IRIS Università degli Studi di Bolognahttps://cris.unibo.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Wed, 25 Nov 2020 14:37:55 GMT2020-11-25T14:37:55Z10631Coping with saturating projection stages in RMPI-based Compressive Sensinghttp://hdl.handle.net/11585/128686Titolo: Coping with saturating projection stages in RMPI-based Compressive Sensing
Abstract: Though compressive sensing hinges on extracting linear measurements from the signals to acquire, actual implementations introduce nonlinearities whose effect can be far from negligible. We here address the problem of saturation in the circuit blocks needed by a Random Modulation Pre-Integration architecture. To allow a fair a comparison with previous analysis, we rely on a model capturing the essentials of saturations in actual implementations while being able to reproduce more abstract settings considered in the literature. Based on this, we analyze some methods already proposed to cope with simplified saturation mechanisms, briefly discussing their underlying principles. Finally, we introduce a novel approach that takes into account the more realistic model and, at the cost of an almost negligible hardware overhead, is extremely effective in countering saturation effects.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/11585/1286862012-01-01T00:00:00ZRakeness in the Design of Analog-to-Information Conversion of Sparse and Localized Signalshttp://hdl.handle.net/11585/128685Titolo: Rakeness in the Design of Analog-to-Information Conversion of Sparse and Localized Signals
Abstract: Design of random modulation preintegration systems based on the restricted-isometry property may be suboptimal when the energy of the signals to be acquired is not evenly distributed, i.e., when they are both sparse and localized. To counter this, we introduce an additional design criterion, that we call rakeness, accounting for the amount of energy that the measurements capture from the signal to be acquired. Hence, for localized signals a proper system tuning increases the rakeness as well as the average SNR of the samples used in its reconstruction. Yet, maximizing average SNR may go against the need of capturing all the components that are potentially nonzero in a sparse signal, i.e., against the restricted isometry requirement ensuring reconstructability. What we propose is to administer the trade-off between rakeness and restricted isometry in a statistical way by laying down an optimization problem. The solution of such an optimization problem is the statistic of the process generating the random waveforms onto which the signal is projected to obtain the measurements. The formal definition of such a problems is given as well as its solution for signals that are either localized in frequency or in more generic domain. Sample applications, to ECG signals and small images of printed letters and numbers, show that rakeness-based design leads to nonnegligible improvements in both cases.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/11585/1286852012-01-01T00:00:00ZRakeness-based approach to compressed sensing of ECGshttp://hdl.handle.net/11585/128690Titolo: Rakeness-based approach to compressed sensing of ECGs
Abstract: Compressed sensing is an analog signal acquisition technique that aims at converting the intrinsic information contained in the signal when some a priori assumptions can be made on its structure. The most common of these assumptions is that the signal is sparse. We here present a methods that works when the signal to acquire is not only sparse but also localized. Benefits of this method will be shown by applying it to ECG signals.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/11585/1286902011-01-01T00:00:00ZA rakeness-based design flow for Analog-to-Information conversion by Compressive Sensinghttp://hdl.handle.net/11585/400087Titolo: A rakeness-based design flow for Analog-to-Information conversion by Compressive Sensing
Abstract: Classical design of Analog-to-Information converters based on Compressive Sensing uses random projection matrices made of independent and identically distributed entries. Leveraging on previous work, we define a complete and extremely simple design flow that quantifies the statistical dependencies in projection matrices allowing the exploitation of non-uniformities in the distribution of the energy of the input signal. The energy-driven reconstruction concept and the effect of this design technique are justified and demonstrated by simulations reporting conspicuous savings in the number of measurements needed for signal reconstruction that approach 50%.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11585/4000872013-01-01T00:00:00ZAnalog-to-information conversion of sparse and non-white signals: Statistical design of sensing waveformshttp://hdl.handle.net/11585/109047Titolo: Analog-to-information conversion of sparse and non-white signals: Statistical design of sensing waveforms
Abstract: Analog to Information conversion is a new paradigm in signal digitalization. In this framework, compressed sensing theory allows to reconstruct sparse signal from a limited number of measures. In this work, we will assume that the signal is not only sparse but also localized in a given domain, so that its energy is concentrated in a subspace. We will present a formal and quantitative discussion to explain how localization of sparse signals can be exploited to improve the quality of the reconstructed signal.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/11585/1090472011-01-01T00:00:00ZA Pragmatic Look at Some Compressive Sensing Architectures With Saturation and Quantizationhttp://hdl.handle.net/11585/134301Titolo: A Pragmatic Look at Some Compressive Sensing Architectures With Saturation and Quantization
Abstract: The paper aims to highlight relative strengths and weaknesses of some of the recently proposed architectures for hardware implementation of analog-to-information converters based on Compressive Sensing. To do so, the most common architectures are analyzed when saturation of some building blocks is taken into account, and when measurements are subject to quantization to produce a digital stream. Furthermore, the signal reconstruction is performed by established and novel algorithms (one based on linear programming and the other based on iterative guessing of the support of the target signal), as well as their specialization to the particular architecture producing the measurements. Performance is assessed both as the probability of correct support reconstruction and as the final reconstruction error. Our results help highlighting pros and cons of various architectures and giving quantitative answers to some typical design-oriented questions. Among these, we show: 1) that the (Random Modulation Pre-Integration) RMPI architecture and its recently proposed adjustments are probably the most versatile approach though not always the most economic to implement; 2) that when 1-bit quantization is sought, dynamically mixing quantization and integration in a randomized ΔΣ architecture help bringing the performance much closer to that of multi-bit approaches; 3) for each architecture, the trade-off between number of measurements and number of bits per measurements (given a fixed bit-budget); and 4) pros and cons of the use of Gaussian versus binary random variables for signal acquisition.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/11585/1343012012-01-01T00:00:00ZRakeness-based compressed sensing on ultra-low power multi-core biomedicai processorshttp://hdl.handle.net/11585/525402Titolo: Rakeness-based compressed sensing on ultra-low power multi-core biomedicai processors
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/11585/5254022014-01-01T00:00:00ZEnergy Analysis of Decoders for Rakeness-Based Compressed Sensing of ECG Signalshttp://hdl.handle.net/11585/622406Titolo: Energy Analysis of Decoders for Rakeness-Based Compressed Sensing of ECG Signals
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11585/6224062017-01-01T00:00:00ZSpectral shaping of spreading sequences as a mean to address the trade-off between narrowband and multi-access interferences in UWB systemshttp://hdl.handle.net/11585/109030.1Titolo: Spectral shaping of spreading sequences as a mean to address the trade-off between narrowband and multi-access interferences in UWB systems
Abstract: This paper presents a way to cope with the need of simultaneously rejecting narrowband interference and multi-access interference in a UWB system based on direct-sequence CDMA. With this aim in mind, we rely on a closed-form expression of the system bit error probability in presence of both effects. By means of such a formula, we evaluate the effect of spectrum shaping techniques applied to the spreading sequences. The availability of a certain number of degrees of freedom in deciding the spectral profile allows us to cope with different configurations depending on the relative interfering power but also on the relative position of the signal center frequency and the narrowband interferer.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/11585/109030.12011-01-01T00:00:00ZAn Architecture for 1-Bit Localized Compressive Sensing with Applications to EEGhttp://hdl.handle.net/11585/109045Titolo: An Architecture for 1-Bit Localized Compressive Sensing with Applications to EEG
Abstract: Compressed sensing exploits special signal features to extract its information content with a smaller amount of samples with respect to acquisition based on Nyquist theorem. While many theoretical results have proved the capabilities of this new paradigm, hardware implementations are still far from being practical. Here, we present a new architecture of analog to information converter that produces 1-bit compressive measurements. The performance of the architecture can be boosted if the signal to acquire features, beyond the classically required sparsity, also some sort of localization of its energy. The effectiveness of the architecture and of its enhancement is shown in the measurement of EEG, that presents a non-uniform spectral profile.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/11585/1090452011-01-01T00:00:00Z