On MAC optimization for large-scale wireless sensor network

The media access control (MAC) performance of a large-scale wireless sensor network (L-WSN) determines the efficiency of the wireless communication channel. A good MAC protocol could reduce network energy consumption and network delay, which are two problems to be solved urgently in L-WSN. In this paper, we proposed a multi-level integrated MAC protocol (MI-MAC) to solve the overall performance optimization problem of L-WSN. Compared with other protocols, MI-MAC has two mainly improved performances: (1) It improved binary exponential backoff algorithm by twice back off strategy; (2) It designed a sending and receiving algorithm based on the threshold value to recognize control frames (small frames), which effectively avoids the collision probability of data frame. The simulation results show that the MI-MAC protocol improves network throughput and delay performance, significantly reduces energy consumption, and obtains overall network optimization.     

FTTH网络结构分析

文章描述了光纤到户（FTTH）在通信网中的位置及作用,FTTH系统的网络结构及功能要求。在FTTH的网络结构方面,通过对各种方案进行比较,建议在不同的应用环境中采取不同的网络方案。这些方案包括光纤到大楼（FTTB）的光网络,基于点到点的纤分方式,基于点到点结构的有源光网络,基于IEEE的以太网无源光网络（EPON）系统和基于ITU—T的吉比特无源光网络（GPON）的系统。     

FTTH场景下OLT建设方式的探讨

本文对不同环境下OLT设备在光纤接入网络中部署的位置、OLT建设方式、OLT上联方式等内容进行了讨论,希望本文的结论在FTTH网络设计和建设工作中起一定的参考作用。     

建设灵活的低成本的FTTH网络

针对FTTH建设中存在的问题、成本构成进行了分析,提出了建设灵活的、低成本的FTTH网络的思路和技术措施;结合实际场景分光器的应用对端口利用率的影响进行了探讨,对FTTH设计、建设提供参考。     

基于FTTH的光网络保护系统的研究

针对FTTH光纤线路的保护问题,提出了一种无源光网络光纤线路切换保护系统.光纤线路切换设备通过不同的光纤链路连接远端设备的两个光通信端口,当某一个与远端设备连接的分支光纤链路出现故障时,光纤线路切换设备通过连接备用的分支光纤链路,保障通信的及时恢复.实验结果表明,ONU能够在50ms内自动完成在光口1和光口2间的识别与光路保护切换,极大地提高了PON光纤线路保护的可靠性和生存性,有利于FTTH/B的应用.     

大型住宅小区FTTH接入网规划建设方案

目前住宅小区家庭宽带FTTH接入驻地网建设主要采用传统的一级集中分光建设模式,本文对该传统建设模式进行了较为全面的分析,并通过研究其主要的优势与劣势,提出了优化后的二级分散分光规划建设方案,减少了大量的工程施工量和资源占用。     

大规模ASON中路由协议优化的研究

路由协议是自动交换光网络(ASON)控制平面的重要组成部分,其负责泛洪网络的链路状态信息,并进行路由计算.在ASON的实际运行过程中,路由协议存在一些不足,如占用大量数据通信网(DCN)带宽以及链路状态数据库同步时延过大等,这些问题对网络的可扩展性有较大影响.文章针对上述问题提出了路由协议的优化方案,包括为路由信息的泛洪设定阈值,以及给路由协议增加数据库自更新功能.     

Group-scheduling mechanism for large-scale time-sensitive network

In order to achieve the deterministic delay of time-triggered traffic in a large-scale time-sensitive network,a kind of group-scheduling mechanism was proposed.By designing a topology pruning strategy and a flow grouping strategy based on spectral clustering,the impact of the rapid increase in network topology scale and traffic scale on the speed of scheduling response was avoided,and the scheduling calculation efficiency was improved.The results of experiment show that the mechanism can solve the model in a relatively short time for large-scale scheduling problem and achieve a relatively high scheduling success rate.     

大规模网络管理中的任务分解与调度

集中式的管理模式和简单的基于移动agent的网络管理方法都已不能满足大型网络管理的需要,为此,在给出基于多agent的网络管理框架的基础上,提出了一种基于任务依赖关系的任务分解算法,把网络管理任务分解为具有不同优先级的子任务,处于同一优先层次的子任务可以并行执行,根据子任务的优先级产生结合网络管理特点的调度策略,理论分析和实验表明:在大规模网络管理中采用任务分解技术能够提高时间效率和减轻网络负载。     

Profiling of a large-scale municipal wireless network

Pervasive connectivity is an essential underlying substrate for smart cities, leading municipalities to start programs where Wi-Fi is the fundamental building block to develop public Municipal Wireless Networks. Even though hundreds of cities around the world offer some form of Wi-Fi access, there are no widely available results regarding the network Quality of Service (QoS), user Quality of Experience (QoE), and overall utilization profile. The Municipality of São Paulo operates a free Wi-Fi Internet program in 120 public spaces called digital squares. We collected user connection data, network performance, and service availability for more than 2 years from the 120 squares and undertook experiments with video streaming in five squares. We used this unique large dataset to evaluate the impact of current admission control practices in public Wi-Fi networks on the network QoS, user QoE and service availability, also providing insights into the most common QoS/QoE issues and their causes. We also leveraged the data set to establish and verify a correlation between the number of users access in the network and specific events occurring in the area.

     

Exploiting agent mobility for large-scale network monitoring

As networks become pervasive, the importance of efficient information gathering for purposes such as monitoring, fault diagnosis, and performance evaluation increases. Distributed monitoring systems based on either management protocols such as SNMP or distributed object technologies such as CORBA can cope with scalability problems only to a limited extent. They are not well suited to systems that are both very large and highly dynamic because the monitoring logic, although possibly distributed, is statically predefined at design time. This article presents an active distributed monitoring system based on mobile agents. Agents act as area monitors not bound to any particular network node that can "sense" the network, estimate better locations, and migrate in order to pursue location optimality. Simulations demonstrate the capability of this approach to cope with large-scale systems and changing network conditions     

快速发展的日本FTTH市场

快速发展的日本互联网 自2001年始．日本政府先后提出了“信息技术基本法”和“e—Japan战略”,通过加快三网融合．促进企业信息化、加快信息内容开发和流通等措施,极大推进了日本信息产业、尤其是互联网的发展。据统计,1997年日本互联网用户数为1155万,普及率为92％;截至2005年年底,用户数达8529万,     

SDH网络中网管监控优化方案设计

随着通信行业的高速发展和人力成本的提高,通信网管网络的稳定运行已成为运营商关注的焦点。本文通过对SDH网络中的ECC通信的特点、通信原则、组网能力等方面进行分析,结合实际应用中SDH网管有时会出现的网元大面积脱管、网元数据及告警信息提取更新速度慢等隐患,提出了解决的几个有效方法,并通过应用于实际日常维护工作中,使SDH传输设备网管的有效性和可靠性得到了大幅的提高。     

超大型网络圆锥曲线密码管理解决方案

二进制域上圆锥曲线密码是一种新型的公钥密码系统,在随机选取曲线参数,明文嵌入方面较椭圆曲线有优势.针对在超大型网络系统中,各种密码管理混乱、安全隐患严重的问题,利用圆锥曲线的优点,提出了一种安全的密码管理解决方案,该方案利用圆锥曲线/AES混合加密的方式保证密钥传输中的机密性、完整性、不可否认性.该方案对于强化超大型网络系统的运维管理有一定的实际意义.     

Access network survivability: an architecture approach for monitoring, protection and restoration in FTTH application

This paper presented a simple monitoring, protection switching, and fast restoration approach for fiber to the home passive optical network (FTTH-PON) using Access Control System (ACS). ACS is developed for centralized monitoring and failure detection from central office (CO) in downstream direction (from CO towards customer sides). The proposed system architecture incorporating low cost and enable the network service providers and field engineers to remotely control the testing module from anywhere in the world and automatically identify any fiber fault and address the failure location in the fiber field. Another unique function of ACS is to provide the activation for optical switching in a restoration scheme which implemented at the drop region of FTTH-PON. A protection device named Customer Protection Device that comprises of programmable optical switches will be employed at the customer sides, just before the optical network unit, for rerouting the disrupted signals to the protection line when failure occurs in the working line to ensure continuous service delivery to customers.     

SDH网络优化的解决方案

随着业务需求的改变，数据业务量全面超过话音业务量成为电信领域的主导。传统SDH网络是基于电路交换的，链路带宽由网管中心静态配置。然而，数据业务具有突发性、不可预测性等特征，将传统SDH网络作为数据业务的传送平台势必引发多种问题。网络演进和业务需求等后向兼容的问题是现有网络优化过程中的关键所在。因此，为适应高速数据网络的发展要求，在保留SDH网络固有优点的基础上，可以明确现有网络的优化目标为：* 改善数据业务带宽的预先超额配置方式，实现网络带宽资源的共享；* 灵活便捷地分配任意带宽容量，用于TDM或电路交换…     

Numerical optimization of large-scale fiber-optic splitting tree uniformity

In order to split the optical power of a signal into many fibered outputs, large-scale optical splitting trees (splitters) are used. In most applications, the optical power should remain constant from output to output. Large-scale splitting trees (typically 1 : 32 or 1 : 128) may be composed of a single-stage or of cascaded small splitters (typically 1 : 2). In the former case, power uniformity is determined by the design and manufacturing tolerances. In the latter case, considered here, uniformity may be optimized by a proper choice of the positions of the small splitters in the tree. Simulations show that less than 1-dB uniformity may be reached.     

LTE网络优化技术

LTE(Long Term Evolution)网络是继第三代移动通信网络之后国际上的新一代主流移动通信网络.介绍了LTE网络在特定场合采用的各种网络优化技术,包括在室内覆盖的家庭基站技术、在信号盲区和偏远地区覆盖的中继技术、在同频组网情况下抑制小区间干扰的小区间干扰协调技术,以及在小区边缘传输速率受限区域的多点协作技...     

GSM网络优化中的三个问题

在实际工作中常常发现很多掉话是因为切换造成的。在图1所示的例子中,B基站的Cell3只定义A基站的Celll、Cell2为相邻小区,在CDD中一般也是这样定义,我们常常主观地认为B基站的Cell3只会跟A基站的Celll和Cell2有切换。但在实际路测中常常发现B基站的信号会越过A基站而跑列A基站的Cell3覆盖区,在局部形成其信号强度高于A站Cell3且成为最强小区的情况,即常见的“孤岛效应”。