A solution for transparent mobility with route optimization in the IP multimedia subsystem

This paper presents TRIM+, an architecture for transparent mobility management with route optimization in IMS based networks. The design of our architecture is based on a previous work referred to as TRIM. TRIM was originally devised to provide transparent mobility support in the IMS, although transparency came at the cost of using a suboptimal data path between communicating end points. TRIM+ maintains transparency as a design criterium, and thus end-user applications, running at the mobile node and its correspondent communication peers, are unaware of mobility management procedures. Additionally, the proposed design defines a set of route optimization procedures, allowing compliant devices to use the optimal data path for media communications. Furthermore, TRIM+ addresses packet loss management in scenarios where the media path cannot be maintained during the handover of the MN. To this end, our architecture enables the MN to request buffering capacity in its home network to temporarily store incoming media traffic during the handover, which would otherwise be dropped. This mechanism, as well as route optimization procedures, are executed transparently to the end-user applications running at the communicating end points. As a proof-of-concept, we have implemented a software prototype of the TRIM+ architecture, deploying it over a real IMS testbed. By means of a set of experiments, we have validated the mechanisms proposed in this paper, considering both UDP and TCP user traffic.     

Design and implementation of a distributed service invocation function for the IP multimedia subsystem

Within the standard IMS framework, the value-added service is executed in the Application Server (AS) when the expected event happens. In order to be aware of the event, the AS should be inserted into the SIP signaling path at the beginning of the call to monitor the call progress. As a result, all SIP messages related to the session have to be relayed to the AS to determine whether the service is to be executed or not. However, some services are rarely executed; that is, the procedure of relaying messages to the AS seems unnecessary for most cases of these services. This paper proposes a distributed service invocation function (DSIF) to eliminate the unnecessary relay. The DSIF works as an overlay on the top of the current IMS infrastructure that enables operators to deploy it without any change in the existing IMS core; thus, it can be applied transparently to SIP dialogs between the S-CSCF and the AS. The DSIF consists of two functional entities: the Core network-SIF (C-SIF) and the Application side-SIF (A-SIF), and one database node: DB-DSIF. The C-SIF is responsible for allowing the messages to be relayed to the AS only when the service really needs to be executed. The operation of C-SIF is based on two new defined types of filter criteria: trigger Filter Criteria (tFC) and execution Filter Criteria (eFC), which are stored in the DB-DSIF. The A-SIF is in charge of interacting with the AS for service invocation. Our study indicates that the DSIF achieves a shorter service invocation time with a lower message transmission cost. We also demonstrate its feasibility by implementing a prototype on Open IMS Core platform.     

IP网络QoS体系性能的研究

MPLS流量工程通过优化IP网络资源的使用以提高网络性能,同时结合约束路由和面向连接的标记交换路径提供了端到端的QoS保障。在网络上层,DiffServ和MPLS相结合,DiffServ将业务分类、整形、聚合,MPLS再将处理过的数据转换成不同的标签进行转发。在网络底层,MPLS与WDM光网络技术相结合,从而实现更快、更智能的数据传送。     

Power and performance analysis of multimedia applications running on low-power devices by cache modeling

High processing speed is required to support computation intensive applications. Cache memory is used to improve processing speed by reducing the speed gap between the fast processing core and slow main memory. However, the problem of adopting cache into computing systems is twofold: cache is power hungry (that challenges energy constraints) and cache introduces execution time unpredictability (that challenges supporting real-time multimedia applications). Recently published articles suggest that using cache locking improves predictability. However, increased cache activities due to aggressive cache locking make the system consume more energy and become less efficient. In this paper, we investigate the impact of cache parameters and cache locking on power consumption and performance for real-time multimedia applications running on low-power devices. In this work, we consider Intel Pentium-like single-processor and Xeon-like multicore architectures, both with two-level cache memory hierarchy, using three popular multimedia applications: MPEG-4 (the global video coding standard), H.264/AVC (the network friendly video coding standard), and recently introduced H.265/HEVC (for improved video quality and data compression ratio). Experimental results show that cache locking mechanism added to an optimized cache memory structure is very promising to increase the performance/power ratio of low-power systems running multimedia applications. According to the simulation results, performance can be improved by decreasing cache miss rate down to 36 % and the total power consumption can be saved up to 33 %. It is also observed that H.265/HEVC has significant performance advantage over H.264/AVC (and MPEG-4) for smaller caches.     

Systematic performance modeling and characterization of heterogeneous IP networks

Accurate measurement and modeling of IP networks is essential for network design, planning, and management. Efforts are being made to detect the state of the network from end-to-end measurements using different techniques and paradigms. In this paper we propose a novel concept to use in the modeling of real network scenarios under measurement and analysis. We called this new concept Service Condition. We explain our proposal's motivations and we use some simple examples to show how to apply the Service Condition concept to the study of real heterogeneous network scenarios. To show the real applicability of our proposal, preliminary results from a performance evaluation study over real heterogeneous networks (where the integration of LAN, WLAN, ADSL, UMTS, and GPRS is present) are given.     

IP protection and restoration

Protection and restoration together connote an additional layer of reliability, availability and integrity wherever they are applied. Protection ensures that the desired service will not be permanently disrupted in the event of a component failure. Restoration ensures the desired service will be returned following a component failure. For many years, IP has provided a form of protection and restoration by enabling packets to be dynamically rerouted around link or node failures. Coupled with TCP's reliable transport service, it is easy to see how TCP/IP based networking has achieved a reputation for robustness. The temporal dimension to this IP rerouting mechanism could, however, limit its usefulness for applications with real-time service-level requirements. It takes an IP network some time (usually tens of seconds) to detect a failure, propagate the information to other routers around the network, and then have each router compute a new path. The paper considers how efforts are under way in the research and vendor communities to develop faster and more robust protection and restoration mechanisms for IP networks     

Conceptual modeling of multimedia documents

An approach to the document-retrieval problem that aims to increase the efficiency and effectiveness of document-retrieval systems by exploiting the semantic contents of the documents is presented. The document retrieval problem is delineated, and conceptual document modeling basics and requirements are discussed. An experimental system, the Multimedia Office Server (Multos), which implements some of the document-model concepts described, is presented     

Survey on modeling and indexing events in multimedia

Events have gained increasing interest in the area of multimedia in recent years. There have been many approaches published and research conducted on how to extract events from multimedia, represent it using appropriate models, and how to use events in end user applications. In this paper, we conduct an extensive analysis of existing event models along commonly identified aspects of events. In addition, we analyze how the different aspects of events relate to each other and how they can be applied together. Subsequently, we look into different approaches for how to index multimedia data. Finally, we elaborate on how to link the multimedia data with events in order to provide the basis for future event-based multimedia applications.     

DCCP下的一种流媒体重传机制

由于差错重传机制存在各种缺点,并不适合流媒体传输,若它的处理过程占用最小网络带宽和时间,将大大提高流媒体的质量。提出了一种基于DCCP的源端控制的选择重传机制（TBSR）,其重传由决策算法决定,而发送速率和拥塞控制由TFRC控制。仿真结果表明,机制能大大提高流媒体视频质量。     

UML在物流运输运力调度子系统建模中的应用

物流运输管理系统主要是将先进的仓储系统、接单中心、运力调度、结算系统等平台有机的结合起来,为客户、供应商提供第3方的物流及其它增值服务.该应用以开发运力调度管理子系统为例,结合软件工程和面向对象技术(uml)规范了各个环节的业务流程模块开发过程,建立了系统的用户需求模型、分析模型、设计模型,并在某物流运输企业中得到了应用,对于提高企业的销售管理水平,具有良好的效果.     

一种改进的高性能处理器网络子系统架构设计

针对传统处理器网络子系统在高速网络环境下的性能瓶颈,特别是BD管理效率低、数据传输延迟大等问题,提出一种改进的网络子系统架构。该架构将BD管理功能从NIC上移至处理器,并扩展了BD信息,同时增加了cache的查找和读后无效操作。通过Simics模拟器对系统架构进行了仿真及评估。实验结果表明,较传统的架构和采用DCA技术的架构相比,改进后架构在取得了更高带宽利用率的同时,降低了CPU利用率,更好地保持了性能和资源的平衡。     

IEEE 802.15.4区分服务协议性能分析与建模

针对IEEE 802.15.4协议的无线传感网络不能提供数据流优先级区分的问题,提出一种基于区分服务的马尔可夫链模型以支持实时多媒体应用。该机制的主要思想是根据服务质量要求（时延敏感与否）为不同的数据流分配不同的优先级。不同优先级的数据采用不同的增长因子来更好地减少冲突。此外,为了弥补低优先级数据流,高优先级的数据流在第二次空闲信道评估发现信道空闲时并不立即接入信道而是以一定的概率竞争信道。数学分析表明,对不同数据流设置合理的增长因子和竞争概率能够显著提高高优先级数据流的性能并对低优先级数据影响较少。     

MPLS over ATM and IP over ATM methods for multimedia applications

This paper presents fundamental aspects of MPLS over ATM method, IP over ATM method and multimedia application traffics with different quality of service (QoS) requirements. Using a simulation tool, the MPLS over ATM method providing ABR, CBR and VBR QoS support, and the IP over ATM method providing a primitive UBR QoS support for transferring data, voice and video traffics are modeled. Having simulated the models under varying offered loads, obtained simulation results are presented. Comparing the average end-to-end delay and delay variation graphs, not only does the MPLS over ATM method provide improved results for all of the multimedia traffics but also overcomes the worst disadvantage of the IP over ATM method producing similar and erratic results for the data, voice and video application traffics.     

BACnet/IP在广域网的建模仿真与传输性能分析

BACnet是楼宇自动控制系统通信协议。利用NS_2对BACnet/IP进行了建模。分析了BACnet广域网的延迟特性,包括分析：节点数量,报文长度对网络传输延迟的影响,并对几种最常见的证实服务和非证实服务进行了模拟。分析结果可以用于调整BACnet应用层服务的网络参数,并且对设计和操作BACnet远程控制系统有指导意义。     

一种全IP宽带移动P2P网络结构及性能分析

提出一种全IP宽带移动P2P网络结构,通过在数据网关上增加分布式用户服务器实现异构网络的互联,形成了虚拟的二维覆盖网络,采用IMS为核心控制网络,基于此结构可开展各种移动P2P业务。以资源共享流程为例,对比分析了该结构和基于IMS的P2P网络结构的差异,结果表明该网络结构在具有更小的系统开销。     

基于IP组播的网络多媒体教学系统的设计与实现

IP组播是IP领域的最新技术，它为网络实时多媒体传输和批量数据传输提供了解决方法。设计并实现了一个基于IP组播的纯软件的网络多媒体教学系统，该系统能保证传输流的服务质量，能有效地拓展会话节点的规模。     

高性能计算应用程序的静态性能分析和建模方法研究

通过对程序源代码和二进制代码的静态分析,能够对代码中不同类型的指令执行情况进行统计。使用多面体模型对循环(循环内包含判断选择结构)函数调用的情况进行建模,将静态分析无法确定的性能数据作为参数保留,结合用户定义的体系结构描述文件,建立起一个参数化的性能模型,提出一种面向高性能计算(high performance computing,HPC)应用软件的性能建模方法。与动态的建模方法相比,避免了反复执行被建模程序所带来的计算资源占用和时间开销,同时又具有较高的灵活性和可用性;在性能模型的精确度上,也与动态的方法非常接近。同时,以参数化的性能模型为基础,能对和程序性能有关的其他重要数据进行进一步的估算。     

基于FPGA的仿真系统数据采集控制器IP核设计

介绍了在大型工业模拟仿真系统中,利用FPGA和软IP核实现数据采集及收发控制的方案,并对其进行设计实现.重点阐述了在发送指令和采集接收两种数据流模式下,该IP核的控制处理逻辑及工作状态机的设计及实现.同时,设计仿真测试对其进行验证.经测试验证,该IP核能实现对前端模拟仿真设备状态实时采集并控制的功能,达到了设计目的.