Power control in the uplink of a wireless multi-carrier CDMA system

This paper addresses the power allocation problem in the uplink of wireless multi-carrier code-division multiple-access (MC-CDMA) in order to guarantee QoS requirements. QoS is evaluated with respect to the signal to interference-noise ratio (SINR), estimated after the detection process at the base station (BS). First, departing of the received signal model in a MC-CDMA system, the SINR is computed by considering the application of linear multiuser detectors and a common transmission power through all subcarriers. By assuming that the measured SINR must follow an objective SINR value, an open-loop solution is introduced to the power allocation problem. Next, an iterative version is derived that relies on an integral correction of the required transmission power. By applying a loop transformation and the small-gain theorem, general distributed controllers can be proposed, where specific stability and performance conditions are introduced. A simulation evaluation is presented at different load levels in the MC-CDMA, and time-varying channel gains. In all the studied cases, the resulting power allocation system was able to allocate transmission power to achieve the objective SINR.