TAILIEUCHUNG - Báo cáo toán học: " Probability distribution analysis of M-QAMmodulated OFDM symbol and reconstruction of distorted data"

Tuyển tập các báo cáo nghiên cứu khoa học ngành toán học được đăng trên tạp chí toán học quốc tế đề tài: Probability distribution analysis of M-QAMmodulated OFDM symbol and reconstruction of distorted data | Yoo et al. EURASIP Journal on Advances in Signal Processing 2011 2011 135 http content 2011 1 135 o EURASIP Journal on Advances in Signal Processing a SpringerOpen Journal RESEARCH Open Access Probability distribution analysis of M-QAM-modulated OFDM symbol and reconstruction of distorted data Hyunseuk Yoo Frédéric Guilloud and Ramesh Pyndiah Abstract It is usually assumed that N samples of the time domain orthogonal frequency division multiplexing OFDM symbols have an identical Gaussian probability distribution PD in the real and imaginary parts. In this article we analyze the exact PD of M-QAM OFDM symbols with N subcarriers. We show the general expression of the characteristic function of the time domain samples of M-QAM OFDM symbols. As an example theoretical discrete PD for both QPSK and 16-QAM cases is derived. The discrete nature of these distributions is used to reconstruct the distorted OFDM symbols due to deliberate clipping or amplification close to saturation. Simulation results show that the data reconstruction process can effectively lower the error floor level. Keywords OFDM discrete probability distribution M-QAM nonlinear amplifier data reconstruction. 1 Introduction A significant drawback of orthogonal frequency division multiplexing OFDM -based systems is their high peak-to-average power ratio PAPR at the transmitter requiring the use of a highly linear amplifier which leads to low power efficiency. For reasonable power efficiency the OFDM signal power level should be close to the nonlinear area of the amplifier going through nonlinear distortions and degrading the error performance. The distortion can be introduced for two main reasons nonlinear amplifier 1 2 and or deliberate clipping 3 . For the first case if an OFDM symbol is amplified in the saturation area of an amplifier its data recovery is not possible. For the second case deliberate clipping makes an intentional noise which falls both in-band and out-of-band. .

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