The Research On Reducing The PAPR Of NC-OFDM System

Non-contiguous OFDM (NC-OFDM) is a variable data transmission technique which used in dynamic spectrum access network. It can achieve high data rates via collective usage of a large number of non-contiguous subcarriers while simultaneously avoiding any interference to the existing transmissions by turning off the subcarriers corresponding to these using spectrum bands. As a special form of OFDM technology, NC-OFDM also suffers the high PAPR problem. Due to the null subcarriers, the input symbols in NC-OFDM system don't hold identically and independently distributed (i.id) which results in different statistical properties for the PAPR of NC-OFDM signals compare to that for OFDM signals. The algorithm used to reduce the PAPR of OFDM systems may not suitable in the NC-OFDM systems or used in the NC-OFDM systems after improved.The thesis mainly studied on how to use the adaptive algorithm to reduce the PAPR in NC-OFDM systems. Specifically including the followings:At the first of the thesis, the principle of cognitive radio technology and NC-OFDM system is introduced.Then high PAPR problem in the OFDM system was analyzed. An extensive overview and taxonomy of the PAPR reduction algorithms and the relative merits of these algorithms are proposed.After that, the extraordinary nature of the NC-OFDM systems and the characteristic of the PAPR in NC-OFDM systems are presented. According the characteristic, algorithms used for PAPR reduction are proposed.At last, the principle of interleaving algorithm and phase shift algorithm are introduced in detail. Based on that, a new adaptive algorithm is put forward. The simulation results are given which show that the adaptive algorithm could reduce the PAPR of NC-OFDM systems efficaciously while the side information is small and the computation complexity is very low.