Optimal power control in cellular wireless systems

In this research work, the problem of optimal Signal-to-Interference Ratio (SIR) based power control in cellular wireless systems is considered. CDMA technology used in 3-G wireless systems relies on accurate power control, not only for maximizing the battery life of mobile terminals, but also as an important technique for maintaining users' Quality-of-Service (QoS) and optimizing system capacity by controlling interference.; An optimal distributed closed-loop SIR-based power control scheme is proposed to minimize the squared SIR error. The power change is proportional to the SIR error. The optimal proportional gain is chosen to achieve the minimum SIR error at the next time instant. An H_∞ filter is applied in the proposed scheme instead of the Kalman filter to facilitate the system filtering regardless of the nature of the system and measurement disturbances. The proposed scheme has very fast convergence speed. It is also a robust scheme, which adapt to interference and channel changes. A joint optimization of the mobile terminal's transmission power and SIR error is also proposed to provide a tradeoff between the provided QoS and the power consumption. Simulation results confirm theoretical analysis in all cases.; A stochastic optimal power control algorithm is proposed, assuming that the SIR measurements are contaminated by white noise. The power control system is a linear time-varying system driven by white noise. The optimal controller gain is obtained by minimization of the sum of the variances of the mobile terminal's transmission power and SIR error. An estimator is proposed to deal with the changes of the link gains. The users' SIR converge to the target value within 40 steps. A proportional derivative controller is added to the proposed power control scheme in order to reduce the overshoot and improve the transient response. Simulation results show that the performance of the proposed power control scheme will not be affected much with quantization.; Some preliminary analytical results on game theoretical approaches are also provided. The proposed power control scheme is proved to achieve the Nash equilibrium point of the system.