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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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The rapid growth of wireless mobile communications raises the critical issue of meeting user expectations and requirements. This paper deals with the subjective assessment of the perceived quality of video calling services delivered on a real LTE/4G network. The main goal is to determine the list of parameters that are predominantly impacting the Quality of Experience (QoE). The influencing parameters considered here include the video sequence content, coding technology and both core and radio access networks. Following the ITU-T Recommendations, subjective quality assessment experiments were conducted. Subjects were shown different representative sequences of video-calling services transmitted using different network conditions. The outcomes of these experiments show that the QoE is mainly affected by packets loss, jitter. However the impact of these parameters, which vary over time and in case of user mobility, seems to be different from that observed with simulated networks.

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International audienceWe present a new and simple method which consists to apply constellation shaping to bit-interleaved turbo-coded modulation (BICTM) over additive white Gaussian noise channels. By assuming the example of a 3-bit/dim 16-PAM BITCM, it is shown that this technique can provide shaping gain of 0.79 dB