ACT-BASED SIGNAL PROCESSING FOR NEAR-FAR RESISTANT DIRECT-SEQUENCE SPREAD SPECTRUM

DIRECT-SEQUENCE SPREAD-SPECTRUM MULTIPLE-ACCESS (DS/SSMA) IS THE TECHNOLOGY OF CHOICE IN A WIDE VARIETY OF MILITARY RADIO NETWORKS WHERE MULTIPLE-ACCESS CAPABILITIES, ANTI-JAMMING, LOW PROBABILITY OF INTERCEPT, AND DYNAMIC TOPOLOGIES ARE IMPORTANT. THE PRINCIPAL SHORTCOMING OF OPERATIONAL RADIO NETWORKS USING DS/SSMA COMMUNICATION SYSTEMS IS THE NEAR-FAR PROBLEM, WHICH REFERS TO THE (POSSIBLY SEVERE) PERFORMANCE DEGRADATION CAUSED BY THE DISSIMILARITY OF THE RECEIVED POWERS OF A SET OF USERS WHO TRANSMIT SIMULTANEOUSLY THROUGH THE SAME CHANNEL. THE EMERGING DISCIPLINE OF MULTIUSER DETECTION HAS OPENED THE THEORETICAL POSSIBILITY OF OBTAINING DEMODULATORS THAT ARE IMMUNE TO THE NEAR-FAR PROBLEM. THIS PRESENTS A VERY SIGNIFICANT WINDOW OF OPPORTUNITY FOR THE DEVELOPMENT OF THE NEXT GENERATION OF DS/SSMA DEMODULATORS. THESE MULTIUSER DEMODULATORS REQUIRE THE IMPLEMENTATION OF WIDEBAND PROGRAMMABLE MATCHED FILTERS WITH HIGH DATA RATES AND LARGETIME-BANDWIDTH PRODUCTS, AND WITH VERY SHORT PERIODS BETWEEN READJUSTMENT OF TAPS. ACOUSTIC CHARGE TRANSPORT (ACT) TECHNOLOGY CONSTITUTES THE MOST PROMISING TECHNOLOGY WITH WHICH TO IMPLEMENT SUCH STRUCTURES, AND THEREBY TO REALIZE THESE GAINS IN PRACTICE. THUS, IT IS THE OVERALL OBJECTIVE OF THE PROPOSED PROJECT TO DEVELOP ACT-BASED SIGNAL PROCESSING ARCHITECTURES FOR NEAR-FAR-RESISTANT DEMODULATION OF DS/SSMA SIGNALS. THIS GENERAL OBJECTIVE CAN BE BROKEN DOWN INTO SEVERAL INTERMEDIATE AND SPECIFIC OBJECTIVES FOR PHASE I, INCLUDING THE DERIVATION OF IMPLEMENTABLE FORMS OF NEAR-FAR RESISTANCE ALGORITHMS; THE DEVELOPMENT OF ACT SIGNAL-MICROPROCESSOR-BASED SIGNAL PROCESSING ARCHITECTURES TO IMPLEMENT THESE ALGORITHMS; THE ASSESSMENT OF THE IMPROVEMENT IN BIT-ERROR RATES THAT CAN BE ACHIEVED BY THESE NEW ARCHITECTURES; AND THE ASSESSMENT OF THE RANGES OF FORMAT PARAMETERS FOR WHICH THESE ARCHITECTURES ARE PRACTICAL. THE RESULTS OF THIS PHASE I EFFORT WILL LEAD DIRECTLY TO A PHASE II EFFORT IN WHICH THE MOST PROMISING NEAR-FAR-RESISTANT SIGNAL PROCESSING ARCHITECTURES IDENTIFIED IN PHASE I WILL BE DEVELOPED