A complex-baseband active-set approach for tone reservation PAR reduction in OFDM systems

In this paper, we present an active-set approach for peak-to-average power ratio (PAR) reduction via tone reservation in complex-baseband orthogonal frequency division multiplexing (OFDM) systems. In the complex-baseband model, the optimization problem of tone reservation turns out to be a quadratically constrained quadratic program (QCQP), which is computationally prohibitive for a practical implementation. To address this problem, we consider the complex-valued samples of an OFDM symbol as vectors in the complex plane and develop an iterative clipping algorithm. In our approach, PAR reduction is achieved by minimizing the radius of the circle that encloses all samples, thus minimizing the maximum power peak. Simulation results show that the proposed algorithm can achieve near-optimal performance with fast convergence and limited complexity.