Patent ID: 7894544

Claim:
A method for transmitting a signal in a signal transmitter of a communication system, comprising: generating an upper pre-encoding symbol stream and a lower pre-encoding symbol stream by pre-encoding an upper transmission vector and a lower transmission vector according to a pre-encoding scheme; generating a space-time mapping matrix by space-time mapping the upper and lower pre-encoding symbol streams according to a space-time mapping scheme based on a number of transmit antennas to be used in the signal transmitter; generating a codeword by multiplying the space-time mapping matrix by a unitary matrix according to whether a null transmission is present in the space-time mapping matrix; and transmitting the codeword, wherein the unitary matrix is set to a Hadamard unitary matrix, when the null transmission is present in the space-time mapping matrix, and is set to an identity matrix, when the null transmission is not present in the space-time mapping matrix, wherein space-time mapping the upper and lower pre-encoding symbol streams according to the space-time mapping scheme comprises space-time mapping the upper and lower pre-encoding symbol streams using a quasi-orthogonal scheme such that the upper and lower transmission vectors are orthogonal in a unit of a predetermined number of vectors, and wherein an upper group element and a lower group element of the codeword are separated based on a square matrix of an error matrix about the codeword.