ISBN 9783843903936

978-3-8439-0393-6, Reihe Kommunikationstechnik

Klaus Hueske
Low Complexity Equalization Concepts for Spectral Efficient Wireless Transmission Systems

199 Seiten, Dissertation Technische Universität Dortmund (2012), Softcover, A5

Zusammenfassung / Abstract

Nearly all current wireless digital transmission systems rely on a block transmission structure, in which successive data blocks are separated by a guard interval of sufficient length to avoid inter block interference. A well-known example is the cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) system, in which the guard interval is inserted as a cyclic extension of the transmit data block. While the insertion of a cyclic prefix enables computationally efficient data estimation methods, the additional transmission overhead significantly reduces the achievable data throughput.

This work analyses different properties of guard interval based block transmission systems in terms of performance and computational complexity. To clarify the impact of interference caused by insufficient guard intervals, the resulting reduction of system capacity is investigated. Various approaches are known that can reduce the guard interval overhead while avoiding the interference induced performance degradation. This work considers three linear processing approaches that show both, adequate performance and reasonable computational complexity.

By providing a detailed analysis of these methods, namely symbol aggregation, channel shortening and overlapping equalization, specific benefits and disadvantages are clarified. Based on the results of the analysis, extensions of these methods are proposed, which either intend to increase system performance or to reduce computational complexity.

Focusing on overlapping equalization, the properties of the resulting transmission systems are analyzed in context of doubly selective channels, peak to average power ratio and channel estimation procedures. An extension of the model for multi antenna scenarios is discussed.

If a reduction of guard interval overhead is not possible due to restrictions in a standardized transmission system, the transmitted redundancy of the guard interval can be used to improve data estimation. It is shown that this can be efficiently realized by overlapping equalization.