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Title: Enhanced channel quality estimation for advanced satellite air-interfaces
Author: Ijaz, Ayesha
ISNI:       0000 0004 2716 6203
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2011
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In this thesis, we investigate robust channel quality estimation algorithms for advanced satellite air-interfaces in order to facilitate the increasing demand for broadband applications in modem wireless communication systems. Signal-to-noise ratio (SNR) is an important channel quality measure required to perform link adaptation to ensure guaranteed availability and quality of service to the end users. DVB-RCS (Digital Video Broadcasting-Return Channel via Satellite) systems have a stringent requirement to perform SNR estimation within one traffic slot duration. Existing SNR estimators suffer from high computational complexity and low estimation accuracy. Therefore, we propose a novel decision directed/non-data-aided SNR estimation algorithm with significantly lower complexity and higher accuracy for efficient mode adaptation in a DVB-RCS system. OFDM (Orthogonal Frequency Division Multiplexing) technology is well suited for satellite broadband services to handheld terminals and adaptive transmission, employing SNR estimation to indicate channel quality, can play an important role in making an efficient use of system resources. Therefore, we propose a novel preamble-based SNR estimator for OFDM systems. Its robustness to frequency selectivity, high accuracy and low computational complexity make it an attractive choice for wireless OFDM systems. Spectrally-efficient modulation schemes introduced in DVB-S2 (Digital Video Broadcasting via Satellite-Second Generation) are very sensitive to nonlinear distortion caused by high power amplifiers. We propose a novel predistorter using support vector regression to compensate for nonlinear distortion. It achieves an acceptable link-level performance even at saturation where the conventional predistorter completely fails. Therefore, the proposed predistorter can help to improve the power efficiency for spectrally-efficient modulations. A multilevel pilot design is also proposed for nonlinear equalization in DVB-S2 systems. The proposed pilot structure significantly improves the BER performance and SNR estimation accuracy as compared to the conventional constant-envelope pilots. A combination of the proposed predistorter and nonlinear equalizer is proposed to further improve the link-level performance in a DVB-S2 system using spectrally-efficient modulations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available