103,438 research outputs found
Metaphors and Politics. An inquiry into the Political Discourse of the Italian Second Republic
No full textInterference suppression in SS systems: a comparison between PTV P/S-type and W-type filters
No full textPublication in the conference proceedings of EUSIPCO, Rhodes, Greece, 199
Modeling and performance analysis of wireless networks with ambient backscatter devices
No full textAmbient backscatter is an intriguing wireless communication paradigm that allows small devices to compute and communicate by using only the power they harvest from far-field radio-frequency (RF) signals in the air. Ambient backscattering devices reflect RF signals emitted by existing or legacy communications
systems, such as digital TV broadcasting, cellular, or Wi-Fi ones, which are designed for transporting information and are not intended for RF energy transfer. This paper deals with mathematical modeling and performance analysis of wireless broadband networks operating over fading channels with ambient backscatter devices. After introducing a detailed signal model of the relevant communication links, we study the influence of physical parameters on the capacity of both legacy and backscatter channels, by considering different receiver architectures. We analytically show that, under reasonable operative conditions, a legacy system—employing an orthogonal frequencydivision multiplexing (OFDM) modulation scheme—can turn the RF interference arising from the backscatter process into a
form of multipath diversity that can be exploited to increase its performance. Moreover, our analysis proves that a backscatter system—transmitting one symbol per OFDM symbol of the legacy system—can achieve satisfactory data rates over relatively short distances, especially when the intended recipient of the
backscatter signal is co-located with the legacy transmitter, i.e., they are on the same device
Convolutive superposition for multicarrier cognitive radio systems
No full textRecently, we proposed a spectrum-sharing paradigm for single-carrier cognitive radio (CR) networks, where a secondary user (SU) can maintain or even improve the performance of a primary user (PU) transmission, while also obtaining a low-data rate channel for its own communication. According to such a scheme, when the SU is able to receive the signal transmitted from the PU, it can superimpose its transmission on the PU signal by simple multiplicative precoding,
without requiring any cooperation between the primary and secondary systems. The scope of this paper is to extend such a paradigm to a multicarrier CR network, where the PU employs an orthogonal frequency-division multiplexing (OFDM) modulation scheme. To improve its achievable data rate, the
SU is allowed to transmit multiple symbols in parallel over the OFDM subcarriers of the primary system. In particular, the SU convolves its block-precoded symbols with the received PU signal in the time domain, which gives rise to the term convolutive superposition. An information-theoretic analysis of the proposed
scheme is developed, which considers different amounts of channel state information at the secondary transmitter, as well as different precoding strategies for the SU. Extensive simulations illustrate the merits of our analysis and designs, in comparison with other CR schemes, by using as a performance indicator the ergodic channel capacity
I progetti di territorio di 42 Comuni in provincia di padova, Verona e Vicenza tra imperativi economici e sviluppo sostenibile
No full textA time-frequency synchronization algorithm for MC-CDMA systems in LMDS applications
No full textPublication in the conference proceedings of EUSIPCO, Toulouse, France, 200
Performance analysis of ambient backscattering for green Internet of Things
No full textIn this paper, we assess the information-theoretic performance of a point-to-point link that exploits ambient backscattering to support green Internet-of-Thing (IoT) communications. In this framework, an IoT passive device transmits its information by reusing ambient radio-frequency signals emitted by an existing or legacy multicarrier communication system. After introducing the signal model of the relevant communication links, the information-theoretic capacity of both the legacy and backscatter systems is derived. It is found that, under reasonable operative conditions, the legacy system can turn the RF interference arising from backscattering into a form of multipath diversity, which can be exploited to increase its own performance. Moreover, it is shown that, even when it employs simple singlecarrier modulation techniques, the backscatter system attains significant data rates over relatively short distances
Amplify-and-forward secondary spectrum access in multicarrier cognitive radio systems
No full textInnovative spectrum sharing policies, possibly leveraged by cognitive radio (CR) technologies, are expected to play a significant role in forthcoming 5G systems, employing multicarrier techniques for modulation and multiple-access. In this paper, we propose an opportunistic amplify-and-forward relaying scheme for a multicarrier CR network, where a secondary user (SU) is allowed to share communication resources with a primary user (PU) transmitting with orthogonal frequency-division multiplexing (OFDM) technology. Instead of minimizing the interference to the PU, the SU transmitter relays the received PU signal on the different OFDM subcarriers by using a precoding matrix depending on the symbols that must be delivered to the SU receiver. The information-theoretic capacity of the proposed protocol is assessed, showing that, under mild conditions, the SU can gain a significant data-rate performance, while not degrading (but even improving) the PU performance
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