新型宽带无线接入系统研发进展

宽带无线接入系统已经成为宽带接入和移动通信领域面向未来演化的主体方向之一，但在实际应用和产业推广过程中却遇到了很大困难，需要进一步定位宽带无线接入系统的典型服务模式，推动宽带无线接入关键技术的创新发展，促进宽带互联网络的骨干支撑作用。文章介绍一种宽带无线多媒体接入系统，尝试将地面数字电视系统与宽带无线接入系统结合在一起，以宽带互联网络为核心网平台，共同构建面向“三网融合”的新型宽带无线接入网络。初步研究结果表明，新型宽带无线接入系统可有效地缓解当前宽带无线接入系统所面临的尴尬局面，并在业务范畴、业务覆盖、频率规划、终端功耗和建网成本等多个方面取得较大竞争优势。     

宽带无线多媒体系统标准化的进展

介绍了正在制定中的宽带无线多媒体系统标准,尝试将地面数字电视系统与自主宽带无线接入系统结合在一起,以宽带互联网络为核心网平台,共同构建面向行业应用、支持三网融合的新型宽带无线网络.初步研究结果表明,宽带无线多媒体系统可有效地缓解当前宽带无线接入系统所面临的尴尬局面,并在业务范畴、业务覆盖、频率规划、终端功耗和建网成本等多个方面取得较大竞争优势.     

中国通信标准化协会简讯

"支持集群业务的SCDMA宽带无线接入系统"系列行业标准审查通过送审稿在无线通信技术工作委员会(TC5)宽带无线接入工作组(WG3)工作会议上,审查通过了"支持集群业务的SCDMA宽带无线接入系统"系列行业标准草案送审稿。支持集群业务的SCDMA宽带无线接入系统基于SCDMA宽带无线接入系统,继承了宽带SCDMA大信道容量、高频谱利用率、抗干扰能力强等诸多优点,可以满足     

高速铁路宽带无线接入系统架构与关键技术

本文阐述了高速铁路(以下简称高铁)宽带无线接入系统的需求,研究了高铁宽带无线接入系统的特点,分析了现有无线接入技术的优势与不足,探讨了一种新型的高铁宽带无线接入结构High Speed Mobile Cell(Himocell),最后讨论了高铁宽带无线接入中的几个关键技术。     

未来移动通信中的宽带接入技术

提供移动多媒体综合业务是未来移动通信发展的重要方向,宽带无线接入技术有力促进了这一目标的实现。该文分析了现有的若干接入方案,归纳出宽带无线接入的特点及影响其发展的几项关键技术。结合第三代乃至第四代移动通信系统对宽带业务的要求,指出宽带无线接入对未来通信系统的影响。     

宽带无线接入系统讲座第一讲绪论

首先介绍了宽带无线接入系统的产生发展情况。然后介绍了通信带宽可与光纤通信相比拟、采用蜂窝式的网络结构可使系统覆盖整个城域范围、能够提供多种业务、系统结构比较复杂及对性能要求高等特点，最后介绍了宽带无线接入的几种制式等。     

宽带城域网的无线接入

文章对城域网及宽带无线接入的基本概念作了介绍,对宽带无线接入的不同技术方式进行了分析和比较,讨论了本地多点分配业务系统和其它无线接入技术在宽带城域网应用中需要关注的关键问题——无线接入的网络管理、调制方式和接入协议,重点讨论了无线接入网的安全问题。     

3.5GHz宽带无线接入技术及其在中国的发展概况

本文从3．5GHz宽带无线接入的系统配置、频段选择、提供的业务、用户信息安全保证、3．5GHz宽带无线接入技术与LMDS接入技术比较与分析、3．5GHz宽带无线接入的地位、3．5GHz宽带无线接入在中国的招标概况、中国3．5G无线设备市场竞争格局等方面。详细地介绍了3．5GHz宽带无线接入技术及其在中国的发展概况。     

固定宽带无线接入技术及其标准的分析

在多种“最后一公里”宽带接入解决方案中,宽带无线接入技术以其经济和易于实施等优点越来越受到人们的关注。本地多点分配业务(LMDS)是一种新型的固定宽带无线接入技术。该技术提供双向语音、数据以及视频图像业务,能够实现2Mbit／s的用户接入速率,具有很高的可靠性。IEEE802委员会专门为固定宽带无线接入的无线接口制定了802．16d标准。本文介绍了802．16d的协议结构及各层功能,重点分析了802．16d的MAC层。     

发展无线接入需注意的若干问题

目前,全球宽带通信市场发展迅速,无线化成为宽带接入的未来发展方向.提出在发展无线接入时需注意的若干问题.当前移动接入与固定接入的界限正逐渐变的得模糊,认为统一的标准有利于推动无线接入技术的发展,而且任何宽带无线接入技术必须支持话音业务.接下来剖析了WiMAX的发展情况,分析了WiMAX与3G的关系.最后提出应重视短距离低速率无线接入系统的发展.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-