by dividing the substitution signal by the normalized channel power application_number US 77149404 A description preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings in the following description a detailed description of known functions and configurations incorporated herein has been omitted for conciseness the terms used herein are defined in consideration of their functions in the invention and can be changed according to a user 39 s intentions and usual practices therefore the definition should be made based on the overall contents of the specification the present invention provides a method for decoding a partially coherent space time block code which does not require a training sequence is robust to channel variation and has a low snr loss by using only estimated power of a channel in decoding a differential space time block code stbc in a transmit diversity system the invention can transmit symbols having different distances from the origin on a multidimension hyper sphere 0049 fig5 is a block diagram illustrating a transmitter using a differential space time block code according to an embodiment of the present invention as illustrated in fig5 the transmitter includes a serial to parallel s p converter 205 multipliers 210 1 210 k an adder 215 a delay 220 a normalizer 225 an encoder 230 and k transmission antennas 235 1 235 2 235 k referring to fig5 the s p converter 205 parallel converts a previously transmitted symbol block s v delayed by the delay.