Abstract: A method and device for decoding in a differential orthogonal space-time block coded system are disclosed. The disclosed method includes: (a) receiving signals from a transmitter during a particular time slot segment, where the signals are encoded by differential orthogonal space-time block coding; (b) transforming to reception signals for two sub-systems by using a sum operation and a difference operation of the signals received in step (a), where the transformed reception signals for the two sub-systems maintain an orthogonality of an orthogonal space-time block coded system; and (c) performing decoding using the reception signals for the two sub-systems transformed in step (b). The method provides the advantage of lowering the level of operational complexity for decoding in a communication system that employs differential orthogonal space-time block coding.