Patent ID: 8577310

Claim:
A method of operating a multi-output wireless transmitter, the method comprising: determining a precoded data stream in accordance with input data, the determining comprising, determining a signal to interference plus noise ratio (SNIR) of a plurality of receivers, determining a channel gain to each of the plurality of receivers, and maximizing a sum of utility functions without using a log detector, wherein each utility function is proportional to the SNIR of each of the plurality of receivers at low SNIR values and asymptotically approaches a constant value at high SNIR values; and transmitting the precoded data stream on the multi-output wireless transmitter, wherein determining the precoded data stream further comprises: updating auxiliary variable W k according to: W k = ( I - H kk ⁢ Q k ⁢ H kk T ( σ 2 ⁢ I + ∑ l = 1 K ⁢ ⁢ H kl ⁢ Q l ⁢ H kl T ) - 1 ) - 1 , ∀ k = 1 , 2 , … ⁢ , K ; and solving the following optimization problem min Q k ⁢ ⁢ Tr ⁡ [ B k ⁢ Q k ] s . t . ⁢ Tr ⁡ ( Q k ) = p k ⁢ ⁢ Q k ⁢ ⁢ μ ⁢ ⁢ 0 , where H kk is a channel matrix from transmitter k (after the precoded data) to receiver k, K is a number of transmitters, H kl is a channel matrix from transmitter l (after the precoded data) to receiver k, H jj is a channel matrix from transmitter j (after the precoded data) to receiver j, H jk is a channel matrix from transmitter k (after the precoded data) to receiver j, Q k is a precoded transmit data covariance matrix of user k, Q l is a precoded transmit data covariance matrix of user l, {tilde over (Q)} k is a previous value for Q k , Q j is a precoded transmit data covariance matrix of user j, and p k is a power constraint of precoded data of user k, B k , represents received interference power from all receivers, I is an identity matrix and σ is a noise standard deviation.