HIGH DATA RATE SATELLITE COMMUNICATIONS

QUALCOMM, INC. PROPOSES TO STUDY THE DEVELOPMENT OF A DIGITAL UHF SATCOM MODEM CAPABLE OF TRANSMITTING THREE TIMES THE INFORMATION RATE IN A GIVEN CHANNEL BANDWIDTH CURRENTLY TRANSMITTED BY CONVENTIONAL MEANS. OVER FLTSAR 25 KHZ CHANNELS TYPICAL CURRENT INFORMATION RATES ARE NOT GREATER THAN 16 KB/S, WHILE THE PROPOSED SYSTEM WOULD TRANSMIT OVER THE SAME BANDWIDTH AT UP TO 48 KB/S, WITH NO GREATER INCREASE IN TRANSMITTED POWER (OR LINK BUDGET) THAN THAT REQUIRED FOR THE THREE-FOLD INCREASE IN DATA RATE. THE TECHNIQUE TO BE USED IS TRELLIS CODING WITH 8PSK AND 16PSK MODULATION. A UNIQUE CODING TECHNIQUE WHICH REQUIRES ONLY MODIFICATION OF EXISTING CONVOLUTIONAL CODERS-VITERBI DECODERS ACHIEVES THIS INCREASED EFFICIENCY.