It has been shown how to cancel the interfrence of MIMO users with 2 transmit antennas using orthogonal
space-time block codes (STBCs). It was believed that the approach can be generalized to users with any number of 
transmit antennas. First, we show that such a generalization is impossible. 
Then, we show how to design such systems for users with more than 2 transmit antennas without using orthogonal STBCs.
Finally, we study the diversity of the above multiuser interference cancellation systems.