Signal-to-interference ratio statistics for AM broadcast groundwave and skywave signals in the presence of multiple skywave interferers

The development of a statistical description of the signal-to-interference ratio (SIR) for AM broadcast groundwave and skywave signals in the presence of multiple skywave interference signals is presented. The analysis assumes that the interfering signal envelope amplitudes are Rayleigh-distributed random variables with a lognormal distribution used to describe the long-term variations of the sum envelope amplitude. The resulting statistical description is used to evaluate the SIR degradation for a number of interference exclusion formulas under consideration for frequency allocation purposes. The results show that adding four equal interferers, each at a level equal to 50% of a first interferer, degrades the 50% time SIR by a little more than 3 dB