A New Mix-Carrier Method Based on Fractional Fourier Transform in Asynchronous CDMA System

In asynchronous communication system, such as MANET or uplink of CDMA system, MAI (Multiple Access Interference) is a problem that cannot be ignored. To suppress the effect of MAI, this paper introduces a new mix-carrier method in asynchronous CDMA system. The proposed method uses both cosine and Chirp as carriers, by using frequency domain filter and Fractional Fourier domain filter at the receiver to suppress MAI. Simulation results indicate that the proposed method reduces MAI effectively, and with the increase of spreading sequence length, user number and the maximum time delay between different users, the BER improvement is more significant.