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991.
We introduce a platform that simplifies the development, performance evaluation, and comparison (DEC) of cross-layer protocols for multi-hop ad hoc networks (MANET). To the best of our knowledge, this is the first platform that provides an integrated API for controlling and assessing, on a per-packet basis, the physical layer and MAC/LLC parameters (e.g. frequency channel, power, rate, coding/modulation, fragmentation, number of retransmissions) for IEEE802.11 network interfaces.Today, performance evaluation of wireless mobile ad hoc networks heavily relies on simulation, which is limited in reflecting real environment scenarios due to the channel modeling approximations. Experimental comparisons of protocols in real-world propagation environment are difficult because of limited reproducibility of the channel propagation, environment, and mobility scenarios. We introduce a DEC platform that provides a network virtualization above the physical/link layers. It runs multiple protocols in TDMA-like timeslots guaranteeing an equitable share of the medium, seamless switching between protocols and synchronization between the nodes, all in a transparent fashion to developers. An extensive experimental evaluation demonstrates the usefulness of the platform. 相似文献
992.
In general conditions,most blind source separation algorithms are established on noisy-free model and ignore the noise that affects the quality of separated sources.Firstly,this paper introduces an improved natural gradient algorithm based on bias removal technology to estimate the demixing matrix under noisy environment.Then the discrete wavelet transform technology is applied to the separated signals to further remove noise.In order to improve the separation effect,this paper analyzes the deficiency of hard threshold and soft threshold,and proposes a new wavelet threshold function based on the wavelet decomposition and reconfiguration.The simulations have verified that this method improves the signal noise ratio(SNR) of the separation results and the separation precision. 相似文献
993.
994.
The increase of renewables in the electricity mix in Europe in the last years and the plans to shut down coal-fired power plants will change the power system operation rules. Expectations are that small unit aggregators can soon provide flexibility and balancing services in several European countries. This paper aims to perform a qualitative comparison of European market rules for small-scale-scale flexibility. The work focused more specifically on the prequalification process that the Balancing Service Providers should develop to participate in Frequency Containment Reserve Services and the specific needs of the small-scale flexibility and balancing providers. Five countries were chosen for the analysis: Switzerland, Belgium, Germany, Portugal, and Spain. Of the five countries compared, the one that appears to have fewer entry barriers and shows greater possibilities of working on a case-to-case basis is Switzerland, followed by Belgium and Germany. Portugal and Spain are developing their ancillary service markets and should soon allow the participation of small-scale balancing providers in ancillary services. 相似文献
995.
Energy consumption in cloud data centers is increasing as the use of such services increases. It is necessary to propose new methods of decreasing energy consumption. Green cloud computing helps to reduce energy consumption and significantly decreases both operating costs and greenhouse gas emissions. Scheduling the enormous number of user-submitted workflow tasks is an important aspect of cloud computing. Resources in cloud data centers should compute these tasks using energy efficient techniques. This paper proposed a new energy-aware scheduling algorithm for time-constrained workflow tasks using the DVFS method in which the host reduces the operating frequency using different voltage levels. The goal of this research is to reduce energy consumption and SLA violations and improve resource utilization. The simulation results show that the proposed method performs more efficiently when evaluating metrics such as energy utilization, average execution time, average resource utilization and average SLA violation. 相似文献
996.
提出了一种基于遗传算法的受限制BAN分类器算法-GBAN(genetic algorithm based BAN)。新算法采用了遗传算法进行网络结构的学习,限制了所学习的BAN分类器结构的复杂度。同时对TAN分类器的结构进行了扩展,得到了一种受限制的BAN分类器。针对这种分类器的结构学习,设计了结合对数似然的适应度函数及相应的遗传算子,并给出了网络结构的编码方案,使得该算法能够收敛到全局最优的结构。实验结果表明,当数据集属性之间关系相对复杂的时候,GBAN比TAN的分类准确率高,分类效果较好。 相似文献
997.
基于TD-SCDMA系统,提出了一种在高速下行分组接入(HSDPA)中将追踪合并算法应用于混合自动重传请求技术的方案,并给出追踪合并HARQ算法,用吞吐量和误块率2个性能指标来衡量该算法的优劣,然后对不同信道条件和参数下的下行链路性能进行了仿真。结果表明,该方案对于提高下行链路的吞吐量和降低误块率具有较好的效果。 相似文献
998.
提出在Schmidl&Cox算法的基础上,设计新的训练序列,并且加入循环前缀对同步性能的影响,将改进的Schmidl&Cox训练符号和循环前缀CP结合起来同时完成符号定时同步.并对改进的算法进行了仿真,结果表明,同步性能得到明显提高. 相似文献
999.
1000.
受硬件成本制约,大规模多输入多输出(massive Multiple Input Multiple Output, mMIMO)基站通常配置低精度模数转换器(Analog-to-Digital Converter, ADC)。低精度ADC下,如果多用户mMIMO系统采用最小均方误差(Minimum Mean Square Error, MMSE)检测,将导致过高复杂度。为此,本文基于三对角迭代法(Tridiagonal Iterative Method, TDIM),结合分块矩阵求逆的初始值确定,提出一种低复杂度的MMSE软输出信号检测算法。数值仿真表明:基于TDIM的软输出信号检测算法经4次迭代即可达到收敛,同时,数值结果验证了ADC量化比特为4时,该算法可取得接近全精度ADC的性能,为低精度ADC下mMIMO系统的上行链路信号检测实现提供了切实可行的方案。 相似文献