High peak-to-average power ratio of the transmit signal is a major drawback of multi-carrier transmission such as Orthogonal Frequency Division Multiplexing, which causes power inadequacy in Radio Frequency section of the transmitter. This paper describe some of the important PAPR reduction techniques for multi-carrier transmission including amplitude clipping and filtering, partial transmit sequence, selected mapping, and active constellation extension. Among various PAPR reduction techniques, neural network is the most powerful techniques in reducing the PAPR due its good generalization properties with flexible modelling and learning capabilities.