Abstract-The aim of this paper is to evaluate and compare different optimization algorithms for Peak to Average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems. Based on Tone Reservation (TR) method, we exploit the unused subcarriers of the studied standard to generate the peak canceling signal without data rate loss. Gradient, Conjugate-Gradient with two directions search and QuasiNewton methods have been investigated and evaluated on the basis of spectral regrowth, convergence speed and ability to improve the high peak-to-average reduction in multicarriers systems. As an example, the simulations are performed in the case of Local Area Network WLAN (IEEE 802.11a standard). Simulation results show that a PAPR reduction gain around 3 dB can be achieved.

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International audienceThe transmission of highly scalable image and video codestream over error-prone networks can be ensured by using Unequal Power Allocation (UPA) in MIMO-OFDM systems. However, UPA schemes are usually designed without taking into account the High Power Amplifier (HPA) nonlinearity, especially in MIMO-OFDM systems which are known to generate signals with a high Peak-to-Average Power Ratio (PAPR). This paper aims to evaluate the impact of HPA nonlinearity on the transmission of scalable image cotents over a precoded Closed-Loop MIMO-OFDM system when the well-known Content-Based Precoder (CBP) is used for UPA. For PAPR reduction, we have considered the Tone Reservation Using Null Subcarriers (TRNS) technique. Simulations are performed under the IEEE 802.11n standard in a realistic urban environment in presence of a commercial 2W class-AB memoryless HPA from RF Micro Devices. The experimental results in terms of Bit Error Rate (BER) and visual quality show that the error-protection of the most sensitive parts of the codestream against channel distortions achieved using UPA is significantly disturbed in presence of HPA nonlinearity. These results highlight the influence of HPA nonlinearity on the scalable image transmission