The present document specifies the minimum performance parameters for terrestrial digital fixed service radio communications equipments operating in the 55 GHz frequency band and is a complete revision of the existing ETS 300 407 [8] specification in the areas of: - introduction of unique system type codes for regulatory reference to the various system types detailed in the present document, refer to new annex C (normative) and related categories of equipment classes of spectral efficiency; - additional systems with higher spectrum efficiency in the new classes 1 to 4; - removal of Analogue services; - digital services restricted to frequency division duple