Amina Piemontese

• University of Parma

In the context of signal detection in the presence of an unknown time-varying channel parameter, receivers based on the Expectation Propagation (EP) framework appear to be very promising. EP is a message-passing algorithm based on factor graphs with an inherent ability to combine prior knowledge of system variables with channel observations. This s...

In this letter, we propose a novel constellation design, specifically tailored to contrast the effect of nonlinear channels. The proposed constellations are based on a spiral expression, which, unlike other unstructured designs, makes them easy to build and optimize. Our design approach allows to optimize the distance between symbols in the angular...

This letter addresses the problem of signal detection in flat-fading channels. In this context, receivers based on the expectation propagation framework appear to be very promising although presenting some critical issues. We develop a new algorithm based on this framework where, unlike previous works, convergence is achieved after a single forward...

Non-terrestrial networks will play a crucial role in future wireless 6G systems to ensure ubiquitous connectivity and to complement terrestrial networks. With reference to a LEO constellation, this letter performs a comparison in terms of pragmatic capacity between the OFDM and the OTFS modulation in a scenario where multi-satellite diversity is em...

This paper aims at tackling the problem of signal detection in flat-fading channels. In this context, receivers based on the expectation propagation framework appear to be very promising although presenting some critical issues. We develop a new algorithm based on this framework where, unlike previous works, convergence is achieved after a single f...

We consider time-frequency-packed systems in an additive white Gaussian noise scenario. With respect to systems employing time packing, thus introducing intentional intersymbol interference only, a further improvement of the spectral efficiency is obtained by packing the adjacent carriers closer in frequency. The adoption of a multiuser detector ca...

We consider the phase noise affecting communication systems, where local oscillators are employed to obtain a reference signal for frequency and timing synchronizations. We try to fill the gap between measurements and analytical models, in case of free-running and phase-locked oscillators. In particular, we propose a closed form expression for the...

In this paper, we consider the design of spiral constellations for channels affected by phase noise. The strength of the proposed constellations resides both on the performance and on the extreme simplicity of the design. The symbols can in fact be expressed in analytical form, and are uniquely defined through a single parameter that accounts for t...

We investigate the use of maximum distance separable (MDS) codes to cache popular content to reduce the download delay of wireless content delivery. In particular, we consider a cellular system where popular files are cached in a distributed fashion in a limited number of the mobile devices using an MDS code and can be downloaded from them using de...

We investigate the use of maximum distance separable (MDS) codes to cache popular content to reduce the download delay of wireless content delivery. In particular, we consider a cellular system where devices roam in an out of a cell according to a Poisson random process. Popular content is cached in a limited number of the mobile devices using an M...

We consider the rates achievable by a user in a multibeam satellite system for unicast applications, and propose alternatives to the conventional single-user symbol-by-symbol detection applied at user terminals. Single-user detection is known to suffer from strong degradation when the terminal is located near the edge of the coverage area of a beam...

We study the benefits arising from the exploitation of interference in two satellite communications scenarios. We show that promising gains, with respect to the classical interference avoidance approach, can be achieved by applying non-orthogonal transmission schemes together with advanced transceiver architectures. We demonstrate that the non-orth...

We address the use of maximum distance separable (MDS) codes for distributed storage (DS) to enable efficient content delivery in wireless networks. Content is stored in a number of the mobile devices and can be retrieved from them using device-to-device communication or, alternatively, from the base station (BS). We derive an analytical expression...

We design new continuous phase modulation (CPM) formats which are based on the combination of a proper precoder with binary input and a ternary CPM. The proposed precoder constrains the signal phase evolution in order to increase the minimum Euclidean distance, and to limit the bandwidth expansion due to the use of a ternary CPM. The resulting sche...

We consider the use of multiple co-located satellites to improve the spectral efficiency of broadcast transmissions. In particular, we assume that two satellites transmit on overlapping geographical coverage areas, with overlapping frequencies. We first describe the theoretical framework based on network information theory and, in particular, on th...

We study the achievable rates by a single user in multibeam satellite scenarios. We show alternatives to the conventional symbol-by-symbol detection applied at user terminals. Single user detection is known to suffer from strong degradation when the terminal is located near the edge of the coverage area, and when aggressive frequency reuse is adopt...

We consider a realistic satellite communications system for broadband and broadcasting applications in a single-carrier-per-transponder scenario. We describe how to compute the spectral efficiency of such a system when suboptimal receivers are employed and we evaluate the performance improvements that can be obtained through the adoption of the tim...

We analyze the asymptotic performance of nonbinary spatially-coupled low-density parity-check (SC-LDPC) codes built on the general linear group, when the transmission takes place over the binary erasure channel. We propose an efficient method to derive an upper bound to the maximum a posteriori probability (MAP) threshold for nonbinary LDPC codes,...

We consider a frequency division multiplexed system where each user adopts a continuous phase modulation (CPM) and multiuser detection is employed at the receiver side. The spectral efficiency (SE) is used as a performance measure to compare, from an information-theoretic point of view, different modulation formats. More precisely, we consider the...

We consider realistic satellite communications systems for broadband and broadcasting applications, based on frequency-division-multiplexed linear modulations, where spectral efficiency is one of the main figures of merit. For these systems, we investigate their ultimate performance limits by using a framework to compute the spectral efficiency whe...

We consider a frequency-division-multiplexed satellite system where nonlinear distortions may originate from the presence of high power nonlinear devices and can cause significant performance degradations. The spectral efficiency is used as a performance measure to compare, from an information-theoretic point of view, different transmission strateg...

We consider detection over linear channels impaired by additive white Gaussian noise. For this general model, which describes a large variety of scenarios, novel detection algorithms are derived by applying the sum-product algorithm to a suitably designed factor graph. Being soft-input soft-output (SISO) in nature, the proposed detectors can be ado...

We investigate the application of time and frequency packing techniques, an extension of the classical faster-than-Nyquist signaling, to long-haul optical links. These techniques provide a significant spectral efficiency increase and represent a viable alternative to overcome the theoretical and technological issues related to the use of high-order...

We propose novel detection algorithms for linear modulations transmitted over nonlinear satellite channels, also impaired by additive white Gaussian noise. These algorithms are derived by using a Volterra-series expansion of the useful signal and by applying the sum-product algorithm to a suitably-designed factor graph. Being soft-input soft-output...

In frequency division multiplexed (FDM) systems, spectral efficiency can be increased by reducing the spacing between two adjacent channels, thus increasing the relevant interference and possibly accounting for it at the receiver. In this paper, we consider a FDM system where each user employs a continuous phase modulation (CPM), serially concatena...

We consider a frequency division multiplexed system where each user employs a continuous phase modulation (CPM). In such a system, the spectral efficiency (SE) can be increased by reducing the spacing between adjacent channels, at the expense of increasing the relevant interference. We investigate this aspect from an information-theoretic point of...

We consider a frequency division multiplexed (FDM) system where each user employs a continuous phase modulation (CPM), serially concatenated with an outer code through an interleaver, and iterative detection/decoding. In such a system, the spectral efficiency can be increased by reducing the spacing between two adjacent channels, thus increasing th...

We consider a frequency division multiplexed (FDM) satellite system where each user employs a continuous phase modulation (CPM), serially concatenated with an outer code through an interleaver, and iterative detection/decoding. In such a system, the spectral efficiency can be increased by reducing the spacing between two adjacent channels, thus inc...

We consider soft-input soft-output detection over linear channels impaired by additive white Gaussian noise. For this general model, which describes a large variety of scenarios, novel detection algorithms are derived by applying the sum-product algorithm to a suitably-designed factor graph. Among the various possible applications, we mainly focus...

We propose a novel iterative method, similar to the generalized Blahut-Arimoto algorithm recently proposed by Kav¿ic¿, to evaluate the Markov capacity of a continuous phase modulated signal over an additive white Gaussian noise channel. One of the novelty of our approach is that we maximize, with respect to the input distribution, the spectral ef...

We consider a terrestrial wireless channel, whose statistical model under flat-fading conditions is due to Clarke. A lot of papers in the literature deal with receivers for this scenario, aiming at estimating and tracking the time-varying channel, possibly with the aid of known (pilot) symbols. A common approach to derive receivers of reasonable co...