DIT

Dar es Salaam institute of Technology (DIT)

ETU 08102

Digital Networks

Ally, J

jumannea@gmail.com

Course Outline SDH Network IP Networks MPLS Fundamentals IP Multimedia Subsystem (IMS) GSM Network UMTS/HSPA Networks LTE Network WLAN Network

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Synchronous Digital Hierarchy (SDH) Network

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IntroductionWhat is Synchronous Digital Hierarchy (SDH)? SDH is a transmission system (protocol) which defines the

characteristics of digital signals, including frame structure, multiplexing method, digital rates hierarchy and interface code pattern

A synchronous digital transport system aimed at providing a more simple, economical, and flexible telecommunications network infrastructure

An International Standard for a high capacity optical telecommunication network

Why did SDH emerge? Need for a system to process increasing amounts of information New standard that allows mixing equipment from different suppliers

What is PDH? The Plesiochronous Digital Hierarchy (PDH) is a technology

used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems.

PDH networks run in a state where different parts of the network are nearly, but not quite perfectly, synchronized.

PDH allows transmission of data streams that are nominally running at the same rate, but allowing some variation on the speed around a nominal rate By analogy, any two watches are nominally running at the

same rate, clocking up 60 seconds every minute. However, there is no link between watches to guarantee

they run at exactly the same rate, and it is highly likely that one is running slightly faster than the other

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PCM-30 System (1/2)

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PCM-30 System (2/2) Digital data and voice transmission is based on a 2.048 Mbit/s

bearer consisting of 30 time division multiplexed (TDM) channels, each running at 64 Kbps.

The 2.048 Mbit/s bearer is known as E1. Channel 0 and 16 are used to transmit additional signaling information within the PCM-30 frame.

Increasing traffic over the past decade has demanded that more and more of these basic E1 bearers be multiplexed together to provide increased capacity.

At the same time, rates have increased through 8, 34, and 140 Mbit/s.

The highest capacity commonly encountered today for intercity fibre optic links is 565 Mbit/s, with each link carrying 7,680 base channels, and now even this is insufficient.

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PDH Systems Worldwide

PDH Multiplexing The common base for the multiplex levels of plesiochronous bearers is

represented by the 64 kbit/s channel. One branch describes the multiplex levels of plesiochronous bearers in the

Japanese standard, one further branch shows the multiplex levels of the American standard and a third one describes the conditions of the European standard.

Within the European standard the multiplex level 1 is made up of bearers with a data rate of 2.048 Mbit/s. This rate is formed by the PCM-30 frame.

The Japanese and American standards possess a data rate of 1.544 Mbit/s. In this case, 24 channels of 64 kbit/s each are multiplexed together. Multiplex level 2 is achieved by multiplexing 4 bearers of level 1.

For the Japanese and American standards, this represents a multiplexed data rate of 6.321 Mbit/s. The European standard has a combined data rate of 8.448 Mbit/s for multiplex level 2.

In the European multiplex structure 4 bearers each of the corresponding hierarchical level are multiplexed together to obtain the bearer for the next higher multiplex level.

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Limitation of PDH Existing PDH is point to point system Optical Fiber capacity is under utilized Difficulty in centralized supervision Restoration of fault is time consuming Manpower requirement is more If 140 Mbps is passing through and the customer

wants one 2 Mbps, then we have to Demultiplex from 140 Mbps to 2 Mbps for providing the 2 Mbps

The use of Justification Bits at different levels of multiplexing means that locating the 2 Mbps in 140 Mbps is not possible

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Disadvantages of PDH (2)

Why use SDH ? No world standard on digital format (three

incompatible regional standards - European, North American and Japanese)

No world standard for optical interfaces Networking is impossible at the optical level

Rigid asynchronous multiplexing structure

Limited management capability

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When do we use SDH ? When networks need to increase capacity,

SDH simply acts as a means of increasing transmission capacity

When networks need to improve flexibility, to provide services quickly or to respond to new change more rapidly

When networks need to improve survivability for important user services

When networks need to reduce operation costs, which are becoming a heavy burden

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SDH Bit Rates Comparison

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SDH Advantages First world standard in digital format First optical Interfaces Transversal compatibility reduces networking cost.

Multi-vendor environment drives price down Flexible synchronous multiplexing structure Easy and cost-efficient traffic add-and-drop and cross

connect capability Network survivability Auto restoration of faults in no time Optimum utilization of optical Fiber Bandwidth Centralized supervision by NMS, Less manpower

required

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SDH Advantages Upgradation of system is easy Existing PDH can work on SDH Network Simplification- A single synchronous

multiplexer can perform the multiplexing function Future Proof Networking – SDH is able to handle

video on demand and all other new systems like ATM, Ethernet, DVB, etc.

As the number of equipment are reduced, the space, power consumption & the maintenance cost also reduced

Bandwidth on demand - Any bandwidth required by customer can be provided in short notice

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Advantages of SDH Compatibility

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Synchronous Network Structure

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SDH EvolutionSDH evolution is possible because of the following factors : Fibre Optic Bandwidth : The bandwidth in Optical Fibre can be

increased and there is no limit for it. This gives a great advantage for using SDH

Technical Sophistication : Although, SDH circuitary is highly complicated, it is possible to have such circuitary because of VLSI technique which is also very cost effective

Intelligence : The availability of cheaper memory opens new possibilities

Customer Service Needs : The requirement of the customer with respect to different bandwidth requirements could be easily met without much additional equipment. The different services it supports are :

1. Low/High speed data. 2. Voice 3. Interconnection of LAN 4. Computer links 5. Feature services like H.D.T.V. 6. Broadband ISDN transport (ATM transport)

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Synchronous Digital Hierarchy (SDH)

VT1.5 VT1.5 VT1.5 VT1.5

VT1.5 VT1.5 VT1.5 TU-11VT1.5 VT1.5 VT1.5

TU-11 TU-11 TU-11 TU-11TU-11 TU-11 TU-11TU-11 TU-11 TU-11

STM-0 STM-0 STM-0

VC-3

DS3

otherother

otherother

otherother

New services, Data,Video, etc.

STM-0

Standard SDH Rates Equivalent voice callsSTM-0 51.84 Mb/s 　　　　 　　 672STM-1 155.52 Mb/s 2,016STM-4 622.08 Mb/s 8,064STM-16 2488.32 Mb/s 32,256STM-64 9953.28 Mb/s 129,024

VC: Virtual ContainerTU: Tributary Unit

TU-11

DS1: Digital signal level-1

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SDH Frame Structure

Bit rate of STM-1= 9*270*8*8000=155.52Mbits/s

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SDH Frame Structure Section Overhead (SOH) Area – operational functions – monitoring functions – control functions

Administrative Unit (AU)-Pointer – shows the beginning of the virtual container of the highest level

Payload Area – transport of the data

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Information Payload Also known as Virtual Container level 4 (VC-4) Used to transport low speed tributary signals Contains low rate signals and Path Overhead (POH) Location: rows #1 ~ #9, columns #10 ~ #270

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Section Overhead (SOH) Fulfills the section layer

OAM functions Types of Section Overhead 1. RSOH monitor the regenerator section 2. MSOH monitor the multiplexing section Location: 1. RSOH: rows #1 ~ #3, columns #1 ~ #9 2. MSOH: rows #5 ~ #8, columns #1 ~ #9

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Administrative Unit Pointer (AU-PTR) Indicates the first byte of VC4 ► Location: row #4, columns #1 ~ #9

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Why do we need pointer Neighboring network elements (NEs) may have different

bit rates In one NE the frequency of input fin may differ from the

output fout Tasks of the Pointer

• The pointer shows the begin of the Virtual Container within the higher structure • Adaptation of the bit rate of the VC to the velocity of the transport channel (AU, TU) • A flag within the pointer signals the changes made • Kind of stuffing will be signalized also

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SDH Multiplexing SDH Multiplexing includes:

Low to high rate SDH signals (STM-1 STM-N) PDH to SDH signals (2M, 34M & 140M STM-N) Other hierarchy signals to SDH Signals (ATM STM-N)

Some terms and definitions:

Mapping - A process used when tributaries are adapted into VCs by adding POH information

Aligning - This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the 1st byte of the VC to be located

Multiplexing - This process is used when multiple low order path signals are adapted into a higher-order path signal, or when high-order path signals are adapted into a Multiplexing Section

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SDH Multiplexing Structure

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STM-1 Signals as Transport PipeA STM-1 Signal Can Transport:

One 140 Mbit/s PDH Signal

Three 34 Mbit/s PDH Signals

Sixty-three 2 Mbit/s PDH Signals

Combinations, eg. twenty-one 2 Mbit/s and Two 34 Mbit/s PDH Signals

ATM cells, FDDI, DQDB Protocols, etc.

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Common SDH Network Element (NE) TM (Terminal Multiplexer) The terminal multiplexer is used to multiplex local tributaries (low rate) to the STM-N (high rate) aggregate. The terminal is used in the chain topology as an end element

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Common SDH NEADM (Add and Drop Multiplexer)The Add And Drop Multiplexer (ADM) passes the (high rate) stm-N through from his one side to the other and has the ability to drop or add any (low rate) tributaryThe ADM used in all topologies

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Common SDH NEREG-RegeneratorIt mainly performs 3R function: 1R – Re amplification 2R – Retiming 3R – ReshapingIt regenerates the clock and amplifies the incoming distorted and attenuated signal. It derive the clock signal from the incoming data stream.

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Common SDH NEDigital Cross Connect (DXC) Permits switching of transmission lines with different bit-

rate DXC can add and drop lower-order signals

PDH and SDH Comparison

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Network Management System (NMS) SDH aims to provide standardized, centralized O&M

system

SDH management

Performance management

Fault/Event management

Configuration management

Accounting management

Security management

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Photonic NetworkOperation System

(GMPLS)

2

λ3

1Photonic LAN/Enterprise Nwk

Regional/Metro Nwk

OXCOXC

OADMOADM

SubmarineTerm.

WDMWDM Term. Term.

Long-Haul TerrestrialBackbone Nwk

SDH/SONETSDH/SONET

Gb/10Gb EtherGb/10Gb Ether100100B-TB-T

OXCOXC

OXCOXC

OADMOADM

OADMOADM

Photonic Networks

Metro/Access Nwk

International/Submarine Network (Nwk)

OXCOXC

GMPLS: Generalized Multi Protocol Label SwitchingGMPLS: Generalized Multi Protocol Label SwitchingPONPON

Residential Nwk

OADMOADM

OADM: Optical Add/Drop Multiplexing, OXC: Optical Cross-connectOADM: Optical Add/Drop Multiplexing, OXC: Optical Cross-connect

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Evolution of Photonic Networks

Optical processing

OXC

Optical Router

YEAR1995 2000 2005 2010

1 st Generation 2 nd Generation 3 rd Generation 4 th Generation

REGILA

TRM WDM

Point - to - pointWDM transmission Add - Drop function

with Ring configuration Optical cross connect function

with Mesh configuration Optical packet/processingcapability with wavelength

conversionOADMILA

REGOADMOADM

OXC

OXC

2015

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2020 -2002 - 2005 2005 - 2010 2010 - 2020Transmission

Capacity

Rate/ch.

Node/Server

Technologies

/Fiber

2 Tb/s

10G/2.5G...10G Ether

OADM/OXC(1 - 5 Tb/s)

Tunable-LDVCSEL

Tunable filterMEMS

5 Tb/s

500

40G/10G...(40G Ether?)

Opt. routing (10Tb/s)

Opt. packet Opt. signal process.

Opt. 3R-conversion

10 Tb/s

1000

160G/40G/10..

All-opt. router( 40Tb/s)

OTDMQ-PSKOpt. IC

Cryptography

100 Tb/s

10000

> 1T

Band 100 nm 200 nm 400 nm 1000 nmNoiseless amp.

DWDMAdaptive

compensation

Quantum computerQuantum optical communication

DevicesShort pulse LD

Photonic crystalHoley fiber

Quantum dots

Opt. nano-deviceOpt. Memory

Lower loss fiber

200

Ubiquitousrouter

CPU/Storage 1 Gb/s(Elec. connect.)

10Gb/s(Elec./Opt. connect.)

100Gb/s(Opt. connect.)

Photonic Technology Roadmap