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下一代蜂窝系统中通过频谱复用来克服小区间干扰已成为当前研究热点.针对LTE小区间干扰协调问题,重点讨论比较了几种频率复用方案,并提出一种自适应的部分频率复用优化方案和具体实现算法,仿真表明该算法能显著改善小区边缘用户的吞吐量性能和公平性参数. 相似文献
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中继蜂窝网络中小区间和小区内的资源分割 总被引:1,自引:0,他引:1
文章提出了一种应用于固定中继蜂窝网络中基于复用分割的小区间频谱分配框架,通过引入有效复用因子这一指标来优化小区内基站和中继之间的资源分割,并比较了不同的链路带宽分配方案对系统性能的影响。理论分析和仿真结果显示,该方案可以在保证小区边缘用户的吞吐量的同时提高小区容量。 相似文献
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在蜂窝系统中,由于干扰的存在,用户性能受到影响,特别是对于小区边缘用户,其通信质量较差。干扰对齐作为一种能够消除干扰、提高系统容量的技术,近年来受到广泛关注。针对多天线两小区蜂窝系统的边缘用户,本文给出了一种系统开销小、需要天线数少的线性干扰对齐算法。该算法利用发送端预编码矢量消除小区内干扰,利用接收端干扰抑制矢量消除小区间干扰。采用本文算法后,在每个小区有 个用户、基站有 根发送天线、用户有 根接收天线的情况下,只需 和 就可以实现上下行的干扰对齐,整个系统可以达到 的自由度,并且在下行链路中不需要小区间反馈,而在上行链路中只需要较小的小区间反馈。仿真结果表明,本文提出的算法能够以较小的开销实现比以往的算法更好的性能。 相似文献
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频率复用作为提高小区边缘用户性能的有效方式已被广为研究。然而,如何在提高小区边缘用户性能的同时,使频谱利用率得到有效提高仍是一个有待解决的问题。在以正交频分多址(OFDMA)为基本多址方式的第4代(4G)系统中该问题尤为突出。为此,该文提出了一种OFDMA系统中的频率复用方法,通过抑制小区间干扰提高小区边缘用户性能;同时,根据小区中心与小区边缘通信环境的差异,分别对其实施不同的频率复用策略使频率复用系数接近于1以提高频谱利用率。仿真结果表明,与未经过频率规划的全频率复用相比,该文提出的频率复用方法提高了系统吞吐量并显著改善了小区边缘用户性能。 相似文献
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为了解决下一代演进移动通信系统在异构网场景由于低功率基站在高功率基站覆盖区域的随意分布而导致的小区间干扰问题及容量速率限制,提出了一种载波聚合系统的成员载波选择和干扰协同方法。该方法基于修正的载波公平比例准则,动态地在小区间协同选择成员载波。为了进一步提高低功率节点的系统容量,设计了新的基于调和平均数的用户小区选择准则及算法。仿真结果表明,与频率复用因子为1的系统相比,设计的方法由于静默了部分高功率节点用户成员载波,从而使低功率节点用户获得更多的选择机会,可提高低功率节点小区的容量。 相似文献
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由于普遍采用频率复用因子为1的方式组网,多小区干扰已经成为限制无线蜂窝系统容量的主要因素.协作多点传输技术可以有效抑制蜂窝系统中多小区干扰问题,提高小区边缘吞吐率.近年来,作为协作多点传输的一种实现形式,干扰对齐技术受到广泛关注,其优势在于可以获得多小区系统最优的发送自由度.本文提出了一种在干扰对齐技术下基于特征子信道的预编码矩阵优化方案.本方案通过选取与最好的特征子信道对准的预编码矢量发送信号,使得信号经历最好的一组特征子信道,改善接收端的信号强度,从而达到提高系统吞吐量的目的.仿真结果表明,相比已有的预编码矩阵的设计方案,本文提出的方案在系统的吞吐量方面有明显的提升. 相似文献
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聚对苯撑苯并双(口恶)唑发光及其器件制备 总被引:2,自引:0,他引:2
采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加. 相似文献
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在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65~4GHz的频带内隔离深度可达-40~75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证. 相似文献
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Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years. 相似文献
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C. Fulk R. Sporken J. Dumont D. Zavitz M. Trenary B. Gupta G. Brill J. Dinan S. Sivananthan 《Journal of Electronic Materials》2005,34(6):846-850
We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron
spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations.
It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311)
had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy,
while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge
site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging
atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites.
This would ensure a nonpolar, B-face growth. 相似文献
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光子晶体微腔发光二极管 总被引:1,自引:0,他引:1
光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。 相似文献
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The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES. 相似文献
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基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC)。该方法有效简化了TAC电路结构,减小了TAC占用面积,显著提高了TOF的满量程范围(FSR)。采用0.18 μm标准CMOS工艺设计。集成TAC的单光子探测器像素单元的填充因子可达到26.8%。后仿真结果表明,该TAC在120 ns的FSR内具有230 ps的定时分辨率,微分非线性(DNL)低于0.05 LSB,积分非线性(INL)低于1.1 LSB。蒙特卡洛仿真表明,512个TAC像素间的不均匀性低于0.5 %。该TAC非常适用于高密度时间相关的单光子计数(TCSPC)探测器阵列。 相似文献
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Fangqiu Wang Chenghua Wang Shengkui Zhou 《International Journal of Electronics》2013,100(10):1765-1788
Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm. 相似文献
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超宽带脉冲信号的光学生成方法研究 总被引:1,自引:0,他引:1
近年来超宽带(UWB)通信技术迅猛发展,在测量、雷达技术、民用和军事无线通信中有着重要的应用,UWB-over-fiber技术已经成为目前研究的热点,其中就包括UWB脉冲信号的产生方法。区别于传统的电子学方法,光子学产生方法不受电子瓶颈制约,可以实现很高的带宽,并且具有抗电磁干扰、重量轻、结构紧凑的优点。通过对比国内外本领域研究成果,讨论及总结了以下三种原理的UWB脉冲信号的光学生成方法:1)相位调制-强度调制转换(PM-IM);2)半导体光放大器(SOA)的非线性效应;3)频谱塑形和色散所致频域-时域映射,然后对各种方案进行了对比分析。 相似文献
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多孔硅发光机制的分析 总被引:4,自引:0,他引:4
从量子力学的基本理论出发讨论了量子限制效应,推导出多孔硅有效禁带宽度增量并用量子限制效应和表面态及其物质在发光中作用的理论解释了PS光致发光的实验现象。 相似文献