A Comparison of Calculated and Observed Performance of Digital Radio in the Presence of Interference

A statistical model of multipath fading and detailed radio characterization measurements made in the laboratory provide the basis for a calculation of the time, during a heavy fading month, that a given digital radio system will be unavailable because of high bit error rates induced by multipath fading, thermal noise, and interference. The author shows that a simple algebraic expression for outage agrees with the detailed calculation over a wide range of possible interference levels. The simple expression also agrees with field observations. Performance is shown to depend on five parameters: three of these (dispersive fade margin, flat fade margin, and carrier-to-noise ratio at critical BER) are characteristic of the radio system as installed on a given path, one describes the interference environment, and one specifies the incidence of fading on the path.