Wilfried Gappmair

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Powerful parameter estimators exhibit a jitter variance which is fairly close to the Cramer-Rao lower bound (CRLB) as the theoretical limit. In contrast to symbol timing and carrier frequency/phase, not very much information is available from the open literature with respect to the signal-to-noise ratio (SNR), i. e., the CRLB has been reported only for the(More)
The recently published Cramer-Rao lower bound for non-data-aided (NDA) estimation of the signal-to-noise ratio (SNR) reveals a considerable gap, when compared to the jitter performance of NDA algorithms available from the open literature. The maximum-likelihood (ML) solution derived in this paper closes this gap. However, the latter provides a set of two(More)
For the design of intelligent receivers, the classification of modulation schemes becomes an increasingly important task. Interestingly, the numerous papers on this subject neglect algorithms for the classification of APSK signals, although these are recommended in the DVB-S2 standard. Therefore, a feature-based method for classification of modulation(More)
Signal-to-noise ratio (SNR) estimation for linearly modulated signals is addressed in this letter, focusing on envelopebased estimators, which are robust to carrier offsets and phase jitter, and on the challenging case of nonconstant modulus constellations. For comparison purposes, the true Cramér-Rao lower bound is numerically evaluated, obtaining an(More)
The signal-to-noise ratio (SNR) estimation problem is addressed for linearly modulated signals over flat-fading channels. A new SNR estimator based on the expectation-maximization algorithm is proposed in order to iteratively maximize a certain approximation to the envelope-based likelihood function. The new method is robust to carrier offsets and can be(More)
For free-space optical (FSO) links in turbulent atmosphere modeled by gamma-gamma distributions, an approximation of the pairwise error probability (PEP) was derived for on-off keying in a recently published paper. It has been assumed that the channel state is perfectly known to the receiver and that the fading samples are independent and identically(More)