Synchronous Digital Hierarchy Network Research Articles

Design and Implementation of Power Communication System SDH Network Simulation Tool Based on EXATA

The power communication system based on synchronous digital hierarchy(SDH) optical, transmission technology is an important component to ensure the safety and stability of power network. After, years of development, the network has been gradually mature, but it still has many problems, such as the weak, structure of the communication network, insufficient network transmission capacity, weak network access and network management. Therefore, it is necessary to do the research and take simulation for the power communication system based on SDH optical transmission technology. The paper builds up the simulation, platform of SDH network in power communication system based on the EXATA simulation tools. For SDH, device, we implemented functions including multiplexing, demultiplexing and digital cross-connection. And, the simulation analysis provides a great theoretical support for constructing equipment models and network, topology.

A novel algorithm to integrate synchronous digital hierarchy networks into Optical Transport Network using mixed line rates

In this era of high data transfer speeds and new age technologies, Optical Transport Network (OTN) along with its newly introduced Optical Transport Hierarchy (OTH) has provided a lease of life to legacy low rate networks. It has provided a common backbone for multiple data rates to coexist on same fiber along with the enhanced transmission reach. The cost effective Optical Transport Network design has always been a complex issue due to the presence of multiple variables like number of fibers on each link, available data rates on each fiber, the wavelength count, transmission reach at each data rate, etc. In this paper an Integer Linear Programming (ILP) model has been presented to solve Routing problem for Synchronous Digital Hierarchy (SDH) over OTN over DWDM design. Optical Transport Hierarchy (OTH) has been used to integrate heterogenous SDH/SONET operating at different rates (STM-16, STM-64 and STM-256) into a single network supporting mixed line rates. These rates can coexist in a same fiber but each rate carries different cost with it. The objective function aims at finding the least cost routing solution by looking at different tradeoffs between the Capital Expenditure and the operational expenditure. Certainly different variables like the number of fibers and wavelengths, transmission reach, etc. are a factor in it. A mechanism has been put to monitor the Bit Error Rate (BER) levels as well. For evaluating the ILP model, 18 Node 38 Link European Optical Network was considered as the reference model and two ordering techniques, namely, full ILP and highest rate first (HRF) were used for deriving the results. The ILP model was designed with minimum of decision variables so in spite of big reference network it converges much faster. Under the given conditions, full ILP gave least cost network whereas HRF ordering took least time for ILP to converge.

Improving the optical network rollout by means of knowledge-based techniques

This paper explores the usage of knowledge-based techniques to manage the Synchronous Digital Hierarchy network more efficiently in a multi-vendor environment, particularly enhancing the deployment and provisioning areas: shorter troubleshooting time, reduction in misalignments (which are caused by inadequate manual procedures), and mitigation of possible knowledge loss by downsizing. The proposed solution has been validated in an operational environment with a concept proof that has yielded with excellent results.

Stealth transmission of temporal phase en/decoded polarization-modulated-code-shift-keying optical-code-division multiple-access signal over synchronous digital hierarchy network with asynchronous detection

An innovative approach for security-enhanced optical stealth transmission in a synchronous digital hierarchy network is proposed and experimentally investigated. The security enhancement is achieved through a signal modulation format, so-called polarization-modulated-code-shift-keying, which is implemented with two superstructured fiber Bragg gratings-based optical-code-division multiple-access encoders and a polarization modulator. The proposed modulation format can provide a constant energy level for both bits 0’s and 1’s, which avoids secure vulnerability of single-stealth-user with on-off-keying modulation before coupling into the host channel and after the cascade of filters. Moreover, a self-made cost-effective gain-switched distributed feedback laser with relatively narrow spectrum is first employed as a stealth optical source, which greatly reduces the system cost and complexity. The stealth signal is recovered and detected asynchronously. The experimental results show high secure performance and robustness against eavesdropping, while keeping a bit error rate below forward error correction limit.

A branch-and-cut for the Non-Disjointm-Ring-Star Problem

In this article we study the realistic network topology of Synchronous Digital Hierarchy (SDH) networks. We describe how providers fulfill customer connectivity requirements. We show that SDH Network design reduces to the Non-Disjoint m-Ring-Star Problem (NDRSP). We first show that there is no two-index integer formulation for this problem. We then present a natural 3-index formulation for the NDRSP together with some classes of valid inequalities that are used as cutting planes in a Branch-and-Cut approach. We propose a polyhedral study of a polytope associated with this formulation. Finally, we present our Branch-and-Cut algorithm and give some experimental results on both random and real instances.

Software complex for finding the path routings in synchronous digital hierarchy networks

Software complex for finding the path routings in synchronous digital hierarchy networks

Achieving interoperability in synchronous digital hierarchy network management through RM-ODP

Ever since the introduction of computerized digital switching systems and related management systems, network operators have been struggling with the question of how to circumvent the issues of customized and proprietary network management solutions. This topic became of paramount importance to network equipment manufacturers and telecommunications service providers with the advent of the SDH and TMN standards in the late 1980s and early 1990s. It is in the context of this problem that the authors and their colleagues, as telecom standards experts, discovered the Reference Model for Open Distributed Processing (RM-ODP). This paper describes the approach taken by the authors and their colleagues to use RM-ODP to these issues in the ITU-T study groups, how those efforts were applied and the relevance of RM-ODP to current computing systems based on the concepts of Cloud Computing. This paper thus describes “real-world” business needs that have been addressed by and illustrate the benefits of RM-ODP.

Path Computation Algorithms for Dynamic Service Provisioning With Protection and Inverse Multiplexing in SDH/SONET Networks

Synchronous Digital Hierarchy (SDH) and Synchronous Optical Network (SONET) are time-division multiplexing technologies widely used in transport networks to provide bandwidth services. Dynamic service provisioning requires the use of online algorithms that automatically compute the path to be taken to satisfy the given service request. SDH/SONET multiplexing structure imposes restrictions on the allocation of bandwidth. Bandwidth services mostly require protection so that they are resilient to failures in the network. Two types of protection techniques—namely, dedicated protection and shared protection—are commonly used to protect bandwidth. Also, SDH/SONET provides standard protection mechanisms like linear MSP/APS, MS-SPRing/BLSR and SNCP/UPSR. In shared protection, complete path information for all the existing connections has to be maintained to maximize sharing for future service requests. This information will be typically very large. To overcome this problem, a minimum information scenario is proposed as a tradeoff between maintaining less information and maximizing sharing. In this work, heuristic algorithms are proposed for dedicated and shared protection that take into account the above-mentioned factors. These algorithms use the path computation algorithms for SDH networks proposed in a previous work of the authors, which compute paths for service requests without considering protection. The performance is evaluated for different values for the relative weight of sharing for the complete and minimum information scenarios. An extension to these algorithms for satisfying bandwidth requests that use various inverse multiplexing techniques is also proposed.

On the topology of optical transport networks

Synchronous Digital Hierarchy (SDH) is the standard technology for information transmission in broadband optical networks. Unlike systems with unplanned growth, such as those of natural origin or the Internet network, the SDH systems are strictly planned as rings, meshes, stars or tree-branches structures designed to connect different equipments. In spite of that, we have found that the SDH network operated by Telefónica in Spain shares remarkable topological properties with other real complex networks as a product of its evolution since 1992. In fact, we have found power-law scaling in the degree distribution (N·P(k) = k−γ) and small-world networks properties. The complexity found in SDH systems was reproduced by two models of complex networks, one of them considers real planning directives that take into account geographical and technological variables and the other one is based in the compatibility among SDH equipments.

Routing Concurrent Video Signals over SDH Networks

Abstract Synchronous Digital Hierarchy (SDH) is a standard for data transmission over telecommunication networks which is often used for framing and synchronization at the physical layer. SDH networks can carry large payloads, but, at the same time, accommodate lower speed signals packed into elementary transport units. The price of this flexibility consists of a potential waste of capacity, due to the complexity of simultaneously determining an efficient signal packing and routing. We address the problem of maximizing the number of communication requests of a given set which can be routed so as to fulfill capacity restrictions (on links and encoders/decoders) and additional constraints imposed by the signal packing mechanism. Despite the technological complexity, we show that a flow formulation can still be provided including signal packing. This formulation shows a nice experimental behavior when tested on the video network of one major Italian broadcasting company.

On the robustness of Spanish telecommunication networks

Complex networks are considered robust against random failures but sensitive to failures in target. Under this perspective we analyze the robustness of the Spanish telecommunication networks for digital transmission, the Synchronous Digital Hierarchy (SDH), considering failures in the equipments that control the flow of information. Our results suggest that the robustness depends not only on the connectivity of equipments removed but also on the capacity and types of links associated with that removal. We have also observed that the robustness of SDH networks depends on the particular initial design and evolution of each Spanish province.

TOPOLOGICAL ANALYSIS OF COMPLEX OPTICAL TRANSPORT NETWORKS

SDH (Synchronous Digital Hierarchy) is the standard technology for information transmission in broadband optical networks. Unlike the Internet, SDH networks are strictly planned — rings, meshes, stars or tree-branches topologies are designed to connect their basic elements. In this work we show that the SDH network operated by Telefónica in Spain presents a power-law scaling in the degree distribution (P(k) ~ k-γ) both at the national and provincial levels. The empirically obtained scaling exponents γ are consistent with those observed in other heterogeneous complex networks. The Spanish SDH network also displays small world properties with a high clustering and short path length similar to the Internet routers network. The province subnetworks experience similar traits with regards to such properties. Considering factors such as network design policies, user demand, geographical location and types of equipment, we propose an ad hoc computational model in order to reproduce these topological properties.

Modeling of Multilayer Networks for Fault Restoration Analysis

As new network technologies appear, the number of different types of networks present around us is even more increasing. Many of them are in a client server relationship. The need for an integrated analysis of their operation is therefore becoming necessary since they are interdependent, not only for achieving a certain level of service to the user but also to have efficient use of resources. The beginning of this analysis is to create a model of the multilayer network. In this paper we outline a methodology we applied to create a model of a multilayer ATM (Asynchronous Transfer Mode) on SDH (Synchronous Digital Hierarchy) network architecture which we used to study a new scheme of integrated fault restoration. Together we describe the most important issues behind creating a model from design and also new issues related to restoration that are born in a multilayer approach.

MODELING THE TOPOLOGY OF SDH NETWORKS

SDH (Synchronous Digital Hierarchy) is the standard technology for the information transmission in broadband optical networks. Unlike the Internet, SDH networks are strictly planned; rings, meshes, stars, or tree-branches topologies are designed to connect their basic elements. In spite of that, we have found that the SDH network operated by Telefónica in Spain shares remarkable topological properties with other real complex networks empirically analyzed, such as the worldwide web network. In particular, we have found power-law scaling in the degree distribution (P(k) ~ k-γ) and properties of small world networks. Considering real planning directives that take into account geographical and technological variables, we propose an ad hoc computational model that reproduces the aforementioned topological traits observed in the Spanish SDH network.

Agent-based throughput response in presence of node and/or link failure (on demand) for circuit switched telecommunication networks

An attractive feature of an agent-based control system is being studied in this paper, with respect to network throughput for a certain amount of traffic and applied to a synchronous digital hierarchy network. Algorithmically complex problems like routing a call in a network, need to be faced with a dynamically adaptive approach such as agent-based probabilistic routing. The performance of a decentralized-based routing scheme that is subject to link and/or node failures is examined while agents are moving across the network and define a cost effective path from a source to a destination. Agent-based routing scheme is proved to increase the service rate and throughput response of the system with significant reduction in call failures. Through various newly introduced metrics and simulation of the proposed scenario, we have shown that agent-based routing offer us a decentralized control in the network and an efficient way to increase overall performance.

Designing radio-mobile access networks based on synchronous digital hierarchy rings

In this paper, we address the SDH network design problem (SDHNDP) which arises while designing the fixed part of global system for mobile communications access networks using synchronous digital hierarchy (SDH) rings. An SDH ring is a simple cycle that physically links a subset of antennae to a single concentrator. Inside a ring, a concentrator handles the total traffic induced by antennae. Technological considerations limit the number of antennae and the total length of a ring. The SDHNDP is a new problem. It belongs to a class of location-routing problems that introduce location into the multi-depot vehicle routing problem. In this paper, we precisely describe the SDHNDP and propose a mixed integer programming-based model for it. Furthermore, we devise a heuristic algorithm that computes a feasible solution. We report the results of our computational experiments using the CPLEX software, on instances comprising up to 70 antennae or six concentrator sites. An analysis provides insight into the behavior of the lower bound obtained by the LP relaxation of the model, in response to the network density. This lower bound can be improved by adding some valid inequalities. We show that an interesting cut can be obtained by approximating the minimum number of rings in any feasible solution. This can be achieved by solving a “minimum capacitated partition problem”. Finally, we compare the lower bound to the heuristic solution value for a set of instances.

SDHTOOL: Planning Survivable and Cost-Effective SDH Networks at Chunghwa Telecom

SDHTOOL, a decision-support system developed by Chunghwa Telecom Co., Ltd. (CHT), applies heuristics to plan synchronous digital hierarchy (SDH) network architecture and evolution. Planning SDH networks is complex and must be done quickly because of keen competition and rapid changes in telecommunications. A flexible, easy-to-use, state-of-the-art planning tool is needed. SDHTOOL simplifies the planning process, selecting the most appropriate network architecture in terms of cost and survivability. It helps planners to achieve global optimization, ensuring that networks meet service and protection objectives economically and maintain compatibility between new and old equipment during the transition. Compared to conventional labor-intensive planning, SDHTOOL reduces planning time and cuts costs 15 to 33 percent.

SDHTOOL: Planning Survivable and Cost-Effective SDH Networks at Chunghwa Telecom

SDHTOOL, a decision-support system developed by Chunghwa Telecom Co., Ltd. (CHT), applies heuristics to plan synchronous digital hierarchy (SDH) network architecture and evolution. Planning SDH networks is complex and must be done quickly because of keen competition and rapid changes in telecommunications. A flexible, easy-to-use, state-of-the-art planning tool is needed. SDHTOOL simplifies the planning process, selecting the most appropriate network architecture in terms of cost and survivability. It helps planners to achieve global optimization, ensuring that networks meet service and protection objectives economically and maintain compatibility between new and old equipment during the transition. Compared to conventional labor-intensive planning, SDHTOOL reduces planning time and cuts costs 15 to 33 percent.

The impact of mapping wander on the performance of SDH AU-4 and TU-3 uniform pointer processors

Pointer processors in Synchronous Optical Networks (SONET)/Synchronous Digital Hierarchy (SDH) networks may be placed into three categories: fixed threshold, adaptive threshold modulation and uniform. Fixed threshold pointer processors produce gapped pointer sequences during SONET/SDH holdover mode, when one or more node's clock has lost its synchronization reference, as a result of the periodic effects of the SONET/SDH frame overhead bytes. These gapped pointer sequences cause mapping wander in the underlying Plesiochronous Digital Hierarchy (PDH) payloads. Uniform pointer processors can smooth the gapped pointer effects caused by the Synchronous Transport Module (STM), Administrative Unit (AU) and Tributary Unit (TU) overhead bytes. However, uniform pointer processors cannot remove the additional gapped pointer effects caused by the Virtual Container (VC) overhead bytes. Mathematical analysis and simulation results, for fixed threshold pointer processors in SDH networks where VC-3 uses TU-3 to transport an E3-rate PDH payload or VC-4 uses AU-4 to transport an E4-rate PDH payload, illustrate the wander caused by the gapped pointer effects. A proposed uniform pointer processor algorithm shows the residual mapping wander caused by the VC-3 and VC-4 overhead bytes. Finally, a lower bound on the Maximum Time Interval Error (MTIE) that can be achieved with a uniform pointer processor is calculated for these two cases.

The role of data networking in the management of BT‘s SDH network

This paper outlines the history behind the current realisation of the management data communications network for synchronous digital hierarchy (SDH), explaining the various international standards inputs, supplier implementations and illustrating the architecture employed. Message addressing methods are discussed together with the protocols over which they are used. The dimensioning of this network is a key issue of ongoing discussion and impacts the provisioning rates and response times for SDH.