TELECOMMUNICATION SYSTEMS

TELECOMMUNICATION

SYSTEMS

IP Networking Through Telecommunication System

System Engineering BSc Full-time

Overview

•

Phone Line Modems

• PSTN modem • ISDN modem

•

ADSL

Acoustic modems

• Connection management by hand (dialing, putting down the phone handset)

• 300 or 1200 b/s (ITU-T V.21, V.22)

• Curiosity: were able to work with the part of todays phone modems

modems

• 1970s - early of 1980s

• No direct connection to the network

• Was enabled to connect only the post office devices • Nowadays that is a forgotten history

PSTN

Circuit - Switching

1. Real Time Voice Transmission 2. Point To Point Networks

3. Bandwidth is constant

4. Data Transmission

4. Data Transmission

• PSTN & ISDN & TDM

Circuit – Switching Network

• Circuit - Switching telephone network • Carries analog voice

Data Transfer Over PSTN

• Digital lines between santrals

• E1 Tranks: 32 channels X 64Kbps 3 X E1 Trank Users Analog Analog Santral 1 Santral 2 Users Users Digital 32X3=96 calls

• Modem converts: Digital data to Analog voice • 28 Kbps

How to connect net over PSTN?

ISDN

Overview

• Define ISDN, its standards and the type of services offered

• Describe the two main types of services, namely BRI and PRI

• Give examples of ISDN links • Give examples of ISDN links

• Simple SOHO line, ISDN remote bridges etc

ISDN Defined

• Known as the Integrated Services Digital Network • Data, audio, image and video transmission

• It is a switched digital telecommunication line that can be delivered over regular copper wires

• Possible to provide end-to-end digital communications • Possible to provide end-to-end digital communications

ISDN Application Examples

• On/off ramp to the information super-highway to

communicate at speeds of 128 Kbps for a single ISDN line

• Multiple ISDN lines can be combined together to achieve

higher communication speeds

• Home use

• On/Off ramp to the Internet • Business world

• Provide remote access to LANs

ISDN Standard and Connection

• There is a national ISDN standard known as the NI standard

• It is being implemented in phases

• Current implementation is termed as NI-1 to indicate that it is in phase 1 of the implementation process

it is in phase 1 of the implementation process

• Can be obtained from a local telephone company in the same way an analog connection is obtained

• Phone companies offer different types of ISDN connections

ISDN Basic Characteristics

Inverse Multiplexing of B Channels

B (64 Kbps)

128 Kbps 128 Kbps

B (64 Kbps)

ISDN Service Connections

• There are two different types of ISDN services that are widely available

• One is known as the Basic Rate Interface or BRI • Used for home or SOHO connection

• Used for home or SOHO connection

• The other is known as the Primary Rate Interface or the

In Summary

• ISDN is a switched digital network

• Can be used for establishing a point-to-point digital connection

• BRI and PRI

• Number of B Channels vary in each case • Number of B Channels vary in each case

• B channels can be combined together to achieve a higher communication speed

BRI Characteristics

• Basic Rate Interface • 2 B Channels

• 1 D Channel

B channels are known as bearer channels • B channels are known as bearer channels

• Carry information

• D channel is known as the Delta channel • Used for signaling purposes

A Simple BRI Connection to a

Microcomputer

NT 1

ISDN BRI Line 2B +D

Network Terminator

ISDN Terminal Adapter

The Channels

• Channel B

• 64k bps per channel

• The two B channels can be inverse multiplexed or boded together • Achieve a maximum aggregate communication speed of 128 Kbps • Channel D

• Channel D • 16 Kbps

• Entire bandwidth is not used for signaling purpose

• Excess of 9.6 Kbps is available for packet switched data

transmission applications

• Excess bandwidth usage - climate control, security alarm system

In Summary

• BRI is the basic ISDN service

• Composed of 2 B channels and a D channel • B Channels are circuit switched

• D Channel is packet switched

Excess capacity can be utilized for packet switched applications

PRI Service

• Primary Rate Interface

• More sophisticated service compared to BRI

• PRI service offers 23 B channels and 1 D channel • B channel properties

• Each B channel operates at a speed of 64K bps • The B channels are used for carrying data

• B channels can be combined together to increase the aggregate

communication speed

• D channel properties

• Each D channel operates at a speed of 64 Kbps • Considerably faster than the D channel in BRI

PRI Channel Delivery

• PRI channels are delivered over a T1 line • T1 speed

• 1.544M bps

• Aggregate speed of PRI from all 23 B channels and the single D Channel is computed as follows:

Sample Services (PacBell)

• Centrex ISDN

• For businesses that already have the Pac Bell’s centrex phone

system

• SDS-ISDN

• BRI service offered for small businesses • BRI service offered for small businesses • Charges

• Per channel

Sample Services (ISDN)

• Home ISDN

• Offers a BRI connection

• 2B + D

• Charges are cheaper especially during off-peak hour

• Per channel

• Per channel

• Per minute

• SDS-56

Sample Cost Comparison

Service Month Inst. Usage

Cen-ISDN 31.65 220.75 Bus. Measured

Cen-ISDN 31.65 220.75 Bus. Measured

SDS-ISDN 26.04 190.75 Bus. Measured

Home 24.50 159.75 8-5 Bus. Measured

ISDN Flat Otherwise

PRI 220.00 750 Bus. Measured

SDS- 56 45.00 500 Bus Measured

Use of ISDN Adapters

NT1 NT1

Pub. Switched Network

Computer Computer Computer

Remote ISDN Access to a LAN

NT1 NT1

PSN

BRI BRI _Remote

ISDN Bridge Computer ISDN Adapter NT1 ISDN Router NT1 Ethernet Bridge 128K bps 28.8K bps to 56K bps

Remote Access Over PRI

Important Features of the PRI Connection

• Communication links can be established between: • remote computers and this LAN

• this LAN and remote locations • this LAN and other remote LANs

• Link is established using a powerful router

• A separate DSU/CSU unit is used as opposed to the NT1 network terminator used in the case of BRI

Commercial Examples of ISDN

Equipment

• ISDN adapter • 3Com Impact IQ • ISDN routers

• Ascend and Cisco are sample manufacturers

Ascend Pipeline 50 and Ascend Pipeline 100 are examples of

• Ascend Pipeline 50 and Ascend Pipeline 100 are examples of

such routers

• For the latest information on ISDN equipment access the manufacturers’ web sites

ISDN Use in Video Conferencing

• Dynamic bandwidth allocation • Circuit switched

ADSL

Introduction

• ADSL is a form of DSL, a data communications

technology that enables faster data transmission over copper telephone lines

• ADSL is capable of providing up to 50 Mbps, and supports • ADSL is capable of providing up to 50 Mbps, and supports

voice, video and data.

• ADSL is the #1 Broadband Choice in the World with over 60% market share

What does ADSL mean

• Asymmetric - The data can flow faster in one direction than

the other. Data transmission has faster downstream to the subscriber than upstream

• Digital - No type of communication is transferred in an

• Digital - No type of communication is transferred in an

analog method. All data is purely digital, and only at the end, modulated to be carried over the line.

• Subscriber Line - The data is carried over a single twisted

ADSL standards :

ADSL standards :

Standard name Common name Downstream rate

Upstream rate

ITU G.992.1 ADSL (G.DMT) 8 Mbit/s 1.0 Mbit/s

ITU G.992.2 ADSL Lite (G.Lite) 1.5 Mbit/s 0.5 Mbit/s

ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s

ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s

ITU G.992.3/4 Annex J ADSL2 12 Mbit/s 3.5 Mbit/s

ITU G.992.3/4 Annex L RE-ADSL2 5 Mbit/s 0.8 Mbit/s

ITU G.992.5 ADSL2+ 24 Mbit/s 1.0 Mbit/s

ITU G.992.5 Annex L RE-ADSL2+ 24 Mbit/s 1.0 Mbit/s

Hybrid Fibre/Copper

Pure Fibre

ADSL Speed Comparison

FTTH ISDN ADSL FTTx, VDSL2, ADSL2plus Enhanced Copper Voice band Modem

ADSL Range

• In general, the maximum range for DSL without a repeater is 5.5 km

• As distance decreases toward the telephone company office, the data rate increases

Data Rate Wire gauge Wire size Distance

• For larger distances, you may be able to have DSL if your phone company has extended the local loop with optical fiber cable

1.5 or 2 Mbps 24 AWG 0.5 mm 5.5 km

1.5 or 2 Mbps 26 AWG 0.4 mm 4.6 km

6.1 Mbps 24 AWG 0.5 mm 3.7 km

ADSL Speed Factors

• The distance from the local exchange • The type and thickness of wires used • The number and type of joins in the wire • The number and type of joins in the wire

• The proximity of the wire to other wires carrying ADSL, ISDN and other non-voice signals

ADSL network components

• The ADSL modem at the customer premises(ATU-R) • The modem of the central office (ATU-C)

• DSL access multiplexer (DSLAM) • Broadband Access Server (BAS)

• Splitter - an electronic low pass filter that separates the

analogue voice or ISDN signal from ADSL data frequencies DSLAM.

ADSL Loop Architecture

Voice Switch

DSL

ISP

ADSL Requirements

• Phone-line, activated by your phone company for ADSL • Filter to separate the phone signal from the Internet signal • Filter to separate the phone signal from the Internet signal • ADSL modem

How does ADSL work

• ADSL exploits the unused analogue bandwidth available in the wires

PSTN

PSTN UpstreamUpstream DownstreamDownstream

• ADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies

4 25,875 138 1104 KHz

PSTN

ADSL Modulation

• Modulation is the overlaying of information (or the signal) onto an electronic or optical carrier waveform

• There are two competing and incompatible standards for modulating the ADSL signal:

modulating the ADSL signal:

• Carrierless Amplitude Phase (CAP) • Discrete Multi-Tone (DMT)

Carrierless Amplitude Phase

• Carrierless Amplitude Phase (CAP) is an encoding

method that divides the signals into two distinct bands: 1. The upstream data channel (to the service provider), which is

carried in the band between 25 and 160kHz

1. The downstream data channel (to the user), which is carried in

the band from 200kHz to 1.1MHz .

• These channels are widely separated in order to minimize the possibility of interference between the channels.

Discrete Multi-tone (DMT)

• Discrete Multi-Tone (DMT) separates the DSL signal so that the usable frequency range is separated into 256 channels of 4.3125kHz each.

• DMT has 224 downstream frequency bins (or carriers) and 32 upstream frequency bins.

• DMT constantly shifts signals between different channels to ensure that the best channels are used for transmission

The DMT frequency bands

• Frequency Division Multiplexing (FDM)

Asynchronous Transfer Mode

• ATM is a connection-orientated technique • ATM provides cell sequence integrity

• Cells are much smaller than standard packet-switched • Cells are much smaller than standard packet-switched

networks (53 bytes)

• The quality of transmission links has lead to the omission of overheads

Types of ATM services

• Constant Bit Rate (CBR)

• Variable Bit Rate (VBR)

• Unspecified Bit Rate (UBR)

ATM Layer

• The ATM layer transport information across the network • ATM uses virtual connections for the information transport • The connections are divided into two levels:

• The connections are divided into two levels: • The Virtual Channels

• The Virtual Path

ATM Connections

• The connection between two endpoints is called a Virtual Channel (VC).

• A Virtual Path (VP) is a term for a bundle of virtual channel links that all have the same endpoints.

• Each VC and VP has a unique identifier

• Virtual paths are used to simplify the ATM addressing structure.

ATM Adaptation Layer (AAL)

• The ATM Adaptation Layer (AAL) converts information from the upper layers into ATM cells

• The standard used for ATM over ADSL services is AAL5 • AAL5 Encapsulation Methods

• Virtual Channel Multiplexing (VCMux) • LLC/SNAP

ADSL Protocol stacks

Point-to-Point Protocol over Ethernet

over ATM (PPPoEoA)

Conclusion

• ADSL advantages

• Simultaneous Internet and voice/fax capabilities over a

single telephone line

• Uninterrupted, high-speed Internet access that's always

on-line

• Cost-effective solution for society • Cost-effective solution for society

• Data Security that exceeds other technologies • Fast download speeds

• ADSL disadvantages:

• Distance-sensitive

• Slower upload speeds • Phone line required

ADSL Equipments

Modem

ADSL DSLAM

DSLAM

(Digital Subscriber Line Access Multiplexer)

XDSL

xDSL

• Optical network expanding (getting closer to subscriber)

• Optical Network Unit ONU at curb or basement cabinet • FTTC (curb), FTTB (building)

• These scenarios usually dictates low power

• Rates can be very high since required reach is minimal!

xDSL Technology

Type Meaning Coding/Tech. Reach/Speed/Range Application

DSL Digital

Subscriber Line

2B1Q line Duplex: 160 kbit/s (2B(64k)+D(16k)+mana gementt) Range: 5,5km ISDN- voice & data HDSL High-bit-rate DSL CAP researched by AT&T Duplex: 2Mbit/s, 2 or 4 wire, Range : 3-8km E1 (2 Mbit/s) networking SDSL Symmetric DSL (Single Line)

Modulating _{Duplex: 2Mbit/s}

Range : 3 km

Synchron user networking

xDSL Technology

Type Meaning Coding/Tech. Reach/Speed/Range Application

ADSL Asymmetrical DSL DMT coding (Discrite or Multiple modulation – 4kHz Asymmetric Downlink: 1,5 – 8 Mbit/s Uplink: 16 – 640 kbit/s Range : 1. Mbit/s……4800m Fast Internet, far LAN networking, VoD, multimedia

channels) 1._{6 Mbit/s……3600m}Mbit/s……4800m

8 Mbit/s……2700m

VDSL Very high bit rate DSL =ADSL / stricter requirements, smaller range Asymmetric Downlink: 13-52 Mbit/s Uplink: 1,6-2,3 Mbit/s Range : 13 Mbit/s……1350m 26 Mbit/s……. 900m 52 Mbit/s……..300m

The same like ADSL+HDTV

VDSL2

DMT line code (same 4.3125 kHz spacing as ADSL)

VDSL uses BW of 1.1 MHz - 12 MHz (spectrally compatible with ADSL)

VDSL2 can use 20 kHz - 30 MHz

• new band-plans (up to 12 MHz, and 12-30 MHz) • new band-plans (up to 12 MHz, and 12-30 MHz) • increased DS transmit power

• various algorithmic improvements

• borrowed improvements from ADSL2 • 3 user data types - STM, ATM and PTM

VDSL2 band plans

North American bandplan

US0 (if present) starts between 4 kHz - 25 kHz

and ends between 138-276 kHz

Europe - six band plans (2 A and 4 B)

A (998) US0 from 25 DS1 from 138 or 276 US1 3750-5200 DS2 5200-8500

B (997) US0 from 25 or 120 or nonexistent

DS1 from 138 or 276