Demand-assigned service for the Intelsat global network

Communications satellites have been in commercial operation for more than five years. With the growth of traffic requirements, particularly those of the developing nations, the early methods used in the Intelsat network for multiple access have had to be updated. The full potential of satellite communications can be realized by using the satellite to provide connections between any two users on demand. This article traces the development of the multiple-access techniques employed with Intelsat from the two access methods associated with Early Bird to the demand-assignment technique planned for Intelsat IV. This latter method, SPADE, is to be the first operational demand-assignment multiple-access system and is scheduled for use in 1971. Details of the SPADE system and its use for other applications are reviewed.