Digital Signal Design for Meteor-Scatter Communications
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
This thesis is concerned with the efficient design of digital modulation and error-control schemes for point-to-point meteor-scatter communication systems. The methods introduced exploit the unique properties of the meteor-scatter channel. A channel model is derived based on the work of other researchers. The channel model includes expressions for meteor arrival rate, burst duration, and received power. Meteor arrivals are modeled as a Poisson random process and the properties of the Poisson process are used extensively. Channel noise is modeled as additive, white, and Gaussian distributed. The multipath structure of the channel is evaluated only to the extent that it affects channel bandwidth. New expressions for long run average bit rate and mean message waiting time. Bounds on the improvement in mean waiting time over the fixed-rate modem are derived. M-ary modulation methods are investigated to find the optimal modulation for the fixed-rate modem and adaptive-symbol-rate modem. It is shown that the adaptive-symbol-rate modem is not optimal on a bandwidth-limited channel. An alternative scheme, called adaptive quadrature amplitude modulation QAM is evaluated and shown to outperform adaptive-symbol-rate modulation on a bandwidth-limited channel.
- Radiofrequency Wave Propagation