SDH Transmission Research Articles

Comparative Analysis of Transmission and Switching Technologies

This paper compares the advantages and disadvantages of OTN, SDH, WDM, ASON and other transmission and switching technologies, as well as the carrying schemes, and focuses on the analysis of the advantages of OTN-based ASON network in networking, capacity expansion, protection and other aspects.

Analysis of the Communication System SDH Transmission Network Fault and its Maintenance Technology

SDH transmission mode is a new concept of digital transmission. SDH transmission network can not only improve the efficiency of network management, and can greatly improve the utilization of network resources, reduce the management cost and maintenance cost, to ensure that the network operation and maintenance is flexible operation, reliable and efficient. Social and economic development promotes the development of railway transportation in our country, and the combined railway transportation with communication technology, making up a highly digital railway communication network. In the railway communication network, most of which the transmission technology of SDH transmission network has been adopted. SDH transmission network plays an important role in railway communication network.

Development and Simulation of Next Generation SDH Network Management System

In present scenario Network Management System of Next Generation SDH is not performing Offline reporting, offline analysis of alarms, offline performance management and Configurations of network like real time. Any offline configuration of a network when implemented on a real time environment leaves some shortcomings and wrong configuration attributes due to non-availability of Alarms and Performance Management in the presently available offline utility. A simulated platform is developed for implementation of a traffic matrix in an offline environment before implementing over a real time NG SDH Transmission network to reduce the chance of faults or any network disaster.

The Impact of LCAS Dynamic Bandwidth Adjustment on SDH/SONET Network

For the new generation MSTP device, applying LCAS is the extension of VC technology, which allowed the adjustment of link capacity hitless in transmission network without any break to incurrent service or reserved bandwidth resource. The article introduces the operation mechanism of LCAS in SDH/SONET network and point out that even though LCAS really brings us much more advantages in SDH transmission network, it also brings some drawback to us. The paper mainly analysis the time delay problem of SDH network that introduced by LCAS according to the related protocols for LCAS and practical system application. The time delay derives from the LCAS technology itself could take for the necessary cost of flexibility and control [1] ]. The most practical contribution of the adjustment delay results is in the link delay determination. This knowledge of link delays, at best only loosely estimated today, provides the critical support for rolling out next-generation applications over the transport infrastructure.

동기망과 전송망에서의 동기클럭 성능 분석을 위한 시뮬레이터 개발

The synchronized clock performance in the synchronization network and SDH transmission network design is an important element in aspect of guaranteeing network stability and data transmission. Consequently the simulator which can applicable various parameters and several input levels from the best state to the worst state for performance analysis of the synchronized clock is required in case of network design. Therefore, in this paper, 1 developed the SNCA and TNCA for analysis of the synchronized clock in the synchronization network and transmission network. And utilizing these simulators with various wander generation, node number and clock state, 1 obtained the synchronized clock characteristics and maximum network nodes In NE1, NE2 and NE3 transmission network and DOTS1, DOTS2 synchronization network.

QSN: A model to the network-service interface

Transmission networks are mainly used to connect the switches of an operator. Only a few customers as banks, service providers, etc. required some services directly from the transmission network to connect the main sites they owned. Nowadays, the number and the variety of services (leased lines) has increased and the management requirements are changing everyday. Equipments which are supporting these services have a wide spectrum of providers with proprietary management solutions. Furthermore, the SDH transmission technology is now replacing the current PDH technology but they will have to coexist for a long time, allowing a leased line to be set up through different technologies. In order to meet these considerations, Telefonica has developed an information model for the interface between the TMN network and service layers. This model was developed for the SDH management system, but thinking of extending it to other OS's at network level for interoperating with leased lines SOS. Telefonica information model was designed with two main objectives: to follow the current standards (Facto and jure) and to facilitate the extensibility to other transmission technologies,.

Additive time synchronous system in existing SDH networks

A simplified SDW (synchronous digital hierarchy)-based time synchronous system that does not need modification of existing SDH transmission equipment (STE) and clock supply equipment (CSE) is proposed. The system has auxiliary time synchronizing equipment attached to existing STE and CSE, where frequency and time are separately synchronized, and which enables us to partially time-synchronize an SDH network or to introduce a time synchronous system locally. Experimental time synchronizing devices using a data communication channel (DCC) in the section overhead (SOH) showed potentially satisfactory performance; synchronization errors of a 4-link system are of the order of sub-microseconds.

Hitless frame switching scheme for SDH networks

In current SDH transmission equipment, channel switching for channel cutoffs and hardware failures, etc., is automated. However, instantaneous signal loss can occur with such channel switching. Protecting a system from failures with a high reliability for network failures is an important task. In this paper, a new hitless frame-switching scheme that triggers switching by detecting bit errors for each frame is proposed. This scheme does not allow a loss of even one bit in downstream equipment even when a sudden failure occurs. In addition, it improves the error rate of the downstream equipment under normal operating conditions by switching to an error-free frame for each frame. It has been confirmed in a trial LSI with a path (virtual container-4: VC-4) as a frame that these capabilities are realized with precision. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (1): 24–34, 1997

Bit-interleaved Hamming code for linearly repeateredterrestrial SDH transmission systems

A bit-interleaved SEC shortened Hamming code is proposed for all SDH levels. The error caused by ASE noise in a 156 Mbit/s optical preamplifier is successfully corrected.

High-speed regenerator section terminating LSIs

The Letter reports the first four-chip set for the STM-64 regenerator-section terminator, a key component of the next generation SDH transmission system. The Si-bipolar gate-array LSIs are fabricated and tested to confirm operation at 1.244 Gbit / s. This result makes it feasible to construct the line terminators needed.

Demonstration of a high speed optical drop function using a tunable DFB laser

A high speed optical drop function was observed using the continuous and discontinuous tuning range of a two-electrode DFB laser. Transmission at 1.7 Gbit/s was examined, and the switching signal enabled two bytes to be dropped. This demonstration is suited to SDH or ATM transmission and confirms the interest in multielectrode sources for optical crossconnect applications.

An HDTV bit-rate reduction codec at the STM-1 rate of SDH

An HDTV bit-rate reduction codec was developed, aimed at the transmission of an HDTV signal for distribution use. This codec can perform the coding of an 1125 lines/60 Hz HDTV video signal accompanied with 4-channel sound signals at about 133 Mbit/s, and transmit it at the STM-1 rate of 155.52 Mbit/s in the xynchronous digital hierarchy (SDH). The sampling frequencies are selected considering the simple relation with the studio standard as well as the required bandwidth for HDTV distribution. A hybrid DPCM/DCT coding scheme is employed as a bit-rate reduction algorithm, where intrafield 8 × 8 DCT is first performed and then interframe DPCM is carried out in the DCT coefficient domain. An adaptive intrafield/interframe mode selection is performed only for low-frequency DCT coefficients and the intrafield mode is always used for high frequency coefficients because the interframe correlation of the high frequency coefficients is fairly weak. Computer simulation experiments were carried out to examine the performance of this coding scheme. The codec hardware was implemented and transmission experiments, as well as laboratory experiments, were carried out using actual SDH transmission systems. From these experiments, it was confirmed that this codec can transmit HDTV at the STM-1 rate with a picture quality satisfactory for distribution use. The technical and operational feasibilty of HDTV digital transmission through SDH transmission systems was also demonstrated.