Congestion of the radio-frequency spectrum has necessitated the sharing of frequencies between a number of services, involving both terrestrial and space systems. The possibilities of interference arise therefore between terrestrial and satellite systems and between systems of the same type. Thus, the designer needs to take account of potential interference when designing systems. Clearly, due account needs to be taken of existing, planned and future systems when allowing for interference in the system design. In order to estimate mutual interference between different radio systems it is necessary to know the statistical distribution of the difference in decibels of the level of the interfering signal and the level of the wanted signal. For most radio systems, except transhorizon radio-relay links, the wanted signal level may be considered to be approximately constant, although multipath fading of the wanted signal can cause complications. Therefore, it is essential for the engineer to have statistics describing the occurrence of the interference, the variability of which is due to the existence of several different propagation mechanisms, each of which is itself subject to variations arising from the nature of the tropospheric propagation medium. Changes in the medium are a function of climate, and it is necessary to take into consideration both the effects due to the propagation characteristics in clear air and phenomena which may arise owing to the presence of hydrometeors in the propagation path.

Inspec keywords: tropospheric electromagnetic wave propagation; satellite communication; interference suppression; statistical distributions; radiofrequency interference; radio links; fading; spread spectrum communication

Other keywords: radio systems; terrestrial systems; satellite communications systems; interference; radio-relay links; statistical distribution; multipath fading; radiofrequency spectrum; tropospheric propagation medium; hydrometeors; frequency sharing

Subjects: Satellite communication systems