A space-time-frequency encoding scheme, for use in wireless communication systems, transforms a plurality of input element pairs into a plurality orthogonal element pairs, each of the plurality of input element pairs and corresponding orthogonal element pairs forming an orthogonal matrix. A first element, second element and a duplicate of the second element in each of the plurality of input element pairs and corresponding orthogonal element pairs are mapped as channel elements to three predetermined time-frequency cells in respective first and second two-dimension time-frequency matrixes for transmission via different antennas. As the input element pairs and corresponding orthogonal element pairs, transmitted via different antennas, are orthogonal in both the space-time domain and the space-frequency domain at the same time, two-dimension space-time transmit diversity gain and space-frequency transmit diversity gain can be achieved at the same time.