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进入信息时代,随着高技术兵器的广泛使用,美军从真正意义上实现了“决胜于千里之外”,之所以取得两次对伊战争的胜利,从很大意义上讲和美军信息作战计划的制定密不可分。本文简要介绍了美军信息作战计划的制定,分阶段阐述了信息作战计划制定中应重点考虑的因素。  相似文献   

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从企业信息资源计划的需求出发,探讨基于微软SharePoint门户技术实现企业信息资源计划,对企业信息门户部署提出一些建议。  相似文献   

4.
张德民 《数字通信》1998,25(1):3-5,9
介绍了日本“日本通信研究开发基本计划”该计划勾画了21世纪日本在信息通信领域中的发展趋势,对我国信息通信技术的发展具有一定的借鉴意义。  相似文献   

5.
“维纳斯”启示录   总被引:1,自引:0,他引:1  
<正> 美国微软公司董事长兼首席执行官比尔·盖茨于今年3月10日在深圳发布和演示了该公司专为中国市场开发的新产品“维纳斯”,而实施该产品在中国的市场化行动被命名为“维纳斯计划”。这是基于微软开发的嵌入式操作系统Windows CE的一种新型消费电子产品。它将计算机技术与家用电器设备(如VCD、电视机、电话机等)有机结合,据称其宗旨是为中国百姓提供一种简便经济的上网、学习和娱乐的工具。 与中国业界精英的争相加盟和中国政府的积极介入形成鲜明对照的是,国内几乎所有重要媒体都对此作出了极其强烈的反应。舆论的态度褒贬不一,但持反对意见的明显占了上风。赞成者认为“维纳斯计划”将会使中国百姓“轻松上网”的美梦成真,中国厂家因此而抱上了一个“金娃娃”;反对者认为微软是想  相似文献   

6.
美国司法部要求Alltel和Western Wireless提供有关其并购计划的更多信息。  相似文献   

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国外信息基础设施的发展情况   总被引:1,自引:0,他引:1  
对近来国外信息基础设施的发展情况作了较为详细的介绍,包括负责实施信息基础设施的机构,建设信息基础设施的有关政策以及各国的信息基础设施实施计划。重点介绍了美国,加拿大,欧盟,日本和韩国的情况。  相似文献   

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针对当前国家和国防信息安全基础设施及安全防护体系建设的需要,文章简要介绍并分析了美国网络信息保障的发展战略与具体的发展计划,结合“保护、检测、响应与恢复”这一信息保障原则,阐述了美国在加强网络保障、身份保障和信息保障,以及在增强网络监视与侦察能力、动态防御能力和网络身份敌我识别能力等方面采取的具体措施,并基于中国信息安全保障体系建设的现状,提出了建设原则和建议,对中国网络安全和信息保障体系建设有借鉴和启发意义。  相似文献   

9.
张捷 《电信网技术》2003,(12):25-28
对ITU-T建议E.129的产生背景、主要内容以及实施情况进行了介绍。  相似文献   

10.
提出了按电气信息类宽口径专业培养人才的思路,并进行了大量的调查研究,提出了改革方案。以西安交通大学电气信息试点班为载体,进行了研究探索与实践,取得了一定的经验和成果。  相似文献   

11.
鲍晶晶  赵兴华 《通信技术》2011,44(7):7-9,12
提出一种基于空时分组编码的异步正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)协同分集方案。提出的方案在中继节点实现OFDM调制及OFDM符号的时间反转和复共轭,信宿节点接收信号的每个OFDM子载波都具有Alamouti空时分组编码结构。信宿节点采用最大似然(ML,Maximum Likelihood)译码准则译码。仿真结果表明,提出的异步OFDM空时协同分集方案无需两个中继节点的同步可获得二阶分集增益,且与其它协同分集方案相比,该方案的误比特率和实现复杂度都更低。  相似文献   

12.
 异步环境下,空时协作传输系统的各中继站点无法精确同步,导致不能直接使用正交空时分组码;异步还可能导致采样时刻的不理想,由于脉冲成型滤波器的缘故,使得平衰落信道变成频率选择性衰落信道,严重影响系统性能.针对这些问题,本文提出一种基于单载波频域均衡的异步空时协作传输机制.各中继站点基于正交空时分组码的思想对数据执行逆序共轭等简单操作后发送;目的站点对接收数据进行快速傅立叶变换(FFT)后,通过线性组合分离重叠在一起的数据帧,然后对组合输出的数据执行频域均衡,最后执行快速傅立叶逆变换(IFFT)还原发送数据.由于FFT和IFFT有快速算法,因此新机制有较低的复杂度.理论分析和仿真结果表明:即使在异步环境下,提出的新机制也能获得空时分组码所提供的分集增益.  相似文献   

13.
We propose a decode-and-forward (DF) based cooperative phase steering scheme and analyze its outage probability. The cooperative phase steering scheme is to make the received signals from multiple relay nodes co-phased at a destination node by pre-adjusting the phase differences.With a reasonable amount of feedback information from a destination node, the cooperative phase steering scheme circumvents the drawbacks of conventional cooperative diversity techniques such as maximal ratio combining (MRC) reception, maximal ratio transmission (MRT), and opportunistic relay selection schemes. Our analytical and simulation results show that the cooperative phase steering scheme outperforms the opportunistic relay selection scheme and approaches the MRT scheme known as a theoretically optimal cooperative diversity technique. It is also shown that cooperative phase steering has sufficient robustness to phase incoherence.  相似文献   

14.
In this paper, we present a hierarchical modulation-based cooperation (HMC) scheme to overcome capacity degradation due to half-duplex transmissions in conventional cooperative relay systems. In the HMC scheme, two relay terminals are used for both transmit and receive operations, i.e., full-duplex transmission. This scheme reduces the required number of time slots for cooperation. Utilizing this cooperative mechanism, the HMC scheme achieves cooperative diversity at the destination node by combining the signals delivered from the source and relay nodes. In addition, we derive a closed form of the end-to-end bit error rate for the HMC scheme, which is utilized to determine an optimal power ratio for hierarchical signals at the source node. In concurrence with the HMC scheme, we develop the best relay selection scheme for a practical wireless communication networks.  相似文献   

15.
In this paper, we propose a cooperative transmission scheme using quasi-orthogonal space-time block codes (QOSTBCs) for multiple-input multiple-output (MIMO) relay networks. Comparing with the conventional cooperative transmission scheme using orthogonal space-time block codes (OSTBCs), the proposed scheme can achieve higher bandwidth efficiency with the same decoding complexity. Moreover, an adaptive decode-and-forward (ADF) relaying protocol is proposed based on one-bit channel state information (CSI) feedback. According to the CSI feedback, a better transmission mode can be selected between the direct transmission and decode-and-forward (DF) cooperative transmission. In addition, the outage performance of the proposed scheme is investigated and a closed-form upper bound on the outage probability is derived. The performance analysis shows that the proposed scheme can achieve a full diversity order, which is higher than that of the direct and DF cooperative transmissions.  相似文献   

16.
赵贤敬  郑宝玉 《信号处理》2008,24(2):183-188
本文提出了一种采用分布式差分空时分组编码和检测的协同分集方案,在不需要信道状态信息(CSI)的情况下可以实现满分集和全速率发射,并推导了相关瑞利信道下该方案误码率(BER)性能上限的解析表达式。传统的差分空时分组编码对整个码块进行差分,而协同分集下的任何一个协同用户进行差分编码时都不知道整个码块的信息。本文所提出的差分BPSK调制方案,通过将两协同用户的信息分别被调制到相互正交的实轴和虚轴上,从而将码块的联合差分转化为各用户独立差分。分析了在协同用户间不同的信道状态信息(CSI)和协同用户到接收用户不同的CSI情况下本文所提出发射方案的性能。仿真结果表明本文所提出的方案获得了明显的分集增益,同时也较好的吻合了理论分析的结果。  相似文献   

17.
王爽  周斌  卜智勇  于伟 《信号处理》2021,37(6):1105-1112
研究了具有三个全双工源节点的协作通信系统,为提升系统有效性和可靠性,提出了两种信源间全双工协作通信的空时编码方案。将正交空时码理论应用其中,可以有效利用空间分集增益,抵抗多径衰落,提高系统性能。方案分为共享兼传输阶段与协作传输阶段。在共享兼传输阶段进行信源间的信息共享同时也会向目的节点发送信息,在协作传输阶段,源节点间形成虚拟MIMO向目的节点发送信息。推导了系统各个接收端的中断概率,仿真结果表明,与现有源节点工作在半双工模式下的协作传输方案对比,该方案有效提升了吞吐量和中断概率性能,在中断概率为10-3时,该方案有1.5 dB左右的信噪比增益,与无协作传输对比,该方案有约8 dB左右的信噪比增益。   相似文献   

18.
We propose a cross-layer design which combines truncated ARQ at the link layer and cooperative diversity at the physical layer. In this scheme, both the source node and the relay nodes utilize an orthogonal space-time block code for packet retransmission. In contrast to previous cooperative diversity protocols, here cooperative diversity is invoked only if the destination node receives an erroneous packet from the source node. In addition, the relay nodes are not fixed and are selected according to the channel conditions using CRC. It will be shown that this combination of adaptive cooperative diversity and truncated ARQ can greatly improve the system throughput compared to the conventional truncated ARQ scheme and fixed cooperative diversity protocols. We further maximize the throughput by optimizing the packet length and modulation level and will show that substantial gains can be achieved by this joint optimization. Since both the packet length and modulation level are usually discrete in practice, a computationally efficient algorithm is further proposed to obtain the discrete optimal packet length and modulation level.  相似文献   

19.
编码协作分集研究与展望   总被引:2,自引:0,他引:2  
用户协作方案是协作分集研究的一个重要方面。在慢衰落和快衰落信道条件下,均能带来传输性能改善的编码协作分集方案,是目前协作分集方案中备受关注的一种。尤其在将空时编码的思想引入该方案后,更带来了编码协作分集在快衰落信道条件下的良好性能。用户要想从协作中受益,协作伙伴/中继节点的选取是编码协作分集中一个重点。  相似文献   

20.
In a multi-user communication system, cooperative diversity allows single-antenna mobile sets to achieve transmit diversity. Cooperative diversity improves the communication capacity and enhances the robustness of a wireless link when a single channel alone is not reliable. In this paper, a novel cooperative diversity scheme is introduced that enables simultaneous transmission of non-redundant data from all cooperative terminals. By taking advantages of both high-rate full-diversity space-time codes and the cooperative diversity, the proposed method provides high diversity gain beyond the number of physical transmit antennas without compromising the data rates. In essence, the proposed system aims at higher data rates over the non-cooperative counterpart, while maintaining the full diversity gain.  相似文献   

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