A subgradient algorithm for low complexity DMT PAR minimization

An iterative peak-to-average power ratio (PAR) reduction algorithm for discrete multi tone (DMT) based systems, such as OFDM and VDSL, is introduced. The proposed algorithm uses reserved or unused tones to minimize the l_∞ norm of the DMT symbol vector iteratively based on a subgradient optimization technique. The resulting iterative algorithm has a very simple update rule and, therefore, a low computational complexity. Furthermore, the PSD level constraints can be easily incorporated into the algorithm. The proposed algorithm´s performance is illustrated for an OFDM system with 256 carriers. It is shown that a high PAR reduction is achieved, especially for the cases where the PAR reduction tones are allowed to exceed the PSD mask level.