Design and Evaluation of DNS as Location Manager for HIP

Host Identity Protocol (HIP) is designed to provide secure and continuous communication by separating the identifier and locator roles of the Internet Protocol (IP) address. HIP also has efficient solutions to support host mobility. In this paper, we propose a location management scheme based on Domain Name System (DNS) for HIP. In the proposed scheme, a new DNS HIP resource record is used to translate a domain name into a host identity tag and an IP address. We also develop an analytical model to study the performance of DNS as location manager in terms of success rate, which takes into account the velocity of mobile nodes, the radius of a subnet, the regional network size, the packet transmission delay between the mobile node and the rendezvous server, and the packet processing delay at the DNS and the rendezvous server. The performance results show that for a reasonable range, the DNS is a feasible solution for location management with high success rate for HIP.

Enabling multiparty karaoke over Internet based on low‐level computers: practice and experiment

Karaoke is a system for amateur singing. The traditional online karaoke system does not allow multi‐singers to sing a song in one session. This study designs and implements multiparty karaoke over Internet (MKI) based on low‐level computers. The MKI is an online karaoke system of distributed architecture that allows multi‐singers to sing a song in one session. The MKI must deal with the problems of feedback, asynchronous audio latency at singers’ nodes, round‐trip latency at an inviter's node, and multi‐singers singing a song in one session. The acoustic isolation between microphone and speakers avoids feedback. Network Time Protocol avoids asynchronous audio latency. The third method's round‐trip latency in this study is within 86 ms, and all participants experience the simultaneous singing of the inviter and the invitees. MKI can be used for increasing leisure time, singing skills, and interpersonal relationships. Copyright © 2011 John Wiley & Sons, Ltd.     

Satellites for communications and broadcasting: The evolving european market

The paper traces the development of the market for communications and direct broadcasting satellites in Europe, since the original specification of the European Communications Satellite (ECS) in 1977. It reviews the experiments undertaken on the Orbital Test Satellite (OTS) and the way in which demonstrations with this satellite have influenced the way in which ECS is being developed. It continues by considering the impact of television on the market, first cable television and its distribution requirements, then direct broadcasting by satellite, where the introduction of homes into the customer configuration will bring with it programme content as a salient feature in market development. Finally it speculates on the possibilities for the future, both in terms of the effect of new and higher frequencies on satellite communications systems, and the possible effects that interaction from small earth-stations could have on satellite design.     

数据广播在文化传媒领域的合理化运作

数据广播是现阶段一种新的文化传媒体系,随着数字电视的不断发展完善,数据广播在信息产业飞速发展的今天,逐渐成为新时期信息传播的主要媒介方式,阐述数据广播在当今社会信息领域的存在形态、发展方向以及如何合理、高效地运营这样一种增值业务。     

GB28181标准与ONVIF协议媒体播放兼容性的研究与实现

针对ONVIF协议和GB28181标准关于媒体播放流程不一致问题,提出了一种通过RTSP代理服务器的方式来解决这一问题。论文分析了系统总体结构,媒体请求会话流程以及RTSP代理程序流程并实现。实验结果表明,RTSP代理服务器方式很好的解决了ONVIF协议和GB28181标准媒体播放会话流程不一致的问题。     

基于Yahalom协议终端间视频通信实现

终端间视频通信应用Vaha lom协议将保证通信的安全性。分析了Yaha lom协议的基本原理,并基于此原理对可视电话的视频安全通信进行了研究,分别对视频通信中的三个子流程：建立网络互联、建立安全协议、加密视频通信进行了详细阐述,提出了终端间视频通信的设计方案。     

Multicast with a new switching structure in optical networks

The emergence of new services demands for a multicast function in optical networks. At the same time, wavelength converters are introduced to increase the efficiency of wavelength usage. It is because of the high cost and complex architecture of optical multicast and wavelength conversion technology, that a new switch structure is introduced, in which optical splitters and wavelength converters are shared per-node. In order to accommodate this architecture, a multicast routing and wavelength assignment algorithm in a splitter–converter-sharing optical network and a changing link weight policy to balance network traffic are proposed. By extending RSVP-TE (Resource ReSerVation Protocol-Traffic Engineering) and OSPF-TE (Open Shortest Path First-Traffic Engineering), an optical multicast mechanism is provided, and message type, signaling flow, and finite state machine model are given. Simulations of NSFNET show that, when the number of splitters and converters are 50% and 12.5% of the full equipment respectively, the performance is close to the ideal case. Using a changing link weight policy can improve performance greatly, when there are enough splitters and converters.     

基于SIP的Internet电话

文章先给出了基于ＳＩＰ（会话初始化协议）的Ｉｎｔｅｒｎｅｔ电话的协议结构,随后对其中传输数据的ＲＴＰ（实时传输协议）和ＲＴＣＰ（实时传输控制协议）进行了介绍和分析,并对会话初始化协议的组成实体、命名、寻址、操作进行了详细的论述。     

基于ODMRP的贪婪稳定路由协议

针对ODMRP协议在拓扑频繁变化的移动自组网中存在的不足,提出一种贪婪稳定路由协议GS-ODMRP,通过贪婪转发机制建立主路径,每条链路的备用路径基于链路保持连接时间建立,从而提高协议的鲁棒性.仿真结果表明,相比ODMRP协议,GS-ODMRP协议提高了分组传输成功率,并且降低了网络开销和传输时延.     

数字地面多媒体广播外辐射源雷达目标探测实验研究

数字地面多媒体广播(DTMB)是我国具有自主知识产权的数字地面电视广播标准,该文介绍了利用武汉大学研制的多通道外辐射源雷达实验平台开展DTMB外辐射源雷达研究的情况。论述了该体制雷达的工作原理、关键技术、探测设备和外场实验,给出了目标探测初步实验结果,从实验上证实了利用DTMB信号实现目标探测的技术可行性。