Recursos VoIP - Enlaces

Fuente: University of Hong Kong
Formato: PDF

Voice-over-IP (VoIP) is an important application on the Internet. With the emergence of WLAN technology and its various advantages compared with the traditional wired LAN, it is fast becoming the "last-mile" of choice for the overall Internet infrastructure. This paper considers the support of VoIP over 802.11b WLAN. It shows that although the raw WLAN capacity can potentially support more than 500 VoIP sessions, various overheads bring this down to only 12 VoIP sessions when using GSM 6.10 codec. A novel multiplexing scheme for VoIP is proposed which exploits multicasting over WLAN for the downlink VoIP traffic.

Fuente: Award Solutions
Formato: PDF

The Session Initiation Protocol has been selected as the main signaling protocol of the Third Generation Partnership Projects IP Multimedia Subsystem. This paper will show the architecture of the IP Multimedia Subsystem and how the Session Initiation Protocol has been used to achieve the goals of the Third Generation Partnership Projects. This paper will include a discussion of the architecture, the motivation for the evolution to this architecture and some examples of how this architecture can be used to provide advanced services.

Fuente: Award Solutions
Formato: PDF

The Session Initiation Protocol has been chosen by the 3GPP for establishing multimedia sessions in UMTS Release 5 (R5) networks. This paper discusses the operations of the UMTS R5 IP Multimedia Subsystem (IMS) in great detail. The paper discusses where SIP is used in UMTS IMS and the interaction between the various components of the IMS networks. The changes and enhancements made to the Internet telephony signaling protocols such as SIP, SDP and Megaco are discussed.

Fuente: Institute of Electrical and Electronics Engineers
Formato: PDF

This paper reviews practical video delivery technologies, examining existing mobile networks, commercialized or standardized transport, and coding technologies. Compression efficiency, power dissipation, and error control are intrinsic issues in wireless video delivery. Among these issues, error control technologies are evaluated at four layers: layer-1/2 transport; end-to-end transport layer such as TCP/IP or RTP/UDP/IP; error-resilience tool and network adaptation layer and source coder layer. Emerging mobile network quality of service will have a large variation of bandwidth and delay. Thus, adaptive rate control and error recovery are identified as more crucial issues for future research.

Fuente: 3G Americas
Formato: PDF

The CDMA Development Group (CDG) and 3G Americas participated in a series of joint workshops to identify key elements necessary to insure that Multimedia Messaging Service deployments are fully interoperable within the Americas region. This paper presents the outcome of these discussions. Through consensus, the participating operators and vendors have developed the following guidelines, covering Multimedia Message routing, MMS Relay/Server network connectivity and MM charging.

Fuente: Motorola
Formato: PDF

Multi-carrier Wideband CDMA signals are required for testing 3G wireless base stations. This paper shows how to create a source able to generate those signals, using the Agilent Technologies Advanced Design System 2001 (ADS 2001) environment. Innovative solutions are proposed to reduce the simulation time, and the source is capable of clipping. Possible applications are also discussed in the paper.

Fuente: Avaya
Formato: PDF

This paper presents experimental studies on the use of IEEE 802.11b wireless Ad Hoc networks for Multicast. The experiments show that the maximal throughput achievable in such networks is 1.76 Mbps for an 802.11 Data Rate of 2 Mbps. This paper studies the behavior of VoIP traffic in such networks in multi-hop scenarios with and without hidden stations. The maximal number of hops for VoIP multicast traffic over 802.11 is four as critical loss ratios are approached for more hops. While loss turns out to be problematic, round trip time and delay characteristics of the VoIP streams remain acceptable in all scenarios.

Fuente: Effnet Holding
Formato: PDF

In 2.5G (GPRS) or 3G (WCDMA/CDMA2000) networks, the radio link has high bit errors. The standards specifications include the use of header compression for better utilization of the radio resource. In some applications, like IMS - IP Multimedia Subsystem, it is a critical component for successful operation. The header compression module is used in RNC as per the UMTS standard or SGSN as per the GPRS standard or PDSN as per the CDMA2000 standard together with the mobile terminal as specified in all the standards.

Fuente: Nortel Networks
Formato: PDF

3G operators are exploring network infrastructure sharing solutions in order to reduce the amount of upfront investment in building networks. Sharing network infrastructure will enable faster time-to-revenue, decrease the overall capital and operational expenditures. In addition, there are environmental benefits by reducing the number of radio sites required to deliver service. The Nortel family of Base Stations (BTS) is capable of supporting 20 MHz in a single cabinet without requiring additional support equipment. This will enable two 10 MHz license holders to deploy service with minimum footprint. The advantages of this are reduced site construction and acquisition costs.

Fuente: Columbia University Department of Computer Science
Formato: PDF

Supporting mobile Internet multimedia applications requires more than just the ability to maintain connectivity across subnet changes. We describe how the Session Initiation Protocol (SIP) can help provide terminal, personal, session and service mobility to applications ranging from Internet telephony to presence and instant messaging. We also briefly discuss application-layer mobility for streaming multimedia applications initiated by RTSP. We begin by outlining the principles of operation of the Session Initiation Protocol (SIP) in Section II, followed by a discussion of four modes of mobility, terminal, session, personal and service mobility in Sections III through VI.

Fuente: Lucent Technologies
Formato: PDF

In wireless networks new services will be rolled out ever faster and must meet customers expectation in terms of promptness, capacity and quality of service. This is why the performance of such systems must be assessed in an early system design stage. A simulation methodology based on Message Sequence Charts (MSCs) to analyze alternative network architectures and protocol stacks with respect to performance is described in this paper.

Fuente: Avaya
Formato: PDF

The number of mobile workers worldwide continues to grow rapidly. In the US alone, this number is expected to reach 103 million by 2008, comprising a staggering 72% of the total employment workforce. To better understand enterprise communication needs in this changing work environment, Avaya has undertaken in-depth global research to examine the impact of mobility on communication and working practices.

Fuente: Directv Group
Formato: PDF

This white paper introduces the application of new point-to-multipoint (PMP) radio systems for backhauling traffic in 2G and, particularly, 3G mobile networks. It discusses how PMP systems by nature offer capabilities that cannot be matched by the point-to-point (PTP) radio or leased line approaches currently in use. It also discusses how, by virtue of its inherent ability to share radios, PMP can offer a much more cost-effective backhaul solution than PTP approaches. This paper's intended audience is the technical and business staffs of telecommunications service providers who are or are considering taking advantage of the AIReach 9000 system for broadband wireless access networks.

Fuente: National Technical University of Athens
Formato: PDF

The main goal towards which nearly all research activities in the field of digital wireless communications are oriented is the development of a global wireless access network, capable of offering real-time bandwidth-demanding multimedia applications and enabling for anytime/anywhere access. This paper proposes a wireless access network, which is a result of the convergence of telecommunications and digital broadcasting, two sectors in which Europe is a global pioneer.

Fuente: Unified-View
Formato: PDF

Person-to-person communications in the business world and for consumers is converging both from a technology infrastructure perspective, as well as for communication devices on the desktop and wireless, handheld devices for mobile communications. This is changing the way people initiate contact with others, interact with them, and control their communication activities. In particular, technology convergence is having the greatest impact on real-time communications, including voice, video, and real-time messaging.