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Rate control for streaming media transmission
over WLAN
ZHU Xiaoliang, DU Xu, ZHU Xiaoliang
Front. Electr. Electron. Eng.. 2008, 3 (3): 309-312.
https://doi.org/10.1007/s11460-008-0049-8
In order to solve the problems of link layer retransmission and packet fragment strategies for IEEE 802.11, this paper proposes a variable packet TCP-friendly rate control (VPTFRC) scheme for streaming media transmission over wireless local area network (WLAN) by researching on the policy of packet size adjustment in transport layer based on the minimum retransmit-delay constraint. Unlike other proposals, this process considers the impact of wireless packet error ratio (PER) on the packet size adjustment and the performance of rate control. Simulation results demonstrate that our proposed process can simultaneously achieve higher throughput, better fairness, shorter transmission delay and less jitter than TFRC. Among them, the ratio of delay, jitter and packet loss rate can reach a maximum improvement ratio of 58%, 42% and 85% respectively.
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Wireless sensing experiments for structural vibration
monitoring of offshore platform
YU Yan, OU Jinping
Front. Electr. Electron. Eng.. 2008, 3 (3): 333-337.
https://doi.org/10.1007/s11460-008-0051-1
In order to validate the feasibility of applying wireless sensing technique to structural monitoring of offshore platform, the experiment of wireless sensor network on offshore platform is presented in this paper. First, wireless sensor network and its topology structure is put forward, and the design of sensor nodes, base station, communication protocol is discussed according to self-developed wireless sensor network. Second, true offshore platform and its experimental model are introduced. Finally, wireless sensing experiment for offshore platform structure is completed and the analysis of the experimental result is given. The research shows that wireless sensor network applied to offshore platform can reflect the vibration of the structure; the sensor nodes are fixed and removed expediently, which saves the cost of signal line as well as installation time.
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Blind source separation algorithm for communication
complex signals in communication reconnaissance
FU Weihong, LIU Nai'an, ZENG Xingwen, YANG Xiaoniu
Front. Electr. Electron. Eng.. 2008, 3 (3): 338-342.
https://doi.org/10.1007/s11460-008-0015-5
Most blind source separation algorithms are only applicable to real signals, while in communication reconnaissance processed signals are complex. To solve this problem, a blind source separation algorithm for communication complex signals is deduced, which is obtained by adopting the Kullback-Leibler divergence to measure the signals’ independence. On the other hand, the performance of natural gradient is better than that of stochastic gradient, thus the natural gradient of the cost function is used to optimize the algorithm. According to the conclusion that the signal’s mixing matrix after whitening is orthogonal, we deduce the iterative algorithm by constraining the separating matrix to an orthogonal matrix. Simulation results show that this algorithm can efficiently separate the source signals even in noise circumstances.
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Design of magnet arrays for permanent magnetic
linear motor
MAO Junhong, LUO Junhang, JIANG Qiang, XIE Youbai, JIANG Qiang
Front. Electr. Electron. Eng.. 2008, 3 (3): 358-363.
https://doi.org/10.1007/s11460-008-0052-0
An iron-less single side permanent magnetic linear motor structure is presented, and two-dimensional analytical formulae for its magnetic field are deduced to design the types of magnetic arrays, the thickness of permanent magnet, and the duty ratio of magnet arrays, etc. With certain design parameters, conventional arrays are used instead of a piecewise Halbach arrays, and the machining and assembling of the motor are greatly simplified. Calculation results coincide with that of ANSYS. The analytical formulae can be used in designing cored linear motors by modifying boundary conditions. A linear motor driven bench with a single degree of freedom is realized, where the travel reaches 27 mm, the mass of the moving parts is 1.4 kg, and the maximum acceleration is 11.5 m/s2.
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Study on precision piezoelectric rotary step
motors with inner anchor/loosen and outer drive
LIU Jianfang, YANG Zhigang, ZENG Ping, FAN Zunqiang
Front. Electr. Electron. Eng.. 2008, 3 (3): 364-369.
https://doi.org/10.1007/s11460-008-0062-y
A new precision rotary piezoelectric (PZT) actuator is proposed to improve its drive performance. Based on piezoelectric technology, the actuator adopts the principle of bionics, with a new method of stator inner anchor/loosen/rotor outer drive and a distortion structure of a thin shelf flexible hinge. This structure improves the stability of the anchor/loosen and step rotary. Its characteristics are evaluated by finite element analysis. The experiment shows that the new rotary PZT actuator works with higher frequency (40 Hz), higher speed (325 ?rad/s), wider movement (360°), high resolution (1 ?rad/step) and high torque (30 N·cm). The novel actuator can be applied in wide movement and high resolution driving devices such as those for optics engineering, precision positioning and some other micro-manipulation fields.
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21 articles
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