QoS on LEO satellites

This paper discusses the role played by wireless network infrastructure in mobile commerce applications. The user's perception of service quality depends on the available resources and capabilities of the network. The new generation of low earth orbit (LEO) mobile satellite networks, deployed at altitudes ranging from 500 km to 2000 km, are well suited to handle multimedia traffic and to offer end-users equipped with hand-held devices at low cost-per minute access to network services. A wide range of multimedia services and applications are expected to provide users with QoS based asynchronous transfer mode (ATM) technology. LEO satellite networks provide significant wide area coverage, unique broadcast capability, ability to meet different QoS requirements, the ability to communicate with hand-held devices and low cost access. The main resources in the LEO networks are satellite radio bandwidth and the buffer capacity of the onboard ATM switch. The most important ATM resource management function is connection and call admission control. The real objective of this article is to introduce the general framework of resource reservation in multimedia LEO satellite networks which offers a unified approach to handle all the important aspects of resource reservation and radio-resource management functions required by E-commerce and mobile commerce applications.     

Adaptive bandwidth framework for provisioning connection-level QoS for next-generation wireless cellular networks

The next generation of wireless cellular networks is expected to support real-time multimedia services with different classes of traffic and diverse bandwidth requirements. Bandwidth is a scarce resource in wireless networking that needs to be carefully allocated amid competing connections with different quality of service (QoS) requirements. In this paper, an adaptive framework for supporting multiple classes of multimedia services with different QoS requirements in wireless cellular networks is proposed. The framework combines the following components: (1) a threshold-based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes among different classes of handoff calls by assigning a threshold to each class; (2) an efficient threshold-type call admission control (CAC) algorithm; and (3) a bandwidth adaptation algorithm (BAA) that dynamically adjusts the bandwidth of ongoing multimedia calls to minimize the number of calls receiving lower bandwidth than they had requested. Numerical results show that the proposed adaptive multimedia framework outperforms existing non-adaptive schemes in terms of the handoff call dropping probability and effective utilization.     

An adaptive resource reservation strategy for handoff in wireless CDMA cellular networks

A threshold-based adaptive resource reservation scheme for soft handoff calls in wireless code division multiple access (CDMA) cellular networks is proposed. The scheme gives handoff calls a higher admission priority than new calls, and is designed to adaptively adjust the reservation-request time threshold according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come, first-served basis. With the proposed scheme, a minimum grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities can be achieved. Simulation results are given to demonstrate the improvement in the GoS performance in comparison with other schemes.     

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources. It provides the network with better quality-of-service (QoS) guarantees, such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks. Simulation results show that, compared with other bandwidth allocation schemes, the proposed scheme offers very low call dropping probability for real-time connections while, at the same time, keeping resource utilization high. Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods. Translated from Journal on Communications, 2006, 27(8): 10–17 [译自: 通信学报]     

一种有效的802.16 BWA系统MAC层QoS框架

IEEE 802.16系列标准定义了WiMAX的无线空中接口,尽管标准详细的定义了MAC层信号机制,但并没有一套完整的资源管理调度机制,而资源管理和调度是影响QoS性能的重要部分.本文首先简要介绍了IEEE 802.16协议,分析了其QoS机制的主要内容,包括带宽的请求分配机制,准人和调度机制等.然后提出了一套有效的QoS框架,主要包括准入控制策略和上行调度策略.为了让不同业务的QoS得到保证,文章重点探讨了多优先级公平队列算法(MPFQ),通过这套机制,可以为不同级别的业务提供不同等级的Qos服务.     

Performance evaluation of soft handoff for multimedia services in intelligent transportation systems based on CDMA

To support multimedia services in intelligent transportation systems (ITS), CDMA based radio-on-fiber road-vehicle communication systems were proposed. Soft handoff should be provided for multimedia services because these services are required to guarantee real-time property and quality of service (QoS). The performance evaluation of soft handoff is important in view of system management such as determination of optimal resource allocation, cell configuration, and admission strategy. But, the performance evaluation of soft handoff when multimedia services are serviced has not been previously researched, even though there have been some previous works for voice-call service. In this paper, we develop a new analytical model of soft handoff when multimedia services are served in CDMA based ITS. We evaluate the performance of soft handoff scheme by analytical and simulational method. Blocking probability, handoff failure probability and carried traffic are obtained.     

移动视频业务的EQoS方案及跨层资源管理模型

在分析4G网络的链路特性、视频业务对网路资源的要求和3GPP移动网路QoS方案的基础上,针对移动视频业务在未来ICT网络中的应用特点,提出了移动视频业务扩展QoS（EQoS）方案和基于EQoS方案的跨层资源管理模型。前者引入了移动视频业务细化衡量标准,有利于移动视频业务质量指标的量化;后者在保持原有网络分层模型的基础上,通过EQoS模块实现了跨层无线资源管理。     

Handoff resource prediction in multimedia wireless networks

This paper presents a local-based approach for predicting handoff resources in multimedia wireless networks, where the underlying prediction mechanism is the recursive least-squares (RLS) algorithm. Performance of the proposed handoff resource prediction scheme is evaluated for a multimedia wireless network characterized by various handoff traffic conditions, different bandwidth requirements, and general call and channel holding time distributions. The accuracy of handoff resource prediction is measured in terms of a mean-square-error metric. Results from performance evaluation show that the proposed RLS-based scheme has better resource prediction accuracy than Wiener-filter and autoregressive (AR) processes. It is shown that the proposed RLS-based handoff resource prediction scheme achieves capacity gains of up to 60% and 23% compared to the Wiener- and AR-based schemes, respectively.     

Enhanced soft-handoff scheme for real-time streaming services in intelligent transportation systems based on CDMA

Code division multiple access (CDMA)-based radio-on-fiber road-vehicle communication systems were proposed to support real-time streaming services in intelligent transportation systems (ITSs). Soft handoff should be provided for real-time streaming services because these services are required to guarantee real-time property and quality of service (QoS). However, soft handoff of real-time streaming services causes the shortage of resource in view of the system. In this paper, the double-adjustment soft-handoff (DASH) scheme is proposed to support seamless service regardless of the shortage of resource and maximize the resource efficiency when real-time streaming services are served in CDMA-based ITSs. The DASH scheme adjusts the data rate of a call when it starts and finishes soft handoff. The performance of the DASH scheme is evaluated by analytical and simulation methods. Performances are evaluated with respect to the blocking probability, the handoff failure probability, and the carried traffic. Numerical results show that the proposed scheme can give relative good maintenance of calls and good throughput.     

Dynamic multicast traffic grooming in WDM networks

Dynamic multicast traffic grooming in wavelength division multiplexing (WDM) networks was analyzed to minimize networkwide costs and to increase the network resource utilization. A network model was developed for dynamic multicast traffic grooming with resource constraints and an algorithm that can provide quality of service (QoS) was proposed. The QoS is measured by the maximum number of lightpaths passing between the source and the destinations. The blocking probability of the algorithm was assessed in simulations. The results show that a higher QoS requirement results in higher blocking probability, and when the QoS requirement is low, changes in the QoS requirements have only small effects on the blocking probability. __________ Translated from Journal of Tsinghua University (Science and Technology), 2005, 45(4): 437–440 (in Chinese)     

Policy conflict analysis for diffserv quality of service management

Policy-based management provides the ability to (re-)configure differentiated services networks so that desired Quality of Service (QoS) goals are achieved. This requires implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability as policies can be dynamically changed without modifying the underlying implementation. However, inconsistencies may arise in the policy specification. In this paper we provide a comprehensive set of QoS policies for managing Differentiated Services (DiffServ) networks, and classify the possible conflicts that can arise between them. We demonstrate the use of Event Calculus and formal reasoning for the analysis of both static and dynamic conflicts in a semi-automated fashion. In addition, we present a conflict analysis tool that provides network administrators with a user-friendly environment for determining and resolving potential inconsistencies. The tool has been extensively tested with large numbers of policies over a range of conflict types.     

一种区域自组织的分级网络层移动性管理方法

移动性管理是移动通信系统中的关键技术之一。给出了面向下一代移动通信系统的基于IP扩展技术的网络层移动性管理的体系结构、功能模型。提出了一种基于区域自组织的分级网络层移动性管理方案，即DDA-HNMM(Domain Discovery Assisted Hierarchical Network-Layer Mobility Management)方案。针对网络业务强度的不均匀性，给出了一种切换强度发现算法和区域自组织机制。仿真结果表明，灵活的区域自组织可以明显减少信令开销，提高移动终端的吞吐量。     

A QoS‐supported controlled burst retransmission scheme in OBS networks

Burst retransmission can reduce data loss in burst contention in optical burst switching (OBS) core nodes. However, uncontrolled burst retransmission may significantly increase the network load and data loss probability, defeating the purpose of retransmission. Therefore, controlled retransmission should be studied to achieve reasonable retransmission, particularly to support quality of service (QoS) in OBS networks in which priority traffic exists. In this paper, we develop a QoS‐supported controlled retransmission scheme in OBS networks. Different from previous works in the literature, we set a different value for the retransmission probability at each contention for both high‐ and low‐priority bursts, set different retransmission probabilities for bursts of different priorities for QoS support, and propose a retransmission analytical model for OBS networks. We take into account the load at each link due to both the fresh and the retransmitted traffic and calculate the path‐blocking probability and the burst loss probability for high‐priority and low‐priority bursts to evaluate the network performance. An extensive simulation is proposed to validate our analytical model. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Policy refinement for IP differentiated services Quality of Service management

Policy-based management provides the ability to dynamically re-configure DiffServ networks such that desired Quality of Service (QoS) goals are achieved. This includes network provisioning decisions, performing admission control, and adapting bandwidth allocation dynamically. QoS management aims to satisfy the Service Level Agreements (SLAs) contracted by the provider and therefore QoS policies are derived from SLA specifications and the provider's business goals. This policy refinement is usually performed manually with no means of verifying that the policies written are supported by the network devices and actually achieve the desired QoS goals. Tool support is lacking and policy refinement has rarely been addressed in the literature. This paper extends our previous approach to policy refinement and shows how to apply it to the domain of DiffServ QoS management. We make use of goal elaboration and abductive reasoning to derive strategies that will achieve a given high-level goal. By combining these strategies with events and constraints, we show how policies can be refined, and what tool support can be provided for the refinement process using examples from the QoS management domain. The approach presented here can be used in other application domains such as storage area networks or security management.     

An efficient wireless resource management scheme to support handoff data recovery in packet-switched cellular multicast networks

To support data transfer reliability similar to that of a fixed multicast network, migrating terminals in a packet-switched cellular wireless multicast network supporting reliable multicast data transfer need to recover lost data during handoffs before they can merge into the respective multicast groups in the new cells. The multicast groups in packet-switched wireless networks typically share resources on a statistical multiplexed basis. To minimize impact on other terminals, this paper proposes to allow part of a multicast group's assigned bandwidth to be shared by the handoff terminals for transient data recovery using the proposed Weighted Fair Share (WFS) method with optimal weight selection. Handoff terminals are admitted into the new cell using the proposed Multicast Connection Admission Control (MCAC) scheme. These methods together constitute the Fair and Efficient Wireless Multicast resource management Scheme (FEWMS) presented in this paper. Under FEWMS, a migrating terminal can quickly recover lost data and merge into the existing multicast group during a handoff. Simulations using self-similar traffic sources show that the proposed method reduces the handoff failure probability of migrating terminals and the average packet delay of the multicast group, and increases the overall system throughput, compared with an existing proposal. Evaluations of different performance measures show that the system throughput does not give a complete picture of the system performance, as different resource management schemes may have substantial impact on other performance measures such as average delay and handoff failure probability.     

A QoS control scheme using dynamic window size control for wide area ubiquitous wireless network

This paper describes a quality‐of‐service (QoS) control scheme for a wide‐area ubiquitous wireless network which is designed to accommodate many wireless terminals (WTs), such as sensors and actuators, in a large cell area. The purpose of this paper is to establish a QoS control scheme in a medium access control (MAC) layer that can hold the transmission delay of high‐priority class traffic within a predefined value regardless of how much low‐priority class traffic there is. Several QoS control schemes for wireless communication use have been proposed. However, in the wide‐area ubiquitous wireless network, an access point (AP) accommodates many WTs and the AP traffic volume often drastically changes. Therefore, conventional schemes sometimes cannot control the QoS of high‐priority traffic. To solve this problem, we propose a QoS control scheme that calculates a suitable initial back‐off window size of random access for each QoS class by using equations derived from a Markov chain behavior model. The proposed scheme adjusts the window size so as to prevent increased transmission delay of high‐priority traffic. The scheme's performance is clarified by computer simulation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于DiffServ体系的IPv6网络QoS保证技术

面对对延迟、延迟抖动、丢包率等方面要求较高的多媒体业务在IP网络上的大量应用,IPv6协议相较于IPv4协议对QoS有更好的支持。本文提出了一种基于DiffServ体系结合RSVP信令协议的IPv6网络的QoS保证技术,在接纳控制策略、带宽分配策略等方面进行了阐述。本技术在保持了DiffServ网络灵活性和扩展性的基础上,充分利用了网络资源,提供了端到端的QoS保证。     

电力公网通信资源在线监测技术方案探讨

本文介绍了电力公网通信资源在线监测技术和相应的监测平台;电力公网通信资源主要包括光纤、电路专线、数据网络通道、移动网络、卫星通信等,主要的监测手段是探针技术、拨测技术及公网监测信息提供等;电力公网通信资源的监测平台主要包括集中监控、资源管理、电子运维和统一展示四个横向的管理视图,以及统计评价一个纵向的管理视图,并支持集中监控功能、资源管理功能、电子运维功能、流量统计功能、统计评价、统一展现功能、统一用户界面功能.     

一种电力信息网的新型QoS机制

现有的电力信息网是基于IP技术的服务网络,无法满足各种业务的端到端服务质量(QoS)要求.为了实现各种业务的不同QoS需求,为其提供端到端的QoS,提出了一种基于端口间虚电路的电力信息网的新型QoS机制.给出了端口间虚电路的工作原理和资源管理方法,提出了新的拥塞避免算法,并设计了QoS路由体系结构.在这种QoS机制中,套接字直接与端口间虚电路标识绑定,与传统虚电路不同,它不仅支持资源子网,而且支持套接字机制,从而保证不同业务的不同QoS要求.     

交换路由技术在调度自动化主站网络中的应用

概述了电力调度自动化主站目前常用的计算机网络组网方式。介绍了采用交换路由及相关网络技术，如服务质量（QoS）、虚拟局域网（VLAN）、第3层交换和第4层交换技术，来提高SCADA/EMS数据传输的实时性和安全性的经验。VLAN技术将整个主站计算机网络分成采集子网、Web网，并在主网、子网之间利用交换机的第3层路由功能进行通信；利用第3层交换机的访问列表控制功能来限制数据的非法访问，增强网络的安全性；利用QoS技术对网络中的数据流按优先级别高低分配带宽，实现实时性较强的数据优先通信。