End-to-end optimized TCP-friendly rate control for real-time video streaming over wireless multi-hop networks

Rate control is an important issue in video streaming applications. The most popular rate control scheme over wired networks is TCP-Friendly Rate Control (TFRC), which is designed to provide optimal transport service for unicast multimedia delivery based on the TCP Reno’s throughput equation. It assumes perfect link quality, treating network congestion as the only reason for packet losses. Therefore, when used in wireless environment, it suffers significant performance degradation because of packet losses arising from time-varying link quality. Most current research focuses on enhancing the TFRC protocol itself, ignoring the tightly coupled relation between the transport layer and other network layers. In this paper, we propose a new approach to address this problem, integrating TFRC with the application layer and the physical layer to form a holistic design for real-time video streaming over wireless multi-hop networks. The proposed approach can achieve the best user-perceived video quality by jointly optimizing system parameters residing in different network layers, including real-time video coding parameters at the application layer, packet sending rate at the transport layer, and modulation and coding scheme at the physical layer. The problem is formulated and solved as to find the optimal combination of parameters to minimize the end-to-end expected video distortion constrained by a given video playback delay, or to minimize the video playback delay constrained by a given end-to-end video distortion. Experimental results have validated 2–4 dB PSNR performance gain of the proposed approach in wireless multi-hop networks by using H.264/AVC and NS-2.     

Quality-driven cross-layer optimized video delivery over LTE

3GPP Long Term Evolution is one of the major steps in mobile communication to enhance the user experience for next-generation mobile broadband networks. In LTE, orthogonal frequency- division multiple access is adopted in the downlink of its E-UTRA air interface. Although cross-layer techniques have been widely adopted in literature for dynamic resource allocation to maximize data rate in OFDMA wireless networks, application-oriented quality of service for video delivery, such as delay constraint and video distortion, have been largely ignored. However, for wireless video delivery in LTE, especially delay-bounded real-time video streaming, higher data rate could lead to higher packet loss rate, thus degrading the user-perceived video quality. In this article we present a new QoS-aware LTE OFDMA scheduling algorithm for wireless real-time video delivery over the downlink of LTE cellular networks to achieve the best user-perceived video quality under the given application delay constraint. In the proposed approach, system throughput, application QoS constraints, and scheduling fairness are jointly integrated into a cross-layer design framework to dynamically perform radio resource allocation for multiple users, and to effectively choose the optimal system parameters such as modulation and coding scheme and video encoding parameters to adapt to the varying channel quality of each resource block. Experimental results have shown significant performance enhancement of the proposed system.     

基于多带的2.4 kbit/s波形内插算法

由于传统特征波形内插语音编码算法对特征波形相位信息的忽略,以及对特征波形的整体对齐,往往造成语音高频谐波分量丢失,从而导致语音的噪声感。为了提高合成语音的质量,该文引入语音多带清浊音标志,并以此为依据对波形内插编码模型中的慢渐变波形和快渐变波形的相位谱进行估计,在语音合成时则对特征波形采取部分对齐的方法,最后提出了一种基于多带的2.4 kbit/s特征波形内插算法。与传统算法相比,新算法明显提高了语音的清晰度。与标准2.4 kbit/sMELP算法相比,该算法合成语音质量亦略显优势。     

Cobalt‐Doping in Molybdenum‐Carbide Nanowires Toward Efficient Electrocatalytic Hydrogen Evolution

Efficient hydrogen evolution reaction (HER) over noble‐metal‐free electrocatalysts provides one of the most promising pathways to face the energy crisis. Herein, facile cobalt‐doping based on Co‐modified MoO_x–amine precursors is developed to optimize the electrochemical HER over Mo₂C nanowires. The effective Co‐doping into Mo₂C crystal structure increases the electron density around Fermi level, resulting in the reduced strength of Mo–H for facilitated HER kinetics. As expected, the Co‐Mo₂C nanowires with an optimal Co/Mo ratio of 0.020 display a low overpotential (η₁₀ = 140 and 118 mV for reaching a current density of –10 mA cm^?2; η₁₀₀ = 200 and 195 mV for reaching a current density of –100 mA cm^?2), a small Tafel slope (39 and 44 mV dec^?1), and a low onset overpotential (40 and 25 mV) in 0.5 m H₂SO₄ and 1.0 m KOH, respectively. This work highlights a feasible strategy to explore efficient electrocatalysts via engineering on composition and nanostructure.     

Flexible Plasmonic Metasurfaces with User‐Designed Patterns for Molecular Sensing and Cryptography

Flexible plasmonic metasurfaces have garnered considerable attention because the material's mechanical flexibility enables new functionalities and integrated applications. Here, by adopting low‐cost materials and simple techniques, we demonstrate a method of fabricating large flexible metasurfaces with arbitrary user‐designed iridescent patterns. These naked‐eye recognizable patterns together with their excellent plasmonic activities have yielded new functionalities and novel applications. Demonstrations include plasmonic sensing, reflective displays, developing new encryption strategies and integrated devices, etc. Moreover, the low fabrication cost (?2) would enable the practical use of the material. The metasurface can even be fashioned into an innovative, multifunctional medical ID bracelet. We believe our flexible plasmonic metafilm will inspire the fabrication of many novel applications and open up new horizons in various fields.     

Novel fingerprinting mechanisms for indoor positioning

As wireless communications and microelectronic technology rapidly develop, diverse applications and services based on smart handheld devices have drawn the attention of researchers. The popularity of Indoor Location Based services and applications has also gradually increased. Therefore, how to improve indoor positioning accuracy becomes a very important issue. Although indoor positioning has been performed using various techniques in recent years, the computational complexity of ensuring positioning accuracy and positioning is an unsolved problem. Current indoor positioning systems typically use only the receiver or the transmitter to obtain the reference point data, and only the K‐Nearest Neighbors (KNN) or Trilateration algorithm is used to perform positioning. Therefore, positioning accuracy is limited by the use of reference point data from a single source and by the positioning algorithm used. The Novel Fingerprinting Mechanisms (NFM) indoor positioning system proposed in this study, however, uses both the receiver and transmitter to obtain positioning data and employs six positioning mechanisms to improve the current positioning accuracy. The experimental results show that the average error distance is 1.18 m in the NFM indoor positioning system. That is the system outperforms both KNN and Trilateration systems, which have average error distances of 1.35 m and 2.23 m, respectively. This study proves that the positioning accuracy is actually improved. Copyright © 2015 John Wiley & Sons, Ltd.     

彩信业务典型问题的分析及优化方法的探讨

主要以当前网络中增长较快的彩信业务存在的QoS低的问题为出发点,详细分析了彩信业务的关键流程及环节,确定了影响彩信业务QoS的关键因素。进一步介绍了彩信业务优化方法,进行了优化前后网络指标的对比。提出了终端规范性管理方式及智能支撑分析系统的建设思路。     

电源滤波器在医用电气设备中的应用

本文通过分析电磁干扰的主要类型以及其在医用电气设备中的危害,着重讨论将电源滤波器应用于医用电气设备中,以解决医用电气设备的电磁干扰现象。     

Design and application of a depletion-mode NJFET in a high-voltage BiCMOS process

A novel depletion-mode NJFET compatible high-voltage BiCMOS process is proposed and experimentally demonstrated with a four-branch 12-bit DAC(digital-to-analog converter).With this process,an NJFET with a pinch-off voltage ofabout-1.5 V and a breakdown voltage of about 16 V,an NLDDMOS(N-type lightly-dosed-drain in MOS) with a turn-on voltage of about 1.0 V and a breakdown voltage of about 35 V,and a Zener diode with a reverse voltage of about 5.6 V were obtained.Measurement results showed that the conver...