共查询到20条相似文献,搜索用时 125 毫秒
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通用组帧规程(GFP)是一种具有实现简单和低开销特点的新型数据链路协议,其帧同步采用基于帧标头循环冗余校验(CRC)的多个帧搜捕器方案。采用状态转移法对其帧同步性能进行研究,并给出计算和数值分析结果。针对该方案帧失步平均持续时间过长的缺点,提出了一种GFP帧同步机制的改进方案。理论分析和计算结果表明,此方案可以有效降低GFP帧同步的失步平均持续时间,改善GFP帧同步系统的性能。 相似文献
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无线传感器网络主要是针对物理环境进行信息采集并将此信息有效的传输给感兴趣的人,那么网络覆盖和路由协议就至为关键.基于这个要求,采用接近实际的节点概率感知模型进行建模,对满足覆盖冗余节点的要求进行分析,并对传统分簇路由协议LEACH进行改进提出创新的覆盖路由协议LEACH-C,并通过MATLAB进行仿真分析.仿真结果表明... 相似文献
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动态频谱接入是认知无线电技术的一个重要应用,它利用通信过程中出现的频谱空洞机会式地接入频谱,能极大地提高频谱的利用率。文章基于马尔可夫理论提出了一种改进的频谱预留接入方案,即按照业务需求对用户进行用户模型改进,并根据优先级不同进行接入策略改进。仿真结果显示该方案能有效保障高优先级用户的服务质量。 相似文献
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针对当前几种主要的激光光束质量检测方法的优点和不足,本文提出了一种改进的测量激光能量分布的方法.并根据该方法的特点设计了一种先对模拟信号差分后再进行A/D转换的测量电路方案.使用MATLAB对该方法和方案进行仿真分析,证明了该方法能准确还原复杂的能量分布图形和该测量电路能有效提高测量精度. 相似文献
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Juyeop Kim Dong-Ho Cho 《Wireless Communications, IEEE Transactions on》2009,8(11):5431-5435
An advanced MAP transmission scheme for improving Media Access Control(MAC) overhead in the IEEE 802.16e systems is proposed. In the IEEE 802.16e system, when a Base Station(BS) broadcasts a MAP message, which is a control message about scheduling information, it applies a robust Modulation and Coding Scheme(MCS) level and allocates a large amount of radio resources, which induce a huge MAP overhead. Our proposed scheme utilizes piggybacked MAP IEs, in which control messages are concatenated with data packets and transmitted with the MCS level applied to data transmission. Due to the fact that the rate at which data is transmitted is generally higher than the rate at which broadcasting messages are transmitted, the proposed scheme can increase average data rate of a MAP transmission and consequently reduce the amount of resources allocated to the MAP transmission. Numerical analysis and simulations are presented to show that the MAP overhead is critical to system performance and can be improved by the proposed scheme. 相似文献
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针对三节点传输系统,研究了基于功率分配能量采集的全双工放大转发协作中继方案。考虑源和目的地之间存在直达链路,全双工中继节点采用天线选择技术以最小化中继自干扰,目的节点采用最大比合并技术以最大化目的地接收信噪比。在延迟受限传输模式下,运用高斯-切比雪夫积分推出了系统吞吐量的近似闭合表达式。在延迟容忍传输模式下,运用凸优化推出了系统吞吐量下界的闭合表达式。在多中继情况下考虑了最佳中继选择策略和机会式中继选择策略。数值分析和蒙特卡洛仿真表明,增加中继个数或者减小速率阈值均能提高系统吞吐量。 相似文献
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Multi-hop packet transmission error due to packet collision is a serious issue for realizing large-scale wireless ad hoc networks. In order to solve the issues, a multicode-reception spread-spectrum (MCR-SS)-CSMA/CA scheme is proposed as multiple access scheme for layered-tree networks. This scheme is further improved by adding a time group access (TGA) technique to gain higher interference reduction between nodes. The proposed TGA scheme divides the layered-tree network into upper subnets group and lower subnets group, thus reducing collision probability among subnets. Network throughput and data delivery ratio for the proposed scheme are analyzed by simulations based on the IEEE 802.15.4/ZigBee specification. Simulation results show that the proposed schemes can improve packet delivery ratio and network throughput remarkably. 相似文献
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Based on the orbital angular momentum and pulse position modulation, we present a novel passive measurement-device-independent quantum key distribution (MDI-QKD) scheme with the two-mode source. Combining with the tight bounds of the yield and error rate of single-photon pairs given in our paper, we conduct performance analysis on the scheme with heralded single-photon source. The numerical simulations show that the performance of our scheme is significantly superior to the traditional MDI-QKD in the error rate, key generation rate and secure transmission distance, since the application of orbital angular momentum and pulse position modulation can exclude the basis-dependent flaw and increase the information content for each single photon. Moreover, the performance is improved with the rise of the frame length. Therefore, our scheme, without intensity modulation, avoids the source side channels and enhances the key generation rate. It has greatly utility value in the MDI-QKD setups. 相似文献
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We propose a concatenated coding scheme, which effectively reduces bit errors induced by soliton-soliton collisions (SSC) in wavelength division multiplexing (WDM) soliton transmission systems. A block line coding scheme, the sliding window criterion (SWC) code, is developed based on the nature of SSC-induced timing jitter in soliton communications. We show, by simplified collision model simulations, that the SWC code alone can decrease the SSC-induced timing jitter and, by concatenation to a Reed-Solomon (RS) code, improve both the bit rate and the channel spacing capacity in WDM systems. We compare the performance of our scheme both analytically and by simulations with those of various RS codes and concatenated RS-convolutional code used in optical fiber transmission systems, and show that high redundancy (overhead) does not always give better code performance. Finally, by using full simulations, we show that the SWC code is an effective and promising technique for dispersion-managed fiber WDM systems 相似文献
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