Joint transmitter adaptation and power control for downlink wireless systems with target SIR requirements

In this paper we study joint transmitter adaptation and power control in downlink wireless systems with target values imposed on the signal-to-interference+noise-ratios (SINR) at the receiver terminals. We use a general framework based on block transmissions and linear precoders that is applicable to a wide range of wireless systems to formulate this as a constrained optimization problem for which we discuss the conditions that must be satisfied by the optimal solution. We also present an algorithm which adapts the transmit precoder and power values incrementally until a fixed point is reached where the specified target SINRs are achieved with minimum transmitted power. Convergence of the proposed algorithm is investigated and is illustrated with numerical examples obtained from simulations.