Modeling deterministic echo state network with loop reservoir

Echo state network (ESN),which efficiently models nonlinear dynamic systems,has been proposed as a special form of recurrent neural network.However,most of the proposed ESNs consist of complex reservoi...     

移动分组业务的小区-时间流量分布

对于在国内GPRS现网Gn接口采集的数据样本进行了流量分布规律研究。发现大多数小区一天中大多数时段处于低速状态,突发的极少数大流量观测值集中在少数小区少数时段。用指数分布对样本的经验分布进行拟合,拟合效果较好。对现网不同区域和不同时段的小区流量数据使用Q-Q图等方法进行了指数分布的有效性验证,发现上述结论具有一定普遍性。     

泊松过程在用户上下线模型中的应用

提出了基于非齐次泊松过程的宽带拨号上网(ADSL)用户上下线模型.对用户上下线行为进行建模,并基于现网真实数据,使用模型计算用户24 h内的每时刻退出登录的平均概率,将模型的预测值与现网实测数据进行对比,分析了不同用户组退出登录概率一天内的变化和持续在线平均概率的变化.分析结果表明,提出的ADSL宽带用户上下线模型可以有效、量化地描述用户上下线行为,在ADSL宽带用户上下线行为的异常检测和舆情分析等领域具有较好的工程应用价值.     

Dynamic modeling and fuzzy logic control of vibrations of a railway vehicle for different track irregularities

Safe and comfortable transportation of passengers and goods on railways can be achieved by solving the vibration problem. In this study, the dynamic modeling of the full railway vehicle is used to perform vibration analysis in order to observe displacements and accelerations. The full railway vehicle model consists of 54 degrees of freedom which are defined by differential equations. Additionally, wheel–rail contact problem (i.e. creepage factors and hertzian spring stiffness of rails) is analyzed by finite element method. Dynamic modeling and vibration analysis are carried out using Matlab–Simulink software. Using the developed model, the car body vibrations, caused by a lateral and two vertical sinusoidal track irregularities, are controlled by fuzzy logic controllers placed between the car body and bogies. The fuzzy logic algorithm herein is used for realizing the active control of car body vibrations. The simulations of vibration analysis are obtained in time and frequency domains and compared with passive controlled status. The robustness of the designed controller is verified by simulations, carried out for the cases of car body mass variations. The results show the effectiveness of the proposed algorithm.     

Interference of human’s ankle to the channel characteristics of near surface WUSN简

Because of its potential applications in agriculture, environment monitoring and so on, wireless underground sensor network（WUSN） has been researched more and more extensively in recent years. The main and most important difference of WUSN to terrestrial wireless sensor network（WSN） is the channel characteristics, which determines the design methodology of it. In this paper, the propagation character of electromagnetic（EM） wave in the near surface WUSN is analyzed, as well as the path loss model of it is given. In addition, the influence of human＇s ankle to the channel characteristics of near surface WUSN is investigated by electromagnetic theory analysis, simulation and experiment. A novel path loss model of near surface WUSN which takes the interference of human＇s ankle into consideration is proposed. It is verified that the existing of human above the WUSN system may cause additional attenuation to the signal of near surface WUSN which propagates as lateral wave along the ground. Moreover, the relation of the attenuation and operating frequency is deduced, which gives a reference to extend the frequency band applied in WUSN.     

Nash bargaining solution based multi-cell and multi-user interference alignment scheme for cellular networks

In wireless cellular networks, the interference alignment （IA） is a promising technique for interference management. A new IA scheme for downlink cellular network with multi-cell and multi-user was proposed, in the proposed scheme, the interference in the networks is divided into inter-cell interference （ICI） among cells and inter-user interference （IUI） in each cell. The ICI is aligned onto a multi-dimensional subspace by multiplying the ICI alignment precoding matrix which is designed by the singular value decomposition （SVD） scheme at the base station （BS） side. The aligned ICI is eliminated by timing the interference suppression matrix which is designed by zero-forcing （ZF） scheme at the user equipment （UE） side. Meanwhile, the IUI is aligned by multiplying the IUI alignment precoding matrix which is designed based on Nash bargaining solution （NBS） in game theory. The NBS is solved by the particle swarm optimization （PSO） method. Simulations show that, compared with the traditional ZF IA scheme, the proposed scheme can obtain higher data rate and guarantee the data rate fairness of UEs with little additional complexity.     

Research on orbital angular momentum communication technology

As the good orthogonality between the different modes of orbital angular momentum (OAM),the application of OAM technology in wireless communication has gained increasing popularity in recent years with great potential for capacity improvement.OAM-based wireless communication technology can effectively improve spectrum utilization,but also brings some challenges.Firstly,the research status and progress of OAM technology in the field of wireless communication were introduced and the relationship between OAM and MIMO technology was compared and analyzed combined with the basic principle of OAM.Moreover,the dispute “Does OAM provides a new dimension?” was concluded.Then,the generation and reception methods of OAM were summarized.The key techniques and application fields were overviewed.Finally,the challenges of the technology in practical application were analyzed and the future development trends and follow-up research directions were point out,which would provide a reference and help for the research in this field.     

Simultaneous wireless information and power transfer for relay assisted energy harvesting network

The simultaneous wireless information and power transfer in an energy harvesting system is investigated, where a relay is self-sustained by harvesting radio-frequency (RF) energy from the transmitter and multiple user devices are distributed according to a homogeneous Poisson point process. A joint time switching and power splitting protocol for relay-assisted transmission is proposed, in which each time slot is split into two stages. In the first stage, the relay utilizes a portion of received RF signal power for energy harvesting and the remaining power for information processing. In the second stage, information is delivered from the relay to its closest destination node with the harvested energy. The outage probability, network throughput and energy efficiency are derived and analyzed in closed form. On this basis, the optimal power splitting and time switching ratio which maximizes network throughput is obtained. Simulation results are also provided to validate our theoretical analysis.     

Cooperation-enabled energy efficient base station management for dense small cell networks

Dense small cell networks are deployed for future wireless communication to meet the ever-increasing mobile traffic demand. However, network densification will significantly increase the energy budget and lead to energy inefficiency due to the constant operation of network hardware. In this paper, we consider cooperation-enabled dynamic base station (BS) management for downlink dense small cell networks. By introducing two traffic-aware sleep modes, i.e., deep sleep mode and opportunistic sleep mode which are operating in different time and energy consumption scales, the network hardwares are turned to be the resources that can be occupied and released dynamically. Small cell BSs (SBSs) with zero or low load are completely switched off and reside in deep sleep mode during a predefined time interval. At each time slot, SBS dynamically turn some antennas and associated physical components into opportunistic sleep mode according to the short term traffic distribution, and the users are jointly served by the remaining antennas via cooperative transmission. The corresponding sleep mode decision making are presented respectively to find the optimal number of SBS and antennas that should be switched off. Numerical results are then presented to illustrate the superior performance in terms of energy efficiency gain. In summary, the proposed cooperation-aided sleep strategies for dense small cell networks take both traffic features and optimal cooperative transmission into account, and can achieve great energy saving while maintaining required quality of service.     

基于相关性概率的信息中心网络协作缓存策略

信息中心网络(ICN)的节点缓存功能有助于海量内容的高效分发,缓解链路拥塞并减少流量冗余. 传统的缓存策略不利于提高全网缓存的内容多样性和缓存节点的平均命中率,现有研究能在一定程度上解决这些问题,实现了公平的内容流复用,但没有充分考虑节点之间的协作,导致节点缓存的利用率不均. 为了解决上述问题,从当前节点缓存状态对其他节点的影响入手,提出一种基于相关性概率的ICN协作缓存策略,根据路径及相邻节点信息做出本节点的缓存判断,从而有效控制缓存冗余. 仿真结果表明,该方法可以减轻服务器负载,丰富全网内容多样性,有利于提高交错复杂网络节点的命中率和利用率,减少请求跳数.