The Relevant Standards Bodies

Two major bodies have been involved in standards relevant are the Internet Engineering Task Force (IETF) (www.ietf.org) and the International Telecommunications Union—Telecommunications Standardization Sector (ITU-T) (www.itu.int). ITU-T has also issued a set of data communications standards (the X-series) in collaboration with the International Organization for Standardization (ISO) (www.iso.ch). The ISO Open Systems Interconnection (OSI) suite has had much influence on the basic concepts and terminology presently used in the IETF, and many IETF protocols have the OSI genes.


Another important organization, formerly named the European Computer Manufacturers’ Association, is now known only by its acronym, ECMA (www.ecma.ch/). ECMA is an international industry association chartered for standardizing information and communication systems.


The International Telecommunications Union (ITU), a specialized agency of the United Nations, has been standardizing everything related to traditional telephone networks since the time they first appeared—ITU began in the 1860s, standardizing telegraphy. Historically, almost all telephone networks were operated by government agencies, which explains the place of ITU in the United Nations. Membership in ITU is open to all governments that belong to the UN, while private sector network providers, equipment vendors, and other international organizations may hold individual memberships, as Sector Members, in one or more of the three Sectors of ITU: ITU-T (Telecommunication Standardization), ITU-R (Radiocommunication), and ITU-D (Telecommunication Development). The governments, or Member States as they are known in ITU, belong to the three ITU Sectors as a matter of right. In general, membership involves paying a membership fee.


For the period from 1997 to 2000, ITU-T has fourteen active Study Groups, each of which leads standardization in a particular area (e.g., transmission, operations and management, switching and signaling, multimedia, network management). Each Study Group further divides its work among Working Parties. Specific, focused studies are performed within the Working Parties in what are known as Questions.


Any member may submit ideas in a contribution to the relevant Study Group, and as work progresses and a draft standard is developed, it will be published in the official reports of the Study Group meetings. When the draft is determined to be sufficiently mature, it is sent to all Member States and Sector Members for final comment and then consideration for approval at a Study Group meeting. The results of this process are international standards called ITU-T Recommendations. This term reflects on the subtlety that the documents serve as Recommendations to Member States, which could (but do not have to) adopt them. With the role of the governments in standardizing telecommunications diminishing, the industry more and more views ITU-T Recommendations as standards. Although the process of preparing the Recommendations is based on the consensus of participants reached at the meetings, the Recommendations are presently approved by the Member States present at the Study Group meeting at which final text is considered for approval. When published by ITU-T, the Recommendations are available to anyone for a fee; however, the interim drafts and working documents are available free, but only to members.


The Internet Engineering Task Force (IETF) [unlike its umbrella organization, the Internet Society (ISOC)] has no legal status and no defined membership. Nevertheless, for a nonexistent (at least legally) organization, the IETF has done a remarkable job in producing stable and widely implemented Internet standards. The IETF is divided into eight broad expertise areas: the Applications Area, Internet Area, Operations and Management Area, Routing Area, Transport Area, Security Area, User Services Area, and General Interest Area. Areas are in turn divided into working groups, which focus on specific subjects of standardization. The decisions are typically made online (by consensus—there is no voting in the IETF), and anyone with access to the Internet can participate in any working group and get hold of any IETF documents for free. The terminology involved in naming the IETF documents requires some further elucidation.


A contribution to the IETF takes the form of an Internet Draft. Anyone can submit his or her ideas in such a document, which is published by the IETF upon request without prescreening for relevance or technical accuracy. The publication of an Internet Draft implies no IETF endorsement. The Internet Drafts are working documents, which are stored by the IETF for a period of six months and then automatically removed. Some are working group documents, but many are just individual publications whose authors want the IETF to take a look at them. 


RFCs are approved and published by the RFC editor (in many cases, the RFCs are developed by respective working groups and then approved by the IETF) and stored permanently under unique numbers.


The term RFC, however, can denote a nonstandard document (such an RFC can be either informational or experimental) as well as a standards track document. Unless otherwise specified, the RFCs referred are always the standards track ones. The maturity levels (based on the maturity of a specification, existence of interoperable implementations, and deployment) are proposed standard, draft standard, and standard. The criteria for assigning these levels (as part of the comprehensive specification of the Internet standards process) are published in RFC 2026. Finally, yet another subseries of the standards RFC is called best current practice (BCP), which, according to RFC 2026, is “designed to be a way to standardize practices and the results of community deliberations.” RFC 2026, for example, is a BCP.


Although ITU-T had implicitly used (and referred to) IETF documents in the past, until recently it could not do so explicitly. Since 1996, however, cooperation between the two organizations has made progress, and as ISOC became a member of ITU-T, the official cross-group representation has been maintained on several projects. This cooperation has already resulted in reducing duplication of effort. For obvious reasons, in the area of the integrating Internet and telecommunications, this partnership is crucial to the success of future standards.


Other important standards bodies whose work is relevant to the subject include:


The European Telecommunications Standards Institute (ETSI) (www.etsi.org), which has played an important role both in developing telecommunications standards for the European Union and contributing to ITU-T. The ETSI Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON) project has become an international effort dedicated to the architecture and protocol requirements in support of IP telephony.


The Institute of Electrical and Electronics Engineers, Inc. (IEEE) (www.ieee.org). The IEEE has standardized local area network (LAN) protocols, among many other things.


The ATM Forum (www.atmforum.org) has had a major influence on the work on broadband ISDN in ITU-T and overall development of the concept and technology in support of quality of service.


The Telecommunications Industry Association (TIA) (www.tiaonline.org) and T1 (www.t1.org). TIA and T1 have been developing American National Standards for wireless communications and the PSTN, respectively. Both have addressed interworking with IP networks.

Systems : NTSC, PAL, SECAM, MPEG, and DOCSIS

There are several systems that are used for video distribution. The system (standards) used in CATV systems include: NTSC, PAL, SECAM, MPEG, and DOCSIS.

National Television Standards Committee (NTSC)
The NTSC system is an analog video system that was developed in the United States and is used in many parts of the world. The NTSC system uses analog modulation where a sync burst precedes the video information. The NTSC system uses 525 lines of resolution (42 are blanking lines) and has a pixel resolution of approximately 148k to 150k pixels.

The NTSC system uses 6 MHz wide radio channels that range from 54 MHz to 88 MHz (for VHF channels 1-6), 174 MHz to 216 MHz (for VHF channels 7-13) and 470 MHz to 806 MHz (for UHF channels 14-69). Initially, the frequency range of 806 MHz to 890 MHz was available for UHF channels 70 to 83. The FCC reallocated these channels for cellular and specialized mobile radio (SMR) use in 1983.

When used in the United States, NTSC systems have a maximum transmitter power level that varies from 100 kWatts for low VHF channels (1-6), 316 kWatts for high VHF channels (7-13) to 5 million Watts for UHF channels (14-69). Television transmission limits are also established based on the class of service (local or wide area) for the authorized television broadcast company.

Phase Alternating Line (PAL)
The PAL system was developed in the 1980’s to provide a common television standard in Europe. PAL is now used in the Middle East and parts of Asia and Africa. The PAL system uses a phase alternation process to enhance the video signal’s resistance to chromatic distortions as compared with the NTSC video signal. Although PAL and NTSC systems are similar in function, they are not compatible. A converter box is required between the two systems.

The system provides 625 lines per frame, 50 frames per second. A modified version of PAL (PAL-M) is used for the Brazilian television system. PAL-M provides 525 lines per frame and 60 frames per second. The PAL system uses 7 or 8 MHz wide radio channels.

Sequential Couleur Avec Memoire (SECAM)
Sequential Couleur Avec Memoire (SECAM) is a video transmission system that was developed by France and the former Union of Soviet Socialist Republics to improve on the NTSC video transmission system. This translates to “sequential color with memory.” SECAM is a color video transmission system that provides 625 lines per frame and 50 frames per second. This system transfers color difference information sequentially on alternate lines as a FM signal. The SECAM system requires 8 MHz of bandwidth.

Motion Picture Experts Group (MPEG) Compression
There are several digital video compression systems. The most common form of digital video compression of video signals conforms to the motion picture experts group (MPEG). There are various levels of MPEG compression; MPEG-1 and MPEG-2. MPEG-1 compresses by approximately 52 to 1. MPEG-2 compresses up to 200 to 1. MPEG-2 ordinarily provides digital video quality that is similar to VHS tapes with a data rate of approximately 3.2 Mbps. MPEG-2 compression can be used for HDTV channels, however this requires higher data rates.

Data Over Cable Service Interface Specifications (DOCSIS)
The data over cable service interface specifications (DOCSIS) is a standard used by cable systems for providing Internet data services to users. The DOCSIS standard was primarily developed by equipment manufacturers and CATV operators. It details most aspects of data over cable networks including physical layer (modulation types and data rates), medium access control (MAC), services, and security. The DOCSIS cable modem specifications are available from CableLabs® at http://www.cablemodem.com/specifications.html.

The downstream information flows to all users that are tuned to a specific RF channel on the cable system. There may be several RF channels used to serve many cable modem users in a system. Each individual cable modem decodes their portion of the data on a specific RF channel. For transmitting on the upstream side, each user is assigned time of a few milliseconds each where the user can transmit short bursts of data. Dividing the channel into small slices of data is well suited for short delays to keyboard commands.

To convert the Internet data into a format suitable for delivery on a cable channel, a CATV upconverter is used at the head-end of the cable system. The CATV upconverter handles both digital and analog television signals. Usually 10-20 upconverters are installed into a single equipment chassis. To allow cable modems to connect to data networks (such as the Internet), a cable modem termination system (CMTS) is used. The CMTS an interface device (gateway) that is located at the head-end of a cable television system to send and adapt data between cable modems and other networks.

A single 6 MHz wide television channel is capable of 30-40 Mbps data transmission capacity. This is because coaxial cable offers a communication medium that is relatively noise free (compared to radio or unshielded twist pair cable) that allows the use of complex modulation technologies (combination of amplitude and phase modulation). These modulation technologies can transfer several bits of data for each Hertz of bandwidth (bits per Hertz). In 2001, cable modems could transmit data using 64 QAM modulation technology. To increase the data rate, even more complex modulation technologies such as 256 QAM or even to 1024 QAM have been demonstrated [13].

The DOCSIS system is focused around packet service such as Internet Protocol (IP) and asynchronous transfer mode (ATM) to provide a variety of services (e.g., variable bit-rate, constant bit-rate) with the ability to offer varied levels of quality of service (QoS). This allows the DOCSIS system to offer multiple channels to a home or business that can provide for various services such as voice (constant bit-rate), data (high reliability), and video (high-speed data).