An anti-multipath CDMA system using complementary code sequences with dummy chips

Code division multiple access (CDMA) systems may be designed to be tolerant of alternate current (AC) components of the received noise if complementary code sequences are used. To eliminate the direct current (DC) component included in the interference noise, modified complementary code sequences with dummy chips are explored. The dummy chips of a desired signal are removed by a masking circuit at the receiver. As a consequence, the modified code sequences asynchronously arrived may be viewed as almost AC component for the receiver, resulting in giving little disturbance to the demodulation. Some candidate sequences giving little DC disturbance when they arrive via multipath, or they are used as other user's sequences, are explored by computer simulation. An interference free system operating at multipath channels may be designed if proper code sequences are used, also the system capacity will be considerably increased.