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Multicast routing in cognitive radio networks: algorithms and protocols
ZHOU Kunxiao, ZHAO Hui, YUAN Huaqiang
Journal of Computer Applications    2017, 37 (2): 422-426.   DOI: 10.11772/j.issn.1001-9081.2017.02.0422
Abstract558)      PDF (1068KB)(646)       Save
Cognitive Radio Network (CRN) plays a critical role in achieving better wireless bandwidth utilization and improving the quality of wireless applications. Multicasting in CRN is a challenging problem due to the dynamic nature of spectrum opportunities available to the secondary users. Researchers have proposed a variety of schemes for efficient multicast in cognitive radio networks, including schemes based on optimization theory, network coding, machine learning, and game theory. The algorithms and techniques for solving the multicast problem effectively were summarized, and a comprehensive survey of protocols was given. Finally, future research directions were identified.
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Research on properties of shared resource matrix method based on double cross linked list
YANG Peng, ZHAO Hui, BAO Zhonggui
Journal of Computer Applications    2016, 36 (3): 653-656.   DOI: 10.11772/j.issn.1001-9081.2016.03.653
Abstract620)      PDF (641KB)(379)       Save
Concerning the high time-complexity of shared resource matrix method based on array storage in the detection of system covert channel, an improved algorithm based on double cross linked list was proposed. Firstly, traditional array storage was improved by double cross linked list storage in transitive closure operation. Secondly, a probability model for shared resource matrix method was constructed. Finally, the time-complexity of the improved algorithm and features of shared resource matrix were analyzed under the probability model. When the shared resource matrix was a sparse matrix, using the improved algorithm based on double across linker storage could prompt 67% time efficiency of shared resource matrix compared to traditional realization based on array storage. When the scale of shared resource matrix was quite great, the property of transitive closure operation would cause quick filling of elements in shared resource matrix, then the time efficiency advantage of improved algorithm based on double cross linker was declined compared to traditional algorithm based on array storage. This property of transitive closure operation was proven through theoretical deduction under the probability model.
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Deep space data delivery strategy based on optimized LT code
ZHAO Hui, FANG Gaofeng, WANG Qin
Journal of Computer Applications    2015, 35 (4): 925-928.   DOI: 10.11772/j.issn.1001-9081.2015.04.0925
Abstract568)      PDF (765KB)(662)       Save

Focusing on the shortcomings such as long delay, high Bit Error Rate (BER), asymmetric channel in deep space communication, high redundancy and low decoding success rate of short LT codes, a new deep space data delivery strategy based on Optimized LT (OLT) codes was proposed. First, the OLT codes was given by adjusting the degree distribution function, and adopting new packet selection strategy and joint decoding algorithm. Then, a deep space data delivery strategy based on OLT codes was presented, in which the sender encoded the data file and sent it out, and the receiver got the data by decoding the encoded packets by use of joint decoding algorithm. The simulation results show that compared with LT codes, OLT codes can improve decoding success rate and reduce redundancy. Besides, compared with CFDP, the proposed strategy can effectively reduce the delay and improve the validity and reliability of data delivery, especially in the case of high packet loss rate.

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Video shot boundary detection method based on pre-processing
ZHANG Yikui ZHAO Hui
Journal of Computer Applications    2014, 34 (11): 3327-3331.   DOI: 10.11772/j.issn.1001-9081.2014.11.3327
Abstract155)      PDF (777KB)(547)       Save

To solve the high consumption problem of fast video Shot Boundary Detection (SBD), an improved Shot Boundary Detection (SBD) method was proposed based on video pre-processing. Adaptive threshold was taken to select the candidate segments which may contain shot boundaries, the beginning frame was detected by comparing the similarity value between the first frame and the rest frames in the candidate segments, and then cut was detected immediately. Gradual transition would be detected if no cut was detected. Candidate segments had to be adjusted to ensure the whole transition was located in the same segment. Ending frame was confirmed by comparing the similarity value between the beginning frame and the rest frames in segment. Experimental results demonstrate that the proposed algorithm achieves an accuracy above 90% and the time cost is reduced 15.6%-30.2% compared with inverted triangle pattern matching method. The proposed algorithm satisfies the need of accuracy and improves detection speed compared with the traditional methods which need detection for both cut and gradual transition.

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Facial feature point tracking of active appearance model based on prediction of strong tracking filter
TONG Lei ZHAO Hui
Journal of Computer Applications    2013, 33 (02): 511-514.   DOI: 10.3724/SP.J.1087.2013.00511
Abstract719)      PDF (629KB)(392)       Save
Active Appearance Model (AAM) can locate facial feature points of video sequences. When the initial position is far away from the destination, the fitting process often falls into local minimum, so that the iteration cannot converge to the correct location, resulting in locating failure. Concerning this problem, a facial feature point tracking method of AAM using prediction of strong tracking filter (STF-AAM) was proposed. Firstly, it viewed the head movement in the video as a dynamic system and used Strong Tracking Filter (STF) to predict and track it. So the fitting initial position of each frame was found and fitting algorithm was executed. This method could find the fitting initial position of each frame of video sequences and achieve a more accurate and more rapid tracking result. The experimental results show that the proposed method performs better than the traditional method in the tracking speed along with the fitting accuracy.
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New power control scheme with maximum energy efficiency in wireless transmission
ZHAO Hui ZHANG Xue LIU Ming GONG Haigang WU Yue
Journal of Computer Applications    2013, 33 (02): 365-381.   DOI: 10.3724/SP.J.1087.2013.00365
Abstract861)      PDF (735KB)(424)       Save
Energy efficiency is an important metric in wireless Ad Hoc networks. Until now, there is no universally accepted definition of energy efficiency, and the related results are asymptotic or qualitative, which has limited its applicability. By regarding a bit as a physical particle with one unit of mass, the authors assumed that a bit in transmission possessed a certain amount of kinetic information energy. As a result, the energy efficiency of wireless transmission was defined as the ratio of information energy to physical energy. A quantitative analysis on energy efficiency in wireless transmission was carried out and meaningful results were obtained. It is concluded that the energy efficiency changes non-monotonously with the transmission power, and there is an optimal transmission power, with which the maximum energy efficiency will be acquired. The optimal transmission power was given to help the protocol design. Based on the theoretical results, a practical solution for transmission power control was proposed, and an extensive experimental study of it was given on the CC2420 radio. The results show the effectiveness of the proposed transmission power control scheme.
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OWL-based Web service component
ZHAO Hui-jie,SHEN Jian-jing
Journal of Computer Applications    2005, 25 (03): 634-636.   DOI: 10.3724/SP.J.1087.2005.0634
Abstract1152)      PDF (146KB)(852)       Save

Based on component technology, a method of OWL-based Web service was proposed. Combined with atom-component and ontology, the Web service component granularity became a single function component. The application of OWL and ontology improved Web service at information and knowledge.

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