SATELLITE-BASED, LAND-MOBILE COMMUNICATIONS

THE STATED POWER AND BANDWIDTH EFFICIENCY REQUIREMENTS DICTATE THE USE OF A PHASE-COHERENT MODULATION FORMAT. RECENTLY, THERE HAS BEEN INTENSIVE RESEARCH INTO A VARIETY OF INTEGRATED CODING/MODULATION SYSTEMS, SUCH AS UNGERBOECK CODES, TRELLIS CODING, AND CONTINUOUS PHASE MODULATION, WHICH OFFER EXCELLENT BER WITH A MINIMUM OF BANDWIDTH FOR THE AWGN CHANNEL. WE PROPOSE TO EXTEND AND COMPARE THESE TECHNIQUES FOR THE FADING MULTIPATH CHANNEL. SPECIFICALLY, WE WILL COMPARE THESE APPROACHES WITH RESPECT TO THE EASE AND ACCURACY OF CARRIER PHASE AND SYMBOL TIMING RECOVERY ANDTHE IMPACT OF THESE ERRORS ON BER PERFORMANCE. THIS COMPARISON WILL BE DONE USING A BLOCK PHASE ESTIMATION APPROACH (FEED FORWARD), RATHER THAN THE COVENTIONAL PHASE-LOCK LOOP APPROACH (FEEDBACK) WHICH PERFORMS POORLY INA FADING ENVIRONMENT. SEVERAL PROMISING CANDIDATE SYSTEMS WILL BE COMPARED BY COMPUTER SIMULATION AND A RECOMMENDATIONMADE. THE BLOCK PHASE ESTIMATION APPROACH WILL BE MADE ADAPTIVE (TO MATCH THE CHANNEL CHARACTERISTICS) AND THE PERFORMANCE GAINS DETERMINED. IF THE GAIN WARRANTS THE INCREASED COMPLEXITY, THE RECOMMENDED INTEGRATED CODING/MODULATION/DETECTION SYSTEM WILL INCORPORATE THIS ADAPTIVE FEATURE. A FUNCTIONAL SYSTEM DESIGN WILL BE PRESENTED THAT WILL SERVE AS A BASIS FOR FURTHER TESTING, DETAILED DESIGN, AND BREADBOARD IMPLEMENTATION IN PHASE 2.