Proof on the maximal rates of space-time block codes from complex orthogonal design

In this study, the authors present a novel proof on the maximal rates of space-time block codes from complex orthogonal design (COD). The method of the proof is derived from an observation about the CODs, which reveals some inherent laws of their structure. The proof is applicable to any CODs, rather than to some specific designs, and does not need any auxiliary matrix or matrix transformation. The conclusion in this study also indicates that the upper bound of the CODs´ rate conjectured by the authors is tight and achievable.