DS SSMA WITH SOME IC REALIZATIONS

A code-division multiple-access (CDMA) system is not only useful in military communications, but it also has varied commercial applications. A direct-sequence spread-spectrum multiple-access system was examined, realized (hardware), and tested. Essentially, two transmitters were built, one with voice capability, while the other transmitted only binary data. Gold codes were used for the spreading sequence. The PN synchronization employed a serial search technique for acquisition, and a tau-dither loop for tracking. A squaring loop and a differential encoding scheme (for carrier phase ambiguity) was employed in the demodulation process, which was followed by conversion to a voice output when desired. The system was found to perform quite well under both single and multiple-access conditions. As a demonstration of the feasibility of implementing the system on chips, a few small blocks were put on IC’s (using CMOS technology). These performed as expected, and clearly demonstrated both the feasibility and attractive of a VLSI implementation. © 1990 IEEE