INFRARED COMMUNICATION SYSTEMS FOR THE NAVIGATION IN INDOOR ENVIRONMENTS

The navigation systems are widely diffused in various fields of application. The most popular navigation system is well known as Global Positioning System (GPS): it is used essentially in an outdoor environment, due to the fact that the buildings introduce an extremely high attenuation to the satellite signals. In order to provide a navigation service inside the buildings, it is necessary to implement a communication system capable to retrieve the user\u2019s position and to deliver the navigation data in an appropriate format. This thesis describes the architecture of a navigation system for people that need to be guided through indoor environments, e.g., public buildings, hospitals, where orientation is very critical. The system has to provide both navigation and context aware information to people that may be in difficult emotive state as it happens to patients and visitors in a hospital. As it is widely explained in the whole thesis, the communication system uses an InfraRed (IR) optical link, thus a general overview to the IR light, and the modulations used in the optical communication systems is given. Moreover, one of the main topic of this thesis is to illustrate a complete study of the optimized architecture suitable to navigate an user inside a building. The IR navigation system developed in this thesis has stemmed out from a first reverse engineering step where an existing IR analog solution suited to transmit only voice signals has been analyzed. A number of tests have been carried out to characterize the existing analog solution, the modulation used (FM) and its main parameters. The need to have a new digital communication system is suggested by the possibility to improve the performance, developing a numerical transmission architecture: this allows to identify and, consequently, to locate an user. In this thesis a complete study on the feasibility of the digital architecture is proposed. All the technical details and justifications will be illustrated and discussed, including the study made upon the analog solution, keeping always in mind the need to maintain the compatibility with the analog solution. The thesis will also illustrate the development of the analog blocks that compose both transmission Front End and reception Front End. A particular attention will be paid to the Front End implemented on the receiver device, where the Received Signal Strength (RSS) value is needed. In fact, the user must point the receiver device to the transmitter illuminator as directly as possible (the : to do it correctly, a visual (or audible) indication of the RSS could be useful. Since the receiver device must be pointed in direction of the illuminator, it should be useful to understand if the system\u2019s performance in an indoor environment could be corrupted by the reflections of the IR beams: these reflections are caused by the walls, windows or any other reflective surfaces. This effect, called multipath is taken into account: a generic analytical expression of the total received signal will be derived, and a simulation of the performance degeneration will be shown. Finally, the implementation of a working prototype is presented, with the focus on the user interface. The navigation system has been installed at the Oncology Reference Center (CRO) hospital in Aviano (Italy), in the framework of the EasyMob project. The EasyMob project will be introduced in this thesis, giving an overview about the entire set of technologies used to navigate an user into a confined space (e.g., colored visible light path guides and Thin Film Transistor (TFT) displays). Moreover a deep study on a number of IR navigation architectures is given, illustrating pros and cons of the infrastructure chosen and explained in the whole thesis

Radio-Communications Architectures

Wireless communications, i.e. radio-communications, are widely used for our different daily needs. Examples are numerous and standard names like BLUETOOTH, WiFI, WiMAX, UMTS, GSM and, more recently, LTE are well-known [Baudoin et al. 2007]. General applications in the RFID or UWB contexts are the subject of many papers. This chapter presents radio-frequency (RF) communication systems architecture for mobile, wireless local area networks (WLAN) and connectivity terminals. An important aspect of today's applications is the data rate increase, especially in connectivity standards like WiFI and WiMAX, because the user demands high Quality of Service (QoS). To increase the data rate we tend to use wideband or multi-standard architecture. The concept of software radio includes a self-reconfigurable radio link and is described here on its RF aspects. The term multi-radio is preferred. This chapter focuses on the transmitter, yet some considerations about the receiver are given. An important aspect of the architecture is that a transceiver is built with respect to the radio-communications signals. We classify them in section 2 by differentiating Continuous Wave (CW) and Impulse Radio (IR) systems. Section 3 is the technical background one has to consider for actual applications. Section 4 summarizes state-of-the-art high data rate architectures and the latest research in multi-radio systems. In section 5, IR architectures for Ultra Wide Band (UWB) systems complete this overview; we will also underline the coexistence and compatibility challenges between CW and IR systems

Advanced DSP Techniques for High-Capacity and Energy-Efficient Optical Fiber Communications

The rapid proliferation of the Internet has been driving communication networks closer and closer to their limits, while available bandwidth is disappearing due to an ever-increasing network load. Over the past decade, optical fiber communication technology has increased per fiber data rate from 10 Tb/s to exceeding 10 Pb/s. The major explosion came after the maturity of coherent detection and advanced digital signal processing (DSP). DSP has played a critical role in accommodating channel impairments mitigation, enabling advanced modulation formats for spectral efficiency transmission and realizing flexible bandwidth. This book aims to explore novel, advanced DSP techniques to enable multi-Tb/s/channel optical transmission to address pressing bandwidth and power-efficiency demands. It provides state-of-the-art advances and future perspectives of DSP as well

UWB communication systems acquisition at symbol rate sampling for IEEE standard channel models

For ultra-wideband (UWB) communications, acquisition is challenging. The reason is from the ultra short pulse shape and ultra dense multipath interference. Ultra short pulse indicates the acquisition region is very narrow. Sampling is another challenge for UWB design due to the need for ultra high speed analog-to digital converter.A sub-optimum and under-sampling scheme using pilot codes as transmitted reference is proposed here for acquisition. The sampling rate for the receiver is at the symbol rate. A new architecture, the reference aided matched filter is studied in this project. The reference aided matched filter method avoids using complex rake receiver to estimate channel parameters and high sampling rate for interpolation. A limited number of matched filters are used as a filter bank to search for the strongest path. Timing offset for acquisition is then estimated and passed to an advanced verification algorithm. For optimum performance of acquisition, the adaptive post detection integration is proposed to solve the problem from dense inter-symbol interference during the acquisition. A low-complex early-late gate tracking loop is one element of the adaptive post detection integration. This tracking scheme assists in improving acquisition accuracy. The proposed scheme is evaluated using Matlab Simulink simulations in term of mean acquisition time, system performance and false alarm. Simulation results show proposed algorithm is very effective in ultra dense multipath channels. This research proves reference aided acquisition with tracking loop is promising in UWB application