MULTI-RATE TRELLIS-CODED MODULATION FOR MULTIPATH FADING CHANNELS

MULTIPATH FADING ON RADIO CHANNELS SERIOUSLY HAMPERS HIGH SPEED DIGITAL COMMUNICATIONS. TIME-VARYING AMPLITUDE AND PHASE FORCE CONVENTIONAL SYSTEMS TO OPERATE AT DATA RATES FAR BELOW CHANNEL CAPACITY. DIVERSITY AND ERROR-CORRECTION CODING TECHNIQUES HAVE NOT SOLVED THE PROBLEM COMPLETELY ANDHAVE INTRODUCED UNDESIRABLE SIDE EFFECTS IN THE PROCESS. WEPROPOSE TO INVESTIGATE A NEW APPROACH THAT ADAPTS THE SYSTEM DATA RATE TO THE TIME-VARYING SIGNAL-TO-NOISE RATIO AT THE RADIO RECEIVER. OUR RESEARCH OBJECTIVES ARE TO INVESTIGATE THE FEASIBILITY OF RATE CHANGING ALGORITHMS AND ADAPTIVE SYNCHRONIZATION; DEVELOP A MEASURE OF WAITING TIME PERFORMANCE; AND DETERMINE THE EFFECTS OF QUEUING, A NOISY FEEDBACK CHANNEL, RATE CHANGING OVERHEAD, AND PROPAGATION DELAY. OUR APPROACH EMPLOYS TRELLIS CODED MODULATION IN AN ADAPTIVE SCHEME WHERE THE DATA RATE VARIES BY CHANGING THE NUMBER OF BITS PER CHANNEL SYMBOL. PRELIMINARY RESEARCH INDICATES THAT THIS TECHNIQUE WILL PROVIDE CODING GAINS ON THE RAYLEIGH FADING CHANNEL OF 37 DB(@ BIT-ERROR-RATE = 10(-5) WITHOUT BANDWIDTH EXPANSION AND WITHOUT INTERLEAVING. POTENTIAL APPLICATIONS INCLUDE CELLULAR RADIO AND LINE-OF-SIGHT MICROWAVE RADIO. IF SUCCESSFUL, THIS RESEARCH WILL CONTRIBUTE TO THE UNITED STATES' TECHNICAL COMPETITIVENESS, ESPECIALLY IN DIGITAL MICROWAVE RADIO WHERE OUR PRINCIPAL COMPETITOR IS JAPAN.