Space-time spreading multilayered CDMA system

As the information theory has suggested that deploying multiple transmit and receive antenna would bring about huge capacity gain, future development is driven towards designing system that would realize this gain in practice. Here, we consider the performance of a new space-time multi-layered CDMA structure. The data stream is divided into layers, each of which is modulated with an unique space-time spreading sequence. At the receiver, the linear multiuser MMSE detector is used to recover all layers. Simulation results show that the capacity grows linearly with the number of transmit and receive antenna. We investigate the issue of selecting good space-time sequences to reduce co-interference from other layers. Results show that the joint space-time orthogonal codes exhibit good performance. The proposed structure also provides better immunity against signal loss, when any antenna element experiences failure.