Chaotic Precoder Techniques In OFDM-PON For Physical-layer Security Transmission

With the development of bandbroad service,the demands of bandwidth are increasing,passive optical network?PON?provides advantages such as:big data capacity,low cost and energy sufficient.For these reasons,OFDM are getting more and more attention and is a promising candidate for next generation PON technology.However,the OFDM signals enjoy high peak-to-average-power-ratio?PAPR?,which can lead to power saturation and nonlinear distortion.Besides,considering the broadcast structure of downstream traffic in OFDM transmission and big number of subcarriers,the data transmission became more susceptible to malicious attacks,thus physical-layer encryption becomes desirable but challenging.Since the introduction of chaos theory,the chaos system has attracted people's attention for its advantages:such as randomness and high sensitivity to initial values.To overcome the disadvantages of OFDM-PON,many schemes have been approved.Among these techniques,chaos based techniques are prominent.This thesis combines chaos system with traditional PAPR-reduction techniques in optical OFDM-PON to create chaos-based precoder matrix.The structure of our thesis consists of three parts:?1?Based on conventional ZCMT precoder matrix,the thesis introduceschaos system to change the parameters of traditional ZCMT matrix and then permutate the row and column index of ZCMT precoder.Chaos-based ZCMT precoder is created dynamically to precode transmitted information.As we have shown in our paper,the PAPR-reduction property of conventional ZCMT matrix remains,which guarantee the transmission performance of OFDM signals.Further,chaos system improves the physical layer security.Results of experiment show that,the BER performance of the encrypted signals is improved by^BER@-and the key space is about,which makes it impossible to encrypt the transmitted information via brutal attack.?2?A novel method for reconstruct ZCMT matrix is put forward to bothreduce the PAPR of OFDM-PON and improve the security of the system.In the new scheme,the chaotic ZCMT matrix is generated by randomly extraction operation.Compared with the scheme proposed in part?1?,the new scheme decrease the computational complexity.?3?A novel chaotic pilot insertion scheme is put forward.With the helpof chaos,we first change the order of the column index of the pilot data;and then replace static pilot interval with chaotic pilot interval;at last,we do row and column permutation to the encrypted pilot data,which makes the pilot data disordered completely.By setting up experiment,we can find the encryption scheme needs no side-band information and the enhanced key space of¹0³³⁰³ is achieved in comparison with the reported encryption schemes based on pilot in IMDD-based OFDM-PON...