Alamouti scheme based affine projection decoder in a Multiuser MIMO downlink system

For a downlink of Multiuser (MU) Multiple-Input, Multiple-Output (MIMO) system with 2 transmitting antennas at the base station and N receiving antennas at each user, in this paper, new decoding methods, named as affine projection decoders, will be proposed and illustrated based on the Almouti scheme, under assumptions that the transmitter does not have channel state information (CSI), and transmits signals simultaneously to each user. In these decoders, techniques of affine projection will be applied, and user's interference can be eliminated completely. Moreover, the wanted signal can completely be preserved, which is different from decoders based on the orthogonal projections where this signal is damaged. Also, performances of these new decoders, such as the achievable rate regions, the regions of degree of freedom (DoF), are analyzed. Simulations confirm our analysis.