ADAPTIVE TRELLIS-CODED MODULATION FOR BAND-LIMITED METEOR BURST CHANNELS

This paper investigates the throughput performance of three adaptive information rate techniques on the bandlimited meteor burst channel. Closed-form expressions for throughput are derived based on the channel model commonly used in the literature. Throughput performance is compared to the conventional fixed information rate modem and upper bounds on throughput improvement over the fixed-rate modem are derived. It is shown that an adaptive technique that uses trellis coded modulation (TCM) with three PSK signal sets can increase throughput over the conventional fixed-rate modem by more than a factor of 3. Data from the USAF High Latitude Meteor-Scatter Test Bed confirm the superiority of the adaptive TCM technique. A practical implementation is suggested that uses a sigle rate 1/2 convolutional code for all three PSK signal sets. The use of this single code, versus the three best Ungerboeck codes, results in a throughput loss of less than 2%. An expression for the theoretical information capacity of the bandlimited meteor burst channel is derived based on Shannon's well-known capacity formula. This new capacity expression serves as a point of reference against which future adaptive schemes can be judged.