[PDF] - Organization of telephone services The telephone message are routed PDF Document

SLIDE 1

Applied Network Research Group Department of Computer Engineering, Kasetsart University 1/28

Digital Carrier Systems

Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan

Last updated: 8 Feb 2001 Applied Network Research Group Department of Computer Engineering, Kasetsart University 2/28

Organization of telephone services

The telephone message are routed through :

a switch at the central office (CO) for a local calls
a switching center for out-of-area calls
toll exchanges for long distance calls

CO CO CO CO CO CO

switch switch

to local call

local loop

Toll exchange Toll exchange

Area toll change

Inter-office trunk (IOT)

The original IOT

connections were made

ver an analog system

called N-carrier.

The T-carrier system

was the first widely deployed digital transmission system

The original IOT

connections were made

ver an analog system

called N-carrier.

The T-carrier system

was the first widely deployed digital transmission system

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Digital Services

Switched/56 Switched/56 Digital Data Services Digital Data Services Services Services Digital Carrier Systems Digital Carrier Systems

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Switched/56

DSU

A switched digital service that allows data rate 56 Kbps over

switched synchronous line

Switched/56 lines are digital and do not require a modem
Data Service Unit (DSU) is required to convert signals from LAN

devices/multiplexer into the digital signals used by the digital lines

Telephone Network (Switching) DSU router router

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Digital Data Services

DSU

A digital leased line is used with a maximum data rate of 64

Kbps

DSU Telephone Network (Leased) router router

Check!

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Digital carrier standard

T-carrier North America, Japan E-carrier Europe, South America SONET/SDH world-wide new standard

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Comparison of the layer

Physical Data link Network Transport Session Presentation Application Physical Physical OSI T-1 SONET/SDH

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T-1 carrier system

CH1 CH2 CH24

PCM

CH1 CH2 CH3 CH23 CH24 CH23 x x x x x x x x MSB

(sign bit)

LSB

24 voice channels are sampled, quantized and

encoded into a TDM PCM signal

T-1 carrier has a transmission rate of 1.544 Mbps
Bipolar encoding
B8ZS for T-1
B3ZS for T-3
Full duplex
Channel-based digital transmission
Bipolar encoding
B8ZS for T-1
B3ZS for T-3
Full duplex
Channel-based digital transmission

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T-1 frame

CH 1 (8 bit) CH 1 (8 bit) CH 2 (8 bit) CH 2 (8 bit) . . . . . . . . . . . . . . CH 24 (8 bit) CH 24 (8 bit)

1 frame bit

192 bits

T-1 bit rate : (24x8 +1 bit)/125 μs = 1.544 Mbps

125 μs

The early frame standard called D1, D2 and D3 were used.
There are two framing standard for the T-1, called D4

(superframe) and extended superframe (ESF)

The T-3 used the M13 framing
The early frame standard called D1, D2 and D3 were used.
There are two framing standard for the T-1, called D4

(superframe) and extended superframe (ESF)

The T-3 used the M13 framing

Applied Network Research Group Department of Computer Engineering, Kasetsart University 10/28

Frame and Superframe

T-1 carrier frames are transmitted in

groups of 12 called superframes

F-bit in even-numbered frame has a

pattern of 101010 for synchronization

Signaling information is accomplished

by robbing the LSB position of each

channel. This is performed only in the

6th and 12th frame to keep distortion minimum

Fcombine 1 1 1 1 1 1

F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12

Feven 1 1 1 Fodd 1 1 1

1 superframe = 12 frames (2316 bits in 1.5 ms) Frame # F data (192 bits) 1 1 dddd dddd -- dddd dddd 2 dddd dddd -- dddd dddd 3 dddd dddd -- dddd dddd 4 dddd dddd -- dddd dddd 5 1 dddd dddd -- dddd dddd 6 1 dddd dddX -- dddd dddX 7 dddd dddd -- dddd dddd 8 1 dddd dddd -- dddd dddd 9 1 dddd dddd -- dddd dddd 10 1 dddd dddd -- dddd dddd 11 dddd dddd -- dddd dddd 12 dddd dddX -- dddd dddX

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Extended Superframe

ESF framing groups 24 frames into an ESF superframe
every 193rd bit are used for the above purposes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Remote configuration and monitoring (4Kbps) CRC Frame synchronization

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Multiplexing

CSU (Channel Service Unit)
performs several protective and

diagnostic functions

DSU (Data Service Unit)
convert the digital data from a (for

example) router to T1 voltages and encoding.

CSU/DSU MUX router phone

T-carrier

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T-carrier Digital Multiplexing Hierarchy

DS1 DS1C

DS2

DS3 DS4

DS1C

DS2 DS2 DS2 DS2 DS2 DS2

DS3 DS3 DS3 DS3 DS3

DS1

Two 1.544 Mbps DS1 channels are multiplexed into a single 3.152 Mbps DS1C channel Two DS1C channels are multiplexed into a single 6.312 Mbps DS2 channel Seven DS2 channels are multiplexed into a single 44.736 Mbps DS3 channel Six DS3 channels are multiplexed into a single 274.176 Mbps DS4 channel

T1 T2 T3 T4 T1-C

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E1-frame

CH CH CH 1 CH 1 CH 2 CH 2 CH 16 CH 16 CH 31 CH 31

125 μs

frame synchronization signaling channel

30 voice channels+2 control channels T1 bit rate : (32x8 bit)/125 μs = 2.048 Mbps

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E-carrier

E1 E1 E1 E1

E2 E2 E2 E2 E3 E3 E3 E3 E4 E4 E4 E4 E5

Thirty two 64 Kbps channels are multiplexed to create one 2.048 Mbps E1 channel Four E1 channels are multiplexed into a single 8.448 Mbps E2 channel Four E2 channels are multiplexed into a single 34.368 Mbps E3 channel Four E3 channels are multiplexed into a single 139.264 Mbps E4 channel Four E4 channels are multiplexed into a single 565.148 Mbps E5 channel Applied Network Research Group Department of Computer Engineering, Kasetsart University 16/28

Digital carrier comparison

2.048 2.048 8.448 8.448 34.368 34.368 139.264 139.264 564.992 564.992 1.544 1.544 6.312 6.312 44.736 44.736 274.176 274.176 1.544 1.544 6.312 6.312 32.064 32.064 97.728 97.728 397.200 397.200 64 64 J1 E1 T1 J2 E2 T2 J3 E3 T3 J4 E4 T4 J5 E5

x32 x24 x24 x 4 x 2 x 4 x 4 x 7 x 5 x 4 x 6 x 3 x 4 x 4

Europe USA Japan 3.152 3.152 T1C

x 2

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PDH

PDH = Plesiochronous Digital Hierarchy
Digital transmission systems (T-carrier, E carrier) combine

lower order multiplex stream to get higher bit rate

Each device runs its own free-running clock
Different streams have small differences in clock signals.
Solve by adding justification bit

almost synchronous

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PDH deficiencies (I)

140 M LTE

140 34 34 8 8 2 140 34 34 8 8 2

140 M LTE

34 Mbps 8 Mbps 2 Mbps Customer site

Lack of flexibility

impossible to identify a lower bit rate channel from the higher-order

bit stream.

demux the high bit rate down to the lower level remux back into higher level for onward transmission

Extraction of 2 Mbps channel from 140 Mbps channel

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PDH deficiencies (II)

Lack of performance

No standard for monitoring the performance of traffic channel No management channel

Lack of ‘Mid-Fibre meet’

undefined interface specification on the line side of a line

transmission

LTE G.703 interface non standard line code and

ptical levels

standard Network Node Interface (NNI) functional integration

f MUX and LTE

PDH SDH

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SDH & SONET

What is SDH/SONET ?

Standard interface developed for using in the public network multiplexing standard for optical fiber transmission

SONET = Synchronous Optical Network

refers to the system used within the U.S. and Canada

SDH = Synchronous Digital Hierarchy

international community term (ITU-T recommendations)

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SDH/SONET goals

Goals

make it possible for different carrier to interwork unify the U.S., European and Japanese digital system Provide a way to multiplex multiple digital signal together provide support for operations, administration, and

maintenance

Characteristics

use single master clock to synchronize Bit stream can be a added or extracted directly Basic transmission rate = 155.52 Mbps Applied Network Research Group Department of Computer Engineering, Kasetsart University 22/28

SDH/SONET topology

Typical SDH/SONET

topology is a dual ring (fiber optics)

One ring is the working

facility, and the other ring is the protection facility (standby)

End-user devices operating
n LANs or other transport

systems are attached through terminal adapter

ADM DCC ADM

DS1 DS3 DS1 DS3 DS1 DS3

Other SONET/SDH networks

TA TA

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SDH/SONET System

consists of switches, mux and repeaters

section section section section line line path

mux repeaters repeaters mux mux

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Multiplexing level

SONET SDH Bit rate (Mbps)

STS-1/OC-1 51.84 STS-3/OC-3 STM-1 155.52 STS-9/OC-9 STM-3 466.56 STS-12/OC-12 STM-4 622.08 STS-18/OC-18 STM-6 933.12 STS-24/OC-24 STM-8 1244.16 STS-36/OC-36 STM-12 1866.24 STS-48/OC-48 STM-16 2488.32

STS = Synchronous Transport Signal OC = Optical Carrier STM = Synchronous Transport Module

(Not defined)

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SDH Basic Frame structure

1 frame = 2430 bytes in 125 μs 1 2 3 4 5 6 7 8 9

STM-1

Overhead :

for system management information (OAM) SOH = Section Overhead LOH = Line Overhead TOH = Transport Overhead

Payload : user data

row/column mapping 261 bytes 3 bytes 6 bytes 9 bytes 9 bytes SOH LOH

Payload

TOH Applied Network Research Group Department of Computer Engineering, Kasetsart University 26/28 87 bytes 3 bytes 6 bytes 9 bytes

SONET Basic Frame structure

1 frame = 810 bytes in 125 μs

1 2 3 4 5 6 7 8 9

STS-1/OC1

3 bytes SOH LOH

Payload

TOH

Overhead :

for system management information SOH = Section Overhead LOH = Line Overhead TOH = Transport Overhead

Payload : user data

row/column mapping

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STM-1 Frame

9 bytes 261 bytes SOH LOH pointer SOH LOH pointer frame #1 frame #2

Payload #1 Payload #1 Payload #1 Payload #1 Payload #2 Payload #2 POH #1 POH #2

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SDH mux scheme

AUG AU-4 VC-4 TUG-3 TU-3 VC-3 C-4 VC-3 AU-3 TUG-2 TU-2 VC-2 C-2 TU-12 VC-12 C-12 TU-11 VC-11 C-11 C-3

x1 x3 x3 x7 x7 x1 x3 x4

140 Mbps 45 Mbps 34 Mbps 6 Mbps 2 Mbps 1.5 Mbps STM-1 SONET-specific Europe-specific Universal

PDH Tributaries

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Administrative Unit Tributary Unit Group

SDH Elements

Containers Virtual Containers Tributary Unit Administrative Unit Administrative Unit Group

path overhead

pointer

Tributary Unit Group Tributary Unit Tributary Unit

section overhead

STM-1

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