Importance

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Abstract

In a satellite communications system, a unique word is transmitted from a central station at frame intervals to the satellite and broadcast to terminal stations. Blocks of data from the central station are composed into packets which are exclusively encrypted, and asynchronously transmitted to the satellite by giving priority to the unique word by interrupting the transmission of packets. A copy of data signals from the central-station data terminals is stored and retransmitted to a terminal station in response to a repeat request signal received therefrom. In each terminal station, the unique word is detected to generate a timing signal in response to which the encrypted packet is deciphered. The deciphered packets are decomposed into blocks of data, and sent to a destination data terminal. If there is an error in the decomposed packets, a repeat request signal is transmitted from the terminal station through a terrestrial link to the central station to cause retransmission of a copy of the stored version of the disrupted packet.

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First Claim