351 research outputs found
Models, Statistics, and Rates of Binary Correlated Sources
This paper discusses and analyzes various models of binary correlated
sources, which may be relevant in several distributed communication scenarios.
These models are statistically characterized in terms of joint Probability Mass
Function (PMF) and covariance. Closed-form expressions for the joint entropy of
the sources are also presented. The asymptotic entropy rate for very large
number of sources is shown to converge to a common limit for all the considered
models. This fact generalizes recent results on the information-theoretic
performance limit of communication schemes which exploit the correlation among
sources at the receiver.Comment: submitted for publicatio
Orthogonal Multiple Access with Correlated Sources: Feasible Region and Pragmatic Schemes
In this paper, we consider orthogonal multiple access coding schemes, where
correlated sources are encoded in a distributed fashion and transmitted,
through additive white Gaussian noise (AWGN) channels, to an access point (AP).
At the AP, component decoders, associated with the source encoders, iteratively
exchange soft information by taking into account the source correlation. The
first goal of this paper is to investigate the ultimate achievable performance
limits in terms of a multi-dimensional feasible region in the space of channel
parameters, deriving insights on the impact of the number of sources. The
second goal is the design of pragmatic schemes, where the sources use
"off-the-shelf" channel codes. In order to analyze the performance of given
coding schemes, we propose an extrinsic information transfer (EXIT)-based
approach, which allows to determine the corresponding multi-dimensional
feasible regions. On the basis of the proposed analytical framework, the
performance of pragmatic coded schemes, based on serially concatenated
convolutional codes (SCCCs), is discussed
Cyclic redundancy check-based detection algorithms for automatic identification system signals received by satellite.
This paper addresses the problem of demodulating signals transmitted in the automatic identification system. The main characteristics of such signals consist of two points: (i) they are modulated using a trellis-coded modulation, more precisely a Gaussian minimum shift keying modulation; and (ii) they are submitted to a bit stuffing procedure, which makes more difficult the detection of the transmitted information bits. This paper presents several demodulation algorithms developed in different contexts: mono-user and multi-user transmissions, and known/unknown phase shift. The proposed receiver uses the cyclic redundancy check (CRC) present in the automatic identification system signals for error correction and not for error detection only. By using this CRC, a particular Viterbi algorithm, on the basis of a so-called extended trellis, is developed. This trellis is defined by extended states composed of a trellis code state and a CRC state. Moreover, specific conditional transitions are defined to take into account the possible presence of stuffing bits. The algorithms proposed in the multi-user scenario present a small increase of computation complexity with respect to the mono-user algorithms. Some performance results are presented for several scenarios in the context of the automatic identification system and compared with those of existing techniques developed in similar scenarios
Detection of Linear Modulations in the Presence of Strong Phase and Frequency Instabilities
Noncoherent sequence detection algorithms, recently proposed by the authors, have a performance which approaches that of coherent detectors and are robust to phase and frequency instabilities. These schemes exhibit a negligible performance loss in the presence of a frequency offset, provided this offset does not exceed an order of 1 % of the signaling frequency. For higher values, the performance rapidly degrades. In this paper, detection schemes are proposed, characterized by high robustness to frequency offsets and capable of tolerating offset values up to 10 % of the signaling frequency. More generally, these detection schemes are very robust to rapidly varying phase and frequency instabilities. The general case of coded linear modulations is addressed, with explicit reference to-ary phase shift keying and quadrature amplitude modulation
A Conic Model for Electrolyzer Scheduling
The hydrogen production curve of the electrolyzer describes the non-linear
and non-convex relationship between its power consumption and hydrogen
production. An accurate representation of this curve is essential for the
optimal scheduling of the electrolyzer. The current state-of-the-art approach
is based on piece-wise linear approximation, which requires binary variables
and does not scale well for large-scale problems. To overcome this barrier, we
propose two models, both built upon convex relaxations of the hydrogen
production curve. The first one is a linear relaxation of the piece-wise linear
approximation, while the second one is a conic relaxation of a quadratic
approximation. Both relaxations are exact under prevalent operating conditions.
We prove this mathematically for the conic relaxation. Using a realistic case
study, we show that the conic model, in comparison to the other models,
provides a satisfactory trade-off between computational complexity and solution
accuracy for large-scale problems
Electrolyzer Scheduling for Nordic FCR Services
The cost competitiveness of green hydrogen production via electrolysis
presents a significant challenge for its large-scale adoption. One potential
solution to make electrolyzers profitable is to diversify their products and
participate in various markets, generating additional revenue streams.
Electrolyzers can be utilized as flexible loads and participate in various
frequency-supporting ancillary service markets by adjusting their operating set
points. This paper develops a mixed-integer linear model, deriving an optimal
scheduling strategy for an electrolyzer providing Frequency Containment Reserve
(FCR) services in the Nordic synchronous region. Depending on the hydrogen
price and demand, results show that the provision of various FCR services,
particularly those for critical frequency conditions (FCR-D), could
significantly increase the profit of the electrolyzer.Comment: Accepted for IEEE SmartGridComm 202
Flexibility of Integrated Power and Gas Systems: Modeling and Solution Choices Matter
Due to their slow gas flow dynamics, natural gas pipelines function as
short-term storage, the so-called \textit{linepack}. By efficiently utilizing
linepack, the natural gas system can provide flexibility to the power system
through the flexible operation of gas-fired power plants. This requires
accurately representing the gas flow physics governed by partial differential
equations. Although several modeling and solution choices have been proposed in
the literature, their impact on the flexibility provision of gas networks to
power systems has not been thoroughly analyzed and compared. This paper bridges
this gap by first developing a unified framework. We harmonize existing
approaches and demonstrate their derivation from and application to the partial
differential equations. Secondly, based on the proposed framework, we
numerically analyze the implications of various modeling and solution choices
on the flexibility provision from gas networks to power systems. One key
conclusion is that relaxation-based approaches allow charging and discharging
the linepack at physically infeasible high rates, ultimately overestimating the
flexibility
Linear predictive receivers for phase-uncertain channels
In this paper, we propose linear predictive receivers for phaseuncertain channels. These receivers are attractive from a conceptual viewpoint because they generalize previous solutions based on noncoherent sequence detection. On the practical side, the proposed algorithms lend themselves to the implementation of adaptive receivers capable of copying with possible time variations of the statistics of the underlying phase model. 1
- âŠ