Adaptive beamforming scheme for DS-MIMO-CDMA systems in frequency-selective fading channel.

摘要

CDMA is an advanced digital technology; it is attracting a lot of attention because it increases data rates and channel capacity thereby enhancing the performance of the next generation wireless communication systems. However, the high data rate users may cause large MAI due to their increased transmission power, it may degrade the system's performance. It is very desirable to combine some other techniques with CDMA in order to mitigate the degradation by MAI and other interferences.; In this thesis, a new MIMO Beamformer-Rake CDMA wireless system scheme is proposed. In conventional beamforming systems, digital signal processing algorithms are employed to adaptively update the beamforming weights, so that a single beam radiation pattern of the array can be dynamically and adaptively shaped to track the desired signal and to suppress co-channel interference. In an STC system, each user is producing more than one transmitted signal that appear independent to the smart antenna receivers. Beamforming algorithms, in such cases, should be able to track more than one transmitted signal from the same desired user; thus, the diversity gain is achieved. The proposed system is shown to improve substantially the performance of the conventional system in the multipath Rayleigh frequency selective fading circumstance.