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Articles by Zhijiang Xu
Total Records ( 8 ) for Zhijiang Xu
  Kai Zhou , Limin Meng , Zhijiang Xu , Gang Li and Jingyu Hua
  Wireless sensor networks (WSN) is an energy limited system, thus this study presents an energy-aware quality of service (QoS) routing algorithm for it, which can also run efficiently with best-effort traffic. Furthermore, our work differs from existing algorithms in two ways: (1) We improve the first order energy consumption model with dynamic clustering; (2) We use clustering to build the multi-objectives programming model to support QoS. Simulations and comparisons with some typical route algorithms show that our algorithm is robust and effective.
  Limin Meng , Jingyu Hua , Ying Zhang , Zhijiang Xu and Gang Li
  This study presents a novel initial frame synchronization scheme of TD-SCDMA system. This algorithm uses the implicit power transition in the special frame structure and introduces a different power ratio detector comparing with the conventional non-coherent algorithms, which makes it less complicated and more reliable. We verify our algorithm by computer simulations and the results show a good and robust performance in a wide range of signal-to-noise ratios (SNRs).
  Limin Meng , Weihuang Fu , Zhijiang Xu , Jiangxing Zhang and Jingyu Hua
  This study presents a novel Ad hoc On-Demand Vector (AODV) routing protocol based on mobility prediction, named as MAODV. The algorithm controls route discovery, route keeping and route switching according to the distance and mobility estimation of the neighbor nodes. Simulations demonstrate that MAODV reduces the end-to-end delay effectively and enhance the real-time characteristics.
  Limin Meng , Jingyu Hua , Zhijiang Xu and Gang Li
  In this study, we propose a novel estimator under the time-varying multi-path channel and with its performance robust to Signal-to-Noise Ratio (SNR). This estimator is derived with the help of noise influence analysis and realized through the iterative process. We verify our algorithm by computer simulations and observe a great performance improvement in a wide range of velocities and SNRs.
  Zhijiang Xu , Liting Wang and Kang Wang
  Through the analysis of binomial cascade process, a Cauchy distribution multiplier with variable scale parameter was set up to establish a multifractal cascade model for network traffic. Compared with the moments, partition function and multifractal spectrum of the original data, it was proved that not only the statistical properties of the model can well fit the original data, but also the multifractal characteristic was similar to the actual network data.
  Jingyu Hua , Zheng Gao , Wankun Kuang , Zhijiang Xu and Chengfeng Ruan
  The Weighted Least Squares (WLS) principle is popular in filter design due to its flexibility, where it can output equiripple filters with appropriate target function and weighted function. Therefore, this research studies the influence of the target function in linear phase Finite-Impulse-Response (FIR) filter design by comparing different target functions in WLS iterations. Compared with the traditional one, simulations show that the proposed target function can obtain more accurate stopband start frequencies which will be useful if the stopband start frequency must be precise in applications.
  Qionghua Zhu , Yuan Wu , Peng Hong , Liping Qian , Jingyu Hua , Zhijiang Xu and Limin Meng
  This study investigates the joint sensing assignment and resource allocations for Cognitive Radio (CR) systems where multiple Secondary Users (SUs) opportunistically share the channels of Primary System (PS) through cooperative sensing. The key questions concerned here are how to assign different SUs to sense different channels and how to allocate the transmission power and bandwidth for SUs such that the detected idle channels of PS are fully utilized. Specifically, the cooperative spectrum sensing improves the detection accuracy and reduces the potential interference to PS due to mis-detection. However, the cooperative spectrum sensing and the consequent reports of sensing results consume additional energy which should be taken account of in the SU resource allocations. Hence, the coupling effect between the spectrum sensing and the consequent resource allocations is critical for CR to optimize its performance. Based on these considerations, the problem of joint sensing assignment and resource allocations for CR is formulated as a mixed binary nonlinear programming problem and a two-layer procedure is proposed to obtain the optimal solutions. The extensive results show that due to the energy overhead for sensing and reporting, the optimal number of SUs assigned to sense the PU channel does not increase in the idle probability of the channel monotonically. Meanwhile, to maximize the SUs throughput, the consequent optimal transmission power and bandwidth allocations heavily depend on the sensing accuracy determined by the optimal sensing assignment.
  Zhijiang Xu , Jing Yuan , Kang Wang , LiMin Meng and Jingyu Hua
  A novel structure of secure communication system is proposed. The alpha stable noise sequence which is used for random carrier, is modulated by the binary message sequence to achieve the purpose of secure communication in some scenarios, such as military communications. The correlation between the first and the latter half symbol period of a stable non-Gaussian noise sequence carries the binary information. The receiver of the proposed random communication system demodulates the received signal by calculating the correlation coefficient between the first and the latter half sybmol period of the transmitted noise sequence to recover the binary message sequence. The proposed communication system significantly simplifies the structure of the transceiver because only one alpha-stable noise source in the transmitter and a simple non-coherent demodulation in the receiver are required. To evaluate the proposed system, the Bit Error Rate (BER) performance under additive white Gaussian noise channel is analyzed. And simulation results show that the BER of the system is very low, thus proving that system proposed is rational and secure.
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