Xiulin Hu

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Group-oriented applications are urgent in network communications for bandwidth economizations. The security issues in multicast are also urgent to be addressed. And the group key management is the foundation stone of multicast security. It has been extensively studied in recent years. In this article, we introduce the security problem in multicast-oriented(More)
—Scarcity of the spectrum resource and mobility of users make Quality-of-Service (QoS) provision a critical issue in wireless networks. This paper presents a fuzzy call admission control scheme to meet the requirement of the QoS. It searches automatically the optimal number of the guard channels in a base station to make an effective use of resource and(More)
A novel time-varying Doppler frequency synthesizer is presented in this paper. Time-varying Doppler frequency synthesis is one of the most critical problems in high dynamic GPS signal simulator. The presented frequency synthesizer which may be easily implemented by software and hardware in digital domain can accurately control Doppler frequency and its(More)
—A novel high-accuracy ranging method based on code and carrier without carrier-cycle integer ambiguity resolution is proposed. Firstly, get a coarse range measurement value with low measurement accuracy base on the pseudorandom code phase measurements. Secondly, select the carrier frequencies by using the coarse range value and accuracy to make the(More)
—In this paper, a new PRN code optimal design based on unequal-length code modulation is proposed. The better performance of code acquisition in weak signals will be achieved by using this method, because the cross-correlations between different signals have been sliding, thus suppressing multiple access interference effectively. Theoretical analysis and(More)
Scarcity of the spectrum resource and mobility of users make quality-of-service (QoS) provision a critical issue in cellular mobile multimedia networks. This paper presents a fuzzy call admission control scheme to meet the requirement of the QoS while prioritizing handoff call requests over new call requests. It searches automatically the number of the(More)