Academic literature on the topic 'Synchronous digital hierarchy (SDH)'

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.

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.

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.

Pembangunan jaringan telekomunikasi antara Pulau Bangka – Pulau Belitung menggunakan radio microwave dengan teknologi SDH (Synchronous Digital Hierarchy) yang dapat memenuhi kapasitas yang besar dan kehandalan yang cukup tinggi. Pemilihan komunikasi dengan radio microwave pada link ini disebabkan banyaknya kendala pada proses implementasinya, dimana link ini melewati lautan, oleh sebab itu tidak memungkinkan membangun komunikasi kabel laut dalam waktu relatif singkat. Maka sistem komuikasi radio microwave memberikan suatu solusi. Sistem ini merambat dalam garis pandang (line of sight) atau ruang bebas sehingga tidak diperlukan syarat utama yang harus dipenuhi dalam membangun komunikasi radio microwave. Sebelum membangun sistem komunikasi radio microwave maka dibutuhkan perencanaan agar sistem ini memenuhi kebutuhan suatu sistem komunikasi. Perencanaan dilakukan terdiri atas beberapa tahap seperti penentuan lokasi, penentuan rute radio link, konfigurasi radio link dan path analisys. Tahap-tahap tersebut dilaksanakan agar mendapatkan hasil yang maksimal pada suatu perencanaan. Hasil perencanaan dapat digunakan sebagai referensi penentuan penggunaan perangkat yang sesuai dengan spesifikasi dalam pembangunan komunikasi radio microwave dengan rute Pulau Bangka – Pulau Belitung agar mendapatkan hasil yang sesuai dengan standarisasi internasional. Dalam hal ini standar yang digunakan mengacu pada ITU-R.

Smart gird, integrated power network with communication network, has brought an innovation of traditional power for future green energy. Optical fiber technology and synchronous digital hierarchy (SDH) technology is widely used in smart grid communication transmission network. It is a challenge to reduce impact of the availability of smart grid communication services caused by random failures and random time to repair. Firstly, we create a service channel violation risk degree (SCVRD) model to precisely track the violation risk change of communication service channel. It is denoted by the probability of service channel cumulative failure duration exceeding the prescribed duration. Secondly, a service channel violation risk degree routing mechanism is proposed to improve the availability of communication service. At last, the simulation is implemented with MATLAB and network data in one province are used as data instance. The simulation results show that the average service channel failure rate of availability-aware routing based on statistics (AAR-OS) algorithm and risk-aware provisioning algorithm are reduced by 15% and 6%, respectively.

Pembangunan jaringan telekomunikasi antara Sulawesi Utara (Manado) dan Maluku Utara (Sofifi) menggunakan radio microwave dengan teknologi SDH (Synchronous Digital Hierarcy) yang dapat memenuhi kapasitas yang besar dan kehandalan yang cukup tinggi. Pemilihan komunikasi dengan radio microwave pada link ini disebabkan banyaknya kendala pada proses implementasinya, dimana link ini melewati lautan. Oleh sebab itu tidak memungkinkan membangun komunikasi kabel bawah laut (Sub Marine) dalam waktu relatif singkat maka sistem komunikasi radio microwave memberikan suatu solusi. Hasil perencanaan dapat digunakan referensi penentuan penggunaan perangkat yang sesuai dengan spesifikasi dalam pembangunan komunikasi radio microwave dengan rute Sulawesi Utara (Manado) – Maluku Utara (Sofifi) agar mendapatkan hasil yang sesuai dengan standarisasi internsional. Dalam hal standar yang digunakan mengacu pada ITU-R.

Microwave line-of-sight radio relay (RR) systems are a constitutive part of a telecom operator transport network, as an alternative to optical transmission systems when the latter are not technically possible or rational to implement. Nowadays, RR links are quite often used in the access network for connecting mobile radio base stations, thus also enabling traffic aggregation, and so on. In this paper, we focus on a practical, real-life, five-section heterogeneous RR network, comprising classic synchronous digital hierarchy (SDH) and SDH new generation network (NGN) architecture, hybrid parallel and mutually independent transmission of native Ethernet and TDM services, and all-IP network parts. Specifically, the main task of this work is to answer whether such a diverse RR system could satisfy the quality norms for Ethernet-based services, meaning whether a tolerable RR unavailability will necessarily imply the according Ethernet quality of service (QoS) degradation. This question is addressed by the comprehensive in-service and out-of-service testing of an operational hybrid RR transmission system. After extensive practical testing and appropriate analysis of the achieved results, it came out that the impact of RR-level impairments that determine the performance prediction affected the Ethernet QoS to the extent that BER values increased to the acceptability threshold values. We believe that the preliminary results reported here could serve as a hint and a framework for a more comprehensive cross-layer test strategy in terms of both test diversity and repeating rate, which contemporary network operators need to implement in order to enable the appropriate quality of experience for users of their services.

Pembangunan jaringan telekomunikasi antara pulau Maluku – Papua<br />menggunakan radio microwave dengan teknologi SDH (Synchronous Digital Hierarchy)<br />yang dapat memenuhi kapasitas yang besar dan kehandalan yang cukup tinggi. Pemilihan<br />komunikasi dengan radio microwave pada link ini disebabkan banyaknya kendala pada<br />proses implementasinya, dimana link ini melewati lautan, oleh sebab itu tidak<br />memungkinkan membangun komunikasi kabel laut dalam waktu relatif singkat. Maka<br />sistem komuikasi radio microwave memberikan suatu solusi. Sistem ini merambat dalam<br />garis pandang (line of sight) atau ruang bebas sehingga tidak diperlukan syarat utama yang<br />harus dipenuhi dalam membangun komunikasi radio microwave. Sebelum membangun<br />sistem komunikasi radio microwave maka dibutuhkan perencanaan agar sistem ini<br />memenuhi kebutuhan suatu sistem komunikasi. Perencanaan dilakukan terdiri atas beberapa<br />tahap seperti penentuan lokasi, penentuan rute radio link, konfigurasi radio link dan path<br />analisys. Tahap-tahap tersebut dilaksanakan agar mendapatkan hasil yang maksimal pada<br />suatu perencanaan. Hasil perencanaan dapat digunakan sebagai referensi penentuan<br />penggunaan perangkat yang sesuai dengan spesifikasi dalam pembangunan komunikasi<br />radio microwave dengan rute pulau Maluku – Papua agar mendapatkan hasil yang sesuai<br />dengan standarisasi internasional. Dalam hal ini standar yang digunakan mengacu pada<br />ITU-R

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.
A Synchronous Digital Hierarchy (SDH) point-to-point bi-directional link was implemented at a base Synchronous Transfer Mode level 1 (STM 1) signal rate. The full STM-1 multiplexer was implemented and the functional code developed to Virtual Container level 4 (VC4) level. The implementation was realized using a Software Defined Radio (SDR) architecture that managed and linked the SDH atomic units into a STM-1 SDH multiplexing structure. These atomic units have been well defined in recommendation G.707 [1]. The functional description of each unit was based on the G.783 [8] recommendation which specifies a library of basic building blocks and set of rules by which these atomic functions should be combined into various functional layers. These layers interconnect to ultimately form a bi-directional path in the SDH network. A SDH Management Sub network (SMS) was implemented using a graphical user interface to perform a monitoring function for the bi-directional link.

Approved for public release; distribution is unlimited
A study of SONET network management applications and the load they impart to the network is conducted to provide a better understanding of the capability of various management approaches. In this study, a SONET network is set up in the Advanced Networking Laboratory of the Naval Postgraduate School using four Cisco ONS 15454s. Next, two Element Management Systems, the Cisco Transport Controller and the Cisco Transport Manager, are deployed onto the SONET network. Subsequently, the network traffic of the Element Management Systems is captured and analyzed using a packet analyzer. Link utilization of the two tools is computed using the first-order statistics of the captured traffic distributions. In addition, the Hurst parameter is estimated using the variance-index plot technique (which uses higher-orders statistics of the modeled distributions) to determine the captured traffic's degree of self-similarity. Finally, the calculated utilization is extrapolated to obtain the link utilization for 2500 network elements (the maximum number supported by the Cisco Transport Manager). The result obtained is useful in determining the maximum number of network elements (Cisco ONS 15454s) that the Cisco Transport Manager can support from a network loading point of view.
Civilian, Ministry of Defense, Singapore

La arquitectura de las redes de transporte actuales está basada en la tecnología de transporte SDH (Synchronous Digital Hierarchy). Las redes SDH se han diseñado y están optimizadas básicamente para el transporte del tráfico de voz. Actualmente, se está experimentando un crecimiento exponencial del volumen de tráfico de datos. Este crecimiento se debe a que el protocolo IP se está consolidando como capa de integración para servicios múltiples, algunos de ellos con requerimientos de Calidad de Servicio (QoS) y también a la introducción de tecnología de acceso de alta velocidad. Las características estadísticas del tráfico de datos son diferentes respecto a las del tráfico telefónico. De hecho, el tráfico IP se caracteriza no solo por su asimetría sino por su naturaleza dinámica, ya que presenta fluctuaciones o picos difíciles de predecir a priori.
Como consecuencia, ha surgido la necesidad de emigrar desde las actuales redes hacia una estructura más flexible y dinámica, optimizada para el transporte de tráfico de datos.
La evolución de las actuales redes de transporte incluye trasladar todas las funcionalidades de SDH (conmutación, monitorización de la calidad de la señal, protección frente a fallos) a nivel óptico. El resultado consistirá en una red de transporte óptica (Optical Transport Network, OTN) basada en tecnología DWDM, con Optical Cross Connects (OXC) para encaminar canales ópticos de forma permanente o conmutada (Automatic Switched Optical Network, ASON).
Uno de los principales problemas a solucionar por las operadoras de red es la eficiente gestión de la capacidad disponible, y así evitar por un lado la necesidad de sobredimensionar la red de transporte y por el otro optimizar la utilización de los recursos mediante la definición de estrategias de ingeniería de tráfico.
La introducción de las redes de transporte a conmutación automática (ASON), capaces de proporcionar conexiones ópticas bajo demanda, es considerada como la solución de red que puede proporcionar el rápido y flexible aprovisionamiento de ancho de banda. Tal funcionalidad, posible gracias a la definición de un plano de control basado en el paradigma GMPLS, puede ser usada para gestionar de manera dinámica los recursos disponibles, tanto a nivel SDH como a nivel óptico, respondiendo de forma eficiente a las fluctuaciones del tráfico generado por la red cliente.
Sin embargo, el problema que surge es el diseño de un mecanismo para disparar automáticamente las peticiones de establecimiento de circuitos SDH/canales ópticos conmutados.
En este sentido, la primera contribución de esta Tesis es el diseño de un mecanismo de disparo de peticiones de circuitos SDH/canales ópticos basado en la monitorización y predicción del tráfico de la red cliente (IP). Además, el mecanismo diseñado incluye la definición de políticas de ingeniería de tráfico para la optimización de la utilización del elevado ancho de banda proporcionado por las conexiones ópticas. Concretamente, el mecanismo diseñado se caracteriza por la interoperabilidad entre la capa cliente y la capa de transporte.
La Tesis incluye también una contribución sobre el diseño de una metodología para el dimensionado de la redes ASON, basada en la caracterización del tráfico de llegadas de peticiones de establecimiento de conexiones, mediante su valor medio y el factor de peakedness.

Por otro lado, la optimización de los recursos disponibles es muy crítica cuando se produce un fallo en la infraestructura de red debido a la necesidad de encontrar rutas alternativas para el tráfico afectado. Debido al gran volumen de tráfico a transportar, un fallo en la infraestructura de red puede tener graves consecuencias económicas. Por ejemplo, un corte de una única fibra óptica produce el fallo de todas las longitudes de onda que transporta; de esta manera la pérdida de cada longitud de onda operante a 2.5 Gbps o 10 Gbps puede resultar en el corte de un enorme número de conexiones en curso. Por lo tanto, a mayor capacidad, mayor es la importancia de la rapidez y rendimiento de los mecanismos de protección y recuperación.
Las estrategias de protección frente a fallos deben ser simples, minimizar las pérdidas de tráfico y deben utilizar eficientemente los recursos disponibles.
La recién estandardizada tecnología para redes de entornos metropolitanos, Resilient Packet Ring (RPR) se caracteriza por mecanismos de protección optimizados para minimizar el tiempo de recuperación en caso de fallos. Además, tales mecanismos no requieren la asignación a priori de recursos de red a utilizar solamente en caso de fallos.
Por lo que respecta a los mecanismos de recuperación, se puede optar por una estrategia de recuperación en una sola capa (single layer recovery) o alternativamente por una estrategia de recuperación en múltiples capas (multi-layer recovery), donde en la recuperación intervienen diferentes capas de la estructura de red. El esquema de recuperación multi-capas más fácil de implementar es el consistente en ejecutar los mecanismos de protección/recuperación de los distintos niveles de manera paralela e independiente. Esta estrategia no es, sin embargo, la más eficiente. La interoperabilidad entre los mecanismos de protección de las diferentes capas permite reaccionar más rápidamente a los fallos que se pueden producir.
La segunda contribución de esta Tesis es el diseño de una política de coordinación entre los mecanismos de protección proporcionados por RPR y los mecanismos de protección definidos por la capa óptica. Concretamente, la estrategia diseñada se basa en la interoperabilidad entre la capa RPR y la capa de transporte (OTN) para redes de entornos metropolitanos. La estrategia diseñada permite, además, la optimización de los recursos de red.
The main objective of the traffic engineering (TE) strategies is the efficient mapping of the actual traffic onto the available network resources.

Legacy Time Division Multiplexing-based networking architecture was basically designed to transport symmetric voice traffic. However, the volume of data traffic is increasing at explosive rate and already dominates the voice traffic. This is due to a progressive migration of many applications and services over the Internet Protocol (IP) and also to a deeper and deeper introduction of high-speed access technologies. Also there is the convergence towards the IP of real-time applications (i.e. multimedia applications) which have very strict QoS requirements.
The statistical characteristics of the data traffic are rather different from those of telephone traffic. Specifically, IP traffic is highly dynamic showing predictable and unpredictable traffic surges/peaks. Such surges are caused by unexpected events such as user' behaviours, weather conditions, accidents, fault, etc. This can cause significant fluctuations of the aggregated data traffic to be carried by the transport networks.
The current SONET/SDH transport networks (but also the incoming Optical Transport Networks) tend to be static, which means that connections (SONET/SDH circuits and light paths) are provided manually through the Network Management System. The manual configuration is time consuming, which means that weeks or even months are needed to provide high bandwidth connections.
The highly dynamic IP traffic pattern does not match with the static provisioning of capacity of the optical transport networks, leading to non-optimal utilization of the resources (i.e. network congestion or under-utilization of resources).
Thus, the problem that arises for Network Operators is how to efficiently manage the network resources in the transport network to efficiently respond to the changes in the traffic demands reaching, in such a way, traffic engineering objectives.
The introduction of the Automatic Switched Optical Networks (ASON), which is able to provide dynamically switched connections on demand, is recognized as the enabling solution to meet the requirement of fast and flexible end-to-end bandwidth provisioning. The automatic set up and tear down of optical connections can be used for the dynamic management of the transport network resources to track significant variations in the volume of the network client traffic. In such a context, a mechanism that triggers demands to set up/tear down light paths as a function of the variation of the client traffic to be transported is required.
The design of a multi-layer traffic engineering (MTE) strategy for IP/MPLS over ASON/GMPLS networks to face with the dynamic traffic demands is the first contribution of this Ph.D. Thesis. It has to be underlined that the policies for the set up of the light paths are out of the scope of this work. In fact, it is assumed that the set up/tear down of the switched connections is in charge of the ASON control plane, namely the GMPLS-based routing and signalling protocols.

As a second contribution, it is presented a practical approach for ASON networks dimensioning purposes based on the approximate characterization of the traffic arrival process, through its mean and the peakedness factor.

On the other hand, the optimization of the utilization of network resources is very critical when failures occur in the network as a consequence of the need of rerouting the affected traffic. The increase of the capacity and number of wavelengths that can be multiplexed onto the same fibre, each one carrying 2.5 or 10 Gbps client signals, implies that outages of the network infrastructure can have serious economical and social consequences.
Network recovery/resilience, i.e., the capability of the networks to efficiently recover from failures, has become of vital importance. Thus, optical transport networks need to be very robust to face failures. The protection mechanisms should be designed basically with the aim to be simple, to minimize the traffic losses and to optimize the utilization of the network resources.
Survivability strategies in current transport networks are based on the pre-allocation of network resources to be used only to switch (route) the affected traffic in case of failures.
In legacy multi-layer networks, each layer (e.g. IP, SDH) has its own protection mechanism built in, independent from the other layers. Network recovery basically relies on the SONET/SDH network layer. Indeed, different mechanisms, based on the protection approach, have been proposed that allow fast recovery within the target of 50 ms. Nevertheless, SONET/SDH protection is mainly limited to ring topologies and it is not able to distinguish between different priorities of traffic and it has not vision of higher layer failures.
The emerging packet-based Resilient Packet Ring (RPR) technology for metropolitan networks provides powerful protection mechanisms that minimize the time needed to restore the traffic without the pre-allocation of resources.
To face to failures, the resilience single-layer strategy (a single layer has the responsibility for the recovery) is very simple from the implementation point of view. However it may not be able to efficiently recover the network from all kind of failures that can occur. Therefore, multi-layer resilience (various network layers can participate to the recovery actions) provides better performance not only in terms of protection but also in terms of resources optimization.
Multi-layer resilience strategies require coordinating the recovery mechanisms provided by each layer. In such a context, another contribution of this Ph.D. Thesis is the design and evaluation of a multi-layer resilience mechanism to be used in the IP over RPR over intelligent optical transport network for metropolitan environment to efficiently face with a wide range of network outages, while optimizing the utilization of the network resources. Its novelty relies on the interworking required between the RPR and the optical transport layer.

Finally, the fourth contribution of the Thesis deals with the optimization of the bandwidth utlization of the RPR rings taking benefits from the automatic switching of optical connections capabilities of the underlying ASON/GMPLS networks.