ITU-T Specification Research Articles

Design, implementation and evaluation of a Fiber To The Home (FTTH) access network based on a Giga Passive Optical Network GPON

Requirements such as high bandwidth and capacity for high speed internet, High Definition Television “HDTV” and Voice Over Internet Protocol “VOIP”, lead to the proposals for Fibre To Home FTTH Access Network. FTTH based on Giga Passive Optical Network (GPON) technology is one techniques that can provide triple play services at a reasonable cost. It uses only passive equipment except at the central office and the customer premises. Most telecom operators now use FTTH networks based on GPON due to its flexibility in handling extended technologies and services in the future. For a GPON technology, a maximum of 128 uses can be included in a network with maximum reach of 60 ​km and maximum distance between consecutive optical network terminals of 20 ​km as per G.984.6 ITU-T specification. GPON uses 2.44 Gbps downstream and 1.24Gbps upstream data transmission.

NG-SDH망에서 측정된 클럭잡음을 이용한 다양한 클럭상태에 따른 동기클럭 성능분석

NG-SDH망에서 측정된 클럭잡음을 이용한 동기클럭 성능분석 연구가 필요하다. 따라서 본 논문은 NG-SDH망에서 측정된 클럭잡음을 이용하여 다양한 클럭상태에 따른 동기클럭 성능을 분석하고 최대 망노드수를 도출하기 위한 연구를 수행하였다. 또한 측정된 클럭잡음을 이용하여 적합한 클럭잡음모델을 생성하였고, 다양한 클럭상태에 따른 시뮬레이션을 수행하였다. 시뮬레이션 결과를 통해 볼 때 정상상태에서 최대노드수는 80개 노드 이상 이였고, 단기위상변위(SPT)상태에서는 37개 이하였고, 장기위상변위(LPT)상태에서는 50개 이상으로 나타났다. 따라서 3가지 클럭상태에서 ITU-T 규격을 만족할 수 있는 최대 노드수는 37개 이하 임을 알았다. 또한 DOTS 이전의 NE망에서 SPT이나 LPT상태가 발생하면 정상상태의 안정된 다른 동기원 소스로 절체해야 함을 알았다. A study about performance analysis of synchronization clock using measured clock noises is required. Therefore this paper executed the study for performance analysis of synchronization clock and acquirement of maximum number of network node with various clock states using measured clock noises in NG-SDH networks. Also this paper generated a suitable clock model using measured clock noises, and carried out simulations with various clock states. Through the simulation results, maximum numbers were 80 or more network nodes in normal state, and were below 37 nodes in short-term phase transient(SPT) state, and were 50 or more in long-term phase transient(LPT) state. Accordingly this study showed that maximum numbers to meet ITU-T specification were below 37 network nodes in three clock states. Also this study showed that when SPT or LPT states occur from NE network before DOTS system, synchronization source must change with other stable synchronization source of normal state.

PLL design technique by a loop-trajectory analysis taking decision-circuit phase margin into account for over-10-Gb/s clock and data recovery circuits

A design technique for an over-10-Gb/s clock and data recovery (CDR) IC provides good jitter tolerance and low jitter. To design the CDR using a PLL that includes a decision circuit with a certain phase margin affecting the pull-in performance, we derived a simple expression for the pull-in range of the PLL, which we call the limited pull-in range, and used it for the pull-in performance evaluation. The method allows us to quickly and easily compare the pull-in performance of a conventional PLL with a full-rate clock and a PLL with a half-rate clock, and we verified that the half-rate PLL is advantageous because of its wider frequency range. For verification of the method, we fabricated a half-rate CDR with a 1:16 DEMUX IC using commercially available Si bipolar technology with f/sub T/=43 GHz. The half-rate clock technique with a linear phase detector, which is adopted to avoid using the binary phase detector often used for half-rate CDR ICs, achieves good jitter characteristics. The CDR IC operates reliably up to over 15 Gb/s and achieves jitter tolerance with wide margins that surpasses the ITU-T specifications. Furthermore, the measured jitter generation is less than 0.4 ps rms, which is much lower than the ITU-T specification. In addition, the CDR IC can extract a precise clock signal under harsh conditions, such as when the bit error rate of input data is around 2/spl times/10/sup -2/ due to a low-power optical input of -24 dBm.

Efficient transport of packets with QoS in an FSAN-aligned GPON

The standardization of passive optical networks capable of transporting Ethernet frames at gigabit-per-second speeds, currently in progress in both ITU-T and IEEE, constitutes a major milestone toward cost-effective photonization of the last (aka first) mile. The article presents an Ethernet gigabit PON (GPON) system aligned with the philosophy of the evolving FSAN (full service access network) ITU-T specification, which focuses on the efficient support of any level of quality of service. The intelligence of this system, in terms of traffic quality guarantees, lies in the MAC protocol, which controls the distributed multiplexing/concentration function by allocating variable length slots to every user of the shared upstream (toward the network) medium. The way transport of information is organized in an ITU-T GPON system and the operation of a MAC protocol that preserves all QoS guarantees are presented and evaluated.

Analysis on jitter tolerance of optical 3R regenerator

The dynamic jitter tolerance of the 40-Gb/s optical 3R regenerator was analyzed for a wide range frequency up to 80 MHz according to the ITU-T specification, for the first time. The tolerance was investigated using the cross absorption modulation (XAM) effect of electroabsorption modulators. The tradeoff relation between the jitter suppression effect and the jitter tolerance was experimentally confirmed.

Voice over IP

The authors begin by discussing the components of voice over IP (VoIP). They go on to consider SS7, H.323, SIP (session initiation protocol), voice coders, ITU-T specifications, RTP (real time transport protocol), gateway control, wireless networks, quality of service, packet loss, jitter, latency and bit rate.

A signalling server prototype for the support of multipoint to multipoint multimedia services

In the context of the ACTS project MULTICUBE, a prototype of Signalling Server was implemented, in order to support CSCW applications for automotive and aerospace users. As the standardised signalling capabilities do not support Multipoint to Multipoint configurations for advanced services, a set of protocols was chosen as a basis for the development of a new general purpose protocol, compliant with ITU-T specifications, supporting every advanced service including videophones, teleworking, and applications such a social care. It will cover corporate, public, and customer premises networks; from basic technology development through the pilot implementation of advanced services.

Applications of ATM in global networks

This article describes the market drivers, objectives, and consequences of introducing ATM into public and private networks. To serve the diverse needs of environments and applications, ATM presents a broad choice of characteristics to users and providers. To harness this diversity and bring structure to the choices, this article discusses ATM transfer capabilities (ATCs) and quality of service (QoS) classes as specified in ITU-T Study Group 13. Industry aims to achieve consistency between the ITU-T and ATM Forum specifications. This article includes consideration of AALs and interworking in developing network strategies. Providers will offer a selection of the possible services defined for ATM. Also, each provider will communicate their strategy for preferred network utilization and efficient traffic through incentives to users.

Resource allocation for worst case traffic in ATM networks

This paper addresses the problem of resource allocation for ATM connections carrying either CBR or VBR applications, for the first generation of ATM equipments. Evaluating the resources needed for the transfer phase of an ATM connection is a first step in the design of a CAC taking into account both call and transfer level QoS. The required amount of resources is estimated on the basis of traffic characteristics negotiated at call set-up, under the assumption that the offered traffic is a purely periodic pattern of active and inactive periods; this assumption is currently considered to yield upper bounds for the amount of resources which must be allocated to a connection. The traffic characteristics, and the corresponding periodic patterns of traffic are obtained using the ITU-T specification of ATM traffic control. We identify three frameworks (allocation on the basis of PCR, burst loss and burst delay framework in case of statistical multiplexing) and principles on which resource allocation can be based in each of these frameworks are highlighted.

Managing telecommunications networks using TMN interface standards

The article presents the scope of TMN standards, identifies the role and importance of interface standards, and describes the key elements of a TMN interface. TMN activities within the ITU-T, from an organizational perspective, are summarized and a more detailed description of the ITU-T specifications, organized primarily by interface element categories is given. The author examines the availability of TMN standards in support of synchronous digital hierarchy (SDH) management. (In North America, SDH is known as the synchronous optical network, or SONET.) The role of regional and national standards bodies in TMN is covered. Efforts to speed the availability of TMN implementations are briefly noted and the author describes major TMN challenges and new directions driving its evolution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>