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Iterative receivers for interference limited environments Open Access


Other title
joint detection
multi antenna systems
interference cancellation
Type of item
Degree grantor
University of Alberta
Author or creator
Krzymien, Lukasz
Supervisor and department
Jing, Yindi (Electrical and Computer Engineering)
Schlegel, Christian (Computing Science)
Examining committee member and department
Ho, Paul (School of Engineering Science, Simon Fraser University)
Fair, Ivan (Electrical and Computer Engineering)
Nikolaidis, Ioanis (Computing Science)
Department of Electrical and Computer Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Interference dominated wireless communications systems are considered. Joint detection methods are applied to combat the negative effects of the temporal and spatial interference. However, practical joint detectors are not commonly used due to their high complexity. Therefore, there is a constant need to deliver reduced complexity solutions that approach substantial fraction of the channel capacity. In the first part of this thesis it is shown that simple transmission technique employing repetition coding and interleaving combined with interference cancellation is an asymptotically optimal processing strategy when high interference is experienced, for instance due to the relatively high ratio of the number of signals to the number of orthogonal dimensions. Surprisingly, strong, capacity achieving codes exhibit inferior performance and are not well suited for iterative interference cancellation due to their sharp threshold characteristics. Motivated by this observation partitioned modulation is introduced and applied to a multiuser spread spectrum system, which inherently encompasses a repetition coding mechanism. The detection of the resulting signals employs a parallel interference cancellation approach, where the repetition code exchanges information iteratively with the canceller. Precise signal-to-noise ratio evolution of the proposed receiver as a function of demodulation iterations is given. It is shown, that for equal received power system, partitioned demodulator outperforms linear minimum mean squared error processor at a fraction of complexity. This receiver processing for a wide range of parameters delivers estimates that coincide with the optimal processing based on exhaustive search. For unequal received signal powers these advantages are even more visible and for a particular exponential power allocation the proposed system reaches the capacity of the channel. The analytical investigations are verified using computer simulations. In the second part of this dissertation, multi-user MIMO systems compliant with 3GPP LTE standard are considered. Turbo near-far resistant interference cancellation receiver is proposed. It jointly removes multi-user, multi-antenna and inter-symbol interference and outperforms traditional demodulation/decoding method adopted in the LTE standard. Semi-analytical method of predicting the performance of this joint receiver for any system setup is outlined. This approach makes it possible to tune up the performance of the system without running extensive bit-error-rate simulations.
License granted by Lukasz Krzymien ( on 2011-04-07T18:39:10Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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File title: Iterative Receivers for Interference Limited Environments, Ph. D. Thesis
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