Heidi Steendam

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This contribution considers turbo synchronization, that is to say, the use of soft data information to estimate parameters like carrier phase, frequency, or timing offsets of a modulated signal within an iterative data demodulator. In turbo synchronization, the receiver exploits the soft decisions computed at each turbo decoding iteration to provide a(More)
In mobile radio communication, the fading channels generally exhibit both time-selectivity and frequency-selectivity. Orthogonal frequency-division multiplexing has been proposed to combat the frequency-selectivity, but its performance is also affected by the time-selectivity. In this paper, we investigate how various parameters, such as the number of(More)
This paper is devoted to turbo synchronization, that is to say the use of soft information to estimate parameters like carrier phase, frequency offset or timing within a turbo receiver. It is shown how maximum-likelihood estimation of those synchronization parameters can be implemented by means of the iterative expectation-maximization (EM) algorithm [1].(More)
In this paper, we consider different types of guard intervals for OFDM systems, i.e. cyclic prefix (CP), zero padding (ZP) and known symbol padding (KSP). We compare the different OFDM systems with respect to their SNR performance. We show that CP-OFDM and ZP-OFDM have exactly the same performance, whereas KSP-OFDM has a slightly worse performance. Further,(More)
In OFDM systems, the symbol timing synchronization is needed to find an estimate of where the symbol starts. The most popular of the pilot-aided timing estimators is the one proposed by Schmidl and Cox (S&amp;C) ["Robust Frequency and Timing Synchronization for OFDM," <i>IEEE Transactions on Communications</i>, vol. 45, no. 12, pp. 1613-1621, Dec. 1997].(More)
In this paper, we derive the Cramér-Rao bound (CRB) for joint carrier phase, carrier frequency, and timing estimation from a noisy linearly modulated signal with encoded data symbols. We obtain a closed-form expression for the CRB in terms of the marginal a posteriori probabilities of the coded symbols, allowing efficient numerical evaluation of the CRB for(More)
In this letter, we express the Cramer-Rao Bound (CRB) for carrier phase estimation from a noisy linearly modulated signal with encoded data symbols, in terms of the marginal a posteriori probabilities (APPs) of the coded symbols. For a wide range of classical codes (block codes, convolutional codes, and trellis-coded modulation), these marginal APPs can be(More)
In this letter we consider the Cramer–Rao bound (CRB) for the estimation of the carrier phase and frequency of a noisy linearly modulated signal with random data symbols. The observation vector consists of the matched filter output samples taken at the symbol rate, assuming known symbol timing. Because of the presence of the random data, the evaluation of(More)
In this paper, we propose a new low-complexity data-aided channel estimation algorithm for known symbol padding (KSP) OFDM. Besides the pilot symbols in the guard interval, additional pilots are put on some of the OFDM carriers. The received time-domain samples are first converted to the frequency domain, and the channel estimation is based on the(More)