On the Cramer-Rao bound for carrier frequency estimation in the presence of phase noise

We consider the carrier frequency offset estimation in a digital burst-mode satellite transmission affected by phase noise. The corresponding Cramer-Rao lower bound is analyzed for linear modulations under a Wiener phase noise model and in the hypothesis of knowledge of the transmitted data. Even if we resort to a Monte Carlo average, from a computational point of view the evaluation of the Cramer-Rao bound is very hard. We introduce a simple but very accurate approximation that allows to carry out this task in a very easy way. As it will be shown, the presence of the phase noise produces a remarkable performance degradation of the frequency estimation accuracy. In addition, we provide asymptotic expressions of the Cramer-Rao bound, from which the effect of the phase noise and the dependence on the system parameters of the frequency offset estimation accuracy clearly result. Finally, as a by-product of our derivations and approximations, we derive a couple of estimators specifically tailored for the phase noise channel that will be compared with the classical Rife and Boorstyn algorithm, gaining in this way some important hints on the estimators to be used in this scenario

Conditioned pilots for ISI channels

One of the proposals to increase the spectral efficiency of the DVB-S2 standard is based on time-frequency packing. This technique causes intersymbol and interchannel interferences to arise, requiring a significant growth of the number of pilots used to carry out frequency and phase synchronization. Therefore, a new pilot design will be introduced and suited optimal and suboptimal reduced-complexity algorithms derived. We will show that the proposed pilot strategy may outperform the classical one in terms of bit error rate and spectral efficiency

Spectrally efficient systems for satellite communications

In questa Tesi verranno proposte tre diverse soluzioni il cui scopo è l'incremento dell'efficienza spettrale nei sistemi satellitari. Per prima cosa, considereremo uno scenario multi-utente a multiplazione di frequenza, che è uno degli scenari inclusi nello standard DVB-RCS. Useremo modulazioni a fase continua (CPM) concatenate serialmente ad un codificatore tramite un interleaver. La già elevata efficienza spettrale delle CPM può essere ulteriormente aumentata sfruttando la tecnica del "frequency packing". Un tale incremento però rende necessaria un'accurata sincronizzazione affinché il ricevitore funzioni correttamente. Pertanto verranno progettati e testati degli stimatori iterativi di fase e frequenza. In seguito, ci concentreremo su sistemi a divisione di codice basati sulle CPM. Verrà quindi proposta una nuova tecnica di espansione spettrale, progettata ad hoc per le CPM. Mostreremo come ottenere facilmente delle densità spettrali di potenza larghe, piatte e lisce, senza ricorrere a sequenze di spreading, e senza tutte le problematiche di progettazione a queste collegate. Inoltre, ricaveremo degli algoritmi di rivelazione multi-utente subottimi che saranno impiegati per mostrare come il sistema proposto possa superare le prestazioni di tutti gli altri sistemi in letteratura, sia in termini di probabilità d'errore che di efficienza spettrale. Infine, considerando lo scenario previsto dallo standard DVB-S2, proporremo di incrementarne l'efficienza spettrale attraverso la tecnica del "time and frequency packing". Questa tecnica causa l'insorgenza di interferenza intersimbolica e intercanale, che a loro volta provocano l'aumento del numero di simboli pilota necessari per una corretta sincronizzazione di fase e frequenza. Sarà pertanto introdotto un nuovo design dei piloti, e saranno derivati opportuni algoritmi di rivelazione ottimi e subottimi a ridotta complessità. Mostreremo come il sistema proposto possa superare le prestazioni dello standard DVB-S2 sia in termini di probabilità d'errore che di efficienza spettrale.In this Thesis we propose three different solutions aiming at increasing the spectral efficiency in satellite communications. First, we will consider a multi-user scenario with frequency multiplexing, that is one of the scenarios included in the DVB-RCS standard. We will adopt continuous phase modulations (CPMs) serially concatenated with an outer code through an interleaver. The high spectral efficiency of CPMs can be further increased exploiting the frequency packing technique. Such an improvement does not come for free, in fact an accurate synchronization has to be guaranteed to allow the detector to work properly. To this purpose, new iterative frequency and phase estimators will be derived and the synchronization accuracy tested. Then, we will focus on code division multiple access (CDMA) systems employing CPMs. A brand new spectral spreading technique, especially tailored to CPMs, will be presented. We will show how to easily obtain a large, flat, and smooth power spectral density, without resorting to spreading sequences and then getting rid of all the design problems that come with. Moreover, we will derive some suboptimal multi-user detectors that will be employed to show that the proposed system outperforms all the other considered systems, found in the literature, in terms of bit error rate and spectral efficiency. Finally, considering the DVB-S2 scenario, we will propose to increase the spectral efficiency through time and frequency packing. This technique will cause intersymbol and interchannel interferences to arise, requiring a significant increase in the number of pilots used to carry out frequency and phase synchronization. Therefore, new pilot designs will be introduced, and suited optimal and suboptimal reduced-complexity algorithms derived. We will show that the proposed systems may outperform the DVB-S2 standard in terms of bit error rate and spectral efficiency

Realization of Integrated Coherent LiDAR

LiDAR (Light Detection and Ranging) captures high-definition real-time 3D images of the surrounding environment through active sensing with infrared lasers. It has unique advantages that can compensate the fundamental limitations in camera-based 3D imaging via vision algorithms or RADARs, which makes it an important sensing modality to guarantee robust autonomy in self-driving cars. However, high price tag of existing commercial LiDAR modules based on mechanical beam scanners and intensity-based detection scheme makes them unusable in the context of mass produced consumer products.The focus of thesis is on the integrated coherent LiDAR with optical phased array-based solid-state beam steering, which has great potential to dramatically bring down the cost of a LiDAR module. It begins with an overview of LiDAR implementation options and system requirements in the context of autonomous vehicles, which leads us to conclude that beam-steering coherent FMCW LiDAR in optical C-band is indeed the best implementation strategy to realize low-cost automotive LiDARs. Motivated by this observation, a quantitative framework for evaluating FMCW LiDAR performance is also introduced to predict the design that satisfies car-grade performance requirements. Then the thesis presents the silicon implementation results from our single-chip optical phased array and integrated coherent LiDAR prototype. Our implementations leverage the 3D heterogeneous integration platform, where custom silicon photonics and nanoscale CMOS fabricated at a 300 mm wafer facility are combined at the wafer-scale to minimize the unit cost without I/O density issues. After discussing remaining challenges and possible ways to enhance the operating range and system reliability, this thesis finally addresses the problem of fundamental trade-off between phase noise and wavelength tuning in FMCW laser source, and present circuit- and algorithm-level techniques to enable FMCW measurements beyond inherent laser coherence range limit

Storia delle telecomunicazioni

Focusing on the history of scientific and technological development over recent centuries, the book is dedicated to the history of telecommunications, where Italy has always been in the vanguard, and is presented by many of the protagonists of the last half century. The book is divided into five sections. The first, dealing with the origins, starts from the scientific bases of the evolution of telecommunications in the nineteenth century (Bucci), addressing the developments of scientific thought that led to the revolution of the theory of fields (Morando), analysing the birth of the three fundamental forms of communication – telegraph (Maggi), telephone (Del Re) and radio (Falciasecca) – and ending with the contribution made by the Italian Navy to the development of telecommunications (Carulli, Pelosi, Selleri, Tiberio). The second section, on technical and scientific developments, presents the numerical processing of signals (Rocca), illustrating the genesis and metamorphosis of transmission (Pupolin, Benedetto, Mengali, Someda, Vannucchi), network packets (Marsan, Guadagni, Lenzini), photonics in telecommunications (Prati) and addresses the issue of research within the institutions (Fedi-Morello), dwelling in particular on the CSELT (Mossotto). The next section deals with the sectors of application, offering an overview of radio, television and the birth of digital cinema (Vannucchi, Visintin), military communications (Maestrini, Costamagna), the development of radar (Galati) and spatial telecommunications (Tartara, Marconicchio). Section four, on the organisation of the services and the role of industry, outlines the rise and fall of the telecommunications industries in Italy (Randi), dealing with the telecommunications infrastructures (Caroppo, Gamerro), the role of the providers in national communications (Gerarduzzi), the networks and the mobile and wireless services (Falciasecca, Ongaro) and finally taking a look towards the future from the perspective of the last fifty years (Vannucchi). The last section, dealing with training and dissemination, offers an array of food for thought: university training in telecommunications, with focus on the evolution of legislation and on the professional profiles (Roveri), social and cultural aspects (Longo and Crespellani) as well as a glance over the most important museums, collections and documentary sources for telecommunications in Italy (Lucci, Savini, Temporelli, Valotti). The book is designed to offer a compendium comprising different analytical approaches, and aims to foster an interest in technology in the new generations, in the hope of stimulating potentially innovative research