Inmarsat Limited

International Mobile Satellite Organization

France Telecom Sa

Francois-Arnaud Remael

Howard Ray Feldman

Nobuyuki Kawai

Joan Obradors

Richard Douglas Lane Smith

An interface between a data terminal and a digital communications link implements protocols and frame formats designed to reduce delays in a data communication with a remote terminal. The interface overcomes the need to send or receive an HDLC SABME or UA control signal for establishing an asynchronous balanced mode, and allows data to be sent over the digital communications link as soon as the communication parameters are established. In a non-ARQ (error correction) mode, the interface sends control signals and data over the communications link in frames subdivided into many small subframes of fixed length, each subframe having a length code indicating an amount of valid information but without CRC, address or control information. The interface, when arranged for connection to the data terminal through a telephone network, encodes call progress signals from the telephone network for sending over the digital communications link. The interface encodes and decodes interrupt signals for sending between the data terminal and the digital communications link when an interrupt signal is detected.

Communication method and apparatus

A communications link for data communication via satellite includes interface apparatus comprising a satellite link interface for connection to a satellite link and a PSTN interface for connection to a PSTN. The interface apparatus supports different data compression modes in the communication link. Mode A allows data compression over the PSTN but not over the satellite link. Mode B allows data compression over the PSTN and over the satellite link, but enables decompression and recompression of data flowing in each direction through the interface apparatus. Mode C allows compressed data to pass transparently between the PSTN and the satellite link, while the interface apparatus performs error correction on the satellite link and on the PSTN.

Communication method and apparatus using data compression

Growing community of inventors

Pleumeur Bodou, France

Francois-Arnaud Remael