Applications of Lattices over Wireless Channels

dc.comment.hiddenThere is a journal paper related to this thesis under review. It would be great if the web access is delayed for four months. Moreover, if it is accepted, the publisher does not require written permission.en
dc.contributor.authorNajafi, Hossein
dc.date.accessioned2012-09-26T21:09:27Z
dc.date.available2012-09-26T21:09:27Z
dc.date.issued2012-09-26T21:09:27Z
dc.date.submitted2012
dc.description.abstractIn wireless networks, reliable communication is a challenging issue due to many attenuation factors such as receiver noise, channel fading, interference and asynchronous delays. Lattice coding and decoding provide efficient solutions to many problems in wireless communications and multiuser information theory. The capability in achieving the fundamental limits, together with simple and efficient transmitter and receiver structures, make the lattice strategy a promising approach. This work deals with problems of lattice detection over fading channels and time asynchronism over the lattice-based compute-and-forward protocol. In multiple-input multiple-output (MIMO) systems, the use of lattice reduction significantly improves the performance of approximate detection techniques. In the first part of this thesis, by taking advantage of the temporal correlation of a Rayleigh fading channel, low complexity lattice reduction methods are investigated. We show that updating the reduced lattice basis adaptively with a careful use of previous channel realizations yields a significant saving in complexity with a minimal degradation in performance. Considering high data rate MIMO systems, we then investigate soft-output detection methods. Using the list sphere decoder (LSD) algorithm, an adaptive method is proposed to reduce the complexity of generating the list for evaluating the log-likelihood ratio (LLR) values. In the second part, by applying the lattice coding and decoding schemes over asynchronous networks, we study the impact of asynchronism on the compute-and-forward strategy. While the key idea in compute-and-forward is to decode a linear synchronous combination of transmitted codewords, the distributed relays receive random asynchronous versions of the combinations. Assuming different asynchronous models, we design the receiver structure prior to the decoder of compute-and-forward so that the achievable rates are maximized at any signal-to-noise-ratio (SNR). Finally, we consider symbol-asynchronous X networks with single antenna nodes over time-invariant channels. We exploit the asynchronism among the received signals in order to design the interference alignment scheme. It is shown that the asynchronism provides correlated channel variations which are proved to be sufficient to implement the vector interference alignment over the constant X network.en
dc.identifier.urihttp://hdl.handle.net/10012/7041
dc.language.isoenen
dc.pendingfalseen
dc.publisherUniversity of Waterlooen
dc.subjectWirelessen
dc.subjectLatticeen
dc.subjectFadingen
dc.subjectMIMO decodingen
dc.subjectInterference Alignmenten
dc.subjectCompute-and-Forwarden
dc.subjectSoft-outputen
dc.subjectLattice Decodingen
dc.subjectX networken
dc.subjectDegrees of Freedomen
dc.subjectLattice Reductionen
dc.subjectAsynchronous Networksen
dc.subjectAsynchronous Communicationsen
dc.subjectMatched Filteren
dc.subjectMaximum Likelihooden
dc.subjectLLLen
dc.subjectDILLLen
dc.subjectX channelen
dc.subjectAdaptive Decodingen
dc.subjectClosest Point Searchen
dc.subject.programElectrical and Computer Engineeringen
dc.titleApplications of Lattices over Wireless Channelsen
dc.typeDoctoral Thesisen
uws-etd.degreeDoctor of Philosophyen
uws-etd.degree.departmentElectrical and Computer Engineeringen
uws.peerReviewStatusUnrevieweden
uws.scholarLevelGraduateen
uws.typeOfResourceTexten

Files

Original bundle

Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
Najafi_Hossein.pdf
Size:
983.97 KB
Format:
Adobe Portable Document Format

License bundle

Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
250 B
Format:
Item-specific license agreed upon to submission
Description: