Wireless sensor network, which is constitute of autonomous sensors, is used for monitoring physical or environmental conditions like temperature, sound, pressure, and so on. The dispersed sensors or nodes will respectively pass their data through the network to the main location. Currently, several standards are ratified or in developing for wireless sensor network, like Wireless Hart, ISA, 100.11a, WIA-PAA, IEEE 802.15.4, etc. Among the standards, Zigbee is often used in industrial applications that require short-range and low-rate wireless transfer. In the research, all the data is collected under industrial environment using IEEE 802.15.4 compliant physical layer, some packets are interfered only by multi-path fading while others are also interfered by Wi-Fi interference. The goal of the thesis is to find out the dependence between the received power (RSS), correlation value (CORR) and bit error rate (BER) of the received message, and their distribution in situations both when the packet is lost or not. Besides, the performance of bit error rate such as the distribution and the features of burst error length under Wi-Fi interference or not will also be tested. All of them are based on a precise statistical processing.

<p>In our homes and in the enterprise, in our leisure and in our professions, mobile computing is no longer merely "exciting;" it is becoming an essential, ubiquitous tool of the modern world. New and innovative mobile applications continue to inform, entertain, and surprise users. But, to make the daily use of mobile technologies more gratifying and worthwhile, we must move forward with new levels of sophistication. The Mobile App Stores of the future must be built on stronger foundations. </p><p>This dissertation considers a broad view of the challenges and intuitions behind a diverse selection of such new primitives. Some of these primitives will mitigate existing and fundamental challenges of mobile computing, especially relating to wireless communication. Others will take an application-driven approach, being designed to serve a novel purpose, and be adapted to the unique and varied challenges from their disparate domains. However, all are related through a unifying goal, to provide a seamless, enjoyable, and productive mobile experience. This dissertation takes view that by bringing together nontrivial enhancements across a selection of disparate-but-interrelated domains, the impact is synergistically stronger than the sum of each in isolation. Through their collective impact, these new "building blocks" can help lay a foundation to upgrade mobile technology beyond the expectations of early-adopters, and into seamless integration with all of our lives.</p> / Dissertation

This paper presents a fault-tolerant (fault tolerant) can enhance the communications capabilities, improve the reliability and efficiency of in smart grid signal transmission. Meter layout with PLC or ZigBee in any topology, meter adopt Minimum Spanning Tree algorithm to achieve shortest distance and lost cost in PLC; when device contain wireless receiver, meter adopt Hungarian algorithm can search nearest itself¡¦s device to receive device information. The paper propose two fault tolerant methods: static and dynamic methods. Static method is a meter transmit to another one with regular communication even if a meter tranfmit with ZigBee; dynamic method is a meter transmit another one, ZigBee has low priority according to cost function in effective communication range. The paper simulation in any 100m2 topology, randon produce 13 SmartUnit with different number of meters and coordinate, two fault tolerant method can achieve 100% fault coverage in single link fault case; but static method use FTGDB(Fault Tolerant Generalized De Bruijn algorithm) multiple fault coverage can achieve 43% with d=4 case; dynamic method use Kth shortest path algorithm multiple fault coverage can achieve 61% with d=4 case. In other words FTGDB has average 100 communication line allow average 43 communication line fault tolerant ability with d=4 case in 13 SmartHomeUnit; Kth shortest path algorithm has average 100 communication line allow average 61 communication line fault tolerant ability with d=4 case in 13 SmartHomeUnit. If after fault tolerant achievement, count to demand energy and delay time with PLC and ZigBee, then it can offer electric company information. Electric company evaluate electric cost¡Breal time price etc¡K The paper propose a online demand response method, the method is Online Priority Tree algorithm to be counted end device¡¦s rank priority according to device importance.

<p><!--st1\:*{behavior:url(#ieooui) } --><!--[endif]--> <!-- /* Font Definitions */ @font-face {font-family:Garamond; panose-1:2 2 4 4 3 3 1 1 8 3; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 70.85pt 70.85pt 70.85pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --></p><p>To implement a utility wireless sensor network, investigation of different wireless protocols has been performed. The protocols are Bluetooth, Wi-Fi, IEEE 802.15.4 and Zigbee. Consecutively literature studies have made it comprehensible to understand the function of the protocols that are suitable for development of wireless sensor networks. The importance of low cost, low power, reliable and high-quality properties for long distances are significant. IEEE 802.15.4 and Zigbee protocol are proper to implement as a wireless sensor network.</p><p> </p><p>To reduce the human efforts in the configuration of the system, a comfortable method is implemented to facilitate the procedure. The applied method is based on an automatic configuration of the system. The configuration and the decision taking are implemented in the software. The system is designed to avoid interference to other wireless networks with the possibilities of reconfiguration.</p><p>A uniform hardware and software design with separate functions of the system decided by a subsequent command for configuration is preferable. This imposes an advantage that increases the flexible potential of the system when a uniform solution is implemented.</p><p> </p><p>To support the basic communication principles and control of the system, a buffer implementation has been introduced. The functionality of decision taking is distributed, configured by system commands from the host system. Detecting of system commands requires a properly operating buffer management. In consideration to the power consumption in reference to battery utilizations, the settings of RF-module and microcontroller have a powerful impact to reduce the power consumption. All possibilities of hibernates and avoidance of unnecessarily transmitting, should be deactivated to minimize the power consumption.</p><p> </p>

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.

Η εργασία που ακολουθεί έχει ως σκοπό την μοντελοποίηση ενός ασύρματου καναλιού σε εσωτερικό χώρο. Πιο συγκεκριμένα θα προσπαθήσουμε να βρούμε την κατανομή της ισχύος εντός του χώρου θεωρώντας πως έχουμε εκπομπή ηλεκτρομαγνητικής ακτινοβολίας από δίκτυο wifi που εκπέμπει στα 2.4 GHz. Προκειμένου να μοντελοποιήσουμε το ασύρματο κανάλι μας είμαστε υποχρεωμένοι να γνωρίζουμε τα σημαντικότερα φαινόμενα που λαμβάνουν χώρα κατά την ασύρματη διάδοση, αυτά παρουσιάζονται στο κεφάλαιο 1. Επιπλέον μιας και αναφερόμαστε σε δίκτυα wifi θεωρείται αναγκαίο να καταγράψουμε τα σημαντικότερα χαρακτηριστικά αυτής της τεχνολογίας κάτι που γίνεται στο κεφάλαιο 2 αυτής της διπλωματικής εργασίας. Στη συνέχεια στο κεφάλαιο 3 παρουσιάζονται τα σημαντικότερα μοντέλα εσωτερικού χώρου για την εύρεση της μέσης ισχύς της ηλεκτρομαγνητικής ακτινοβολίας συναρτήσει της απόστασης ,ενώ τέλος στο κεφάλαιο 4 γίνεται η προσπάθεια για την μοντελοποίηση του ασύρματου καναλιού χρησιμοποιώντας τη θεωρία των Rayleigh και Rician διαλείψεων. / The work that follows is intended to model a wireless channel to the inner space . In particular we will try to find the distribution of power within the area that we are considering emission of electromagnetic radiation from wifi network emitting at 2.4 GHz. In order to model the wireless channel we have to know the important events that occur during wireless propagation ,these are presented in Chapter 1. Moreover since referring to wifi networks is considered necessary to record the important features of this technology which is in Chapter 2 of this thesis . Then in Chapter 3 presents the major indoor models to find the average power of electromagnetic radiation as a function of distance, and finally in Chapter 4 is the attempt to model the wireless channel using the theory of Rayleigh and Rician misfire .

Τα τελευταία χρόνια ο όγκος των δεδομένων που διακινείται μέσω δικτυακών συστημάτων είναι συνεχώς αυξανόμενος με την επιτακτική ανάγκη για αξιόπιστη επικοινωνία. Παρόλο που η εξέλιξη της τεχνολογίας επιτρέπει μεγαλύτερη ανοχή σε παρεμβολές στο τηλεπικοινωνιακό κανάλι, ο υψηλότερος ρυθμός δεδομένων προκαλεί παραμορφώσεις στο σήμα και κάνει το τηλεπικοινωνιακό σύστημα πιο επιρρεπές στον θόρυβο. Παράδειγμα τέτοιων συστημάτων αποτελούν εφαρμογές ασύρματων δικτύων όπως τα συστήματα κινητής τηλεφωνίας, οι δορυφορικές επικοινωνίες, ασύρματα τοπικά δίκτυα WiFi καθώς και ενσύρματων επικοινωνιών (ενσύρματα Modem). Η παρούσα διπλωματική επικεντρώνεται στα πρότυπα 802.11 που αφορούν ασύρματα τοπικά δίκτυα και πιο συγκεκριμένα στο πρόσφατο 802.11ac ώστε να τεθούν συγκεκριμένα κριτήρια απόδοσης. Αφενός γίνεται σχεδιασμός και υλοποίηση ενός αποκωδικοποιητή σύμφωνου με το πρότυπο λαμβάνοντας υπόψη περιορισμούς χρονισμού αλλά και επιφάνειας και επαλήθευση αυτών μέσω τεχνολογιών FPGA και ASIC. Αφετέρου μελετώνται διαφορετικές αρχιτεκτονικές υλοποίησης του αλγορίθμου (πχ high radix) και εξετάζονται τα πιθανά σχεδιαστικά trade-off. Εξετάζονται μέθοδοι αύξησης του throughput αλλά και θέματα απόδοσης που αφορούν την ικανότητα διόρθωσης λαθών. / In recent years the volume of data handled by network systems is growing with the need for reliable communication . Although the evolution of technology allows greater tolerance to interference in the telecommunication channel , higher data rate causes distortion to the signal and makes the telecommunication system more susceptible to noise. Examples of such systems are applications of wireless networks such as cellular systems , satellite communications , wireless local area networks WiFi and wired communications ( wired Modem). This thesis focuses on the 802.11 standards regarding wireless LANs and in particular in recent 802.11ac to put specific performance criteria. First is design and implementation of a decoder conforming to the model taking into account timing and surface constraints and verification technologies through FPGA and ASIC. Secondly, different architectures of the algorithm ( eg high radix) are studied and the possible design trade-off is examined. Methods of increasing the throughput and performance issues relating to error correction capability are examined.

Denna rapport syftar till att beskriva arbetet kring att kunna detektera närvaro i ett rum medhjälp av så enkla sensorer som möjligt, kopplade till en Arduino. Samtidigt som detta skerså används också systemet till att med samma sensorer visa klimatet i rummet. Läsaren fåren inblick i problematiken med att detektera människor samt inom funktionen av de valdasensorerna. Utöver detta studeras energiförbrukningen i systemet. Rapportenmynnar ut i enslutsats där en procentuell chans för närvaro presenteras via en internetuppkoppling medhjälp av en omfattande testning av sensorernas beteende.

Large-scale, high-density Wi-Fi networks use hundreds of access points to serve thousands of closelypacked users within a large physical space (hundreds of thousands of square feet or more, such as in a stadium or arena). Because of their scale, these are complex and dynamic systems comprised of several layers and multiple components within each layer, and faults may be present in any one of these components. The problems that manifest from these faults are usually not network-wide and may be localized to a certain physical areas of the network. This makes these problems challenging to detect and diagnose; in most cases, only a small number of devices tend to be impacted by any given problem. However, many such problems may occur simultaneously in different areas of the network. Adding to the complexity is the dynamic nature of such networks, where the physical positions of radios (in end-user devices), human bodies, and other objects in the space are constantly changing, thereby creating a continually-changing RF environment. Taken together, these properties make problem diagnosis in large-scale, high-density Wi-Fi networks challenging. There are many existing techniques for diagnosing problems in Wi-Fi networks. Many of these approaches rely on data from only a single perspective of the network to diagnose problems, for example, either the client, the infrastructure (access points), or external Wi-Fi sensors that passively monitor the network. In addition, many of these approaches require the invasive modification of the network’s components in order to collect data, through techniques such as the installation of specialized software on clients, modifying the firmware on access points, or even physically installing specialized devices in the RF environment of the Wi-Fi network. Finally, many approaches rely on offline analysis of the collected instrumentation, in which case diagnosis cannot be done in real time (minutes or less). Many others require network connectivity for real-time diagnosis, in which case the device must be able to communicate using the Wi-Fi infrastructure (that may be experiencing a problem). As a result, many of these approaches are difficult to deploy in production networks (due to the high financial cost or maintenance effort required), and those that are deployed often fail to detect and diagnose problems that are localized to a small number of devices (10 or less) or problems that are only present for a short time (minutes or less). This dissertation takes a unique approach that contrasts with existing approaches in three key ways. First, we combine the Wi-Fi performance data from multiple layers of the Wi-Fi network and attempt to diagnose problems at all of these layers, rather than focusing on a single layer alone, and we introduce a fault model that includes faults that can occur across all layers of the system. Second, we require no invasive modification of the Wi-Fi network or its components in order collect data and perform problem diagnosis and mitigation. Third, we present an infrastructure-free approach to problem diagnosis that relies on Bluetooth communication with other devices nearby (peers) to perform diagnosis based on multiple perspectives of the Wi-Fi network. With this approach, our diagnosis algorithm is able to collect data from multiple network perspectives without relying on Wi-Fi infrastructure, which may be slow or unavailable. Our approach begins with the construction of an instrumentation and data-collection system to obtain Wi-Fi performance metrics from both the client and infrastructure perspectives of the network. We then build upon our instrumentation to determine when user-visible problems occur. We define a user-visible problem as a Wi-Fi-network-performance problem that causes users to disengage from using the network. Once we have detected a user-visible problem, we then proceed to diagnose the root cause of the problem as one of the faults in our fault model using an approach based on decision trees. Finally, based on the diagnosed fault, we apply an automated mitigation-strategy, which forces the device to associate with a different access point that will likely provide better performance. To validate our approach and demonstrate its real-world impact, we have conducted a number of studies to collect data in support of our approach from both a laboratory testbed and real-world production Wi-Fi networks. We used our instrumentation and data-collection system to obtain data from over 25 real-world, large-scale, high-density Wi-Fi networks located within collegiate and professional stadiums. Our diagnostic system was deployed in a real-world mobile video-streaming application used over the Wi-Fi networks in these stadiums. Using this data, we determined the thresholds for when a Wi-Fi performance problem becomes user visible, based on our study of when users disengage from using the video-streaming application in the face of buffering. In addition to obtaining real-world data, we have studied this phenomenon in a testbed for fault injection and diagnosis that has been deployed both in a lab environment and in an arena to collect data on the behavior of large-scale, high-density Wi-Fi networks and understand how best to diagnose problems. Using this testbed, we evaluated the performance of our problem-diagnosis approach in terms of its precision and recall on injected faults. We also evaluated the performance of our mitigation strategy on our testbed by injecting faults and verifying that the selected mitigation strategy successfully mitigated the problem caused by that fault. We found that our approach diagnoses the correct root cause of faults with high precision and recall (often above 90%) and can mitigate problems via alternative access-point selection in 100% of our test cases. While we have studied our approach in certain test environments and for video-streaming applications, we believe that our approach can be applied to any Wi-Fi network and many other applications outside of video streaming. Our work in this dissertation could be extended through the automated discovery of the parameters for our diagnosis and mitigation algorithms that provide the best performance in other Wi-Fi networks, along with further studies of how Wi-Fi performance problems manifest in other types of applications and under what conditions users disengage with those applications due to problems.

The main research objective of this study was to determine whether Wi-Fi affects customer's loyalty and how its impact differs depending on the type of restaurants: coffee shops, fast food restaurants, and casual dining restaurants. For the study I designed a primary field survey to collect data and performed multiple linear regression analysis to test the study hypotheses. Findings show that Wi-Fi service factors turned out to be significant for all types of restaurants for both attitudinal and behavioral loyalty. Wi-Fi service factors were more important for coffee shop loyalty than fast-food restaurants or casual dining restaurants. However, not all of the Wi-Fi usage factors were significant consistently. Furthermore, Wi-Fi service factors were much more important for coffee shop loyalty than fast food restaurants or casual dining restaurants. Findings are expected to assist hospitality marketers to utilize Wi-Fi service as a point of service towards their customers.