POWER & BAND WIDTH EFFICIENT DIGITAL COMMUNICATIONS

EXISTING DIGITAL RADIO SYSTEMS USE CONTINUOUS PHASE, FREQUENCY MODULATION TECHNIQUES WITH COHERENT DETECTION. THESE SYSTEMS MUST TRADE SPECTRAL EFFICIENCY FOR LOW BIT ERROR RATE AND IN CERTAIN APPLICATIONS SUCH AS SATELLITE AND MOBILE TELEPHONE ARE SUBJECT TO DEGRADATION DUE TO MULTIPATH. WE PROPOSE TO INVESTIGATE THE USE OF TRELLIS CODING OF THE SIGNAL SPACE WITH CP-FM, USING PLL DEMODULATION. THIS INNOVATIVE CODING SCHEME WILL BE APPLIEDFOR BOTH SYMMETRICAL AND ASYMMETRICAL SIGNAL CONSTELLATIONS. WE WILL INVESTIGATE SYSTEM PERFORMANCE IN THE PRESENCE OF FADING, MULTIPATH, DOPPLER INTERFERENCE AND NARROWBAND FILTERING OF THE FM SIGNAL. THESE EFFECTS CAUSE NONLINEAR DISTORTION OF THE MODULATION AND TEND TO CLOSE THE "EYE" OF THE DEMODULATED DATA. SCS HAS PERFORMED INITIAL RESEARCH USING A NONLINEAR ADAPTIVE EQUALIZER WHICH OPENS THE "EYE". FINALLY, WE WILL SELECT, THE OPTIMUM MODULATION SCHEME FOR A GIVEN CODE RATE. A SUCCESSFUL EFFORT WILL RESULT IN FAR MORE EFFICIENT COMMUNICATIONS SYSTEMS FOR THE SPACE STATION. THESE COMMUNICATION SYSTEMS WILL REQUIRE LESS POWER FOR THE SAME BER; REDUCED WEIGHT; HIGHER RELIABILITY; IMPROVED SPECTRAL EFFICIENCY TO REDUCE COSITE AND ADJACENT CHANNEL INTERFERENCE; BETTER MULTIPATH PERFORMANCE; AND LOWER COST.