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Multimedia Services for Location-Aware, Ad-Hoc Collaboration in Wireless Networks.
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... Depending on the application an accuracy of a few meters is adequate – this accuracy can be sufficient for every service categorised in Section 2.1. Simple positioning with a cell-of-origin technique would not be appropriate because the cells are to wide [10] and due to the WLAN standard [9] devices keep connections to access point even if a stronger signal from a new one is available. More accurate techniques use signal strength to determine the devices's location. ...
The steady rise of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. Local services will be one of the most exiting features of the next generation wireless systems. This paper gives an overview of the main concerns of location-based services (LBS) which are already established in the area of mobile phone networks. Transferring LBS to an indoor wireless network, especially WLAN, is the next step. As a first step for any kind of LBS a positioning system is required. Different techniques exist in all major wireless networks which have basic procedures in common. This paper presents, analyses and categorises state-of-the-art techniques for indoor positioning and examines the suitability to support LBS in WLANs.
An operation of indoor and outdoor localization mechanisms cannot be fully integrated because the techniques and operation methods are different. As the consequence, a seamless mobility support in location based services for mobile applications cannot be achieved. They still face discontinuity of services when the mobile users move from indoor to outdoor and vice versa, or between WLANs and cellular networks. This paper presents the operation of Location Based Service Protocol (LBSP) to support the seamless mobility of location based service applications on mobile users. The actual application is implemented to obtain the processing time of LBSP operation when operating indoor and outdoor. The data are collected and used to evaluate the LBSP performance by simulation. The LBSP application is implemented on Android mobile device by using Java, and the simulation is performed by using OPNET Modeler 14.0 Education Version. The performance is evaluated in terms of traffic, throughput, and response time between a server and the mobile users, i.e., mobile station (MS) and user equipment (UE), on the Internet. The simulation results expresses that the LBSP can support the increasing number of mobile users without degrading the traffic. It preserves the response time and throughput when the number of mobile users is increased as well.
This memorandum describes RTP, the real-time transport protocol. RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of-service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers.
Most of the text in this memorandum is identical to RFC 1889 which it obsoletes. There are no changes in the packet formats on the wire, only changes to the rules and algorithms governing how the protocol is used. The biggest change is an enhancement to the scalable timer algorithm for calculating when to send RTCP packets in order to minimize transmission in excess of the intended rate when many participants join a session simultaneously.
This memorandum describes RTP, the real-time transport protocol. RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of-service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers.
The paper describes our recently developed system which captures both whiteboard content and audio signals of a meeting using a digital still camera and a microphone. Our system can be retrofitted to any existing whiteboard. It computes the time stamps of pen strokes on the whiteboard by analyzing the sequence of captured snapshots. It also automatically produces a set of key frames representing all the written content on the whiteboard before each erasure. Therefore, the whiteboard content serves as a visual index to browse the audio meeting efficiently. It is a complete system which not only captures the whiteboard content, but also helps users to view and manage the captured meeting content efficiently and securely.
The peer-to-peer service has entered the public limelight over the last few years. Several research projects are underway on peer-to-peer technologies, but no definitive conclusion is currently available. Compared to traditional Internet technologies, peer-to-peer has the potential to realize highly scalable, extensible, and efficient distributed applications. This is because of its basic functions: resource discovery, resource sharing, and load balancing in a highly distributed manner. An easy prediction is the emergence of an environment in which many sensors, people, and many different kinds of objects exist, move, and communicate with one another; it is called the "ubiquitous communication environment". Peer-to-peer is one of the most important and suitable technologies for ubiquitous networking since it supports discovery mechanisms, simple one-to-one communication between devices, free and extensible distribution of resources and distributed search to handle the enormous quantities of resources.
Multimedia desktop conferencing systems that includes audio, video and application sharing are gaining momentum and increasingly becoming a reality. This paper describes one such system, called Java Collaborative Environment (JCE). The application sharing component of JCE allows the conference participants to share any application written in Java using its Abstract Windows Toolkit (AWT). The audio and video components of JCE are based on the new Java Media Framework (JMF). In this paper, we describe the problems encountered during the use of JMF in a conference with a large number of participants. The problems are caused by using the real-time transport protocol (RTP) within JMF for sending and receiving many audio and video streams. Our solutions to these problems are based on using a video multiplexer and an audio mixer. The video multiplexer is to display the videos of many participants into few video windows and the audio mixer is to combine all audio streams into one. KEY WORDS: ...
This note describes a profile for the use of the real-time transport protocol (RTP) and the associated control protocol, RTCP, within audio and video multiparticipant conferences with minimal control. It provides interpretations of generic fields within the RTP specification suitable for audio and video conferences. In particular, this document defines a set of default mappings from payload type numbers to encodings. The document also describes how audio and video data may be carried within RTP. It defines a set of standard encodings and their names when used within RTP. However, the definitions are independent of the particular transport mechanism used. The descriptions provide pointers to reference implementations and the detailed standards. This document is meant as an aid for implementors of audio, video and other real-time multimedia applications. Changes (This section will not become part of the RFC.) ffl Video frequency changed to 90 kHz. ffl Short reference labels ...
In this thesis, we describe our comprehensive design and implementation of a multicast based shared drawing tool called MediaBoard. Like its predecessor, the LBL whiteboard application, wb, its design follows the principles of application level framing and lightweight sessions. Both applications use the Scalable, Reliable Multicast protocol (SRM) to distribute data over the network. But unlike wb, which embeds the networking code in the application, MediaBoard uses a separate SRM framework library and customizes it to achieve application level semantics and thus performance gains. Based on actual deployment experiences --- MediaBoard was used in an "online classroom" at U.C. Berkeley --- we extended the design to improve its usability, provide increased awareness of remote participants, and integrate support for interactive browsing of the drawing space history. The application is also extremely flexible.
When Peer-to-Peer comes
- G Kortuem
- J Schneider
- D Preuitt
- T G C Thompson
- S Fickas
- Z Segall
G. Kortuem, J. Schneider, D. Preuitt,
T.G.C. Thompson, S. Fickas and
Z. Segall:
When Peer-to-Peer comes
A Platform for Location-Aware, Ad-Hoc Collaboration in Wireless Networks Proceedings of WPNC'04
- O Kao
- U Rerrer
O. Kao and U. Rerrer:
A Platform
for Location-Aware, Ad-Hoc Collaboration in Wireless Networks Proceedings
of WPNC'04 (1st Workshop on Positioning, Navigation and Communication),
Hanover, Germany, pp. 171–178, Shaker
Verlag (2004)