CCITT Recommendations Research Articles

Low-Power Programmable Pseudorandom Word Generator and Clock Multiplier Unit for High-Speed SerDes Applications

This paper presents the design of a low-power programmable pseudorandom word generator (PRWG) and a low-noise clock multiplier unit (CMU) for high-speed SerDes applications. The PRWG is capable of producing test patterns with sequence length of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> -1, 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> -1, 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> -1, 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">23</sup> -1, and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sup> -1 b according to CCITT recommendations, and the random word is 16-bit wide. High-speed and low-power operations of the PRWG are achieved by parallel feedback techniques. The measured jitter of the CMU is only 3.56 ps <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> , and the data jitter at the PRWG output is mainly determined by the CMU. Implemented in an 0.18-mum CMOS process, the power dissipation for the PRWG is only 10.8 mW, and the CMU consumes about 87 mW from a 1.8-V supply. This PRWG can be used as a low-cost substitute for external parallel test pattern generators.

Comparison of some CCITT and computed design parameters

Among the widely used frame synchronization algorithms in digital communication systems are the CCITT recommendations. Although these are used as standards, they become subject to modifications as developments in communication technology continue to produce new algorithms with better performance characteristics. This paper presents a set of new design parameters which show improved performance over some CCITT recommended ones.

A 10-Gb/s silicon bipolar IC for PRBS testing

A 10 Gb/s silicon bipolar IC for pseudorandom binary sequence (PRBS) testing was fabricated and tested. The IC features PRBS generation of the sequences of length 2/sup 15/-1 and 2/sup 23/-1 b up to 10 Gb/s according to CCITT recommendations. Furthermore, the IC is capable of analyzing PRB sequences of the same length and generation polynomials so that a full test of components is possible. In addition, a new PRBS test word synchronization can be provided between two chips for external multiplexing of the sequences up to 40 Gb/s. The IC can be connected to a standard PC, so evaluation of the error test data can be performed in a flexible way. The IC was fabricated with the HP25 process of Hewlett Packard company, the chip size is 32 mm/sup 2/, and it consumes 6.2 W at the nominal supply voltage of -5 V.

Improved frame synchronization performance for CCITT algorithms using bit erasures

For the CCITT recommendations on frame synchronization (as enhanced in Jones and Al-Subbagh, 1985), the performance in the presence of jamming, interference or other disturbance is improved by using bit erasure information. The acquisition time and misalignment detection times are reduced and the false exit time is increased, with only a minor reduction in the already large false entry time. >

Newnes communications technology handbook

Analog systems and concepts antennae or aerials audio signal processing bar code technology codes and coding formats computers in communications digital communication systems digital pulse code modulation electromagnetic compatibility/interference encryption and decryption error control facsimile systems filters frequency bands in use image processing information theory logic measurement of systems parameters memories microwave devices mixer signal processing modulation and demodulation networks noise optical communications, devices and systems photo detector/receivers power supplies propagation quality and reliability radar and navigation systems radio frequency receivers satellite systems semiconductor devices and technology signals spread spectrum techniques standards organizations and associated bodies telephony and associated systems television signal processing and systems transmission lines and waveguides videotex CCITT recommendations abbreviations and acronyms.

Routing names and addresses in the international MHS

Similarly to physical mail, electronic mail needs information to be supplied with a message about its destination: the envelope information. For physical mail a name and address are written on the envelope containing the message. The sender (originator) trusts the postman's ability to read the address and deliver the message to the intended recipient. For physical mail this works well, because physical mailboxes do not move around a lot, and street and city names rarely change. People do not change their personal name too often, and postmen are clever guys. Apart from the personal name part, this stability of address is not found in electronic mail. On the contrary, electronic mailboxes do move around a lot, moving from computer to computer, or from organization to organization. Even the company's name or service provider's name can change, and systems are unfortunately not as smart as postmen. The X.400 standard (the 1988 version of the CCITT recommendations have been adopted by ISO as the ISO/IEC-10021 standard) specifies how to set up an international message handling system (MHS) and how to address electronic messages. The first standards were published in 1984, and since then the X.400 network slowly came to reality. The practice of addressing electronic messages has not developed as envisaged in the standards. Over the last couple of years this has caused a heated debate in the media and standardization world, concentrating on the issue of international PRMDs and the presence of a service provider's name (ADMD name) or country name in the X.400 address. Changing the standards to take into account current user wishes is not likely to happpen, since too much money and effort has been invested in the current X.400 network. This paper takes a closer look at the discrepancies between the user interpretation of naming, addressing and routing and the X.400 definitions. It tries to find an answer to the question of whether the X.400 standard should be modified to incorporate users' wishes, or if this can be achieved in another way.

International standardization of B-ISDN

International standardization of B-ISDN is currently being studied in CCITT. CCITT has made 13 recommendations on various aspects of B-ISDN, such as service, physical layer, ATM layer, ATM adaptation layer, signaling, traffic control and OAM. This paper summarizes the CCITT recommendations on B-ISDN with emphasis on the architectural aspects of ATM standards and the recent CCITT activities. Various research issues in ATM such as provision of connectionless data services, generic flow control and traffic descriptors are also discussed.

Performance analysis of SS7 congestion controls under sustained overload

Congestion controls are a key factor in achieving the robust performance required of common channel signaling (CCS) networks in the face of partial network failures and extreme traffic loads, especially as networks become large and carry high traffic volume. The CCITT recommendations define a number of types of congestion control, and the parameters of the controls must be well set in order to ensure their efficacy under transient and sustained signalling network overload. The objective of this paper is to present a modeling approach to the determination of the network parameters that govern the performance of the SS7 congestion controls under sustained overload. Results of the investigation by simulation are presented and discussed. >

Error‐Correction Coding for High‐Speed Optical Transmission Systems Based on the Synchronous Digital Hierarchy

AbstractThe quality objectives given in the CCITT recommendations concerning fiber optics transmission over the Synchronous Digital Hierarchy (SDH) network are difficult to achieve in high‐speed systems. Equipment imperfections often result in a Bit Error Rate (BER) floor above the recommended BER value of 1CH4. In this paper we propose a simple Reed Solomon (RS) coding scheme for the Synchronous Transport Module level‐1 (STM‐1) frame which leads to a substantial BER performance improvement over uncoded systems. The RS code proposed is a shortened one‐symbol‐correcting code. Experimental results obtained with a laboratory prototype are reported which show that this code reduces the BER floor by four orders of magnitude.

Congestion controls in SS7 signaling networks

The descriptions of the various congestion-control functions for the common channel signaling system No. 7 (SS7), which are spread widely and piecemeal across the CCITT recommendations, are presented. The protocol architecture of SS7, structured according to Open Systems Interconnection (OSI) principles, is described. The message transfer part (MTP) provides the OSI Layer 1 and 2 services, plus part of the Layer 3 network service for the transmission of common channel signaling (CCS) message signal units (MSUs). The full Layer 3 service is provided by the addition of the signaling connection control part (SCCP) (designated Level 4 in the CCS functional model) in conjunction with the MTP. The SCCP provides an enhanced addressing capability over the MTP and enables connectionless services, and, if required, connection-oriented services. The user parts (UPs) make use of the MTP directly, although I5UP may make use of the SCCP for some services. Each UP defines a specific set of signal types to meet the signaling requirements of a user. >

Overview of wideband packet protocols

AbstractWideband packet networks operate at rates equal to, or higher than, 64 kb/s, but lower than the basic broadband rate of 150 Mb/s, on cables or satellite links. Wideband packet protocols are the transmission protocols for these networks. They define open interfaces that can be used for public and private ISDNs. The protocols are defined in CCITT Recommendations G.764 and G.765. This paper describes the objectives of the wideband protocols, and how the objectives were achieved.

Interoperability tests on OSI products in the framework of the OSIRIDE-Intertest initiative

Abstract Products implementing the Open Systems Interconnection (OSI) Standards and CCITT Recommendations (hence forth referred to as OSI Products) are now emerging on the market. To meet user requirements relying on products that interwork effectively, the standards community is addressing conformance testing techniques. However, due to technical and economic reasons, conformance testing alone does not yield a full guarantee of proper interworking. This paper reports on the interworking of the first five lower layers of OSI and on the X.400 (Inthe paper, the terms X.400 and Message Handling System (MHS) are used synonymously) interworking investigated in the framework of an Italian initiative named OSIRIDE-Interest (OSIRIDE stands for “OSI su Rete Italiana Dati Eterogenea” or “OSI on the Italian heterogeneous data networks”). The paper focuses, in particular, on the methodology and architecture which were designed and developed to verify the interworking (not conformance) of OSI Products (not prototypes) provided by six computer manufacturers. Interworking was examined in an environment made up of many computers (Pilot Centers) attached to the Italian X.25 public data network (ITAPAC) while hundreds of users were running on them and not in vitro, i.e., not on computers dedicated to this specific task. The results obtained from the first two phases of our investigation are highlighted.

ATM-layer OAM: principles and open issues (B-ISDN)

The principles of operation and maintenance (OAM) for broadband ISDN access, as well as some general OAM rules for an asynchronous transfer mode (ATM) network, are discussed. Standardization of the OAM functions and mechanisms for the ATM layer, which is based primarily on CCITT Recommendations, is considered. Issues regarding OAM flow at the ATM layer are examined. It is seen that although references can be made both to basic and primary rate ISDN, new solutions are necessary for the OAM of B-ISDN. Issues requiring further study are identified. >

Speech and image coding for digital communications

The paper is presenting a sketch of the main results achieved in the recent years and of the ongoing activities (mainly within the Standardization Bodies) in the areas of audio and video coding for bandwidth reduction. The evolution of the telecommunication Field and the needs which originate the different standards are also considered. The paper is organized in two main chapters: the first one is dealing with the techniques for audio and speech coding while the second presents the main achievements in terms of Recommendations and consolidate algorithms for image coding. Concerning speech and audio coding the paper presents and overview of the coding techniques and then examines the different environments of transmissions (network and mobile communication), the bandwidths required to satisfy the considered applications and the defined speech quality evaluation methods. A similar approach has been used for video coding and the evolution of the coding techniques appearing in the CCITT Recommendations is presented. The ongoing activities within CCIR, CMIT, CCITT and ISO towards new worldwide standards are also outlined providing indications on the areas which will require further developments.

CITT E.700 recommendation series-a framework for traffic engineering of ISDN

Traffic engineering of ISDN (integrated services digital network) has become a key area of CCITT recommendations since 1985. The authors report on the first recommendations formalized in a dedicated series on ISDN traffic engineering, the CCITT E.700 series of recommendations. The authors also report on the ongoing work towards an extension of the series to cover integration of mobile services into ISDN, the E.750 series. Future directions related to such emerging issues as intelligent network services and broadband-ISDN/ATM (asynchronous transfer mode) are also reviewed. >

Global connectivity

Global connectivity is the capability of reaching and being reached by anybody in the world. A usable global connectivity for computers implies a hierarchical naming structure, the hiding of carriers, switches, physical addresses and routes, a similar use of public or private and international or local connections, and ease of connection of new users. There have been two lines of development in the last years: the CCITT recommendations X.25 (PLP) and X.121, and the ISO standard IP. IP is datagram oriented and X.25 is connection oriented. The requirements, including global connectivity, can be satisfied by two different protocol stacks: ISO-IP with TP4 and X.25 and TP0. These are discussed in detail and a slight preference for X.25 and TP0 is expressed.

Error performance in evolving digital networks including ISDNs

Some recent developments on error performance design methodology and the status of international standardization activities on network performance objectives are discussed. The effects of errors in various services and common error performance parameters are outlined, and a fundamental strategy for ISDN (integrated-services digital network) performance design methodology is presented. Error performance under real operating conditions and in-service monitoring of error performance are described. The status of CCITT Recommendations G.821 and M.550 is examined, and the areas that must be addressed by future studies are identified. >

Interworking between teletex and OSI systems

The problem of interworking between systems which conform to the CCITT Recommendations for teletex service (teletex terminals), and systems which conform to the International Standards Organization standards for Open Systems Interconnection systems, is discussed. The solution proposed foresees OSI users utilizing the Virtual Terminal service. After an analysis of the problems related to this interworking, the design of a gateway is approached in terms of both architecture and mapping functions.

ISO 10021 — X.400(88): A tutorial for those familiar with X.400(84)

Abstract Joint work by ISO and CCITT has produced a revised version of the CCITT X.400(84) series of Recommendations. This is currently undergoing its DIS ballot in ISO, and is expected to become both an International Standard and a CCITT Recommendation in October/November 1988. The structure and current status of these documents is outlined. This tutorial reviews the significant changes from the 1984 CCITT X.400 series. The new modelling technique using the Abstract Service Definition Conventions will be the most obvious change, but this is intended to add precision to the definition of the services and not to change the underlying protocols. The addition of new functional components—the Message Store, and Access Units to Telematic and Physical Delivery Services—and the (ISO) private domain interconnectability are described. An extension mechanism has been introduced defining the treatment of extensions and thus enabling MTAs to treat unknown extensions in a consistent manner. This mechanism has been used for P1 extensions adding Distribution Lists; allowing use of ISO 9495/X.500 Directory Names; providing Redirection capabilities; adding Secure Messaging services; and providing for delivery to physical (i.e. paper) recipients. In P2 there is a heading extension mechanism, but the most important enhancement is the ability to define new body part types. Finally, the current differences between the ISO Standard and corresponding CCITT Recommendations are viewed.

An OSI communication system for the public administration of the state Nordrhein-Westfalen

Nordrhein-Westfalen (NRW) is a federal state of the Federal Republic of Germany with about 17 million inhabitants and with important business, trade and industry. The offices of the state administration spread over the area of NRW today use several hundreds of dp-systems covering a wide range of size, supplied by 14 different vendors. The most frequently used communication applications are: file transfer, interactive data processing, information retrieval, office automation. For 8 years these numerous dp-systems work together in a multiple vendors OSI-like communication system, called DVS. A test, service and maintenance center as well as electronic mail and a dp-based information system provide the technical means for DVS-management, compatibility and sufficient user acceptance. New DVS-functions e.g. message handling are fully based on ISO standards and CCITT recommendations. However, it is not an easy task with technical and organizational concerns to replace former national or DVS-specific prestandards by ISO-protocols. In DVS this will be done by an overlay concept taking into account a 24 hrs/day service, cost, user acceptance and no break in further DVS-development. A survey will be given on the DVS state of the art, ISO protocol activities in DVS and further developments.