INVESTIGATION OF A NOVEL DIRECT SEQUENCE, CODE DIVISION MULTIPLE ACCESS RECEIVER WHT NEAR/FAR IMMUNITY

CONVENTIONAL DIRECT SEQUENCE, CODE DIVISION MULTIPLE ACCESS (CDMA) RECEIVERS HAVE LIMITED CAPABILITY FOR PREVENTING MUTUAL INTERFERENCE IN THE RECEPTION AND DEMODULATION OF THE CDMA SIGNALS. THE AMOUNT OF REJECTION OF INTERFERING CDMA SIGNALS IS APPROXIMATELY EQUAL TO THE BANDWIDTH SPREADING RATIO EMPLOYED IN THE CDMA NETWORK. THIS PERFORMANCE LIMITATION ARISES FROM THE FACT THAT THE RECEIVER PROCESSING IS BASICALLY ONLY CORRELATION OF THE RECEIVER INPUT WITH THE SPREAD SPECTRUM CODE OF THE DESIRED SIGNAL. WHEN RECEIVED INTERFERENCE-TO-SIGNAL AMPLITUDE RATIOS EXCEED THIS REJECTION AMOUNT (THE NEAR/FAR PROBLEM), ACCURATE DEMODULATION OF THE WEAKER SIGNALS THEN BECOMES IMPOSSIBLE. THE PERFORMANCE OF A NEW CDMA RECEIVER STRUCTURE WHICH PROVIDES MUCH MORE REJECTION OF THE INTERFERING CDMA SIGNALS FOR A GIVEN BANDWIDTH SPREADING RATIO WILL BE INVESTIGATED. THIS RECEIVER'S SELECTIVITY IS ENHANCED BY USING THE KNOWN SPREAD SPECTRUM CODES OF THE INTERFERING CDMA SIGNALS TO GAIN ADDITIONAL SUPPRESSION WELL BEYOND THAT ACHIEVABLE BY USING ONLY THE KNOWN SPREAD SPECTRUM CODE OF THE DESIRED SIGNAL. THE NEW RECEIVER STRUCTURE APPLIES ITS ADDITIONAL PROTECTION TO EACH OF THE CDMA SIGNALS TO BE RECEIVED USING A HARDWARE-EFFICIENT EMBODIMENT.