Efficient Group-Based Multimedia-on-Demand Service Delivery in Wireless Networks

Recently, an upsurge of interest has been observed in providing multimedia on-demand (MoD) services to mobile users over wireless networks. Nevertheless, due to the rapidly varying nature of mobile networks and the scarcity of radio resources, the commercial implementation is still limited. This paper presents an efficient group-based multimedia-on-demand (GMoD) service model over multicast-enabled wireless infrastructures, where users requesting the same content are grouped and served simultaneously with a single multicast stream. The grouping is fulfilled through a process named "batching". An analytical model is derived to analyse a timeout-based batching scheme with respect to the tradeoff between user blocking probability and reneging probability. Based on the deduced analytical model, an optimal timeout-based batching scheme is proposed to dynamically identify the optimal tradeoff point that maximizes the system satisfaction ratio given a particular system status. The proposed scheme is evaluated by means of simulation and compared with two basic batching schemes (timeout-based, size-based), and two hybrid ones (combined-for-profit, combined-for-loss). The simulation results demonstrate the proposed approach can ensure significant gains in terms of user satisfaction ratio, with low reneging and blocking probabilities     

一种MPLS网络间的IP业务传送技术

当前跨多协议标记交换(MPLS)网络进行网间IP业务传送具有一定的局限性。详细描述了MPLS网络间辅以网关设备的IP业务传送技术,并提出接入网关和互连网关的设计方案,重点阐述了网关的模块组成和接口设计;结合在研的2种典型MPLS网络,利用AX4000测试仪对跨网的端到端IP业务传送性能进行分析,针对业务优先级和利用通道保护能力的IP业务传送指标进行测试,对测试数据和应用效果进行分析总结。     

NetCAPE: Enabling Seamless IMS Service Delivery across Heterogeneous Mobile Networks

An evolving wireless world is constantly providing users with a wider set of access technologies to choose from, each with different capabilities and properties. In this world, IMS as defined by 3GPP provides an enabling, standardized multimedia architecture that is access independent, hence, providing service convergence. This trend is accompanied by an increasing number of multimode terminals so that inter-access- system-service continuity gains relevance. This article presents the architectural framework of NetCAPE (networking context aware policy environment), which addresses the optimization of mobility management in such a heterogeneous environment while interacting with IMS applications to enable seamless service delivery across heterogeneous mobile networks; even as the mobility offered by the underlying network remains transparent to IMS applications. Although the focus is on 3GPP-based mobile networks, the framework also incorporates wired access technologies, hence, taking a further step toward fixed mobile convergence (FMC). First results are presented highlighting the improvements gained by applying NetCAPE concepts.     

ADSL宽带接入网业务分析

认为ADSL是一种全新、快捷和高效的接入方式。介绍了ADSL的发展过程、结构和所承载的业务,将ADSL与N-ISDN、DDN和CABLEModem进行了比较,提出了拓展ADSL市场的策略和要解决的问题等等。     

无人预警机技术特点分析及架构设计

无人预警机预警范围大、预警工作时间长,是预警机的发展方向之一,但系统复杂,研制难度大.本文分析总结无人预警机续航时间长、飞行高度高、载荷能力强、飞行控制自主化的平台特征和结构紧凑化、探测远程化、通信网络化、操控自动化的任务电子系统特征,探讨飞行器平台、雷达天线一体化综合设计及雷达、红外预警探测等系统架构设计技术问题,为无人预警机解决方案制定提供参考.     

基于REST风格的混杂感知车载网信息服务设计

实时可靠地获得全面的车载感知服务信息是车载网络发展的"瓶颈"问题。混杂感知车载网(HSVN)兼有无线传感器网络(WSN)和车载自组网(VANET)的特点,为车载用户提供了大量车载信息,是车载网络的发展趋势。表述性状态转移(REST)架构统一了资源格式和交互形式,在服务器和客户端间进行无状态服务,有利于异构问题的解决。文章基于HSVN的信息服务特征,提出一种新型车载网络框架和服务模型,能提高车载感知信息的服务交互能力;基于REST架构理念,采用HSVN中信息服务资源设计方法,为异构网络下的信息交互系统提供一种轻量化的实现途径。     

Analyze and Design High-Speed Power Delivery Networks Using New Multiinput Impedances in Printed Circuit Boards

In this paper, a new input impedance, the multiinput impedance, which includes all information of the full impedance matrix, is proposed to accurately analyze and design planar power delivery networks (PDNs) in high-speed printed circuit boards and packages. The multiinput impedance includes all of the potential impacts of the other operating active power ports in both low and high frequencies. A systematical power-delivery-network analysis and design method using the multiinput impedance is developed. The global and local characteristics of the decoupled PDN are well demonstrated by the multiinput impedance, which make the analysis and design of the modern decoupled PDNs more accurate and reliable. Numerical and measured results show that the proposed multiinput impedance can characterize both the global and local characteristics of the planar PDNs with high accuracy.      

Analysis of Traffic Access Control Strategies in Integrated Service Networks

A common digital transmission facility provides service to a community of heterogeneous users generating traffic with differing intensity, message length, and bit rate. In order for this type of integrated communication system to handle its traffic demands with high efficiency and flexibility, close control of access and switching at the input node is required. We propose, analyze, and compare two different strategies for managing the access of two types of traffic, a blockable wide-band (WB) type of traffic and a queueable narrow-band (NB) type of traffic, sharing the transmission resource dynamically. The first strategy assigns preemptive priority to the WB traffic over the NB traffic, whereas the second strategy employs a wide-band to narrow-band bit rate compression mechanism. Exact analytic models are developed, and solution methods are presented and implemented. It is shown that the best combined performance is obtained when the two strategies are adaptively combined according to the offered load.     

基于云计算的服务交付模型

针对目前缺少全方位地描述基于云计算的服务交付的标准或者规范的问题,从实际应用中三种类型云服务交付全景的维度出发,在研究国内外标准化组织云服务交付的基础上,梳理出基于云计算的服务交付模型,包括交付内容、交付过程、交付质量和交付管理,为云服务提供商的服务交付提供指导,从而达到保障云服务提供商为云服务用户提供高质量服务的目的。     

The Integrity of Data Delivery in Computer Networks

This correspondence deals with the problem of undetected packet misdelivery in computer networks as a result of node failures. Techniques for reducing its chance of occurrence are discussed.     

Design and Analysis of Actively-Deskewed Resonant Clock Networks

Active deskewing is an important technique for managing variability in clock distributions but introduces latency and power-supply-noise sensitivity into the resulting networks. In this paper, an adaptively deskewed resonant clock network, based on an injection-locked distributed differential oscillator, is described, in which the delay lines required for deskewing are incorporated into the injection-lock source, dramatically improving jitter immunity. A power management system based on automatic amplitude control of the resonant grid further enhances energy efficiency. A prototype system operates at a nominal 2-GHz frequency in a 0.18 mum technology with on-chip jitter and skew measurement circuits and with more than 25 pF/mm² of clock loading.     

警戒雷达自适应频率捷变设计及抗干扰分析

频率捷变是雷达有效的对抗有源干扰的工作模式,而针对干扰环境的自适应频率捷变能将频率捷变的抗干扰效果提高一步。描述了自适应捷变频的基本原理,提出了一种具体的实现方式,并简要分析了电子战设备与自适应频率捷变雷达之间的干扰与抗干扰措施及效果。     

综合业务数字网及宽带综合业务数字网

主要论述了综合业务数字网（ＩＳＤＮ）的概念及特点,简要介绍了ＩＳＤＮ发展的目标———宽带综合业务数字网（Ｂ＿ＩＳＤＮ）及其实现的技术基础。     

LTE-Advanced中继系统中的VoIP业务系统性能研究

对基于中继传输的LTE-Advanced下行系统中的数据包传输机制进行了分析,并提出基于最大时延优先调度准则(MLWDF,modified largest weighted delay first)的分布式中继系统Voice over Internet Protocol(VoIP)业务调度方案.基于LTE-Advanc...     

A Modelled Study of Content Delivery Networks

Delivery Networks (CDNs) appeared at late 90's as a means of reducing response time experienced by Internet users by distributedly placing multiple servers, called surrogates, in the client network neighbourhood. Many companies have deployed their own propietary CDN hiding implementational aspects, which guides to a lack of a general open model that describes CDN behaviour from an analytical perspective. This article proposes a general expression for a CDN considering certain design parameters, such as caching hit rate, delay and number of clients and surrogates.     

Causality Enforcement in Transient Co-Simulation of Signal and Power Delivery Networks

This paper discusses a transient simulation method that co-simulates the signal and power delivery networks in a packaged system. The method includes a novel delay extraction technique that enables the enforcement of causality conditions on the resulting transient waveforms. This paper describes the application of the method on a number of test cases to account for electromagnetic parasitics and cross-talk, and shows the scalability of the method for performing large sized transient simulations     

Large-System-Based Performance Analysis and Design of Multiuser Cooperative Networks

In this paper, the performance of the cooperative multiuser direct-sequence code-division multiple-access (DS-CDMA) system is analyzed in the asymptotic regime where both the spreading codes and the number of users grow unboundedly large with the same ratio. Assuming that each terminal is paired with another user which, in addition to transmitting its own data, estimates and relay the information transmitted from its partner, a simple approximate signal-to-interference-plus-noise ratio (SINR) expression is derived that is independent from the spreading codes and explicitly accounts for the effects of the multiple-access interference (MAI) and the relay noise. The so-obtained SINR expression is then computed based entirely on the available local information and without any knowledge about the interfering users. The results obtained above are then used to optimally design the cooperative system. In particular, it is shown how the amount of cooperation between each collaborating pair can be adjusted to simultaneously achieve a preassigned target SINR for both users. Based on the local information, the globally optimal amount of the relay power is obtained that maximizes the achieved SINR at the access point. It is shown that increasing the relay power does not necessarily result in improving the quality of reception at the access point and, to maximize each user's SINR, its relay power should be carefully adjusted based on the environmental parameters such as the interpartner channel link and the powers of MAI and the relay noise. The connection between the cooperative and the conventional multiuser systems is also studied and simulations are used to demonstrate the validity of the analytical results.      

Guest Editorial Analysis and Design of Multi-Service Wireless Networks

Mobile Networks and Applications -     

车联网中动态TDMA机制的设计与分析

简要介绍了车联网的概念和通信特点,分析了车联网中常见MAC协议的性能缺陷。基于动态TDMA机制,提出了一种自适应车联网中通信节点数量快速变化的动态MAC协议D-MAC。详细介绍了MAC帧结构、时隙扩张机制和冗余时隙回收算法。利用Vanet Mobi Sim交通模拟器和NS-2网络仿真器对本协议进行了仿真实验,结果表明在多种复杂交通环境下本协议的消息传输可靠性高、实时性强。