Liu Zhenzhen, Niu Kai, Dong Chao, Lin Jiaru
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1001
Abstract ( 298 ) PDF (0 KB)( 135 )
Wang Jie, Tao Xiuli, Hu Xiaoguang, Guan Enyi, Ding Zhushun, Li Wen
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1002
Abstract ( 299 ) PDF (0 KB)( 105 )
A segmentation multi-dimensional crest factor reduction (SMD-CFR) algorithm is proposed for multi-service supporting digital radio over fibre (DRoF) system. Benefit from segmentation dynamic clipping threshold and clipping factor got basing on characteristics of all service bands, the SMD-CFR is able to get better peak clipping and peak to average power ratio (PAPR) reduction for multi-band combined signal. Simulation results show that SMD-CFR gets more than 2.3 reduction in PAPR for two-bands combined signal of long term evolution (LTE), which is much better than traditional one dimensional (1D)-CFR. Meanwhile, for 64-quadrature amplitude modulation (QAM) modulation and demodulation link, it has very small effect on bit error rate (BER) and error
vector magnitude (EVM), which are controlled less than 0.1% and 0.2% respectively. For hardware experiment, SMD-CFR obtains 4.5% increase in drain efficiency and about 4 dBc increase in adjacent channel leakage ratio (ACLR). These are very significant for the wide band power amplifier (PA) in multi-service supporting DRoF system.
Li Shunbo, Huang Guangqiu, Wang Yan, Hui Feifei, Peng Jialong
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1003
Abstract ( 327 ) PDF (0 KB)( 122 )
Achterbahn-128 is a stream cipher proposed by Gammel et al. and submitted to the eSTREAM project. Though many attacks have been published, no recovery attack better than Naya-Plasencia‘s results with 256 bit keystream limitation. Similar approach is shown and found a specific parity check and decimation. Then an improved distinguisher is constructed for Achterbahn-128 to recover the key with only O(255) keystream bit and O(2102) time
complexity. Furthermore, this result is much more effective than the former.
Zhang Junsong, Jiang Yongcong, Gan Yong, Zhang Qikun
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1004
Abstract ( 261 ) PDF (0 KB)( 120 )
With the development of wireless network and electronic technologies, the wireless sensor network (WSN) has been widely used in many applications. One of the most important applications is wireless medical sensor network (WMSN), which makes modern health-care more popular. However, most of the sensor data transmitted in the WMSN is patient-related information. The sensor data are important and should be confidential. In addition, the attackers may also maliciously modify these sensor data. Therefore, both security and privacy are two very important issues in WMSN. A user authentication protocol and data security transmission mechanism based on bilinear pairing is proposed to protect data security and privacy. The proposed protocol enables the medical staff to monitor the health status of health care workers and provide timely and comprehensive health care information to the patient. Finally, through security and performance analysis, it can be found that the proposed authentication and key agreement protocol can resist common attacks such as impersonation attack, replay attack, online or offline password guessing attack, and stolen verifier attack. At the same time, this agreement is also in line with the performance of WMSN application environment.
Min Xiangshen, Fan Jiulun, Zhang Xuefeng, Ren Fang
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1005
Abstract ( 291 ) PDF (0 KB)( 177 )
To improve the security of the color image encryption scheme,a color image encryption scheme based on chaotic systems is proposed. Firstly, the proposed scheme sets the color image as a three-dimensional matrix which is scrambled by affine transformation. Second, the Logistic chaotic sequence applied to generate the control parameter and auxiliary key is used to encrypt the three-dimensional matrix. Here, we mainly focus on two methods for
encryption processes. One is to generate a chaotic sequence by Logistic map and Henon map, which is used to perform XOR operation with the scrambled components R‘, G‘, B‘ respectively. The other one is to adopt a binary Logistic sequence to select the pixel position for the scrambled components R‘, G‘, B‘ image, and then applying the Henon map and Logistic map with the auxiliary key to perform the replacement encryption. Based on this, an encrypted image is synthesized. Simulation results show that the proposed image encryption scheme can implement better encryption and achieve higher security performance.
Wang Xiuli, Hao Yakun
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1006
Abstract ( 284 ) PDF (0 KB)( 111 )
Based on the pseudo-symplectic space over F(2v+1) q of characteristics 2, combining the definition of low density parity check (LDPC) codes with the knowledge of graph theory, two kinds of LDPC codes with larger girth are constructed. By the knowledge of bipartite graph and the girth properties of LDPC codes, both the girth of the code C(m1,2v+1,q) and the code C(m2,2v+1,q) are computed are 8. The girth is larger, the performance of LDPC codes is better. Finally, according to the properties of the check matrix and the linear relation between the column vectors of the check matrix, both the minimum distances of the two codes are obtained are 2q +2.
Ding Haiyang, Li Zichen, Bi Wei
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1007
Abstract ( 310 ) PDF (0 KB)( 147 )
(k, n) halftone visual cryptography (HVC) is proposed based on Shamir‘s secret sharing (HVCSSS), and through this method a binary secret image can be hided into n halftone images, and the secret image can be revealed from any k halftone images. Firstly, using Shamir‘s secret sharing, a binary secret image can be shared into n meaningless shares; secondly, hiding n shares into n halftone images through self-hiding method; and then n extracted shares can be obtained from n halftone images through self-decrypt method; finally, picking any k shares from n extracted shares, the secret image can be revealed by using Lagrange interpolation. The main contribution is that applying Shamir‘s secret sharing to realize a (k, n) HVC, and this method neither requires code book nor suffers from pixel expansion. Experimental results show HVCSSS can realize a (k, n) HVC in gray-scale and color halftone images, and correct decoding rate (CDR) of revealed secret image can be guaranteed.
Li Wanghong, Zhu Qi
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1008
Abstract ( 236 ) PDF (0 KB)( 178 )
In heterogeneous wireless networks, there are various kinds of service demands from the users. A network selection algorithm based onthe analytic hierarchy process (AHP) and Similarity is proposed to solve this problem. The services are divided into three classes: Conversational Class, Streaming Class and Interactive Class. According to the characteristics of each service, a different judgment matrix is assigned and then the AHP method is used to
calculate the network attribute weights. Taking the dynamic changes in user demands and network environment into account, a formula based on Lance distance for computing the attributes similarity is derived to evaluate the degree of conformity between user requirements and network attributes, from which the similarity between the user requirements and network attributes is calculated and then the total similarity by weighting. The network with the largest total similarity is the best choice. Simulation results demonstrate the effectiveness of the proposed scheme in improving the quality of service (QoS) according to the user requirements under three kinds of services.
Chen Biyun, Zhang Yerong, Pan Xin
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1009
Abstract ( 262 ) PDF (0 KB)( 117 )
The finite-difference time-domain (FDTD) method is extensively applied in dealing with time-domain microwave imaging(MWI) problems since it is robust, fast, simple to implement. However, the FDTD method is an explicit time-stepping technique, due to the constraint of the Courant-Friedrich-Levy (CFL) stability condition, the time step needs to be as small as the size of the fine cells, which brings a major increase in computational costs. A fast nonlinear electromagnetic reconstruction algorithm for layered loss-y media by using the alternating-direction implicit finite-difference time-domain (ADI-FDTD) method is proposed. This algorithm is based on an adjoint method, and the nonlinear iterations apply the ADI-FDTD method to calculate the forward and adjoint field, and adopt the Polak, Ribiere, Polyar conjugate-gradient (PRP-CG) optimization scheme. By comparing the simulation results based on ADI-FDTD method and the FDTD method, the validity and efficiency of the proposed algorithm have been proved. Furthermore, the relative residual errors (RRE) are introduced as the iterative computation termination conditions, which further prove the accuracy of this algorithm.
Wang Qi, Wang Shigang, Jia Bowen, Du Hailong
The Journal of China Universities of Posts and Telecommunications, 2018, 25 (2). doi： 10. 19682/ j. cnki. 1005-8885. 2018. 1010
Abstract ( 269 ) PDF (0 KB)( 153 )
Due to the scattering effect of suspended particles in the atmosphere, foggy day images have reduced visibility and contrast significantly. Considering the loss of details and uneven defogging results of the contrast limited adaptive histogram equalization (CLAHE) algorithm, a curvelet transform and contrast adaptive clip histogram equalization (HE)-based foggy day image enhancement algorithm is proposed. The proposed algorithm transforms an image to the curvelet domain and enhances the image detail information via a nonlinear transformation of high frequency curvelet coefficients. After curvelet reconstruction, the contrast adaptive clip HE method is adopted to enhance the total image contrast and the foggy day image contrast and detail information. During the histogram clipping process, the clip limit value is adaptively selected based on image contrast and the sub-block image histogram variance. A comparative analysis of the foggy day image enhancement results are obtained by applying CLAHE, and some classical single image defogging algorithms and the proposed algorithm are also conducted to prove the effectiveness of the proposed algorithm with objective parameters.