Study On Joint Algorithm Of PAPR Reduction For O-OFDM Communication System

With the vigorous development of the modern science and technology andinformation industry，the spectrum resource, transmission rate and capacity of existingcommunication system cannot meet the requirement for information of people. As aresult, the optical communication technologies which can realize transmittinginformation with high rate and large capacity have aroused attention of researchers.However, in optical communication system, the transmission capacity andtransmission distance are restricted by chromatic dispersion. So chromatic dispersionis the key point which hinders the development of optical fiber communication system.Orthogonal Frequency Division Multiplexing (OFDM) technology not only can solvethe problems such as chromatic dispersion and polarization mode dispersion, but alsohas the characteristic of high spectrum efficiency. Therefore combining the advantageof optical fiber communication system with OFDM, we can build a novel optical fibercommunication system with large capacity and low cost. For the peak average powerratio (PAPR) existing in OFDM, there is large requirement in the linear range ofoptical devices and optical fiber link, and the cost of the system is improved. So it isextremely necessary to reduce PAPR.In order to study the problem of PAPR reduction in optical OFDM (O-OFDM), asimulation model of O-OFDM communication system is built with Matlab7.0andOptisystem7.0simulation software. After further study all kinds of PAPR reductionmethods, we propose two kinds of joint algorithms that are joint algorithm combiningimproved double PTS with Clipping and joint algorithm combining the grouping ofSLM with Clipping. We employ the two joint algorithms mentioned above and otherimproved algorithms to reduce PAPR in O-OFDM communication system.1. The joint algorithm combining improved double PTS with Clipping: The phase factor sequence is totally searched in traditional PTS algorithm, and we can geta set of phase factor which has the best effect. But in the joint algorithm proposed inthis paper, the search process is divided into inside layer and outside layer, and thePTS sub-optimization is processed respectively. Then the combined signal istransmitted after amplitude limiting.2. The joint algorithm combining the grouping of SLM with Clipping: theOFDM signal sequence is divided into several statistical independent sequenceswhich are processed IFFT separately, and the sequence with smallest PAPR istransmitted in traditional SLM algorithm. But in the joint algorithm proposed in thispaper, the signal is divided into even groups which are processed IFFT separately.The signal with smallest PAPR in each group is combined and then transmitted afteramplitude limiting.The two kinds of joint algorithms are both carried out in OFDM system andO-OFDM system respectively, and proved that they can effectively reduce PAPR intwo systems. The full text is summarized and the research direction in the future isprospected in the end.