DS-CDMA based on orthogonal chaotic signals and Alamouti scheme
Abbas Salman Hameed · 2018
One of the special features of chaotic signals is its very low cross correlation, which make it enormously used in the multi-access communication systems. Chaotic signals with perfect orthogonality property can clearly reduce the multiple access interference (MAI) when they are used to spread each access. At high data rate, Alamouti Multiple-Input Multiple-Output (MIMO) scheme mitigates the effect of channel on the transmission data and produces an improvement in the spectral efficiency. In this paper, orthogonal chaotic signals and Alamouti MIMO scheme are used to achieve a significant enhancement in the performance of direct sequence code division multiple access (DS-CDMA) system. Simulation results showed that an improvement in terms of BER performance and channel capacity are achieved when the proposed system is used compared with the traditional system that use Walsh-Hadamard code as spreading codes. With 16PSK modulation and 2×2 Alamouti configuration, gains in SNR between (2.5-13) dB is obtained with increasing number of users from 4 to 8 respectively for system based on orthogonal chaotic signals compared with system that used Hadamard. Furthermore, in comparison with the traditional system, the results for proposed system showed higher immunity against MAI.