Analysis of a direct-sequence CDMA mobile radio system with reduced set of code sequences

A code-division multiple-access scheme that requires a reduced set of code sequences, in which the size of the set is much less than the number of users in the system, is proposed for mobile radio communications. A direct-sequence spread-spectrum signaling is adopted to exploit the property of high time resolution and combat fading effects through multipath diversity reception. Theoretical performance of the proposed system is analyzed by deriving the collision-free path distribution and determining the proper size of the set without reducing the effect of multipath diversity. In connection with the proposed system, two combining schemes are investigated to characterize the effects of the primary and secondary user interferences and evaluate the behavior of the error rate when compared to the original CDMA system