In meteor-burst communications systems, the channel is bursty with a continuously
fluctuating signal-to-noise ratio. Adaptive data rate systems attempt to use
the channel more optimally by varying the bit rate. Current adaptive rate systems
use a method of closed-loop decision-feedback to control the transmitted data rate.
It is proposed that an open-loop adaptive data rate system without a decision feedback
path may be possible using implicit channel information carried in the first
few milliseconds of the link establishment probe signal. The system would have
primary application in low-cost half-duplex telemetry systems. It is shown that the
key elements in such a system would be channel predictors. The development of
these predictors is the focus of this research. Two novel methods of predicting
channel parameters are developed.
The first utilises early fast Doppler information that precedes many long duration,
large signal-to-noise-ratio overdense trails. The presence of early fast Doppler at
the trail commencement is used as a toggle to operate at a higher data rate. Factors
influencing the use of early fast Doppler for this purpose are also presented.
The second method uses artificial neural networks. Data measured during trail
formation is processed and presented to the neural networks for prediction of trail
parameters. Several successful neural networks are presented which predict trail
type, underdense or overdense, and peak trail amplitude from the first 50ms of the
trail's lifetime. This method allows better estimation of the developing trail. This
fact can be used to implement a multi-rate open-loop adaptive data rate system. / Thesis (Ph.D.)-University of Natal, Durban, 1994.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/6886 |
| Date | January 1994 |
| Creators | Fraser, David Douglas. |
| Contributors | Broadhurst, Anthony D. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0039 seconds