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

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

Information rates of multidimensional front-ends for digital storage channels with data-dependent transition noise

Abstract-A new simulation-based method to evaluate the information rates of multidimensional front-ends applied to digital storage channels with transition noise is presented. First, we propose an algorithm which extends recent work on the information rates of magnetic recording channels affected by colored Gaussian thermal noise, intersymbol interference and signal-dependent transition noise, by using linear prediction and state reduction techniques. Moreover, following a previous study on statistical sufficiency, we extend this algorithm to magnetic channels with a multidimensional front-end. The results suggest that significant gains may be achievable by multidimensional signal processing techniques in transition-noise limited digital storage channels

Joint decoding of TCM and detection of PTS side information: a multiple trellis solution

One of the major drawback of orthogonal frequency-division multiplexing (OFDM) systems is the large Peak-to-Average power Ratio (PAR) of the transmit signal. High levels of PAR may be a limiting factor for power line communication (PLC) where regulatory bodies have fixed the maximum amount of transmit power. Partial transmit sequence (PTS) is a well-known solution for PAR reduction, but its effectiveness depends on an accurate, and possibly error-free, exchange of side information (SI) between the transmitter and the receiver. In this article, a new maximum likelihood (ML) algorithm for joint decoding of trellis code modulation (TCM) and detection of PTS is presented. The proposed algorithm exploits the redundancy introduced by the TCM code to estimate the correct PTS, and represents a practical solution to avoid the explicit insertion of SI into the OFDM signal. The proposed algorithm has been assessed by bit-error rate (BER) simulation, showing a good performance over additive white Gaussian noise (AWGN) channels and amplifier nonlinearities

Improved differential detection of chip-level differentially encoded direct-sequence spread-spectrum signals

In a paper by Cavallini et al. (see IEEE Trans. Commun., vol. 45, p.456-63, Apr. 1997), chip-level differential encoding/detection for direct-sequence spread-spectrum signals was proposed to cope with frequency-nonselective fast fading channels. It was shown that, unlike in the additive white Gaussian noise channel, in time-varying fading channels the system performance may be considerably improved, especially when the spreading factor is increased. In this paper, noncoherent sequence detection, recently proposed by the authors, is the starting point for the derivation of receivers with improved performance with respect to that of standard differential detection. For M-ary phase-shift keying signals, a theoretical analysis is performed and the results are confirmed by means of computer simulation. The performance advantage of taking into account a larger phase memory, with respect to the minimum accounted for by differential detection, is demonstrated. In particular, the amount of phase memory is optimized as a function of the Doppler spread for a Rayleigh frequency-nonselective fading channel. The robustness in the presence of phase noise is also investigated by means of computer simulation