1,721,026 research outputs found
OTFS vs. OFDM in the Presence of Sparsity: A Fair Comparison
Full text linkMany recent works in the literature declare that Orthogonal Time-Frequency-Space (OTFS) modulation is a promising candidate technology for high mobility communication scenarios. However, a truly fair comparison with its direct concurrent and widely used Orthogonal Frequency-Division Multiplexing (OFDM) modulation has not yet been provided. In this paper, we present such a fair comparison between the two digital modulation formats in terms of achievable communication rate. In this context, we explicitly address the problem of channel estimation by considering, for each modulation, a pilot scheme and the associated channel estimation algorithm specifically adapted to sparse channels in the Doppler-delay domain, targeting the optimization of the pilot overhead to maximize the overall achievable rate. In our achievable rate analysis we consider also the presence of a guard interval or cyclic prefix. The results are supported by numerical simulations, for different time-frequency selective channels including multiple scattering components and under non-perfect channel state information resulting from the considered pilot schemes. This work does not claim to establish in a fully definitive way which is the best modulation format, since such choice depends on many other features which are outside the scope of this work (e.g., legacy, intellectual property, ease and know-how for implementation, and many other criteria). Nevertheless, we provide the foundations to properly compare multi-carrier communication systems in terms of their information theoretic achievable rate potential, within meaningful and sensible assumptions on the channel models and on the receiver complexity (both in terms of channel estimation and in terms of soft-output symbol detection)
Method based on the Stokes parameters for the adaptive adjustment of PMD compensators in optical fiber communication systems and compensator in accordance with said method
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Detection of Variable Length PLH Codes for the DVB-S2X System
No full textIn this paper, we address the problem of the detection of variable length Physical Layer Header (PLH) codes. We take as a case study the DVB-S2X standard, and, after selecting a suitable PLH code with variable codeword length, we propose two alternative noncoherent detection strategies. The proposed detection strategies allow to jointly estimate the length of the transmitted PLH field, which is unknown at the receiver, and decoding the PLH code. We demonstrate that it is possible to achieve an excellent detection performance while significantly reducing the overhead due to the transmission of the PLH field with respect to a standard fixed-length PLH
Decoding of Variable Length PLH Codes
No full textIn this paper, we address the problem of the decoding of variable length physical layer header (PLH) codes. We take as a case study the DVB-S2X standard, and, after selecting a suitable PLH code with variable codeword length, we propose two alternative noncoherent decoding strategies. The proposed decoding strategies allow to estimate the length of the transmitted PLH field, which is unknown at the receiver, jointly with the decoding of the PLH code. We demonstrate that it is possible to achieve an excellent decoding performance while significantly reducing the overhead due to the transmission of the PLH field with respect to a standard fixed-length PLH
Estimation of Correlated Gaussian Samples in Impulsive Noise
Full text linkWe consider the estimation of correlated Gaussian samples in (correlated) impulsive noise, through message-passing algorithms. The factor graph includes cycles and, due to the mixture of Gaussian (samples and noise) and Bernoulli variables (the impulsive noise switches), the complexity of messages increases exponentially. We first analyze a simple but suboptimal solution, called Parallel Iterative Scheduling. Then we implement both Expectation Propagation - for which numerical stability must be addressed - and a simple variation thereof (called Transparent Propagation) that is inherently stable and simplifies the overall computation. Both algorithms reach a performance close to ideal, practically coinciding with the lower bound on the mean square estimation error
A New Discrete-Time Model for Channels Impaired by Phase Noise
No full textWe propose a novel discrete-time model for the phase noise signal, in case of free-running and phase-locked oscillators. In particular, we show how the PN can be described by an autoregressive process. The strength of the proposed model is that it can be easily expressed in terms of measurement parameters of practical oscillators. We then analyse the most common discrete-time phase noise channel model with reference to the measurement parameters and to the system bandwidth. The derived analytical models for the discrete-time phase noise signal can be used for the design of estimation/detection algorithms, for performance evaluation, or simply for fast simulations
A parallel VLSI architecture for 1-Gb/s, 2048-b, rate-1/2 turbo Gallager code decoder
No full textThis paper presents a 2048 bit, rate (1)/(2) soft decision decoder for a new class of codes known as Turbo Gallager Codes. The decoder can support tip to 1 Gbit/s code rate and performs up to 48 decoding iteration ensuring at the same time high throughput and good coding gain. In order to evaluate the performance and the gate complexity of the decoder VLSI architecture, it has been synthesized in a 0.18 mum standard-cell CMOS technology
Method based on mean square error for the adaptive adjustment of PMD compensators in optical fiber communication systems and compensator in accordance with said method
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