Can imperfect delayed CSIT be as useful as perfect delayed CSIT? DoF analysis and constructions for the BC,”

"... It is my pleasure to express my thanks to all the people who contributed in many ways to the success of this dissertat ion. Many thanks must begin with my advisers, Prof. Petros Elia and Prof. Raymond Knopp. This dissertat ion would not have been possible without their guidance, support and encourag ..."

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It is my pleasure to express my thanks to all the people who contributed in many ways to the success of this dissertat ion. Many thanks must begin with my advisers, Prof. Petros Elia and Prof. Raymond Knopp. This dissertat ion would not have been possible without their guidance, support and encouragement. My first and sincere apprecia-t ion goes to Prof. Pet ros Elia. I appreciate his cont inuing interact ions and helps, in all stages of this thesis, which made my Ph.D. experience produc-t ive and st imulat ing. I remember that he used to work on a paper with me overnight in the offi ce, and that he used to discuss on a paper with me in a McDonald’s store during the weekend. His at t itude and enthusiasm to re-search inspired me to become a bet ter researcher. I am also thankful to Prof. Raymond Knopp, whose advices and supports were invaluable to me. In addit ion, I would like to thank Prof. Sheng Yang and Prof. Syed Ali Jafar for the insight ful technical discussions on my topic, as well as my the-sis jury members Prof. Daniela Tuninet t i, Prof. Mari Kobayashi, Prof. Dirk

Space-Time Encoded MISO Broadcast Channel with Outdated CSIT: An Error Rate and Diversity Performance Analysis

by Bruno Clerckx , David Gesbert

"... Abstract-Studies of the MISO Broadcast Channel (BC) with delayed Channel State Information at the Transmitter (CSIT) have so far focused on the sum-rate and Degrees-of-Freedom (DoF) region analysis. In this paper, we investigate for the first time the error rate performance at finite SNR and the di ..."

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Abstract-Studies of the MISO Broadcast Channel (BC) with delayed Channel State Information at the Transmitter (CSIT) have so far focused on the sum-rate and Degrees-of-Freedom (DoF) region analysis. In this paper, we investigate for the first time the error rate performance at finite SNR and the diversitymultiplexing tradeoff (DMT) at infinite SNR of a space-time encoded transmission over a two-user MISO BC with delayed CSIT. We consider the so-called MAT protocol obtained by Maddah-Ali and Tse, which was shown to provide 33% DoF enhancement over TDMA. While the asymptotic DMT analysis shows that MAT is always preferable to TDMA, the Pairwise Error Probability analysis at finite SNR shows that MAT is in fact not always a better alternative to TDMA. Benefits can be obtained over TDMA only at very high rate or once concatenated with a full-rate full-diversity space-time code. The analysis is also extended to spatially correlated channels and the influence of transmit correlation matrices and user pairing strategies on the performance are discussed. Relying on statistical CSIT, signal constellations are further optimized to improve the error rate performance of MAT and make it insensitive to user orthogonality. Finally, other transmission strategies relying on delayed CSIT are discussed.

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On the Two-User MISO Broadcast Channel With Alternating CSIT: A Topological Perspective

by Jinyuan Chen, Petros Elia, Syed Ali Jafar , 2014

"... Abstract — In many wireless networks, link strengths are affected by many topological factors, such as different distances, shadowing, and intercell interference, thus resulting in some links being generally stronger than other links. From an information theoretic point of view, accounting for such ..."

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Abstract — In many wireless networks, link strengths are affected by many topological factors, such as different distances, shadowing, and intercell interference, thus resulting in some links being generally stronger than other links. From an information theoretic point of view, accounting for such topological aspects is still a novel approach, that has been recently fueled by strong indications that such aspects can crucially affect transceiver and feedback design, as well as the overall performance. This paper here takes a step in exploring this interplay between topology, feedback, and performance. This is done for the two user broadcast channel with random fading, in the presence of a simple two-state topological setting of statistically strong versus weaker links, and in the presence of a practical ternary feedback setting of alternating channel state information at the transmitter [alternating channel state information at the transmitter (CSIT)] where for each channel realization, this CSIT can be perfect, delayed, or not available. In this setting, the work derives generalized degrees-of-freedom bounds and exact expressions, that capture performance as a function of feedback statistics and topology statistics. The results are based on novel topological signal management schemes that account for topology in order to fully utilize feedback. This is achieved for different classes of feedback mechanisms of practical importance, from which we identify specific feedback mechanisms that are best suited for different topologies. This approach offers further insight on how to split the effort—of channel learning and feeding back CSIT—for the strong versus for the weaker link. Further intuition is provided on the possible gains from topological spatio-temporal diversity, where topology changes in time and across users. Index Terms — Broadcast channel, channel with state, feedback, network topology, channel state information at the transmitter (CSIT), degrees-of-freedom (DoF). I.