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In order to solve the issue of malicious phonily occupying seats for some ticket agents or passengers in the process of air ticket sales, this paper proposed a blockchain system scheme based on the improved PoA consensus mechanism. The scheme used the alliance blockchain as a communication platform among airlines, adopted credit points and dynamic grading to build a new PoA consensus mechanism, protected passengers ' private information with hash algorithm, and achieved digital storage of ID information, registration of passengers, storage and sharing of passenger booking information for airline corporations relying on smart contracts. The prototype system trial operation shows that the system can timely detect and effectively stop the phonily occupying seats behavior. After analysis and evaluation, the program has the characteristics of privacy protection, decentralization and high security, and provides a new reference to solve the long-standing problem of phonily occupying seats in the civil aviation field. [ABSTRACT FROM AUTHOR]

The digital trunking system has the characteristics that the calling mode is mainly group calling and the communication mode is mostly half duplex. For the problem that the traditional user classification method couldn't meet the classification requirements of digital cluster users, this paper proposed a digital cluster user classification method based on improved RFM model. Firstly, it introduced the average speech duration attribute to establish the recency vitality speak (RVS) model. Then, it used the analytic hierarchy process to determine the weight of each parameter in the model. Finally, it used the K-means + + clustering algorithm to classify digital cluster users. The simulation result shows that, by using the user classification method proposed in this paper, the accuracy of digital cluster user classification can reach more than 87. 9% . [ABSTRACT FROM AUTHOR]

For the security problem of the spread of digital image and the digital image encryption from plaintext and too depend on the chaotic systems, this paper proposed a digital image encryption and monitoring algorithm combined with plaintext-related chaotic mapping and SHA-256. The algorithm used the SHA-256 algorithm to calculate the hash value as record to monitor the spread of digital image. Lorenz chaotic mapping generated the corresponding cryptogram by using forward diffusion, associated plaintext scrambling and backward diffusion to encrypt the digital image. The results show that the algorithm can resist many attacks and achieve the security and concealment of image propagation. [ABSTRACT FROM AUTHOR]

To deal with the problem that CIM should consume a lot of pseudo noise (PN) code resources when it increased the information transmission rate by increasing the number of mapping bits. This paper proposed a novel generalized code index modulation (GCIM). It divided the information bits of the transmitter into mapped bits and modulation bits and mapping modulation bits and mapped bits into modulation symbol and the indexes of the PN code groups respectively. The in-phase part and the orthogonal part of the modulation symbol spread spectrum by selecting activate PN code group respectively. What’s more, by increasing the number of the activate PN code of per transmission slot, which could increase the number of mapped bits and improved the spectral efficiency and energy efficiency of the system. The simulation results show that it is not better than CIM about 2 dB in the additive white Gaussian noise channel and about 1 dB in the Rayleigh fading channel at the same spectral efficiency. Nevertheless, compared with CIM, GCIM consumes significantly less PN code resources. [ABSTRACT FROM AUTHOR]

This paper proposed a twice channel estimation algorithm, in which used weighted coefficient to cancel ICI caused by Doppler frequency shift in high speed mobile environment. The algorithm achieved twice channel estimation. The first estimation provided channel state information to cancel the ICI under the premise of ensuring the symbol rate. In the case of ICI cancellation, the second estimation enhanced the channel estimation accuracy. Then the algorithm improved the simplified PIC algorithm, and introduced the weighting coefficient to make the residual error smallest after ICI cancellation based on the minimum mean square error criterion. The simulation results are in good agreement with the theoretical analysis. The proposed algorithm improves the estimation accuracy of rapidly time-varying channels. The maximum value of NMSE performance gain is0. 071 4, when the SNR is 0 dB. [ABSTRACT FROM AUTHOR]