Shaw, Martyn Joseph (1989) Modem design employing real-time channel evaluation. PhD thesis, University of Warwick.

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Abstract

The thesis deals with the area of digital communications over the high frequency (HF) radio channel. It is divided into three main areas of research, the first two dealing with new methods of real time channel evaluation (RTCE) and the third with multi-frequency shift keying (MFSK) modulator and demodulators for use on HF circuits. The HF channel is simulated for use in the investigations.

The first of the RTCE methods employs the technique of counting the zerocrossings of the received signal. The method is investigated mathematically and by simulation. A hybrid error correction/repeat request system is simulated which employs the RTCE method. This is tested over the simulated radio channel and is shown to give a gain in throughput compared to conventional systems.

The second RTCE technique is an extension of the first, whereby higher order crossings (HOX) are counted. These HOX are the zerocrossings of a new series generated by differentiating or integrating the original signal. They are also investigated by mathematical analysis and by simulation.

The third area of work is concerned with MFSK signalling. The method is investigated with respect to the various parameters of the basic format and conclusions are reached as to the best parameters to be used in a number of situation. A demodulation scheme is devised whereby demodulation, synchronisation and channel evaluation are combined into one set of operations. The method is simulated by computer and implemented on a digital signal processor (DSP). Results are presented from the method working over both a simulated HF channel and in the practical situation.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Library of Congress Subject Headings (LCSH):	Digital communications, Data transmission systems, Modems, Shortwave radio, Phase shift keying, Radio frequency modulation, Digital modulation
Official Date:	April 1989
Dates:	Date Event April 1989 Submitted
Institution:	University of Warwick
Theses Department:	Department of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Honary, Bahram
Sponsors:	Science and Engineering Research Council (Great Britain)
Format of File:	pdf
Extent:	xv, 222 leaves : illustrations, charts
Language:	eng

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