Space-time spreading codes for a multiuser MIMO system

We study the use of the spatial dimension in enabling multiple access for the down-link of a cellular communication system and propose a two dimensional spreading code. By using a minimum number of transmit and receive antennas, the bandwidth efficiency is increased over a single antenna system, while diversity is provided at the receiver. A key feature of the proposed technique is that it simplifies the implementation of joint space-time decoding and multiuser detection in each user station. It is supposed that the channel is known only at the receiver.