AN ADAPTIVE CODING SCHEME FOR EFFECTIVE BANDWIDTH AND POWER UTILIZATION OVER NOISY COMMUNICATION CHANNELS

Abstract

Codes for communication channels are in most
cases chosen on the basis of the signal to noise
ratio expected on a given transmission channel.
The worst possible noise condition is normally
assumed in the choice of appropriate codes such
that a specified· minimum error shall result during
transmission on the channel. Hpwever, as the noise
conditions on communication channels vary from
time to time, the use of a particular code that meets
the specified error criteria under the assumption of
worst noise condition may not result in the
optimum utilization of the channel. One can exploit
the variations of the noise level on the channel to
increase the throughput ori a fixed bandwidth
channel without increasing the transmitter power
by the use a coding scheme that adapts itself to the
noise conditions on the channel.
An adaptive coding scheme that utilizes the
different merits of more than one frxed rate codes
and the noise level variations on a communication
channel to achieve an increased throughput has
been implemented in this work. An adaptive coding
scheme using three fixed-rate BCH codes was
developed and implemented on a computer. The
results obtained in transmitting a given text over a
simulated channel indicate a'I improved
performance in terms of download time and coding
gain. The use of the adaptive coding scheme results
in a saving of 28% in download time and a coding
gain of 2.61 dB when compared to the performance
of a given reference code.