This thesis studies the impact of the MU-MIMO and TxBF techniques on radio engineering, system optimization as well as radio planning tools. Indeed, the first part of this thesis deals with refining the sum rate capacity gains by identifying interesting system configurations and optimal system parameters. The second part addresses the beamforming gains in terms of the Signal-to-Noise Ratio (SNR) gain and interference level to have realistic radio coverage modeling.

Indoor use of wireless systems poses one of the biggest design challenges. It is difficult to predict the propagation of a radio frequency wave in an indoor environment. To assist in deploying the above systems, characterization of the indoor radio propagation channel is essential. The contributions of this work are two-folds. First, in order to build a model, extensive field strength measurements are carried out inside two different buildings. Then, path loss exponents from log-distance path loss model and standard deviations from log-normal shadowing, which statistically describe the path loss models for a different transmitter receiver separations and scenarios, are determined. The purpose of this study is to characterize the indoor channel for 802.11 wireless local area networks at 2.4 GHz frequency. This thesis presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, open corridor, classroom, and computer lab. Path loss equations are determined using log-distance path loss model and log-normal shadowing. The chi-square test statistic values for each access point are calculated to prove that the observed fading is a normal distribution at 5% significance level. Finally, the propagation models from the two buildings are compared to validate the generated equations.

In this thesis a theoretical model for indoor propagation in a straight corridor with adjacent rooms is developed and evaluated. One objective is to assess the effect of different conductivities and permittivities in the walls between rooms have on the power levels, in both the corridor and the rooms. Furthermore, a model of a leaky cable is proposed for which the corresponding propagation characteristics are evaluated and compared to that of a dipole antenna to assess if a leaky cable is a viable alternative for radio coverage in an indoor environment. In order to evaluate the model, a wideband measurement campaign has been conducted at 2.44 GHz with a 40 meter long leaky coaxial cable and two vertically polarized dipole antennas. The proposed model is based on the waveguide model in 2D, the mode matching method and cascade coupling of scattering matrices. A section of a corridor is modeled as waveguides with different cross section where one waveguide contains a dielectric medium which models the wall between two rooms. Mode matching is used to determine how the waveguide modes are coupled at the boundaries between the waveguides and the result is collected in a scattering matrix. Multiple corridor sections are then connected together, by cascade coupling the corresponding scattering matrices of each section, into a long corridor with adjacent rooms. Point sources are used to excite the waveguides as an approximation of dipole transmitting antennas. Moreover, the radiating slots in the leaky cable are modeled by multiple point sources that are phase and amplitude shifted in order to achieve the same radiation direction and longitudinal loss as the leaky cable. Finally, the inverse discreet Fourier transform is applied to the wideband electromagnetic field distribution in order to determine the propagation characteristics in the time domain. The results from the model are in good quantitative agreement with the measurement data, and it is shown that a leaky cable give a more even radio coverage in an office corridor compared to a dipole antenna, especially when the internal walls are highly reflective. Moreover, it is shown that the direct path is dominating for transmission between rooms with transparent walls, like plasterboard, while the main propagation path for highly reflective walls is along the corridor.

No description available.

Yes / A modified indoor path loss prediction model is presented, namely Effective Wall Loss Model (EWLM). The modified model is compared to other indoor path loss prediction models using simulation data and real-time measurements. Different operating frequencies and antenna polarizations are considered to verify the observations. In the simulation part, EWLM shows the best performance among other models as it outperforms two times the dual slope model which is the second-best performance. Similar observations were recorded from the experimental results. Linear attenuation and one slope models have similar behaviour, the two models parameters show dependency on operating frequency and antenna polarization.