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https://hdl.handle.net/2142/21085
Description
Title
Adaptive methods for meteor burst communications
Author(s)
Sandberg, Stuart Daniel
Issue Date
1990
Doctoral Committee Chair(s)
Pursley, Michael B.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Computer Science
Language
eng
Abstract
We investigate various methods for making efficient use of the time-varying power received by radio reflection from meteor trails, including applications of variable-rate coding and variable-rate transmission. For variable-rate coding, the code rate is changed periodically during the life of the trail in an attempt to match the rate to the instantaneous signal power. For a system that employs packet transmissions, we develop an algorithm that determines the number of codewords and the rate for each codeword that maximize the probability of successful decoding for the packet. The optimal packet configuration is a function of the length of the message and the underdense trail decay constant. It is shown that the signal power required to obtain a given probability of success is significantly smaller for optimal variable-rate coding than for fixed-rate coding.
We also consider the incorporation of variable-rate coding in automatic-repeat-request (ARQ) protocols. A variation of type-I hybrid ARQ called variable-rate type-I hybrid ARQ is introduced. For one implementation, measurements of the trail parameters are used to select the code rate, while, for another, the selection is based on previous decoding outcomes. The throughput for each implementation is compared with the throughput for optimal variable-rate type-I hybrid ARQ. It is shown that each implementation gives significantly larger throughput than fixed-rate type-I hybrid ARQ and ARQ without forward-error-correction. For type-II hybrid ARQ, code rate variation is inherent in the coding scheme. On the first transmission, the code is effectively of high rate, but if an additional transmission is required, additional redundant symbols are sent, and the code rate is effectively lower for each subsequent transmission. The throughput for type-II hybrid ARQ is compared with the throughput for variable-rate type-I hybrid ARQ. For variable-rate transmission, the pulse length is changed periodically, based on measurements of the signal power at the destination. We have determined the maximum reliable throughput that can be obtained for variable-rate transmission, when the source and destination have perfect knowledge of the signal power and can choose from an infinite number of pulse lengths for each pulse.
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