Algebraic Space Time Coding in a CDMA System over a Rayleigh fading Channel

The originality of this paper consists of combining code division multiple access (CDMA) technique with Multi Input Multi Output (MIMO) antenna system. The main objective of our contribution is to improve the capacity of the existing DS-CDMA systems by supporting an increased number of users and to achieve good performance in terms of bit error rate. This new communication scheme combining the two techniques benefit from perfect codes by employing a spectrally efficient algebraic space time coding (ASTC) and spreading spectrum by using CDMA technique equipped with multi user detector (MUD) that is near far resistant. In our system each user is distinguished by its spreading code signature and its unique channel impulse response (CIR) transfer function. The MIMO-CDMA system, associated by multi user detector, improves the spectral efficiency of wireless system, combat channel fading and reduce narrowband interference. The resulting is a multi-user CDMA- ASTC solution promising high speed communication for 4G cellular wireless networks. Our study and numerical results show the utility of this new wireless communication; a significant BER versus signal to noise ratio (SNR) was achieved thus Multiple access interference (MAI) is suppressed and so supporting a large number of users.