Date of Award

12-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Electrical Engineering

Advisor

Pursley, Michael B

Committee Member

Noneaker , Daniel L

Committee Member

Russell , Harlan B

Abstract

To respond to dynamic channel conditions caused by fading, shadowing, and other time-varying disturbances, orthogonal frequency division multiplexing (OFDM) packet radio systems should adapt transmission parameters on a packet-by-packet basis to maintain or improve performance over the channel. For this to be possible, there are three key ideas that must be addressed: first, how to determine the subchannel conditions; second, which transmission parameters should be adapted; and third, how to adapt those parameters intelligently. In this thesis, we propose a procedure for determining relative subchannel quality without using any traditional channel measurements. Instead, statistics derived solely from subcarrier error counts allow subchannels to be ranked by order of estimated quality; this order can be exploited for adapting transmission parameters. We investigate adaptive subcarrier power allocation, adaptive subcarrier modulation that allows different subcarriers in the same packet to use different modulation formats, and adaptive coding techniques for OFDM in fading channels. Analysis and systems simulation assess the accuracy of the subcarrier ordering as well as the throughput achieved by the proposed adaptive transmission protocol, showing good performance across a wide range of channel conditions.

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