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Beamforming Algorithms for Information Relaying in Wireless Sensor Networks

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Beamforming Algorithms for Information Relaying in Wireless Sensor Networks
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  ABSTRACT Title of dissertation: BEAMFORMING ALGORITHMS FOR INFORMATIONRELAYING IN DENSE WIRELESS NETWORKSMohamed Abdallah, Doctor of Philosophy, 2006Dissertation directed by: Assistant Professor Haralabos C. PapadopoulosDepartment of Electrical and Computer EngineeringIn this dissertation we develop a class of bandwidth-efficient algorithms forinformation relaying in large-scale wireless ad-hoc networks. The settings we con-sider involve a single source communicating its data to a destination via the aid of low-power low-cost relay nodes. In its simplest two-hop relaying form, data directlybroadcasted to the relays from the source are directly relayed to the destinationthrough a shared fading channel. We assume that the relays employ decode-and-forward or amplify-and-forward preprocessing prior to forwarding their data to thedestination via beamforming. The beamforming weights are formed at the des-tination and fedback to the relays via broadcasting. They are constructed usingknowledge of the relay-destination channel coefficients and an  m -bit description of each source-relay channel state information (CSI).For both relay data preprocessing models, we present methods for optimizingthe  m -bit quantizer employed at each relay for encoding its source-relay channel  quality level, and for choosing the beamforming weights at the destination, so asoptimize the destination uncoded bit error rates (Pr( e )). We also study the effectof the relative source-relay relay-destination distances on the Pr( e ) for both relaypreprocessing models. We use our findings to develop locally-optimized adaptivedata-preprocessing algorithms at the relays. We also develop extensions involvingmulti-hop networks with hierarchal cluster-based relaying. At each hop of these relaynetworks, each of the receiving relays obtains a beamformed version of the data of a distinct subset of the transmitting relays. As our simulations and analysis reveal,making available at each cluster head (CH) an optimized one-bit description of theeffective source-relay CSIs associated with the transmitting relays in its cluster issufficient. Specifically, not making fully available to the CHs, the source-relay CSIs,results in only a minimal loss in the Pr( e ).  BEAMFORMING ALGORITHMS FOR INFORMATION RELAYING INDENSE WIRELESS NETWORKSbyMohamed AbdallahDissertation submitted to the Faculty of the Graduate School of theUniversity of Maryland, College Park in partial fulfillmentof the requirements for the degree of Doctor of Philosophy2006Advisory Committee:Professor Haralabos C. Papadopoulos, ChairProfessor Prakash NarayanProfessor Steven TretterProfessor Amr BazProfessor Min Wu  c   Copyright byMohamed Abdallah2006  ACKNOWLEDGEMENTS First, this great achievement and success is all due to Allah. I thank Allahfor HIS great blessings that I have experienced during this long journey.My deep thanks goes to my advisor Babis Papadopoulos. I am so gratefulfor his endless support and advise. Babis has spared no time in discussing andsuggesting a lot of exciting research ideas. I also would like to thank Babis forevaluating, correcting and organizing this dissertation in order to be understandableand presentable.I also thank my dissertation committee: Prof. Prakash Narayan, Prof. StevenTretter, Prof. Amr Baz and Prof. Min Wu, for their invaluable feedback andaccepting to serve in my committee. Special thanks goes to Prof. Prakash Narayanfor his invaluable comments and discussions that provide a lot of insights to thework presented in this dissertation.I am grateful to my family who were beside me all the time giving me endlesspatience and love. I am especially grateful to my father; he was always encouragingme to the best. I also would like to thank my mom for her continuous support andprayers. Deep thanks goes to my younger brother Ahmed and my dear youngersister Sarah. I love you all so much.Special and deep thanks to my soul mate; my wife Aya. She was alwayssurrounding me with her care and love. I will never forget her nice words to mewhile I am depressed. Also, I would like to thank my children Jannah and Omarii
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