Patent ID: 7738843

Claim:
A transmitter for a multi-input multi-output system using multiple antennas, the transmitter comprising: a memory for storing a modulation system and power allocation coefficient for each antenna; a modulating unit for modulating data to be transmitted using the modulation system for each antenna stored in the memory when the data to be transmitted is input; and a power adjusting unit for adjusting the power according to the power allocation coefficient for each antenna stored in the memory to transmit the data to be transmitted, modulated at the modulating unit, via a corresponding antenna, wherein the stored modulation system and power allocation coefficient used for each of the antennas when the data is transmitted comprises: generating a group of available modulation systems and assigning the modulation system to each antenna when the spectral efficiency and the number of transmitting antennas are input; calculating a lower bound of bit error rate for the modulation system of each antenna; selecting a modulation system with which the lower bound of the bit error rate for each antenna is minimized; obtaining a power allocation coefficient for each antenna using a parameter dependent on the selected modulation system; and storing the obtained modulation system and power allocation coefficient in a lookup table, wherein the lower bound of the bit error rate is obtained using P b , i _ ⁡ ( error ) ≈ 1 N t ⁢ ∑ i = 1 N t ⁢ ⁢ α i ⁢ exp ⁡ ( 1 + β i ⁢ P i ⁢ ρ ) - i , where N t indicates the number of transmitting antennas α i and β i indicate parameter values dependent on a modulation system, ρ indicates a signal to noise ratio and P i indicates power assigned to the i-th transmitting antenna and P i is 1 in here.