A new bound and algorithm for star 16-QAM carrier phase estimation

Copyright © 2003 IEEEThe true Cramer-Rao lower bound (CRLB) is derived and evaluated for the estimation of carrier phase of Star 16-quadrature amplitude modulation (QAM) and can be simply applied to carrier frequency estimation. Different geometries are investigated by varying the ring ratio (RR). For signal-to-noise ratios (SNRs) between 6-15 dB, the CRLB with RR=3 is lower than that of Square 16-QAM. A modified phase estimator is presented, which closely follows the new CRLB. Investigation of symbol error performance in short packet length reveals Star 16-QAM to be superior to Square 16-QAM for SNR<13 dB, which is a reasonable operating range for a coded system. Although Square 16-QAM and Star RR=1.8 are optimum for a perfect receiver, when the effect of phase estimation is considered, we find Star RR=3 to be better for SNR below 10 dB.Feng Rice, Mark Rice, and Bill Cowle

Modulation Recognition for MIMO Communications

International audienceThe blind recognition of communication parameters is an important research topic in both commercial and civilian systems. In this paper, we investigate the blind recognition of the modulation. Currently most part of the existing algorithms assumes that the transmitter uses a single-antenna. This study extends the problem for multiple-antennas (MIMO) systems. We adopt a Maximum Likelihood approach for the blind recognition of the modulation and we consider two different situations. First, we assume the channel knowledge at the receiver side and we expose the optimal solution which is called Average Likelihood Ratio Test (ALRT). Then, we relax this assumption and we propose a second method based on a Hybrid Likelihood Ratio Test (HLRT)

On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise

In this paper, first, a new discrete-time model of phase noise for digital communication systems, which is a more accurate model compared to the classical Wiener model, is proposed based on a comprehensive continuous-time representation of time-varying phase noise, and statistical characteristics of this model are derived. Next, the non-data-aided (NDA) and decision-directed (DD) maximum-likelihood (ML) estimators of time-varying phase noise, using the proposed discrete-time model are derived. To evaluate the performance of the proposed estimators, the Cramer-Rao lower bound (CRLB) for each estimation approach is derived and by using Monte-Carlo simulations it is shown that the mean-square error (MSE) of the proposed estimators converges to the CRLB at moderate signal-to-noise ratios (SNR). Finally, simulation results show that the proposed estimators outperform existing estimation methods as the variance of the phase noise process increases

Phase detection based on a single parity check code for low SNR applications

The improvement of carrier phase synchronization through the use of channel decoding information has been recently widely studied. However, an initial synchronization step is necessary prior to the first decoding iteration. When the phase to estimate is not constant (due to frequency error or phase noise), this first step is problematic on relatively long coded words. In this paper we propose to add a short single parity-check code to the transmission scheme for the synchronization purpose. The proposed phase detector is based on the soft symbol decoding of the additional code. Our simulation results show that the proposed synchronization scheme outperforms the classical non data-aided and decision directed algorithms for continuous transmissions with 8PSK modulation, in presence of phase noise. It allows indeed to reduce the phase jitter in considerable proportions. Requiring few additional complexity, it seems well adapted to satellite continuous transmissions.De nombreuses études ont récemment montré l'avantage que l'on peut tirer du décodage canal pour l'amélioration de la synchronisation de phase porteuse à faible rapport signal à bruit. Lorsque la phase à estimer varie au cours du temps (erreur de fréquence, bruit de phase), l'estimation de la phase avant la première étape de décodage pose toutefois problème lorsque les mots de code sont longs. Nous proposons ici un algorithme de synchronisation fondé sur l'introduction d'un code de parité simple et court. Nous montrons que pour une transmission continue et une modulation MDP8, le détecteur proposé permet de réduire sensiblement la gigue de phase à très faible point de fonctionnement et en présence de bruit de phase, par rapport aux algorithmes classiques. De faible complexité, il apparait notamment bien adapté au contexte des télécommunications par satellite

Rapid carrier phase acquisition for large QAM signal constellations

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: p. 94-95.Issued also on microfiche from Lange Micrographics.This work addresses the problem of rapid carrier-phase acquisition for QAM constellations, and specifically for the 32-QAM, 64-QAM, 128-QAM, and 256-QAM constellations, operating over an AWGN channel. It is assumed that there is no frequency or symbol timing error. Seven algorithms in all are derived and tested. The first is the maximum-likelihood (ML) estimator, which is found to be accurate but impractical to implement. A suboptimal ML type estimator is derived from the ML algorithm and is found to be simpler but still impractical. The power-law (PL) estimator is derived as the low SNR limit of the ML estimator, and is found to be very simple, but having poor error performance. A threshold is added to the PL algorithm and the performance is improved, but not enough for rapid phase acquisition for most cases. An algorithm is derived specifically for use on the cross constellations which further improves performance, but this algorithm is superseded by an estimator based on a trellis structure and the Viterbi Algorithm which is developed. Finally a suboptimal version of the trellis algorithm is developed which reduces the complexity of the trellis algorithm by two-thirds. Both the trellis and the suboptimal trellis algorithm perform well enough for phase acquisition and are simple and practical to implement

Estimation de l'erreur de phase d'une modulation QAM conjointement au décodage itératif d'un code bloc

Ce papier présente une nouvelle technique de synchronisation de systèmes exploitant des turbo-codes blocs. L'estimation de la phase repose sur l'exploitation de la valeur extrinsèque en sortie du décodeur pour estimer cet écart en phase conjointement au décodage itératif des symboles. Nous présentons plusieurs résultats montrant que l'algorithme proposé permet de poursuivre des décalages en fréquence, qu'il fonctionne pour des modulations QAM et qu'il fonctionne à faible rapport signal à bruit (RSB). Une comparaison de la variance de cet estimateur à la borne de Cramer-Rao vraie (CRB) et modifiée (MCRB) est également effectuée