Noise tolerance of diversity reception in frequencyadaptive digital transmission systems
Abstract
This study investigates the influence of inaccurate estimation of the signaltonoise ratio on the mean error probability in a frequencyadaptive digital transmission system employing spacediversity reception. The system operates by combining M spatiallyseparated signals and analyzing the equivalent signaltonoise ratio for each of the N frequencies allocated for communications. The best frequency (in terms of the maximum signaltonoise ratio at the output of the combining device) is sent back to the transmitter over the feedback channel, so that the signal can be emitted at the optimum frequency. The analysis assumes that signal feeding in the diversity branches is statistically homogeneous and mutually independent; additive interferences are approximated by normal white noise. It is found that the mean error probability is a strong function of the accuracy with which the signaltonoise ratio is estimated (sample size n); for n = (5  6)N this probability is the same as that of a hypothetical system in which the average signaltonoise ratio in any of M statistically homogeneous diversity branches is assumed to be known.
 Publication:

USSR Rept Electron Elec Eng JPRS UEE
 Pub Date:
 January 1985
 Bibcode:
 1985RpEEE.......39L
 Keywords:

 Digital Systems;
 Errors;
 Probability Theory;
 Signal To Noise Ratios;
 Adaptive Control;
 Estimates;
 Signal Reception;
 White Noise;
 Communications and Radar