Abstract—Non-coherent communication which employs Differential Modulation (DM) technique is an interesting technique to combat the uncertainty of channel in the wireless communication system. This technique also provides a more spectral efficient system than coherent communication because it does not need the presence of signal overhead for channel estimation purpose which usually exists in the coherent transmission. To improve the performance of DM technique, differential unitary modulation technique which is combining DM and Space Time Block Code (STBC) is explored in this paper. In this paper, we modify a quasi-orthogonal STBC (QO-STBC) to be used as a unitary matrix generator, and then we introduce an element-wise calculation concept to minimize the system complexity. The experimental results show the proposed differential unitary modulation technique could be an excellent technique to overcome the uncertainty of channel in a wireless telecommunication system.