用性价比说话--评英国Creek 4330 MK3功放

当我常常用性价比这个指标来评点一部器材的时候．不禁会想到，性价比究竟是生产肯刻意为之的产品指标呢，还是迫于市场与销售份额的压力而不得已的追求?对于一个设计师来讲，是用不惜一切代价但取好声的方法来完成设计任务来得爽呢，还是要在成本与声音之间苦苦寻找平衡，绞尽脑汁地苦苦思索最佳设计方案而更为有趣     

无线传感器网络中基于“k-覆盖问题”的多项式时间算法

针对无线传感器网络的最差覆盖和最佳覆盖,探寻如何解决二维目标区域内的“k-覆盖问题”,提出了一种解决此问题的多项式时间算法。该算法基于扩展圆盘的几何图形提出了一系列的定义和定理,将“k-覆盖问题”转化成了寻找相邻分界线的问题。仿真结果表明,算法可在多项式时间内计算出最优k-违反路径和最优k-支持路径,从而合理规避或选取网络覆盖点。     

局部满意的启发式搜索算法

在经典规划中,目标是找到一系列连续的行为,改变初始状态Z到一些满意的目标状态G.局部满意规划（PSP）问题是规划问题中的核心问题之一.在PSP中,文献[1-2]给出的每个目标有一个功能值ug≥0,代表每个目标对于用户的价值;每个行为a∈A,有一个关联执行代价Ca≥0,代表它执行每个行为的代价.P为所有有效规划集,Gp∈G为目标集,目标是寻找一个规划p在功能ug和执行代价之间寻找最大差,即arg p∈P max sum （ug）from g∈Gp-sum （Ca） from c∈p针对局部满意问题,提出了一种新的启发式搜索算法.该算法经过验证,取得了明显的效果.     

单频网组网优化方法及复杂度分析

首先介绍了单频网覆盖的判定准则,其次针对地面数字电视广播单频网的组网优化问题,提出了一种基于遗传算法的优化方法,并分析了算法的复杂度,着重探究算法参数对算法性能的影响,从而确保在得到最佳优化结果的同时付出最小的代价.     

最佳测试用例选择算法的改进思路

有效和高效的程序测试是软件测试中的一个重要任务。如果被测试的程序较为复杂,选择一个覆盖准则需要最少的测试用例数量,以尽量减少测试工作量。最佳的测试用例的选择问题是选择满足所需的覆盖准则的情况下测试用例的最小数量。目前有很多可行的最佳测试用例的选择问题研究,然而,这些研究各有不足之处。     

基于类电磁机制算法的分布式数据库数据分配研究

针对目前分布式数据库数据分配方法存在的代价公式复杂,算法执行效率较低或所求结果与最佳方案相差较大等问题,本文提出了一种基于类电磁机制算法的数据分配策略.旨在寻找高效的分布式数据库数据分配方法.结果表明:本文提出的分配策略与传统数据分配策略相比具有较高的效率,且与最佳方案更为接近.可应用于陕西省防雷管理信息系统中分布式数据库的建设.     

WFDS：创新的3G室内覆盖解决方案

基于2G网络的传统室内覆盖解决方案，采用功率放大及分配处理技术就能较好地解决网络的覆盖性能，从而获得良好的用户体验。而3G网络由于其码分体制的特性，及高速数据业务的需求，使得3G网络的室内覆盖存在信号干扰、呼吸效应、远近效应等更多复杂性，如果采用2G通过再生和放大无线射频信号的方法，将会使3G网络付出巨大的容量代价和成本代价。在4月25日举办的“2007年中国移动通信产业高峰论坛”上，东方信联技术总监王宗责提出了一种新型的室内分布覆盖技术：WFDS（无线光纤分布系统）。     

基于强化学习的非正交多址接入和移动边缘计算联合系统信息年龄更新

物联网发展对信息时效性的需求越来越高,信息新鲜度变得至关重要。为了维持信息新鲜度,在非正交多址接入(NOMA)和移动边缘计算(MEC)的联合系统中,对多设备单边缘计算服务器的传输场景进行了研究。在该场景中,如何分配卸载任务量和卸载功率以最小化平均更新代价是一个具有挑战性的问题。该文考虑到现实中的信道状态变化情况,基于多代理深度确定性策略梯度(MADDPG)算法,考虑信息新鲜度影响,建立了最小化平均更新代价的优化问题,提出一种寻找最优的卸载因子和卸载功率决策。仿真结果表明,采用部分卸载的方式可以有效地降低平均更新代价,利用MADDPG算法可以进一步优化卸载功率,经比较,MADDPG算法在降低平均更新代价方面优于其他方案,并且适当地减少设备数量在降低平均更新代价方面效果更好。     

无线传感器网络中基于遗传算法的覆盖优化

覆盖控制是廷长无线传感器网络生存期一个有效的方法之一.其方法通过覆盖控制将无线传感网络节点划分成若干不相交最小覆盖连通集(CCS),然后顺序调度不同节点集.然而寻找最小覆盖连通集覆盖为NP问题,文中建立覆盖连通集优化模型,提出一种基于遗传算法(Genetic Algorithm,简称GA)目标覆盖的优化算法,并详细阐述算法实施.仿真结果显示,对于指定目标,该GA优化算法能获得比GIECC算法更好的性能.     

“约会神器”洗白后上市陌陌拟赴纳市融资3亿美元

任何一个试图在中国创业的互联网公司，都不得不面对BAT当道的现实。但是，腾讯并没能消灭陌陌，因为唐岩寻找到了QQ和微信没有覆盖到的缝隙     

Movement-assisted sensor deployment

Abstract-Adequate coverage is very important for sensor networks to fulfill the issued sensing tasks. In many working environments, it is necessary to make use of mobile sensors, which can move to the correct places to provide the required coverage. In this paper, we study the problem of placing mobile sensors to get high coverage. Based on Voronoi diagrams, we design two sets of distributed protocols for controlling the movement of sensors, one favoring communication and one favoring movement. In each set of protocols, we use Voronoi diagrams to detect coverage holes and use one of three algorithms to calculate the target locations of sensors it holes exist. Simulation results show the effectiveness of our protocols and give insight on choosing protocols and calculation algorithms under different application requirements and working conditions.     

TD网络优化干扰问题分析

TD-SCDMA(以下简称TD)目前在我国是关于第三代移动通信技术的标准指标,而且它还是我国自主研发的一项技术.投入使用一段时间之后,我们欣喜得看到TD技术解决了之前的很多网络接通失败、覆盖率低等问题,但是它在稳定性等方面却依然具有很大的空间,有优化的需求.     

研究提升线性场景5G覆盖能力的新方法

普通的5G天线覆盖距离仅为800 m,不能满足超长桥梁的覆盖需求.本文用球型透镜原理实现单波束高增益,采用多层介质球体的折射特性,将单个天线单元的低增益、宽波束的电磁波信号汇集成高增益、窄波束的电磁波信号,工作原理与光学透镜聚焦原理相似,与普通板状天线对比具有高增益和高垂直瓣宽等优势,可广泛应用于4G/5G场景,有效解...     

Polynomial time solution to minimum forwarding set problem in wireless networks under disk coverage model

In this paper, we consider a practical problem, called Minimum Forwarding Set Problem (MFSP), that emerges within the context of implementing (energy efficient) communication protocols for wireless ad hoc or sensor networks. For a given node v, MFSP asks for a minimum cardinality subset of 1-hop neighbors of v to cover v’s 2-hop neighbors. MFSP problem is also known as multi-point relay (MPR) problem. It is shown to be an NP-complete problem for its general case that does not consider the coverage characteristics of wireless transmissions. In this paper, we present two polynomial time algorithms to solve the MFSP problem under disk coverage model for wireless transmissions. In our earlier work, we presented a polynomial time algorithm for this problem under unit disk coverage model. In the current work, we present several observations on the geometric characteristics of wireless transmissions under disk coverage model and build two alternative dynamic programming based solutions with different run time and space complexities to the problem. Disk coverage model is a more general model because it allows nodes to use arbitrary power levels for transmissions. As a result, the presented algorithms provide a more practical solution that can be used as a building block for energy efficient communication protocols designed for wireless ad hoc and sensor networks.     

基于室内场景的多天线技术应用

多天线技术是无线接入网宽带化、高速化的关键技术,在4G移动通信系统中有着广阔的应用前景.室内覆盖是移动通信的主要业务,运用MIMO技术有效解决室内无线通信系统具有重要意义.围绕无线MIMO技术在室内覆盖中的运用这一主题,对MIMO信道容量、室内信道建模、室内覆盖系统等方面进行了深入的研究.     

利用5G技术提升地面数字电视的覆盖效果分析

通地面数字电视是以后数字电视一个关键的传输方法,有着不会受到带宽限制的优势,可是也有着无上行通道、交互性差与现实接收成效不理想等不足。5G这一技术的进步能高效的完善地面数字电视覆盖的不足,处置终端使用者接收的难题,提高广播电视总体的覆盖水准。文章就利用5G技术提升地面数字电视的覆盖效果进行了探析。     

无线传感器网络三维空间最佳覆盖路由协议

本文针对新兴无线传感器网络中的三维空间随机最佳覆盖NP难问题进行了研究.采用计算几何与图论着色方法建立了三维空间的随机最佳覆盖数学模型,给出了一种分布式启发算法,得到了完成最佳覆盖的低能量消耗路径.并在此基础上设计了一种可以实现无线传感器网络三维空间最佳覆盖的优化路由协议.最后进行了协议算法的性能评价以及最佳覆盖和网络生存时间的实验仿真,结果表明协议算法时间复杂度低,并具有可扩展性、有效性和鲁棒性.     

中小城市网络结构优化探索

本文使用百林N-SAT软件对某市进行了无线网络结构评估,通过结构评估找到目前网络存在的问题为覆盖问题。使用扫频数据应用于ASPS软件进行覆盖优化,并对优化后的结果进行了评估。     

Improved approximation algorithms for connected sensor cover

Wireless sensor networks have recently posed many new system building challenges. One of the main problems is energy conservation since most of the sensors are devices with limited battery life and it is infeasible to replenish energy via replacing batteries. An effective approach for energy conservation is scheduling sleep intervals for some sensors, while the remaining sensors stay active providing continuous service. In this paper we consider the problem of selecting a set of active sensors of minimum cardinality so that sensing coverage and network connectivity are maintained. We show that the greedy algorithm that provides complete coverage has an approximation factor no better than Ω(log n), where n is the number of sensor nodes. Then we present algorithms that provide approximate coverage while the number of nodes selected is a constant factor far from the optimal solution. Finally, we show how to connect a set of sensors that already provides coverage.     

Scheduling sensor activity for information coverage of discrete targets in sensor networks

In this paper, we study the problem of scheduling sensor activity to cover a set of targets with known locations such that all targets can be monitored all the time and the network can operate as long as possible. A solution to this scheduling problem is to partition all sensors into some sensor covers such that each cover can monitor all targets and the covers are activated sequentially. In this paper, we propose to provide information coverage instead of the conventional sensing disk coverage for target. The notion of information coverage is based on estimation theory to exploit the collaborative nature of geographically distributed sensors. Due to the use of information coverage, a target that is not within the sensing disk of any single sensor can still be considered to be monitored (information covered) by the cooperation of more than one sensor. This change of the problem settings complicates the solutions compared to that by using a disk coverage model. We first define the target information coverage (TIC) problem and prove its NP‐completeness. We then propose a heuristic to approximately solve our problem. Simulation results show that our heuristic is better than an existing algorithm and is close to the upper bound when only the sensing disk coverage model is used. Furthermore, simulation results also show that the network lifetime can be significantly improved by using the notion of information coverage compared with that by using the conventional definition of sensing disk coverage. Copyright © 2008 John Wiley & Sons, Ltd.