On The Power Control With Non-Cooperative Game Theory

The power control plays an important role in resource management of wireless system. The transmit power will affect the link signal quality and the interference environment of the wireless system. Power control can be employed to efficiently suppress the mutual interference and to reduce power consumption, to improve system capacity. The objective of the power control is to provide acceptable quality of service for each user while minimizing the interference with other users. This thesis briefly introduces the purpose, significance, realization method and criterion of the power control at first, and then some practical application of power control in mobile communication system such as WCDMA, CDMA2000, TD-SCDMA system as well as LTE system will be reviewed to highlight its importance. And delay, bit error rate, moving velocity as well as other factors which dominate the performance of power control are presented to address the challenge in power control design.After a brief introduction of the definition of the game theory, the three basic elements, classification along with Nash equilibrium concept are reviewed to introduce the power control mechanism with game theory. Three classic power control methods which based on the signal to interference ratio balancing criteria, the linear pricing function and energy-efficiency utility function are simulated and compared to introduce the background and motivations of the subjects of this thesis on the non-cooperative power control game and the non-cooperative power and rate joint control game, both with pricing mechanism and additional latency constraint.In traditional non-cooperative power control game (NPG), each user will maximize its own utility as much as possible while ignoring the resulting impact to other users, and the achieved Nash equilibrium is less efficient. On the other hand, the non-cooperative power control game with pricing (NPGP), every user will try to reduce the transmit power while maximizing profits due to the introduction of the cost function, which implies that, the user cooperation can be implicitly enabled by introducing a cost function without changing the non-cooperative power control features and the Pareto area equilibrium effectiveness can be improved. However, the existing NPGP algorithm assumes reliable transmission and only simple environment such as the single-cell system is considered. In this paper, the delay constrained non-cooperative power control game with pricing mechanism (DNPGP) in multiple cell is proposed by modifying the involved utility function to improve the non-cooperative joint power control game performance. Firstly, it is proposed to include the transmission latency in the SIR constraints. Secondly, multi-cell interference is taken into consideration in the SIR metric as well. Instead of the non-coherent FSK modulation in the traditional NPGP, an effective function suitable for PSK modulation is adopted. Lastly, the paper improves the traditional NPGP cost function. More specifically, not only transmit power but also the interference to other users in SIR metric is considered in the new cost function. It is shown that, when the SIR deviates greater from the target SIR, the resultant larger penalty will force the users to adjust their transmit power close to the target SIR. The simulation results are presented to validate that, the proposed DNPGP outperforms the conventional NPGP algorithm thanks to the newly devised effective function and cost function, although the delay will deteriorate the achieved performance to some extent.Most of the traditional non-cooperative power control game consider the power control problem only. How to satisfy the data transmission rate requirements at the same time is another subject this our analysis of the non-cooperative power control game design. On the basis of the DNPGP scheme, the delay constrained non-cooperative power and rate joint control game with pricing mechanism (DNRPGP) is investigated in this thesis. The proposed DNPRGP algorithm can approach the target SIR by dynamically adjusting the transmit power and data rate, and it is shown that the DNPRGP can be employed to reduce the unnecessary resource consumption while ensuring the utility and quality of transmission. Simulation results are presented to confirm that the joint power and the rate control by DNPRGP algorithm can effectively make up for the negative effects brought about by the delay constraint when compared with DNPGP algorithm, and the user can achieve the reasonable data rate with the minimum transmit power.