66 research outputs found
Blind Carrier Phase Recovery for General 2{\pi}/M-rotationally Symmetric Constellations
This paper introduces a novel blind carrier phase recovery estimator for
general 2{\Pi}/M-rotationally symmetric constellations. This estimation method
is a generalization of the non-data-aided (NDA) nonlinear Phase Metric Method
(PMM) estimator already designed for general quadrature amplitude
constellations. This unbiased estimator is seen here as a fourth order PMM then
generalized to Mth order (Mth PMM) in such manner that it covers general
2{\Pi}/M-rotationally symmetric constellations such as PAM, QAM, PSK.
Simulation results demonstrate the good performance of this Mth PMM estimation
algorithm against competitive blind phase estimators already published for
various modulation systems of practical interest.Comment: 14 pages, 12 figures, International Journal of Wireless & Mobile
Networks (IJWMN
Метод непараметричної оцінки кратності фазової маніпуляції сигналу
У статті розглядається метод оцінки кратності маніпуляції MPSK сигналу та його частоти по спостереженню в білому шумі з невідомим законом розподілу. Вивчаються властивості непараметричної оцінки кратності маніпуляції сигналу, отриманої з використанням BDS-статистики, а також властивості фазових портретів таких сигналів. Наведено залежності BDS-статистики від кратності маніпуляції та частоти при різних значеннях сигнал/шум. Результати статті можуть бути використані для автоматизації підходу до «сліпого» визначення параметрів сигналу при невідомих властивостях шуму спостереження
Automatic modulation classification of communication signals
The automatic modulation recognition (AMR) plays an important role in various civilian and military applications. Most of the existing AMR algorithms assume that the input signal is only of analog modulation or is only of digital modulation. In blind environments, however, it is impossible to know in advance if the received communication signal is analogue modulated or digitally modulated. Furthermore, it is noted that the applications of the currently existing AMR algorithms designed for handling both analog and digital communication signals are rather restricted in practice. Motivated by this, an AMR algorithm that is able to discriminate between analog communication signals and digital communication signals is developed in this dissertation. The proposed algorithm is able to recognize the concrete modulation type if the input is an analog communication signal and to estimate the number of modulation levels and the frequency deviation if the input is an exponentially modulated digital communication signal. For linearly modulated digital communication signals, the proposed classifier will classify them into one of several nonoverlapping sets of modulation types. In addition, in M-ary FSK (MFSK) signal classification, two classifiers have also been developed. These two classifiers are also capable of providing good estimate of the frequency deviation of a received MFSK signal.
For further classification of linearly modulated digital communication signals, it is often necessary to blindly equalize the received signal before performing modulation recognition. This doing generally requires knowing the carrier frequency and symbol rate of the input signal. For this purpose, a blind carrier frequency estimation algorithm and a blind symbol rate estimation algorithm have been developed. The carrier frequency estimator is based on the phases of the autocorrelation functions of the received signal. Unlike the cyclic correlation based estimators, it does not require the transmitted symbols being non-circularly distributed. The symbol rate estimator is based on digital communication signals\u27 cyclostationarity related to the symbol rate. In order to adapt to the unknown symbol rate as well as the unknown excess bandwidth, the received signal is first filtered by using a bank of filters. Symbol rate candidates and their associated confident measurements are extracted from the fourth order cyclic moments of the filtered outputs, and the final estimate of symbol rate is made based on weighted majority voting.
A thorough evaluation of some well-known feature based AMR algorithms is also presented in this dissertation
HOS-Based multi-component frequency estimation
We are considering a problem of carrier frequencies recovery for the linear mixtures of two BPSK signals in Gaussian noise. The goal is to simplify further signal analysis: signal separation, modulation identification and parameters estimation. The presented method is based on multidimensional (time-frequencyphase) representation of the Higher Order Statistics (HOS) of the received signal distribution. Performance of the proposed algorithm is verified through extensive simulations and compared to the MUSIC high-resolution spectral estimation method. Corresponding results show that our technique outperforms the latter for all considered frequency shifts, even for high signal-to-noise ratios (SNR)
Asymptotic Performance of the Pth Power-Law Phase Estimator
An expression for the true variance of the Pth powerlaw phase estimator, as the number of samples approaches infinity, is given. This expression is an extension to the linear approximation of Moeneclaey and de Jonghe [1] which is known to be inadequate in some practical systems. Our new expression covers general 2π/P-rotationally symmetric constellations that include those of PAM, QAM, PSK, Star M-QAM, MR-DPSK, and others. This expression also generalizes the known expressions for QAM and PSK. Additionally, our expression reduces to the Cramer-Rao bound given by Steendam and Moeneclaey [9], as SNR goes to zero. Monte Carlo simulations provide experimental verification of the theoretical expression for various constellations
Efficient Maximum-Likelihood Based Clock and Phase Estimators for OQPSK Signals
In this paper we propose an algorithm for joint carrier phase and timing estimation with OQPSK modulations. The derivation is based on the maximum-likelihood criterion, and exploits a very efficient algorithm for the detection of differentially encoded -PSK symbols already described in literature. Though we are mainly interested in measuring the phase and clock parameters, estimates of the transmitted symbols are also obtained as by-products. The resulting scheme has a feedforward structure and provides phase and timing information in a fixed time, differently from closed-loop architectures. It can be implemented in digital form and is particularly suitable for burst mode transmissions. Its performance is investigated by simulation and the results are compared with Cramér-Rao bounds. It turns out that the estimation accuracy is very close to the theoretical limits, even with short observation intervals and small values of the excess bandwidth. In such conditions, the proposed estimators largely outperform other schemes already known in literature. Their superiority becomes less significant as the signal bandwidth increases
Advanced data communication techniques for sub-sea applications
This thesis details research carried out in the through-water data communication field.
An overview of the phenomena that prohibit acoustic communication in long-range
shallow-water channels is constructed. Background research found that robust
communications has not been achieved using single receiver reception in this
environment. This work investigates the modulation technique itself and aims to
improve on existing schemes (that have been applied to this environment). This is
achieved with innovative techniques, based on multiple-frequency-shift-keying
(MFSK) and space-frequency-shift-keying (SFSK). A number of industrial specified
restrictions are placed on this work, including bandwidth restriction. Novel ways of
intrinsically transmitting synchronisation information are therefore implemented. The
development of appropriate systems is covered with general and platform specific
implementation strategies being covered. A single modulation scheme (the three-chip four-frequency-shift-keying, 3C4FSK, scheme) has been put forward for consideration in any future research. Practical lab-based tests and the mathematical analysis is
detailed. Conclusions recommend further funding of long-range shallow sea-water
trails of the 3C4FSK scheme and for the industrial scope of this work to allow
investigation into multiple receiver systems that allow spatial processing of the signal
as these schemes have been shown lately to have potential in long-range channels
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