Cross-Layer-Model Based Power Minimization with Quality-Of-Service Guarantees

We investigate the power control policy which minimizes the average transmit power subject to delay quality of service (QoS) constraints for continuous and discrete constellation multi-level quadrature amplitude modulation (MQAM) schemes. The problem is formulated based on a cross-layer framework. In the framework, the queue at the data link layer is serviced by the power control and modulation schemes at the physical layer, using the theory of effective capacity. The solution for the continuous constellation MQAM case is derived by solving the Karush-Kuhn-Tucker (KKT) optimality conditions. For the discrete constellation MQAM case, we propose the region boundaries related to the required delay QoS. Our analysis provides the fundamental power limits for the fading channels while fulfilling the delay QoS requirement. Furthermore, the numerical results are presented to show the power saving performance of the proposed power control schemes.