Abstract
Orthogonal frequency division multiplexing (OFDM) has been widely used in design of various communication systems due to its advantages of high data rate transmission and immunities to multipath fading channels. One of the major problems associated with OFDM is its high peak-to-average power ratio (PAPR), which may cause severe distortion when the OFDM signal is passed through an RF power amplifier. Many techniques for PAPR reduction have been proposed in this literature; they can be roughly divided into three categories: the signal distortion methods, the coding methods, and the multiple signal representation (MSR) methods. These techniques have their own drawbacks, such as signal-to-noise (SNR) degradation, out-of-band radiation, limitation of the subcarriers’ number and high computational complexity.In this thesis, we propose a new technique to reduce the PAPR. The proposed technique sets appropriate values to the reserved subcarriers on a one-by-one basis so as to reduce the PAPR of the transmitted data signal iteratively. Unlike the signal distortion methods, the proposed method does not involve SNR degradation and out-of-band radiation. As compared with the coding methods, it has no limitation on the subcarriers’ number. The proposed technique also achieves comparable performance to the MSR techniques, such as those based on random interleaving or partial transmit sequences. Moreover, it uses only one inverse fast Fourier transform (IFFT) module and has much lower complexity than the MSR methods that may require several IFFT modules operating in parallel to provide the same processing speed. To demonstrate the effectiveness of the proposed PAPR reduction method, computer simulation results are given for both the IEEE 802.11a wireless local area network and the digital video broadcasting (DVB) system.