Research Of PAPR Reduction In LTE Systems

Global communication techniques are developing rapidly. Requirements of future mobile communication are that can access the internet at high data rates unrestrictedly. The standard of LTE is proposed by the 3GPP organization. Orthogonal frequency division multiplexing (OFDM) is used in LTE downlink, which enables system to reach the peak rate of 100Mbps. It is well known that the OFDM technology is particularly suitable for frequency-selective channels. However, OFDM also has a major drawback of higher peak-to-average-power ratio (PAPR).As a multi-carrier modulation system, OFDM, the output is sum of sub-carrier signals. When some signals have same phase, signal instantaneous power can be much higher than signal average power, resulting in a larger peak average power ratio (PAPR).The high-PAPR can be result in the serious performance of LTE system, which has become an important factor constraining OFDM technology development. If the linear area of system power amplifier cannot satisfy signal power range, it may cause signal amplitude distortion. Signal spectrum may change, orthogonality of sub-carriers are destroyed. Therefore, communication system performance can be worse. It is not an advice that using a better power amplifier. If we use it, there has a problem of power loss in base station. The amplifier, which has a better power amplifier, cannot be used in mobile terminals. Therefore, we must research PAPR reduction technique comprehensively.This article describes PAPR reduction techniques in LTE systems, mainly about following two aspects:(1) Research traditional clipping method and traditional improved clipping method, and an improved traditional signal clipping method is proposed for better system bit-error-ratio (BER) performance.(2) A new method about PAPR reduction is proposed, which utilizes SLM scheme followed by signal clipping. Compared with the SLM-only-based approach, the proposed scheme can offer more efficient PAPR reduction with smaller cost on IFFT computation. In addition, the proposed approach shows lower bit-error-ratio BER in contrast with the traditional clipping method.