The Research Of M-ary Pseudorandom Sequences For Phase-hopping Spread Spectrum

With the rapid development of society,wireless communication has been gradually developed into one of the basic needs of people.At present,wireless communication system uses Frequency-Hopping and Direct-Sequence spread spectrum methods to resist interception and detection.With the improvement of the interception capability and the ability of signal identification and processing algorithms,the anti-interception and the anti-reception capabilities of Frequency-Hopping and Direct-Sequence spread spectrum are becoming increasingly weak.Phase-Hopping spread spectrum modulation can improve the anti-detection performance,anti-interception performance and anti-reception performance of wireless communication systems without increasing the system bandwidth.In order to prevent non-cooperative parties from stealing effective information,the Phase-Hopping sequences serving Phase-Hopping spread spectrum modulation should have good randomness,complexity and unpredictability.The specific work of this thesis is as follows:The related theory of pseudorandom sequence and Phase-Hopping spread spectrum modulation method are studied.In view of the characteristics of Phase-Hopping spread spectrum,key indicators such as Phase-Hopping auto-correlation and cross-correlation are proposed as evaluation criteria,and the construction method of M-ary pseudorandom sequences based on shift register,linear congruence and chaotic sequences are compared.Among them,the construction method based on chaotic sequence has more advantages.This thesis proposes a method for improved chaotic sequences.This construction method generates a sequence by modifying the parameters in the Chebyshev mapping by the modified Logistic mapping,and multiply quantizes the sequence with the sequence generated by the original Chebyshev mapping to obtain the M-ary chaotic sequence.In terms of Phase-Hopping correlation,balance and complexity,a comparative analysis of the improved chaotic sequence and the sequence generated by several single-level mapping methods is performed.The prediction methods based on RBF neural network and RNN are studied as a means to check the security of chaotic sequences.The prediction accuracy,the prediction SNR,the prediction SME and other indicators are used as indicators to evaluate the sequence anti-prediction performance,the improved chaotic sequence is compared with the sequence generated by several single-level mapping methods.The comparison experimental results show that the M-ary pseudorandom sequences generated by the method proposed in this thesis has excellent balance and a sufficient number of available sequences.Using it as a Phase-Hopping sequence for Phase-Hopping spread spectrum modulation can make the modulation more secure and have better anti-reception and anti-prediction capabilities.