Jointly Optimal Signature Sequences and Power Allocation for CDMA Systems

The problems of designing signature sequences and power allocation policy for code-division multiple access (CDMA) are important and have been the subject of intensive research in recent years. Taking the maximization of the system information theoretic sum capacity as the design criterion, most of the previous works only consider the optimizations of signature sequences and power allocation separately. In contrast, this letter presents a jointly optimal design of signature sequences and power allocation for a CDMA system with fixed, but unequal channel gains and under the sum power constraint. The proposed design is of closed-form, and applicable for the general case of correlated signals and colored noise. Numerical results verify the superiority of the proposed design over the existing ones.