A major drawback of orthogonal frequency division multiplexing (OFDM) is its high peak-to-average power ratio (PAPR). Tone reservation (TR) is one of the numerous methods for reducing the PAPR. Two parameters, the weight factor and the clipping ratio have significant impact on the PAPR reduction capability of TR methods. In this paper we thoroughly analyze the effect of these parameters. Based on these investigations two novel schemes, the globally and locally improved clipping ratio are introduced. Both methods rely on the feature that the CR can be adjusted between iterations. The main advantage of the globally improved clipping ratio is that, after offline preprocessing, it improves the PAPR reduction capabilities of the conventional TR scheme with same real-time computation complexity. The locally improved method can further enhance PAPR reduction capabilites on the cost of computation time.
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