多播ATM交换技术

为适应点对多点通信业务的发展,ＡＴＭ交换必须具有多播功能。将ＡＴＭ交换的各种多播实现方式进行分类,并重点介绍了近期关于循环复制多播技术的进展。     

重叠编码放大转发协作通信系统研究

为进一步提升协作通信系统的频谱效率,将重叠编码复用技术引入协作通信,设计了采用重叠编码的放大转发（ampli-fy-and-forward,AF）系统,并采用复数域的Viterbi解码算法对其进行译码。在平坦Rayleigh衰落信道下的仿真表明,通过改变不同的编码复用系数,新系统仅使用二阶调制就能使频谱效率高于1（b/s）/Hz。此外,在相同频谱效率下,较传统高阶调制AF协作通信系统,新系统的误比特率（bit error rate,BER）性能有显著提升,如当BER等于10-3时,新系统的每比特能量与噪声功率谱密度之比（Eb/N0）将减少6～7 dB。     

节能减排技术在移动通信机房中的应用

为推动节能减排技术在移动通信机房中的应用, 从整体上降低移动通信公司能耗, 实现移动通信公司节能减排的目标。在分析移动通信机房能耗状况基础上, 对移动枢纽机房和无线基站机房中的通信主设备、 配套电源设备和机房空调环境的节能减排技术应用进行了论述。提出了机房空调环境的气流组织、 集中或分散供电方式、 分布式基站组网、 载频智能关断、 多密度载频、 开关电源整流模块休眠、 蓄电池恒温箱和基站一体化空调节能系统等节能技术的应用方式。以期为移动通信公司今后的网
络建设及网络运营工作, 提供一些节能减排的技术指导。     

基于GMS的汽车事故求救系统设计

为了在汽车意外事故后伤者能得到及时的救援, 设计了一种基于嵌入式的汽车事故求救系统。该系统以MC9S12XS128为主控芯片, 利用三轴加速传感器MPU6050和GPS(Global Positioning System)判断车辆的姿态信息和位置信息, 并通过GSM(Global System for Mobile Communications)模块将车况数据传给呼叫中心和家
属端, 接收端对事故确认后迅速救援。测试结果证明了该系统的可靠性。     

乌鲁木齐市区移动通信基站电磁辐射水平现状调查

为了解乌鲁木齐市市区移动通信基站电磁辐射水平现状,消除公众对电磁辐射危害的担忧,保障公众成员的身心健康。按照电磁辐射监测规范选取典型通信基站进行监测,监测结果表明乌鲁木齐市市区移动通信基站电磁辐射水平符合国家规定的限值标准,未对周围环境产生电磁辐射污染。     

放大转发协作下多S-R-D节点网络中继选择策略

在多个信源、中继及目的端的环境中,研究了放大转发协作系统的中继选择策略与传输机制.为了求得最优解,在最优中继节点选择策略中使用了穷举算法,此方法计算复杂度会随着中继节点数目增加而大幅上升.在此基础上,提出了改进的中继节点选择策略,该策略先使系统的平均误码率最小,之后再使目的端中断容量最大化.仿真及分析结果表明,该策略除了能达到与最优算法类似的吞吐量之外,复杂度也大大降低.     

Laser intensity induced transparency in atom-molecular transition process

We propose a new transparency mechanism, which is based on photoassociation （PA） laser intensity induced transitional frequency shift for ultracold cesium molecules formed in PA scheme. The PA laser intensity is supposed to change before the atommolecule resonance. Thus, a remarkable transparent effect for PA laser is expected to appear in the vicinity of original resonant transitional line, where the variation of PA laser intensity induces the shift of the excited molecular levels. The mechanism is different from electromagnetically induced transparency effect and interesting for further research on the scattering length for cesium atomic condensate.     

Exploiting cooperative multipath –Doppler diversity in relay-assisted high-speed train communications

Severe doubly selective channel fading, or the time- and frequency-selective fading, prevailing in high- speed train （HST） communications, has been a critical issue that hinders the improvement of system efficiency and reli- ability. In this paper, a relay-assisted HST communication system is considered, and a low-complexity but effective scheme is proposed to cooperatively exploit the joint mul- tipath-Doppler diversity of both the direct link and the relay link and thus to mitigate the negative effect of channel fading and improve the system reliability. In particular, using a special precoding structure followed by two-dimensional Fourier transform, the transmit signal is generated which in effect parallelizes the doubly selective fading channel. As a result, in the transform domain, pointwise combining and equalization, which are of linear complexity, become feasi- ble and diversity gain is obtained. The maximal diversity order is then analyzed under the amplify-and-forward relay settings, which reveals that by cooperative relaying the joint multipath-Doppler diversity of both links can be well exploited. Simulation results verified our analysis.     

Synthesis of Ta C and Ta_2C from tantalum and graphite in the laser-heated diamond anvil cell

The pressure dependence of the onset of the formation of Ta C and Ta2 C from the elements has been investigated by in situ X-ray diffraction and pyrometry.Ta C has been synthesized by the reaction of Ta and graphite at pressures between 8.6 and 14.3 GPa and at temperatures up to 2,300 K using a laser-heated diamond anvil cell. The products were characterized by X-ray diffraction. Ta and graphite begin to react around 1,100 K at ambient pressure conditions, and the reaction temperature increases with increasing pressure. A linear extrapolation of these data is consistent with recent observations of the formation of Ta C at 90 GPa and 3,600 K. We show that diffusion of carbon into tantalum significantly changes the lattice parameter of up to 2 % in the pressure range of up to19 GPa. In some experiments, Ta2 C was formed concomitantly. The experimentally determined bulk modulus of Ta2 C is B0;exp：= 286（5） GPa. Other tantalum carbide phases were not observed.     

具有周期起伏业务流的电信系统的分析

由于通信业务的不断扩展,迫切需要展开对非平稳业务流的分析.该文将传统的处理平稳业务流的方法推广为能处理周期性起伏业务流的新方法.