This Handbook describes the system and service requirements for digital sound broadcasting (DSB) to vehicular, portable and fixed receivers, the related propagation factors, the techniques employed in the digital sound broadcasting systems; and considers relevant planning parameters and sharing conditions. The Handbook also makes reference to common system characteristics of the mixed and hybrid service delivery concepts. The mixed satellite/terrestrial service concept is based on the use of the same frequency band by both satellite and terrestrial broadcasting services to the same receiver. The hybrid delivery concept is based on the use of low power terrestrial “gap-fillers” to improve the satellite coverage.