Analytical distribution of linearly modulated cochannel interferers

The closed form expressions of the probability density function (PDF), the cumulative distribution function (CDF) and the characteristic function of the disturbance due to a multilevel cochannel interferer are obtained. The analysis assumes L-level amplitude shift keying (L-ASK) modulated signals, nonreturn to zero (NRZ) pulses, transmission over a distortion-free channel and matched filter reception. The distribution for the multiple cochannel interferers case can then be obtained by means of the characteristic function method. As an application example, the closed-form expression of the error-floor for an L-ASK system in the presence of one cochannel interferer is given. The comparison with respect to the Gaussian approximation is also discussed.