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771.
With the energy consumption of wireless networks increasing, visible light communication (VLC) has been regarded as a promising technology to realize energy conservation. Due to the massive terminals access and increased traffic demand, the implementation of non-orthogonal multiple access (NOMA) technology in VLC networks has become an inevitable trend. In this paper, we aim to maximize the energy efficiency in VLC-NOMA networks. Assuming perfect knowledge of the channel state information of user equipment, the energy efficiency maximization problem is formulated as a mixed integer nonlinear programming problem. To solve this problem, the joint user grouping and power allocation (JUGPA) is proposed including user grouping and power allocation. In user grouping phase, we utilize the average of channel gain among all user equipment and propose a dynamic user grouping algorithm with low complexity. The proposed scheme exploits the channel gain differences among users and divides them into multiple groups. In power allocation phase, we proposed a power allocation algorithm for maximizing the energy efficiency for a given NOMA group. Thanks to the objective function is fraction form and non-convex, we firstly transform it to difference form and convex function. Then, we derive the closed-form optimal power allocation expression that maximizes the energy efficiency by Dinkelbach method and Lagrange dual decomposition method. Simulation results show that the JUGPA can effectively improve energy efficiency of the VLC-NOMA networks. 相似文献
772.
773.
针对认知无线电网络中基于图着色模型的频谱分配问题,基于其非确定性多项式特性,以最大化网络收益总和为目标,提出了一种基于拟态物理学优化的求解算法. 在拟态物理学优化算法中,将频谱分配问题的解映射为一个具有质量的微粒,通过建立微粒的质量与其适应值之间的关系,并利用万有引力定律定义微粒间的虚拟作用力的大小,使整个群体向更好的方向运动,实现群体寻优. 给出了频谱分配问题的具体求解过程,并根据分配问题的二进制编码特点,改进了微粒的位置更新方程. 仿真实验表明:本文算法能更好地实现网络收益最大化.
关键词:
拟态物理学优化
认知无线电网络
频谱分配
网络收益 相似文献
775.
We are developing an optical layer-2s witch network that uses both wavelength-division multiplexing and time-division multiplexing technologies for efficient traffic aggregation in metro networks.For efficient traffic aggregation,path bandwidth control is key because it strongly affects bandwidth efficiency.For this paper,we propose a dynamic time-slot allocation method that uses periodic information of difference values of traffic variation.This method can derive near-optimal allocation with lower computational cost,which enlarges the maximum available network size compared with conventional time-slot allocation methods.Numerical results show that the proposed method enables dynamic path control in 1K-node-scale optical layer-2s witch network,which leads to cost-effective metro networks. 相似文献
776.
Susanne Burri Patrick Sturm Thomas Baur Matti Barthel Alexander Knohl Nina Buchmann 《Isotopes in environmental and health studies》2014,50(4):497-513
Pulse labelling experiments provide a common tool to study short-term processes in the plant–soil system and investigate below-ground carbon allocation as well as the coupling of soil CO2 efflux to photosynthesis. During the first hours after pulse labelling, the measured isotopic signal of soil CO2 efflux is a combination of both physical tracer diffusion into and out of the soil as well as biological tracer release via root and microbial respiration. Neglecting physical back-diffusion can lead to misinterpretation regarding time lags between photosynthesis and soil CO2 efflux in grassland or any ecosystem type where the above-ground plant parts cannot be labelled in gas-tight chambers separated from the soil. We studied the effects of physical 13CO2 tracer back-diffusion in pulse labelling experiments in grassland, focusing on the isotopic signature of soil CO2 efflux. Having accounted for back-diffusion, the estimated time lag for first tracer appearance in soil CO2 efflux changed from 0 to 1.81±0.56 h (mean±SD) and the time lag for maximum tracer appearance from 2.67±0.39 to 9.63±3.32 h (mean±SD). Thus, time lags were considerably longer when physical tracer diffusion was considered. Using these time lags after accounting for physical back-diffusion, high nocturnal soil CO2 efflux rates could be related to daytime rates of gross primary productivity (R2=0.84). Moreover, pronounced diurnal patterns in the δ13C of soil CO2 efflux were found during the decline of the tracer over 3 weeks. Possible mechanisms include diurnal changes in the relative contributions of autotrophic and heterotrophic soil respiration as well as their respective δ13C values. Thus, after accounting for physical back-diffusion, we were able to quantify biological time lags in the coupling of photosynthesis and soil CO2 efflux in grassland at the diurnal time scale. 相似文献
777.
针对气动力矩严重影响低轨纳卫星姿态控制效果的问题,创新性地提出了利用质量矩技术将气动干扰转化为控制力矩的解决方法.由于气动力矩矢量垂直于大气来流速度方向,因而采用质量矩与磁力矩相结合的方式三轴全驱动控制卫星姿态,从而避免系统欠驱动. 建立双执行机构控制方式的姿态动力学模型,并根据各干扰项的影响简化了控制方程.针对气动力不确定、星体参数误差、未知环境影响等复杂干扰,设计了针对理想控制力矩基于干扰观测器的滑模控制器. 为减小滑块附加干扰力矩,研究了理想控制力矩的最优分配策略. 最后, 为双执行机构搭建了半物理仿真平台,结果表明: 姿态机动过程中, 与滑块加速度相关的附加惯性力矩远大于其他干扰项,最优力矩分配策略能够大幅减小快时变的附加干扰, 优化效果明显; 姿态保持过程中,干扰观测器能有效观测系统慢时变干扰, 提高滑模控制律的姿态控制精度,姿态角收敛误差小于$\pm $0.1$^\circ$.最终验证了在低轨纳卫星上利用质量矩技术控制姿态的可行性. 相似文献
778.
779.
Operations research games: A survey 总被引:1,自引:0,他引:1
This paper surveys the research area of cooperative games associated with several types of operations research problems in
which various decision makers (players) are involved. Cooperating players not only face a joint optimisation problem in trying,
e.g., to minimise total joint costs, but also face an additional allocation problem in how to distribute these joint costs
back to the individual players. This interplay between optimisation and allocation is the main subject of the area of operations
research games. It is surveyed on the basis of a distinction between the nature of the underlying optimisation problem: connection,
routing, scheduling, production and inventory. 相似文献
780.
污染物排放总量分配的群体决策方法研究 总被引:14,自引:0,他引:14
污染物排放总量控制是防治污染的重要途径,污染物排放权的分配是区域污染物排放总量控制工作的核心.本文提出了经济最优性(P1方案)、合理公平性(P2方案)和经济发展连续性(P3方案)的污染物排放权分配原则,研究了以P1方案、P2方案和P3方案为基点的群体决策方法,给出了污染物总量分配的群体决策分配模型. 相似文献