Calculate interference digital microwave links

A method is developed for determining interference into digital radio systems from other digital radio systems. Interference from FDM-FM (frequency division multiplexing/frequency modulation) systems can also be calculated. Once the algorithm for the receiver is found, all that is required to be known of the transmitter is its spectrum characteristics, i.e., amplitude versus frequency characteristics. Essentially, the digital receiver is defined as being a Butterworth filter with a cut-off characteristic related to the symbol rate. Initially it is important to be able to calculate the co-channel C/I (carrier/interference) relationship. This is normally done by using mathematical formulae and complementary error functions. The authors give values for the C/N (carrier/noise ratio) for various modulation schemes and then show how to translate that to a C/I value to be added to the faded signal level. The C/N´s for various modulation schemes are given