A Closed-Loop Transmission Power Control System Using a Nonlinear Approximation of Power-Time Curve

Abstract

In wireless communication networks, it is desirable to achieve energy efficiency, while maintaining quality of service. Overall, energy efficiency can be achieved by minimizing the power output for each communication device. This paper presents a novel energy-saving adaptive transmit power control (TPC) algorithm based on bit error rate (BER) feedback (BER-TPC) that outperforms conventional approaches based on signal-tointerference-plus-noise ratio (SINR) feedback (SINR-TPC). It is a distributed algorithm deployed in both transmitting and receiving devices that can be applied for various wireless network topologies and protocols. This paper addresses the power efficiency of adaptive TPC, in terms of reduced total transmit power of the network by smoothing transmit power transients during adaptive iterations. It is achieved using a distributed closed-loop power control system that applies heuristically estimated dual-rate power adjustments during adaptive iterations. Because the proposed system uses a mathematical formula for power adjustment, operational bounds for stability can be provided using simple analysis. It is demonstrated that the proposed system provides adequate tradeoff between performance and complexity, in terms of reduction in sensitivities and better tracking performance in following the desired reference power curves used in the simulations. Case scenarios are simulated demonstrating approximately 1.39-dB transmit power savings compared to conventional methods.Index Terms-Cognitive radio (CR), energy efficiency, interference avoidance (IA), quadratic approximator, transmission power control (TPC).