Predicting the Compatibility of High Frequency Sky-Wave Communication Systems

A technique for computing the electromagnetic compatibility of HF sky-wave communication systems is described. The circuitreliability methodology,-normally used to estimate expected circuit performance in the absence of interference, has been extended to estimate the expected performance in the presence of sky-wave interference. A measure of the compatibility during co-channel operation, called circuit compatibility, is introduced. Circuit compatibility is the ratio of the estimated circuit reliability considering the operation of an interfering transmitter (without considering other potential interferers) to estimated circuit reliability under interference-free conditions. The techniques involved to estimate circuit compatibility include the determination of 1) the probability of simultaneous transmission by the desired and interfering transmitters, 2) the joint probability that the standard MUF´s on the desired and interfering paths are above their operating frequencies, and 3) the joint probability that the signal-power-to-noise density ratio is above the receiver´s required signal-power-to-noise density ratio for the desired grade of service and that the signal-to-interference is above the signal-to-interference threshold for the desired emission against the interfering emission. The last two probabilities are represented by the bivariate normal distribution. The model is generalized to include problems other than sky-wave communications for frequencies at HF and above.