Reduction Of PAPR In CO-OFDM System By Joint Algorithm Based On Probability

With the development of the modern science and technology,many new emerging data services such as Internet communications,broadband services and multimedia technologies are gradually popularized into people's daily life.The demand for broadband is getting larger and larger.Ordinary wireless transmission and transmission modes can not satisfy people's requirements.Coherent optical orthogonal frequency division multiplexing(CO-OFDM)has the advantages of high spectral efficiency,strong anti-dispersion performance and large transmission rate for combining orthogonal frequency division multiplexing(OFDM)with coherent detection technology.CO-OFDM technology has provided good conditions for high-speed,large-capacity and long-distance transmission and has gradually become one of the main transmission modes for the next generation of high speed optical communication systems.However,the problem of high peak to average power ratio(PAPR)is still one of the main factors that limit the development of CO-OFDM technology.It will not only increase the system complexity of the system,reduce the performance of the system,improve the cost of the system,but also can increase the nonlinearity of the fiber.Aimed at this problem,the traditional probability algorithms are researched and the improved algorithm is proposed to improve the PAPR in CO-OFDM system in this paper.In order to verify the feasibility of the proposed algorithm,the CO-OFDM system is built by using Matlab and Optisystem simulation software.The main contents are as follows:1.Firstly,the research background,development situation,advantages and disadvantages of the CO-OFDM system are introduced.The basic principle of CO-OFDM system and main technologies are introduced.Then the PAPR problem in CO-OFDM system is analyzed including definition,statistical characteristics and classification of traditional methods.In addition,the system simulation platform of CO-OFDM is built by Matlab and Optisystem software.2.The basic principle of iterative partial transmission sequence(IPTS)algorithm and the influencing factors of IPTS algorithm are analyzed.Then the basic principle of the clipping algorithm is introduced.The clipping discrete-cosine-transform and filtering(CDF)algorithm is proposed.And the shortcomings of the limited bit error rate(BER)performance causing by clipping algorithm is improved through the introduction of discrete cosine transform(DCT).Finally,the IPTS-CDF joint algorithm is proposed to further reduce the PAPR of signals.The simulation results show that the PAPR performance of the proposed algorithm is improved by 2.31 dB and 1.23 dB compared with the IPTS algorithm and the CDF algorithm.3.The basic principle of active constellation extension(ACE)algorithm and two different implementations under the algorithm are introduced.Then the basic principle of companding algorithm is analyzed and the repeat companding and filtering(RCF)algorithmis proposed.The RCF algorithm is a repeated iterative process,which can improve the BER performance of the system through multiple iterations.Finally,two algorithms of ACE-RCF and IPTS-RCF are proposed.The simulation results show that the PAPR performance of the ACE-RCF algorithm is improved by 3.22 dB and 1.79 dB compared with the ACE algorithm and the u-companding algorithm.The PAPR performance of the IPTS-RCF algorithm is improved by 3.53 dB and 1.21 dB compared with the IPTS algorithm and the u-companding algorithm.