Patent ID: 7408975

Claim:
A method for transmit power adaptation in a CDMA wireless communication system receiving mobile station signals, said system including a plurality of K mobile stations communicating with at least one base station having a successive interference cancellation receiver, the method comprising: estimating channel gain for each mobile station, to thereby form a corresponding estimated channel gain, in response to received mobile station signals; ordering received signals from the mobile stations on a basis of the corresponding estimated channel gain from the mobile station associated with a highest channel gain G (l) to the mobile station associated with a lowest channel gain G (K) ; determining a transmit power S (i) for each mobile station in response to the ordered channel gains by iteratively calculating: S R (i) =x i S R (1) and S (i) =S R (i) /G (i) , for x 1 =1 and i=2, 3, . . ., K, wherein S (i) R is the received signal power from the mobile station associated with the i th highest channel gain G (i) and x i is a positive number, said determining comprising computing each x i to minimize an average bit error rate P b for signals from each mobile station as: minimize x 2 , x 3 , … ⁢ ⁢ x K ⁢ P _ b = 1 K ⁢ ∑ i = 1 K ⁢ ⁢ Q ⁢ Λ i , where x 1 =1 and P b is an average probability of a bit error and Λ i , is a signal-to-interference -plus-noise ratio associated with the i th strongest user, said minimizing comprising obtaining partial derivatives of P b with respect to each of the x i , i=2, . . . , K, setting the partial derivatives equal to zero, and solving the resulting set of simultaneous equations; and transmitting to each mobile station the determined transmit power associated with that mobile station.