International Telecommunication Union-Telecommunication Standardization Sector Research Articles

Long-haul WDM system through conventional single mode optical fiber with dispersion compensation by chirped fiber Bragg grating

By optimizing the fabrication process of the chirped optical fiber Bragg grating (FBG), we have obtained the ripple coefficient of reflectivity and time delay smaller than 0.2 dB and 12 ps, respectively. We have implemented dispersion compensation with FBG in two conventional single mode optical fiber (G.652) systems (4 × 10 Gb/s, 400 km, and 4 × 10 Gb/s, 800 km), with a power penalty less than 2 dB per-channel. Our results show that the properties of the 4 × 10 Gb/s, 800 km transmission system are better than the criterion of the international telecommunication union-telecommunication standardization sector (ITU-T). We monitored the polarization mode dispersion (PMD) of the 4 × 10 Gb/s, 800 km transmission systems for several months, our results show that the PMD compensation is not necessary for a 10 Gb/s system.

Harmonization, mobility management, and fixed-mobile convergence: Studies in the ITU-T special study group on “IMT-2000 and beyond”

The various sectors of the International Telecommunication Union (ITU) have been addressing the evolution of third-generation and future wireless systems in the context of a comprehensive International Mobile Telecommunications 2000 (IMT-2000) project, and within the ITU's Telecommunication Standardization Sector (ITU-T) a Special Study Group on “IMT-2000 and Beyond” has been established to address the network aspects of these emerging wireless systems. The Special Study Group (SSG) is playing a global role in this general area, in which a number of regional standards development organizations and a variety of industry forums are also active. This paper provides background information on the SSG and describes the SSG's ongoing work addressing medium-term issues relating to convergence of fixed and mobile systems and the harmonization of evolving IMT-2000 systems. The paper also addresses related mobility management aspects.

Telephone numbers, domain names, and ENUMbers

One of the biggest barriers to the development of public IP telephony services has been the lack of a universal addressing system. While IP-enabled devices have long been capable of originating phone and fax calls, it is difficult to call an IP device because they are hard to find. Internet Engineering Task Force (IETF) Request for Comments (RFC) 2916, E.164 Number and DNS, seeks to solve this problem in a simple and perhaps unlikely way. Simple, in that the ENUM protocol converts existing telephone numbers into domain names.The designers of ENUM hope to foster a global megadirectory of communications users who can be reached in any number of ways by means of only one number. While theoretically any character space could be standardized in an attempt to create a universal addressing scheme, ENUM explicitly adopts telephone numbers, presumably to take advantage of their global user acceptance and mature infrastructure. This choice adds a significant public policy dimension to the story. Far from being benign and boring, telephone numbers can present significant communications policy issues, and are regulated both domestically and internationally. The top level of this hierarchy is defined by International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation E.164.

The development of the wireless intelligent network (WIN) and its relation to the international intelligent network standards

This paper summarizes the current International Telecommunication Union — Telecommunication Standardization Sector (ITU-T) intelligent network (IN) standards in the context of the wireless intelligent network (WIN) and relevant parts of the ANSI-41 family of standards developed in the United States. In addition, this paper outlines the concepts on which the standardization of the IN support of wireless networks should be developed internationally. The principal observation of the paper is that, while the mobile networks based on different standards are substantially dissimilar, it is still feasible to define one standard that would allow these dissimilar mobile networks to access the IN to provide telecommunications services globally and seamlessly. WIN sets the direction for such a standard.

Application of the advanced communications technology satellite to teleradiology and real-time compressed ultrasound video telemedicine.

The authors have investigated the application of the NASA Advanced Communications Technology Satellite (ACTS) to teleradiology and telemedicine using the Jet Propulsion Laboratory (JPL)-developed ACTS Mobile Terminal (AMT) uplink. In this experiment, bidirectional 128, 256, and 384 kbps satellite links were established between the ACTS/AMT, the ACTS in geosynchronous orbit, and the downlink terrestrial terminal at JPL. A terrestrial Integrated Digital Services Network (ISDN) link was established from JPL to the University of Washington Department of Radiology to complete the bidirectional connection. Ultrasound video imagery was compressed in real-time using video codecs adhering to the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation H.261. A 16 kbps in-band audio channel was used throughout. A five-point Likert scale was used to evaluate the quality of the compressed ultrasound imagery at the three transmission bandwidths (128, 256, and 384 kbps). The central question involved determination of the bandwidth requirements to provide sufficient spatial and contrast resolution for the remote visualization of fine- and low-contrast objects. The 384 kbps bandwidth resulted in only slight tiling artifact and fuzziness owing to the quantizer step size; however, these motion artifacts were rapidly resolved in time at this bandwidth. These experiments have demonstrated that real-time compressed ultrasound video imagery can be transmitted over multiple ISDN line bandwidth links with sufficient temporal, contrast, and spatial resolution for clinical diagnosis of multiple disease and pathology states to provide subspecialty consultation and educational at a distance.

Network information models and onevision® architecture

Network information models play an essential role in network management systems. A network information model is an abstraction of network resources. When well defined, a network information model facilitates delivery of various customer services by ensuring proper interactions among users, applications, and the managed networking resources in a network management system. A standards-based network information model is the keystone that enables a network management system to operate with other network management systems in an 'open' manner. Historically, 'standard' network information models have been developed by two camps of standards organizations - the telecommunications management network (TMN) camp, and the Internet protocol (IP) camp. Standards from the TMN camp, designed for operations support systems in telecommunications carrier networks, are endorsed by organizations such as the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) and the European Telecommunications Standards Institute (ETSI). Standards from the IP camp, designed for management systems in enterprise networks, are supported by groups such as the Internet Engineering Task Force (IETF) and the Desktop Management Task Force (DMTF). In both camps, information within a network information model can be examined from the viewpoint of a network element or the network. This paper presents an overview and a comparison of different network information models from both camps and discusses the architectural role of the network information model in OneVision® Network Management solutions. It also presents a high-level description of a network information model in the OneVision enterprise solutions.

PHS roaming signaling protocol architecture toward global mobility network

The network for supporting the global personal communication is called the global mobility network (GLOMONET), where global mobility is guaranteed by coordination between intelligent networks (INs). This paper describes the implementation of a roaming signaling protocol for the personal handy-phone system (PHS) GLOMONET, clarifying the concepts of the PHS architecture regarding the GLOMONET. The PHS is a more economical personal communication system than existing cellular systems, by introducing the concept that the PHS service is provided by the most effective use of the existing ISDN and IN functions, where the majority of network functions to provide ISDN services are commonly used for functions for PHS service provision. The PHS mobility function realized by the IN guarantees flexible and effective roaming service provision for the globalization of future personal communication. The proposed PHS signaling protocol architecture is based on the intelligent network capability set 2 (IN CS2) defined by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Study Group 11 and a visitor location register (VLR) database scheme with efficient signal transfer in the GLOMONET. The PHS specific roaming signaling protocol is defined by the service-independent IN application protocol (INAP). The proposed PHS concepts and roaming signaling protocol were reflected to the national telecommunications standards in the Telecommunication Technical Committee (TTC) and standards in the PHS-memorandum of understanding (MoU).

UPC/NPC algorithm for guaranteed QoS in ATM networks

In Broadband Integrated Services Digital Networks (B-ISDN) based on the Asynchrous Transfer Mode (ATM) technology, the required Quality of Service (QoS) must be guaranteed for connection. Cell loss ratio, which is one of the QoS parameters specified by the user in an ATM traffic contract of connection, may depend on the traffic enforcement mechanism known as the Usage Parameter Control/Network Parameter Control (UPC/NPC) or traffic policing. If two UPC/NPC algorithms are not equivalent with respect to cell discarding/tagging for a given traffic configuration, a common understanding about legality between the user and the network operator does not exist. To cope with this legality problem, the concept of cell conformance has been developed by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). However, the Cell Loss Priority (CLP) bit, which ITU-T introduced in the ATM cell header to discriminate between a high priority cell (CLP = 0) and a low priority cell (CLP = 1), may cause the measurement phasing problem in cell conformance testing in ATM networks. This makes it difficult for a network provider to define and commit cell loss ratio as a QoS parameter. In this paper, we investigate measurement phasing problems and difficulties in commitment of the cell loss ratio in ATM networks. We propose a QoS guaranteed UPC/NPC algorithm to commit the cell loss ratio, and show an example of applications of the proposed UPC/NPC algorithm.