宁波GSM系统LAC调整方案

宁波ＧＳＭ系统ＬＡＣ状况 目前宁波ＧＳＭ系统共有ＬＡＣ区２２个,每个ＢＳＣ分配一个ＬＡＣ（除市区ＢＳＣ２３,ＢＳＣ２４外）,这样,某些ＢＳＣ的Ｌｏｃａｔｉｏｎ－Ｕｐｄａｔｅ占ＯＫ－ＡＣＣ－ＰＲＯＣ的比例（后称ＬＵ－ＲＡＴＥ）相当高,如余姚ＢＳＣ８,其ＬＵ－ＲＡＴＥ高达７９．４２％,其ＳＤＣＣＨ负荷相当重,且已导致ＳＤＣＣＨ拥塞,具体每个ＢＳＣ的ＬＵ次数,ＬＵ－ＲＡＴＥＰＡＧＥ－ＲＥＱＵＥＳＴＳ／ＰＡＧＥ－ＲＥＳＰＯＮＳＥ,ＰＡＧＥＳ－ＰＥＲ－ＳＥＣＯＮＤ,ＳＤ－ＣＯＮＧＥＳＴＩＯＮ－ＲＡＴＥ,…     

ABR和UBR业务模型的TCP接入分析

ＡＢＲ和ＵＢＲ业务是ＡＴＭ中新定义的业务类型，主要面向数据传输服务。ＴＣＰ是目前最为流行的数据输协议，采用基于窗口的拥塞控制机制。本文主要讨论了ＴＣＰ接入ＡＢＲ和ＵＢＲ业务时所呈观的一些特点及ＡＴＭ交换机缓存的大小对ＴＣＰ性能的影响。     

数字有线电视技术系列讲座 第十讲 IP技术(上)

1　ＩＰ网与ＩＰ技术ＩＰ是ＩｎｔｅｒｎｅｔＰｒｏｔｏｃｏｌ(网际协议 )的英文缩写。ＩＰ网是以ＴＣＰ ＩＰ协议为基础 ,能够提供实时业务 ,无连接的多媒体业务网。表 1是ＡＴＭ与ＩＰ技术的对比。表 1　ＡＴＭ与ＩＰ技术的对比ＩＰＡＴＭ转发无连接面向连接路由多向双向广播多点对多点一点对多点信令收端ＲＳＶＰ发端Ｑ .2 93 1分组长度可变分组长度固定信元长度对应ＯＳＩ层第 3层第 2层承载应用 ＴＣＰ、ＵＤＰ、ＲＳ ＶＰ通过ＡＡＬ承载ＬＡＮＥＱ .2 93 1等固定比特率 (ＣＢＲ)服务质量尽力而为实时可变比特率 (ＶＢＲ)(ＱｏＳ) 质量…     

ATM信令适配层规范

ＡＴＭ网络的信令系统是参照ＩＴＵ－ＴＱ．９３Ｂ建议来实现的，它通过ＡＡＬ５进行适配以进入ＡＴＭ网络，此时的ＡＡＬ称为信令ＡＡＬ（ＳＡＡＬ），它由业务特定协调功能（ＳＳＣＦ），业务特定面向连接协议（ＳＳＣＯＰ），公共部分汇聚子层（ＣＰＣＳ）和分段重装子层（ＳＡＲ）组成，本文着重介绍了ＳＳＣＦ、ＳＳＣＯＰ的原语、帧格式、状态转移图和有关的操作。     

ATM网络中恒定比特率和可变比特率语音通信

分析了ＡＴＭ（异步转移模式）网络中恒定比特率（ＣＢＲ）和可变比特率（ＶＢＲ）语音通信方式，讨论了ＩＴＵ－Ｔ１９９７年新颁布的ＡＴＭ可变比特率业务适配标准ＡＡＬ２，给出了信元装配实例。针对ＶＢＲ业务相对ＣＢＲ业务有较大不同的网络传输时延特性，着重分析了语音信号作为ＶＢＲ业务采用ＡＡＬ２适配标准时，通过ＡＴＭ网络传输时的装配时延问题。     

ATM网中VPN业务的设计与实现

本文分析了ＡＴＭ网中基于ＶＰ和基于ＶＣ两种层次的ＶＰＮ业务的特点,提出了ＶＰ子层的ＶＰＮ业务的设计,并讨论了一种基于ＴＭＮ和ＣＯＲＢＡ的ＶＰＮ管理系统的实现方案。     

HFC网络中上行信道三种协议的比较

讨论了基于ＨＦＣ（混合光纤同轴电缆）网络上行多址接入信道的数据通信，比较了几种适于ＨＦＣ中ＭＡＣ（媒体输入控制）层上行数据流的协议，包括分布式协议Ｒ－ＡＬＯＨＡ，集中式协议Ｕ－ｎｉＬＮＫ以及一种新的协议ＰＣＵＰ（流水线循环上行流协议）最后得出ＰＣＵＰ协议比较适合ＨＦＣ网中的双向交互式业务的结论。     

无线本地环路系统Beta-2000

无线本地环路系统Ｂｅｔａ—２０００充分利用现有管线资源,为用户提供经济、快速、可靠的接入手段,是常规铜线的理想替代方案。此系统实现了用户终端到本地交换机的全透明、全数字接入,可支持话音、ＦＡＸ、数据及窄带ＩＳＤＮ业务。单系统容量可达到１０００线以上,并且可以方便地实现系统扩展。 １．系统网络结构组成 Ｂｅｔａ－２０００系统包括无线控制中心（ＲＰＣＵ）、基站（ＲＰＵ）及用户单元（ＦＡＵ）。ＲＰＣＵ提供与交换机的Ｅ１接口,支持ＣＡＳ、Ｖ５．１／Ｖ５．２接口协议;此外,通过附加模拟接口单元（ＡＬＵ）,也…     

FTTH—0512系统在CATV中的应用

目前光纤接入网发展很快,形式多种多样。ＦＴ－ＴＨ－０５１２系统是在光纤用户环路（ＦＴＴＬ）技术的基础上开发而成的,它可提供电话业务、数据业务、ＣＡＴＶ业务及其他宽带业务。该系统主要由中央局接口单元（ＣＯＩＵ）、光网络单元（ＯＮＵ）、无源光网络（ＰＯＮ）及ＯＡＭ系统等４个主要部分组成,ＦＴＴＨ－０５１２系统结构如图１和图２所示。 其中ＣＯＩＵ是ＦＴ－ＴＨ－０５１２系统与交换机的接口设备;ＯＮＵ是ＦＴＴＨ－０５１２系统与用户的接口设备;ＰＯＮ是ＣＯＩＵ和ＯＮＵ之间的光分配网络;ＯＡＭ系统负责日常维护…     

一种智能监管方法性能的研究

本文提出了改进的模糊漏桶,用于对ＡＴＭ网络业务进行监管,对ＯＮ／ＯＦＦ业务及ＶＢＲ（ＶａｒａｂｌｅＢｉｔＲａｔｅ）视频ＡＲ（一阶ＡｕｔｏＲｅｇｒｅｓｓｉｖｅ模型）业务的仿真结果表明改进模糊漏桶对业务的监管能力要好于漏桶,即监管违约业务响应快,幅度大,并且合法业务对改进模糊漏桶的计资源要求少。     

一种无线ATM网络的MAC协议

主要研究了无线ATM网络对MAC的需求，并介绍了适用于无线ATM的一种新的MAC方案。该协议支持不同类型信息传输，比如恒定比特率（CBR），可变比特率（VBR），可用比特率（ABR），未指定比特率（UBR）。另外此协议还提供了对宽带ATM主干网的无缝连接。同时也支持与ATM相关的QoS级别。对于该协议关注的各种情况的主要原理进行了讨论。     

A Partially-Blocking Queueing System with CBR/VBR and ABR/UBR Arrival Streams

In this paper we consider an ATM transmission link, to which CBR or VBR and ABR or UBR calls arrive according to independent Poisson processes. CBR/VBR calls (characterized by their equivalent bandwidth) are blocked and leave the system if the available link capacity is less than required at the time of arrival. ABR/UBR calls, however, accept partial blocking, meaning that they may enter service even if the available capacity is less than the specified required peak bandwidth, but greater than the so called minimal accepted bandwidth. Partially blocked ABR/UBR calls instead experience longer service time, since smaller given bandwidth entails proportionally longer time spent in the system, as first suggested in [3] and analyzed in details herein. Throughout the life time of an ABR/UBR connection, its bandwidth consumption fluctuates in accordance with the current load on the link but always at the highest possible value up to their peak bandwidth (greedy sources). Additionally, if this minimal accepted bandwidth is unavailable at the time of arrival, ABR/UBR calls are allowed to wait in a finite queue. This system is modeled by a Continuous Time Markov Chain (CTMC) and the CBR/VBR and ABR/UBR blocking probabilities and the mean ABR/UBR waiting- and service times are derived.     

QoS Performance Bounds and Efficient Connection Admission Control for Heterogeneous Services in Wireless Cellular Networks

Quality-of-Service (QoS) performance and connection admission control (CAC) for heterogeneous services in wireless multiple access networks are investigated. The heterogeneous services include constant bit rate (CBR), variable bit rate (VBR) and available bit rate (ABR) services. Multiple access control is handled by a polling-based scheme with non-preemptive priority. Tight delay variation (jitter) bounds for CBR connections and delay bounds for VBR connections are derived. A CAC scheme based on the derived bounds is developed. The CAC makes use of user mobility information to reserve an appropriate amount of system resources for potential handoff connections to achieve low handoff connection dropping rate (HCDR). Simulation results show that the proposed CAC scheme can achieve both low HCDR and high resource utilization.     

A multiple access scheme for multimedia traffic in wireless ATM

This paper proposes a multiple access scheme for the forthcoming wireless ATM (Asynchronous Transfer Mode) system. Such ATM compatible wireless systems are motivated by the rapidly increasing demand for wireless extensions to broadband networks, which are expected to support mixed broadband services including Constant Bit Rate (CBR), Variable Bit Rate (VBR), and Available Bit Rate (ABR) traffic. Since these different traffics have very different performance requirements, the multiple access scheme design is very challenging. In this paper, we propose a multiple access scheme called Dynamic Time Division Multiple Access with Piggybacked Reservation (DTDMA/PR), attempting to achieve higher statistical multiplexing efficiency in the mixed VBR/CBR/ABR traffic scenario. The basic idea is to exploit two levels of reservation. The first level deals with the isochronous nature of CBR and VBR traffic and the bursty nature of ABR traffic by using the ALOHA reservation procedure. The second level exploits the piggybacked reservation approach to cope with the dynamic feature of VBR traffic in order to increase the multiplexing efficiency. An analytical model is also developed in this paper and verified by simulation. Numerical examples are given to gain some insight into the protocol itself.     

ATM通信量管理技术及其在视频点播中的应用

ATM现有的5种通信量业务类型,即：恒定比特率（CBR）、可变比特率（VBR）、可用比特率（ABR）、不定比特率（UBR）和可保证帧速率（GFR）业务,在应用中各有所长。阐述了将ATM ABR业务运用于视频点播系统时,客户端和服务器端的缓存尺寸设置方法,为ABR业务在视频点播系统中的实际应用提供了有力的理论基础。     

Dynamic reservation TDMA protocol for wireless ATM networks

A dynamic reservation time division multiple access (DR-TDMA) control protocol that extends the capabilities of asynchronous transfer mode (ATM) networks over the wireless channel is proposed in this paper. DR-TDMA combines the advantages of distributed access and centralized control for transporting constant bit rate (CBR), variable bit rate (VBR), and available bit rate (ABR) traffic efficiently over a wireless channel. The contention slots access for reservation requests is governed by the framed pseudo-Bayesian priority (FPBP) Aloha protocol that provides different access priorities to the control packets in order to improve the quality-of-service (QoS) offered to time sensitive connections. DR-TDMA also features a novel integrated resource allocation algorithm that efficiently schedules terminals' reserved access to the wireless ATM channel by considering their requested bandwidth and QoS. Integration of CBR, voice, VBR, data, and control traffic over the wireless ATM channel using the proposed DR-TDMA protocol is considered in this paper. Simulation results are presented to show that the protocol respects the required QoS of each traffic category while providing a highly efficient utilization of approximately 96% for the wireless ATM channel     

Analytical Performance Estimation of a Wireless TDMA System with Traffic Classification

This paper describes an analytical model for performance estimation of a mobile communications system based on a TDMA/TDD access scheme. In accordance with the ATM classification of services and its terminology, three types of traffic have been taken into account: CBR for voice connections, VBR for real-time data applications and ABR for non real-time data services. Both voice and data traffic is modeled following Poisson processes. Moreover, three different policies for data resource assignment are evaluated: FCFS, NPPS and silence exploitation (SAD). Theoretical versus simulated results show the suitability of the model when the real-time traffic load is relatively low compared to non real-time traffic.     

A quantitative comparison of multiple access control protocols forwireless ATM

The multiple access control (MAC) problem in a wireless network has intrigued researchers for years. For a broad-band wireless network such as wireless ATM, an effective MAC protocol is very much desired because efficient allocation of channel bandwidth is imperative in accommodating a large user population with satisfactory quality of service. Indeed, MAC protocols for a wireless ATM network in which user traffic requirements are highly heterogeneous (classified into CBR, VBR, and ABR), are even more intricate to design. Considerable research efforts expended in tackling the problem have resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how time different protocols compare against each other on a unified basis. In this paper, we quantitatively compare seven previously proposed TDMA-based MAC protocols for integrated wireless data and voice services. We first propose a taxonomy of TDMA-based protocols, from which we carefully select seven protocols, namely SCAMA, DTDMA/VR, DTDMA/PR, DQRUMA, DPRMMA, DSA++, and PRMA/DA, such that they are devised based on rather orthogonal design philosophies. The objective of our comparison is to highlight the merits and demerits of different protocol designs     

SMART: a many-to-many multicast protocol for ATM

We present a protocol for controlling a shared ATM multicast tree supporting many-to-many communication. The protocol supports one or several ATM virtual channel connections (VCCs) of the many-to-many type. The number of VCCs is independent of the number of endpoints. The protocol guarantees that there is no interleaving on any VCC of the tree. The protocol also guarantees that the traffic contract associated with the VCCs is respected, thus making it possible to use ordinary VCCs of the constant bit rate (CBR), variable bit rate (VBR), or unspecified bit rate (UBR) class. No resequencing server or cell buffering inside the network is required, and all cell forwarding is performed at the ATM layer. We describe the protocol both informally and formally     

Modelling and analysis of routing and resource allocation techniques in multi‐service networks

In this paper a novel call level model based on the extension of the classical Erlang multi‐rate model for broadband integrated services networks is proposed. We use the model to study routing strategies in multi‐service networks where service classes with/without QoS guarantees coexist. Examples for such networks include ATM and IP‐based integrated networks. In ATM, the CBR and VBR service classes provide QoS guarantees, while the ABR and UBR service classes are of the best effort type. In IP, traditional TCP/IP traffic is of the best effort type, while new protocols like the RSVP or the differentiated services with central resource handling attempt to support QoS parameters. The coexistence of guaranteed and best effort traffic gives rise to new challenging problems since for a given elastic (best effort) connection the bottleneck link determines the available bandwidth and thereby puts constraints on the bandwidth at the other links along the connection's path. Since the available bandwidth fluctuates in time following the load on the links, routing and link allocation in this environment together with blocking probability calculations and fairness issues need to be studied. By means of our proposed model we are able to conduct a survey of various routing and link allocation techniques as well as to develop a modified shortest path routing algorithm which, according to the numerical examples, performs well in this environment. Copyright © 1999 John Wiley & Sons, Ltd.