基于6LoWPAN传感器网关设计

在研究6LoWPAN无线传感器网络以及IPv6网络的基础上,提出一种基于6LoWPAN的传感器网关解决方案,实现6LoWPAN无线传感器网络与IPv6网络之间互联,并对网关中的硬件与软件设计进行论述。最后搭建测试网络,通过对端到端网络的连接性、延时变化、往返延时、丢包率以及吞吐量的测试,对该网络性能作出简要分析。测试结果表明,该网关实现了6LoWPAN无线传感器网络与IPv6网络的互联,并能在实际网络环境中运行。     

面向WLAN的无线传感器网络网关设备及其接入机制

网关是实现无线传感器网络与其他基础网络（如移动通信网、电信网等）互联互通的重要设备。文章设计并实现了一种基于CC2420芯片的网关,实现了与传感器网络的通信,并利用无线网卡模块实现了网关设备与无线局域网的连接,克服了网关硬件设备布置的局限性,扩大了网关设备和无线传感器网络的应用范围。     

无线传感器网络与IPv6网络的互联方式研究

如何实现无线传感器网络(WSN)与TCP/IP(v6)网络的互联是当前的热点研究方向之一,全IP互联方式是当前讨论最为激烈的焦点问题.在WSN内部是否需要采用IPv6,是WSN协议设计需要回答的一个基本问题,其结论将在很大程度上影响今后WSN协议发展的基本走向.本文首先介绍了WSN与IPv6网络互联的各种方式,然后重点对采用全IP互联方式的必要性以及需要解决的关键技术问题进行了分析探讨,分析结果表明:全IP方式是实现WSN与IPv6网络互联的一种非常重要的思路,值得进行深入研究.     

Random early detection gateways for congestion avoidance

The authors present random early detection (RED) gateways for congestion avoidance in packet-switched networks. The gateway detects incipient congestion by computing the average queue size. The gateway could notify connections of congestion either by dropping packets arriving at the gateway or by setting a bit in packet headers. When the average queue size exceeds a present threshold, the gateway drops or marks each arriving packet with a certain probability, where the exact probability is a function of the average queue size. RED gateways keep the average queue size low while allowing occasional bursts of packets in the queue. During congestion, the probability that the gateway notifies a particular connection to reduce its window is roughly proportional to that connection's share of the bandwidth through the gateway. RED gateways are designed to accompany a transport-layer congestion control protocol such as TCP. The RED gateway has no bias against bursty traffic and avoids the global synchronization of many connections decreasing their window at the same time. Simulations of a TCP/IP network are used to illustrate the performance of RED gateways     

下一代网络的业务互通体系结构

以IP为基础的因特网的出现对传统的电信网络带来了巨大的冲击,它的开放性和业务的灵活性为电信网进一步的发展指出了一个方向.但是,由于IP在提供具有质量保证的等级业务方面缺乏技术的保障;局域网技术、广域网技术的发展使得原来被认为功能简单的第二层传输网络具有越来越强的业务能力,例如QoS、多播、VPN以及安全管理能力,将导致多接入、多业务的下一代网络端到端业务控制和业务集成越来越复杂,使得我们需要重新审视网络互连和业务集成的基本思路,建立下一代网络的新的业务概念.本文对这个问题进行了初步的探讨,结论是:下一代网络具有新的集成业务体系结构,其中的关键是业务互通问题;其中IP用于网络互联,SIP用于建立终端和服务器间的业务会话,提供业务之间的互作用,实现端到端业务能力的集成和最终应用的集成需要新的网格业务技术;下一代网络除要有分别支持网络互联、会话建立和业务集成的能力以外,还必须建立网络、会话和业务之间的新的互作用关系,使得下一代网络的目标得以实现.     

H.323: the multimedia communications standard for local areanetworks

This article provides an overview of ITU-T Recommendation H.323, “Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service.” This recommendation applies to multimedia communications over packet-switched networks, such as Ethernet, which run TCP/IP, IXP/SPX, or other related protocols. In addition to the multimedia terminal, other H.323 components are defined which provide for conference admissions (gatekeeper), multipoint communications (multipoint controller, multipoint processor), and interoperability (gateway) with terminals on other types of networks. H.323 has application to a variety of network media, including local area networks, enterprise networks, metropolitan area networks, wide area networks, dial-up line connections to LANs, and the Internet. This provides the capability to have global multimedia communications from the desktop using existing network infrastructures     

基于RTT的TCP流带宽公平性保障机制

TCP端到端的拥塞控制机制使得TCP连接获得的瓶颈带宽反比于RTT(数据包往返时间)。为了缓解TCP对于RTT较小流的偏向,区分服务的流量调节机制在RTT较小的流取得目标速率且获得多余资源的情况下可以确保RTT较大流不至于饥饿。现有的基于RTT的流量调节机制在网络拥塞程度较轻时非常有效,但是当网络拥塞程度较重时,由于对RTT较大流的过分保护而导致RTT较小流饥饿。因此,通过引进自适应的思想提出了改进方法,其主要思想就是根据网络的拥塞程度自适应地调整对RTT较大流的保护程度。大量的仿真试验表明所提的机制能有效保障TCP流的带宽公平性并且比现有的方法具有更好的强壮性。     

Smartphone with Augmented Gateway Functionality as Opportunistic WSN Gateway Device

Sensors and actuators are being increasingly deployed for monitoring and controlling different phenomena and processes in a stand-alone manner or attached to sensor nodes with communication capabilities as part of larger wireless sensor networks (WSN). In addition to the protocols for communication within the WSN, sensor nodes may also provide the gateway functionality towards other networks and/or support communication with other external devices. These devices either represent additional gateways for exposing data and metadata to external networks, or serve as connection points to WSN for instance for the on-site calibration and maintenance. Smartphones as advanced mobile terminals appear particularly suitable for such role. This paper investigates the role a smartphone augmented with WSN gateway functionality can play in WSN with respect to regular dedicated sensor and gateway nodes. As a practical example we show the implementation of a gateway augmented smartphone using a Samsung i8910 phone and a VESNA sensor node connected via Bluetooth. The role of a gateway augmented smartphone is to interface between WSN, which is using a proprietary networking protocol, and the mobile network. The data obtained from WSN can be enriched using smartphone’s embedded sensors before being sent to the remote server. We demonstrate this on an example of geo-tagging the collected data from WSN with the smartphone’s Global Positioning System-based location data.     

Ensuring fairness among ECN and non‐ECN TCP over the Internet

Explicit Congestion Notification (ECN) has been proved to provide a fast indication of incipient congestion and thus better the performance of a TCP/IP network. In this work, we carry out investigations on gateway or router performance in providing fairnesss when both FIM ECN‐capable and non‐ECN‐capable connections are employed. We propose a new packet‐dropping scheme called Fair In‐time Dropping (FID) which drops packets from a connection upon detecting an incipient indication of congestion depending on its share of gateway or router buffer occupancy. We also show that a combination of FIM and FID offers the best fairness compared with a combination of FIM along with other dropping schemes. Copyright © 2003 John Wiley & Sons, Ltd.     

VoWLAN通信平台的设计与实现

VoWLAN也叫VoWiFi或者WiFi VoIP。它是基于无线网络技术和VoIP网络,是两者的有机结合。即是通过WLAN提供VoIP业务,使得终端用户通过WLAN拨打IP电话成为现实。本文提出了在基于Linux操作系统的SIP应用服务器及VoIP网关中,如何通过SIP信令和传统的PSTN数据通信线路与无线网络无缝连接方案,从而实现IP网络与传统电话间的实时语音通信、电话会议、语音信箱、视频通信、短消息、数据传输等业务。本设计已成功应用于某企业的实时语音通信平台,获得良好的效果。     

Secure Service and Network Framework for Mobile Ethernet

Secure cellular data services have become more popular in the Japanese market. These services are based on 2G/3G cellular networks and are expected to move into the next-generation wireless networks, called Beyond 3G. In the Beyond 3G, wireless communication available at a user's location is selected based on the type of the service. The user downloads an application from one wireless network and executes it on another. Beyond 3G expects core and wireless operators and allows to plug-in new wireless access. A security model that can accommodate these requirements needs to be sufficiently flexible for end users to utilize with ease. In this paper, we explain the Mobile Ethernet architecture for all IP networks in terms of the Beyond 3G. We discuss usage scenario/operator models and identify entities for the security model. We separate a mobile device into a personal identity card (PIC) containing cryptographic information and a wireless communications device that offers security and flexibility. We propose a self-delegation protocol for device authentication and use a delegated credential for unified network- and service-level authentication. We also propose proactive handover authentication using the security context between different types of wireless access, such as Third Generation Partnership Project (3GPP) and WLAN, so that the secure end-to-end communication channels established by service software on the TCP/IP are not terminated. Lastly, we raise security issues regarding the next-generation platform.     

Admission control in time-slotted multihop mobile networks

The emergence of nomadic applications have generated a lot of interest in next-generation wireless network infrastructures which provide differentiated service classes. So it is important to study how the quality of service (QoS), such as packet loss and bandwidth, should be guaranteed. To accomplish this, we develop am admission control scheme which can guarantee bandwidth for real-time applications in multihop mobile networks. In our scheme, a host need not discover and maintain any information of the network resources status on the routes to another host until a connection request is generated for the communication between the two hosts, unless the former host is offering its services as an intermediate forwarding station to maintain connectivity between two other hosts. This bandwidth guarantee feature is important for a mobile network to interconnect wired networks with QoS support. Our connection admission control scheme can also work in a stand-alone mobile ad hoc network for real-time applications. This control scheme contains end-to-end bandwidth calculation and bandwidth allocation. Under such a scheme, the source is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real time applications. In the case of ATM interconnection, the bandwidth information can be used to carry out an intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine via simulation the system performance in various QoS traffic flows and mobility environments     

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。     

Interworking of IP multimedia core networks between 3GPP and WLAN

The 3GPP has specified the IP multimedia subsystem (IMS) for the provisioning of multimedia services in UMTS Release 5 and later. Interconnection at the service layer between 3GPP and LAN networks requires interworking between IMS and WLAN functionalities. Studying several interconnection scenarios and the main functionalities of IMS, this article analyzes how the interconnection of 3GPP and WLAN networks may be performed in order to support different levels of service interconnection. Special attention is paid to interconnection at the session negotiation level, using SIP (the base protocol of the IMS) to provide session negotiation with QoS and AAAC support.     

DHTTP: an efficient and cache-friendly transfer protocol for the web

Today's HTTP carries Web interactions over client-initiated TCP connections. An important implication of using this transport method is that interception caches in the network violate the end-to-end principle of the Internet, which severely limits deployment options of these caches. Furthermore, while an increasing number of Web interactions are short, and in fact frequently carry only control information and no data, TCP is often inefficient for short interactions We propose a new transfer protocol for the Web, called Dual-Transport HTTP (DHTTP), which splits the traffic between UDP and TCP channels. When choosing the TCP channel, it is the server who opens the connection back to the client. Through server-initiated connections, DHTTP upholds the Internet end-to-end principle in the presence of interception caches, thereby allowing unrestricted caching within backbones. Moreover, the comparative performance study of DHTTP and HTTP using trace-driven simulation as well as testing real HTTP and DHTTP servers showed a significant performance advantage of DHTTP when the bottleneck is at the server and comparable performance when the bottleneck is in the network.     

Throughput Analysis and Measurements in IEEE 802.11 WLANs with TCP and UDP Traffic Flows

There is a vast literature on the throughput analysis of the IEEE 802.11 media access control (MAC) protocol. However, very little has been done on investigating the interplay between the collision avoidance mechanisms of the 802.11 MAC protocol and the dynamics of upper layer transport protocols. In this paper, we tackle this issue from an analytical, simulative, and experimental perspective. Specifically, we develop Markov chain models to compute the distribution of the number of active stations in an 802.11 wireless local area network (WLAN) when long-lived transmission control protocol (TCP) connections compete with finite-load user datagram protocol (UDP) flows. By embedding these distributions in the MAC protocol modeling, we derive approximate but accurate expressions of the TCP and UDP throughput. We validate the model accuracy through performance tests carried out in a real WLAN for a wide range of configurations. Our analytical model and the supporting experimental outcomes show that 1) the total TCP throughput is basically independent of the number of open TCP connections and the aggregate TCP traffic can be equivalently modeled as two saturated flows; and 2) in the saturated regime, n UDP flows obtain about n times the aggregate throughput achieved by the TCP flows, which is independent of the overall number of persistent TCP connections.     

Design and Implementation of an End-to-End System for DTV Multicasting to Home Over Broadband IP Access Network

This paper describes design and implementation of an end-to-end system which implements digital television (DTV) multicasting to the home over broadband IP access network. We have developed a DTV-IP gateway for introducing DTV programs from broadcasting network into IP network with special considerations of the challenges, which consist of different service models and different protocols when deploying DTV services between the traditional satellite, cable or terrestrial network and the broadband IP network. According to different application scenario, the DTV-IP gateway can output two types of streams: CBR (constant bit-rate) transport stream (TS) over IP and VBR (variable bit-rate) TS over IP. Moreover, we have proposed a method to auto-regenerate the standard CBR TS from VBR TS over IP for the standard set-top-box (STB) with consideration of timing synchronization. This end-to-end system has been verified to work well in the broadband IP access network environment.     

一种安全隧道网关的设计与实现

针对应用层客户/服务器系统安全性欠缺的情况,设计、实现了一套基于SSL/TLS协议的安全隧道网关,以提供无缝的安全集成.客户端隧道网关与服务器端隧道网关之间基于X.509证书进行身份认证,并建立SSL/TLS安全链接转发客户端请求与服务器端响应.隧道网关与客户端、服务器之间采用普通TCP/IP链接进行数据传输.隧道网关使已有客户/服务器系统无需任何修改即可享有机密性、完整性和可认证的数据传输.最后给出了网关测试结果与应用实例.     

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。     

面向物联网的嵌入式3G网关设计

随着信息技术的发展和物联网概念的兴起,感知化、互联化、物联化、智能化的大趋势正在发生。将传感技术、嵌入式技术、3G技术结合起来,设计了一种嵌入式3G网关,该网关以ARM9处理器LPC3250为核心,以嵌入式Linux为实时操作系统,对来自异构传感器网络的数据进行汇聚、处理、转发,实现了异构无线传感器网络融合、3G远距离转发和多种终端设备支持等,用以支持物联网的多种应用。