Highly efficient new methods of channel estimation for ofdm systems

Çürük, Selva Muratoğlu
In the first part, the topic of average channel capacity for Orthogonal Frequency Division Multiplexing (OFDM) under Rayleigh, Rician, Nakagami-m, Hoyt, Weibull and Lognormal fading is addressed. With the assumption that channel state information is known, we deal with a lower bound for the capacity and find closed computable forms for Rician fading without diversity and with Maximum Ratio Combining diversity at the receiver. Approximate expressions are also provided for the capacity lower bound in the case of high Signal to Noise Ratio. This thesis presents two simplified Maximum A Posteriori (MAP) channel estimators to be used in OFDM systems under frequency selective slowly varying Rayleigh fading. Both estimators use parametric models, where the first model assumes exponential frequency domain correlation while the second model is based on the assumption of exponential power delay profile. Expressions for the mean square error of estimations are derived and the relation between the correlation of subchannel taps and error variance is investigated. Dependencies of the proposed estimators’ performances on the model parameter and noise variance estimation errors are analyzed. We also provide approximations on the estimators’ algorithms in order to make the estimators practical. Finally, we investigate SER performance of the simplified MAP estimator based on exponential power delay profile assumption used for OFDM systems with QPSK modulation. The results indicate that the proposed estimator performance is always better than that of the ML estimator, and as the subchannel correlation increases the performance comes closer to that of perfectly estimated channel case.


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Avan, Muhammet; Candan, Çağatay; Department of Electrical and Electronics Engineering (2008)
In this thesis study, joint frequency offset and channel estimation methods for single-input single-output (SISO) systems are examined. The performance of maximum likelihood estimate of the parameters are studied for different training sequences. Conventionally training sequences are designed solely for the channel estimation purpose. We present a numerical comparison of different training sequences for the joint estimation problem. The performance comparisons are made in terms of mean square estimation err...
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Pamuk, Gökhan; Yıldırım, Nevzat; Department of Electrical and Electronics Engineering (2010)
n this thesis, RF sections of a multi tier instantaneous frequency measurement (IFM) receiver which can operate in 2 – 18 GHz frequency band is designed, simulated and partially realized. The designed structure uses one coarse tier, three medium tiers and one fine tier for frequency discrimination. A novel reflective phase shifting technique is developed which enables the design of very wideband phase shifters using stepped cascaded transmission lines. Compared to the classical phase shifters using coupled ...
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Özkaya, Hasan; Hava, Ahmet Masum; Department of Electrical and Electronics Engineering (2007)
The parallel active filter (PAF) is the modern solution for harmonic current mitigation and reactive power compensation of nonlinear loads. This thesis is dedicated to detailed analysis, design, control, and implementation of a PAF for a 3- phase 3-wire rectifier load. Specifically, the current regulator and switching ripple filter (SRF) are thoroughly investigated. A novel discrete time hysteresis current regulator with multi-rate current sampling and flexible PWM output, DHCR3, is proposed. DHCR3 exhibits...
Joint spatial and temporal channel-shortening techniques for frequency selective fading MIMO channels
Toker, Canan; Chambers, JA; Baykal, Buyurman (2005-02-01)
It is well understood that the maximum likelihood estimator is a powerful equalisation technique for frequency selective fading channels, and in particular for MIMO systems. The complexity of this estimator, however, grows exponentially with the number of users and multipath taps, hence limiting the use of this algorithm in MIMO systems. In the paper, the authors propose a joint spatial and temporal channel-shortening filter as a pre-processor to reduce significantly the complexity of a maximum likelihood e...
Sabah, Cumali; Urbani, Fabio; Uckun, Savas (Walter de Gruyter GmbH, 2012-09-01)
In this study, the dispersion relation and the frequency dependence of Bloch impedance in a left handed transmission line (LH-TL) is carried out using the F-matrix formulation and Bloch-Floquet theorem. The artificial LH-TL formed by periodic lumped elements is described and the F-matrix, dispersion relation and the Bloch impedance are formulated according to this description. Numerical results for lossless and lossy LH-TL are presented and discussed.
Citation Formats
S. M. Çürük, “Highly efficient new methods of channel estimation for ofdm systems,” Ph.D. - Doctoral Program, Middle East Technical University, 2008.