Reduction of peak to average power in ofdm systems : a survey

Orthogonal Frequency Division Multiplexing (OFDM) has emerged as one of the main factors for the attainment of high data rates in various wireless technologies used globally. Due to high amplitude fluctuations, conventional OFDM signals suffer from a high value of Peak to Average Power Ratio (PAPR) which in the worst case can be proportional to the square of the number of sub-carriers used. This causes non-linear distortion in high power amplifiers used in wireless communication systems. Therefore employing techniques to circumvent the PAPR problem has been an active area of research. This paper compares various PAPR reduction techniques such as clipping, selective mapping, partially transmitting sequences etc., their complexities pertaining to computation and their practical applicability in terms of implementation on hardware. As data rates and mobility supported by OFDM systems increase, the number of subcarriers needed also increases, thereby leading to high PAPR values. As future applications would demand higher data rates and higher mobility, techniques to reduce PAPR values would become inevitable and occupy high importance. This paper brings out a clear picture of a basic OFDM system, the PAPR problem, existing techniques for reduction of PAPR, their implementation complexity and practical applicability.