MOBILE RADIOS FOR THE MOBILE SATELLITE SERVICE

TO DEVELOP MOBILE RADIO TO TRANSMIT VOICE AND DATA WITHIN A 5 KHZ CHANNEL REQUIRES THE USE OF BANDWIDTH-EFFICIENT MODULATION TO CONSERVE SIGNAL BANDWIDTH, ERROR-CORRECTION CODING TO ENHANCE ITS POWER EFFICIENCY, AND DIGITAL PROCESSING SUITABLE FOR FUTURE VLSI IMPLEMENTATION TO ACHIEVE LOW-COST DEVELOPMENT. TRADE-OFFS STUDIES IN MODULATION AND CODING TECHNIQUES WILL BE PERFORMED IN THE PHASE I EFFORT TO MINIMIZE THE TRANSMIT POWER REQUIRED TO MAINTAIN AN ACCEPTABLE OVERALL SYSTEM BIT-ERROR RATE (BER). THESE STUDIES WILL INCLUDE CIRCUIT ERROR SOURCES IN PRACTICAL RADIO DESIGN, SUCH AS CIRCUIT NONLINEARITIES, FILTER DISTORTIONS, AND INTERFERING SIGNALS GENERATED INSIDEOR OUTSIDE THE RADIO. A PARAMETRIC STUDY OF THE RADIO USING DIFFERENT COMBINATIONSOF CODING AND MODULATION SCHEMES WILL BE PERFORMED USING COMPUTER SIMULATIONS TO ACCURATELY DETERMINE THE OVERALL SYSTEM BER PERFORMANCE. INTEGRATED MODULATION CODING SYSTEMCAN BE DEVELOPED USING RATE R = M/N CONVOLUTIONAL CODES ALONG WITH M = 2N-ARY MODULATION TO PROVIDE OPTIMAL BER PERFORMANCE. CANDIDATE SYSTEM INCLUDES R = 1/2 CODE WITH QPSK MODULATION AND RATE R = 1/3 CODE WITH 8-PSK MODULATION.SOFT-DECISION DECODING CAN BE USED TO MAXIMIZE CODING GAIN. SSB MODULATION IS EFFICIENT IN PROVIDING VOICE TRANSMISSIONS.