Chaotic Precoding Matrix For Physical Layer Security In OFDM-PON

As ever-increasing bandwidth demands as a result of the swift progress in broadband services,passive optical network(PON)provides advantages in high data capacity,low cost and energy efficiency.Recently,orthogonal frequency division multiplexing(OFDM)has been regarded as a promising candidate for the next-generation PON.However,OFDM signals suffer from the high peak-to-average power ratio(PAPR),which leads to power saturation and nonlinear distortion at the optical receiver.Meanwhile,with respect to the broadcasting structure of PON in downstream traffic as well as the large number of subscribers in PON,the data transmission become more susceptible to malicious attacks,thus physical-layer encryption becomes desirable but challenging.This thesis proposes chaotic precoding techniques to enhance the physical layer security by introducing a huge key space associated with chaotic permutation operations on the precoding matrix,in the meantime,the transmission performance is improved due to the effective reduction of PAPR via chaotic precoding.These approaches are verified in terms of theories,simulations as well as experimental demonstrations.The main research results in this thesis are summarized as follows:(1)Chaotic Walsh-Hadamard Transform(WHT)encryption scheme It is shown that the WHT matrix keeps its properties after independent row and column permutation.Therefore,the chaotic row/column permuted WHT matrix is applied as a precoder to improve the transmission through the effective reduction of PAPR of OFDM signals,jointly to enhance the physical layer confidentiality by introducing a huge key space via chaotic row/column permutation in standard WHT matrix.(2)Chaotic discrete Hartley Transform(DHT)encryption scheme Chaotic permutations are applied on the row/column of DHT matrix,chaotic subcarrier allocation and chaotic training sequence for OFDM time synchronization,as a result,a huge key space is created by the multi-fold data encryption to enhance physical layer security.Simultaneously,the transmission performance is improved as a result of the significant reduction of high PAPR due to chaotic precoding for OFDM signals.Furthermore,both of the proposed encryption schemes have the advantages of high spectrum efficiency,as well as low computational complexity.These encryption schemes have been successfully demonstrated by ~10 Gb/s OFDM transmission experiments,which verifies that these schemes could be promising candidates for next generation secure OFDM-PON.