Application of QR decomposition to design of space-time codes for MIMO systems

We introduce the concept of "nulling diversity gains" for a space-time code via QR decomposition of the corresponding channel matrix. This concept enables us to roughly estimate the performance of the space-time code when it is detected by interference suppression and interference cancellation techniques. Based on this concept, we also devise a space-time code for MIMO systems that not only has a high performance and high spectral efficiencies but also allows the simple detection technique to be employed. Computer simulation is provided to demonstrate the nulling diversity gains of some space-time codes as well as to verify performances of our proposed code.