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CHAPTER Modems. Chapter Objectives. Discuss basic modem related issues Standards, Hayes compatibility etc. Describe the different types of practical modems available Internal, external, null, short-haul modems etc. Present the profile of sample practical modems

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Chapter modems
CHAPTER Modems


Chapter objectives
Chapter Objectives

  • Discuss basic modem related issues

    • Standards, Hayes compatibility etc.

  • Describe the different types of practical modems available

    • Internal, external, null, short-haul modems etc.

  • Present the profile of sample practical modems

    • Asynchronous and synchronous modems

  • Show the establishment of a fiber-optic communication link using the fiber-optic interface


Chapter modules
Chapter Modules

  • Modem Functional Considerations

  • Internal, External and Portable Modems

  • A Modem Profile

  • Modem Software Installation

  • A Practical Asynchronous/Synchronous Modem

  • Faster Modem Standards

  • Fiber-optics Connection

  • Null Modem and Short-haul Modem

  • Cable Modem

  • DSL Modem



Module

MODULE

Modem Functional Considerations


Module objectives
Module Objectives

  • List the two types of modem standards

  • Describe the features that are standardized in modem communication

    • Modulation, data compression etc.

  • Explain the relevance of standards to speed

  • Discuss Hayes compatibility

  • List a few common modem features


Major modem standards
Major Modem Standards

  • ITU standard

    • Universal standard

    • Currently in use

  • Bell standard

    • Earlier low speed modem standard

    • No more in use


Standards in modem communication
Standards in Modem Communication

  • Modulation standard

  • Data compression standard

  • Error correction Standard


Speed and modulation standards
Speed and Modulation Standards

  • Each speed is associated with a modulation standard

  • V.34 is an example standard for the communication speed of 28,800 bps

  • Higher speed modems can operate at lower speeds as well

    • E.G 28,800 bps modem can communicate at 14,400 bps




Understanding hayes compatibility
Understanding Hayes Compatibility

  • IBM is to micros what Hayes is to modems

  • Hayes compatibility

    • Ensured by adherence to the Hayes command set known as the AT command set

    • Ensures wide availability of software


Command translation for pcs and modems
Command Translation for PCs and Modems

  • Commands for the PC

    • Translated into machine language and executed

      • E.G. Identifying a file for transmission

  • Commands for the modem

    • Generated in Hayes AT command set form and transmitted to the modem for execution

      • E.G. Command instructing the modem to dial


Command translation
Command Translation

Intel Machine Code

Software

Intel Micro

Modem

Hayes AT Command


Modem features
Modem Features

  • Auto-dial

  • Auto-answer

  • Reverse calling

  • All the above features are standard in today’s Modems



Module1

MODULE

Internal, External and Portable Modems


Overview of internal and external modems
Overview of Internal and External Modems

  • Internal modem

    • Installed in the expansion slot

    • Usually cheaper

    • Occupies one expansion slot

  • External modem

    • Connects to the serial port of the computer

    • More expensive

    • Does not occupy an expansion slot

    • But, it does utilize one of the available communication ports


Internal modems
Internal Modems

Source: Black Box


External modems
External Modems

Source: Black Box


External modem ports and connection
External Modem Ports and Connection

To Com2

Port

To Phone

Jack RJ 11

Connection


Modems for the notebooks or pc card modem
Modems for the Notebooks or PC Card Modem

  • Credit card size

  • Connects to the PCMCIA slot

    • Currently, known as PC card slots

  • PC cards have undergone major refinements

    • Efficient in their operation

    • Support high-speed communication devices


Pc card modems
PC Card Modems

Source: Black Box


Multi purpose pc cards
Multi-Purpose PC Cards

Source: Black Box



Module2

MODULE

A Modem Profile


Module objectives1
Module Objectives

  • Examine the profile of an actual commercial modem

  • Discuss the standards as they relate to speed, data compression and error correction

  • Describe the FAX related communication details of the modem


Profile of a modem black box modem 288 standards
Profile of a Modem : Black Box Modem 288 Standards

  • Standards

    • ITU V.92, ITU V.90, ITU V.34, v.32bis, v.23, v.22bis, v.22, v.21, Bell 101 and Bell 212a

  • Protocols

    • Asynchronous and synchronous

  • Speed

    • V.90 ------ 56Kbps

    • V.34 -------> 28.8 Kbps

    • Others up to 14.4 Kbps

    • Possible up to 115.2 Kbps


Profile operation interface and connectors
Profile: Operation, Interface and Connectors

  • Operation

    • 2 wire dial-up

  • Interface

    • RS-232C

  • Connectors

    • 1 DB25 female

    • 2 RJ11 female


Profile speed and compression standards
Profile: Speed and Compression Standards

  • V.90

    • Supports 56 Kbps

  • V.34

    • Supports 28.8 Kbps

  • V.32

    • Supports 14.4 Kbps

  • V.42bis

    • Data compression standards

    • Up to 4 to 1 compression is possible


Profile error correction and other data compression standards
Profile: Error Correction and Other Data Compression Standards

  • MNP 2-4 and 10

    • Error correction

  • MNP 5

    • Data compression


Combined effect of speed and compression standards
Combined Effect of Speed and Compression Standards Standards

  • Combined effect of v.34 and v.42bis data compression

    • 115.2 Kbps

    • This is only a theoretical reality

    • Practical speeds can be considerably slow


Effect of compression on file transfer
Effect of Compression on File Transfer Standards

  • Highest transfer speeds cannot be achieved in the case of already compressed files

    • Example: jpg, mp3 etc.

    • Because the above files are already compressed


Profile fax communication
Profile: Fax Communication Standards

  • Fax details

    • 14.4 Kbps speed

    • Class 1 and 2 fax software support

    • Works with class 3 fax machines


End of module2
END OF MODULE Standards


Module3

MODULE Standards

Modem Software Installation


Module objectives2
Module Objectives Standards

  • Demonstrate the step-by-step installation of a modem in the Windows 95 operating system


Installation overview
Installation Overview Standards

  • The task is to install a Hayes Accura 28.8 modem on Com2 port

  • Overview of the Steps

    • Open the control panel

    • Choose the Modem icon

    • Proceed with the installation as instructed and finally specify the properties of the installed modem



Accessing modem installation icon through control panel
Accessing Modem Installation Icon Through Control Panel Standards

Start

Settings

Modems

Control

Panel


Modem icon in control panel
Modem Icon in Control Panel Standards

Double Click


Select the modem
Select the Modem Standards


Selecting the modem
Selecting the Modem Standards

Load the driver from the disk

If the modem is not found in

the List.


Non mainstream modem
Non-Mainstream Modem Standards

  • If the modem is not of a popular type, then the driver must be loaded from a location on the disk

  • In the above case, select the option that says “Have Disk”




Installed modem
Installed Modem Standards

1

2

3


Modem general properties increase the speed to the maximum
Modem General Properties StandardsIncrease the speed to the maximum.

1

2

3


Connection properties
Connection Properties Standards

1

2

3

4


Port settings
Port Settings Standards

1

2


Advanced connection settings
Advanced Connection Settings Standards

2

1

4

3


Dialing properties
Dialing Properties Standards

1

2

3


End of module3
END OF MODULE Standards


Module4

MODULE Standards

A Practical Asynchronous/Synchronous Modem


Module objectives3
Module Objectives Standards

  • Examine briefly the profile of an asynchronous/synchronous modem

  • Discuss speed related factors

  • Give an illustration of the typical use of a synchronous modem


Profile of an asynchronous synchronous modem
Profile of an Asynchronous/Synchronous Modem Standards

  • Blackbox 32fast modem

  • Claimed speed

    • 72k bps synchronous

      • Uses sync. Data compression to send data under HDLC/SDLC

    • 115.2k bps asynchronous

  • Best compression is automatically chosen

    • Between v.42 bis and MNP 5


Profile of asynchronous synchronous modem
Profile of Asynchronous/Synchronous Modem Standards

  • Other features

    • Trellis-coded modulation

    • MNP 4 error correction

  • Suggested lines

    • 2 or 4 wired leased lines

    • Switched phone lines may not provide optimum performance

  • UART connection

    • For effective high-speed transmission


Typical use of a synchronous modem
Typical Use of a Synchronous Modem Standards

Front End

Processor

Leased Line

Terminal

Cluster

Controller

Synchronous

Modem

Mainframe


End of module4
END OF MODULE Standards


Module5

MODULE Standards

Faster Modem Standards


Faster modem standards
Faster Modem Standards Standards

  • The current fastest analog modem operates at a speed of 56 Kbps

  • Standards

    • ITU V.90

    • X2

    • K56flex

  • X2 was introduced by US Robotics that has been acquired by 3 Com

  • K56flex standard was introduced by Rockwell and Lucent Technologies


Practical speed considerations
Practical Speed Considerations Standards

  • 56 Kbps has not been achieved in many tests in practice

  • Speed is usually in the region of 45k bps or less

  • FCC restriction on download speed

    • Currently the speed limitation is 53 Kbps


56 kbps v 90 information
56 Kbps /V.90 Information Standards

  • Cedric Walravens’ web site is a good source of information on 56K /V.90 modems and communication


Data compression limitations
Data Compression Limitations Standards

  • High speed modems use compression to increase the throughput

  • Files such as image files are already compressed

    • There is little leeway for further compression

    • Results in a drop in the communication speed


Quality of the phone lines
Quality of the Phone Lines Standards

  • Certain phone lines cannot support 56K bps speed

  • Central office that services a particular area may not have the latest switching equipment

  • Testing the line for 56K bps support

    • X2.usr.com/linetest1.html


Bonding of telephone lines to achieve higher speeds 112 kbps
Bonding of Telephone Lines to Achieve Higher Speeds (112 Kbps)

Modem with

Bonding

Capability

Computer

Phone Lines

Bonding of two phone lines can provide a

total bandwidth of 112K bps.



Module6

MODULE Kbps)

Fiber-Optics Connection


Module objectives4
Module Objectives Kbps)

  • Examine a fiber-optic connection used for extending the length of the communication link

  • Give an illustration of a practical fiber-optic link


Fiber optic connection for rs 232c
Fiber-optic Connection for RS-232C Kbps)

  • Extends RS-232C connection to nearly 2 . 5 miles

  • Fiber interface (line driver) specifications

    • Transfer mode

      • Synchronous and asynchronous

    • Speed

      • 56 K bps for sync.

      • 64 K bps for aysnc.

      • Selectable depending on the connection



Some fiber optic connections fiber modems
Some Fiber-optic Connections : Kbps)Fiber Modems

2.5 miles

Host

RS 232

Terminal

Fiber Line Drivers


Fiber optic line drivers
Fiber-optic Line Drivers Kbps)

Building 1

Building 2

T1

Router,

Bridge.

(Support

Videoconferencing)

Fiber-optic Line Driver




Module7

MODULE Kbps)

Null Modems and Short-Haul Modems


Null modem

Send Kbps)

Send

Comp 1

Null

Modem

Comp 2

Receive

Receive

Null Modem

  • Use for connecting two computers together

    • Communicate through their respective serial ports

  • Digital signals are not modulated


Characteristics of the null modem
Characteristics of the Kbps)Null Modem

  • Cross-over connection

    • Enables the sending and receiving of signals to facilitate communication

  • Instead of a null-modem, one may also use a crossover cable

  • In the past, null modems were used with software like lap-link

    • The primary purpose was for file transfer

  • Null modem is being replaced by a simple null modem cable


Null modem cable connection
Null Modem Cable Connection Kbps)

Comp 1

Null

Modem

Comp 2

Cable 1

Cable 2

Past

Comp 1

Comp 2

Null Modem Cable

Present


Other ways to connect two computers network
Other Ways to Connect Two Computers (Network) Kbps)

NIC

RJ 45Cross-over Cable

Comp 2

Comp 1


Other ways to connect two computers network1
Other Ways to Connect Two Computers (Network) Kbps)

Infrared Port Device

Infrared Connection

Comp 2

Comp 1


Crossover cable use
Crossover Cable Use Kbps)

  • Laplink

    • A software that is used for transferring information between computers

  • The Laplink cable that is used to connect computers together is indeed a crossover cable

    • In this case, the computers are connected either over the serial, parallel or USB ports

  • Nowadays, a popular method of exchanging information between computers is to use Infrared


Short haul modem
Short-Haul Modem Kbps)

  • Purpose

    • Extend the length of a RS-232 serial connection

  • Signals are not modulated

    • The term modem is a misnomer

  • Signals are boosted so that they may be carried over a longer distance


Short haul modem1
Short-Haul Modem Kbps)

SHM

Term.

Asynchronous.

Host

SHM

Term.

SHM

SHM

Term.

Short-

Haul

Modem

Rack

UNIX

Computer

SHM

Term.


Practical implementation
Practical Implementation Kbps)

Source: Black Box


In summary
In Summary Kbps)

  • Traditional modems

    • Perform modulation

  • Nontraditional modems

    • Do not perform any modulation



Module8

MODULE Kbps)

Cable Modems


Cable modem
Cable Modem Kbps)

  • A modem that is used for connecting a computer to the cable TV line

  • The purpose is to facilitate high speed access to the Internet

  • Cable modem is a broadband technology device

    • The cable carries multiple channels including TV channels and upstream and downstream data channels


Typical cable modem connection single ip address
Typical Cable Modem Connection (Single IP Address) Kbps)

Coaxial Cable

Cable

Modem

UTP (Cat 3 – 5)

Computer

NIC


Sharing single ip address with multiple computers 10base2
Sharing Single IP Address with Multiple Computers (10base2) Kbps)

Source:

Tim Higgins

Site

1

2

  • A proxy server can be used.

  • Windows 2000.

  • Windows 98 Second edition supports the sharing of

  • one PC for multiple PC access to the Internet.

1


Sharing single ip address with multiple computers 10baset
Sharing Single IP Address with Multiple Computers (10baseT) Kbps)

Source:

Tim Higgins

Site

1

2

  • A proxy server can be used.

  • Windows 2000.

  • Windows 98 Second edition supports the sharing of

  • one PC for multiple PC access to the Internet.

1


Two computers sharing one ip without a hub
Two Computers Sharing One IP without a Hub Kbps)

1

Source:

Tim Higgins

Site

2

2

3

  • A proxy server can be used.

  • Windows 2000.

  • Windows 98 Second edition supports the sharing of

  • one PC for multiple PC access to the Internet.

2


Cable modem lan connection multiple ip addresses
Cable Modem LAN Connection (Multiple IP Addresses) Kbps)

Coaxial

Cable

UTP (Cat 3 – 5)

Crossover Cable?

Hub

Cable

Modem

UTP (Cat 3 – 5)

Computer

Computer

Computer

NIC

NIC

NIC


Cable modem customer connections
Cable Modem Customer Connections Kbps)

Cable Service

Provider

CMTS

Customer

CM

Customer

CM

Customer

CM

CM: Cable Modem

CMTS: Cable Modem Termination System


Cable modem limitation
Cable Modem Limitation Kbps)

  • Each cable drop is shared by a number of customers

  • As the number of customers increases in a trunk the bandwidth available per customer decreases


Cable modem types
Cable Modem Types Kbps)

  • Internal Modems

    • Installed into a PC’s expansion slot

  • External Modems

    • An external box connected to the computer’s NIC

  • External Web TV Box

    • Used with Web TV setups

    • A return channel may be provided through a POTS line


Cable modem standards
Cable Modem Standards Kbps)

  • The current versions are known as the second generation modems

  • US Standards

    • MCNS/DOCSIS 1.0/1.1

    • A de facto standard

    • IEEE is yet to propose or approve a standard

  • European

    • DVB/DAVIC 1.3/1.4/1.5


The tutorial for cable modems
The Tutorial for Cable Modems Kbps)

  • www.cable-modems.org

    • Contains useful information on cable modems

  • Access to the tutorial

    • http://www.cable-modems.org/tutorial/

  • Access to Q and A

    • http://www.cable-modems.org/Q&A/

  • Appreciation and credit

    • Some of the slides used in this chapter are from the above web site as acknowledged in the appropriate slides

    • Also, visit the site for a description of some of the technical terms associated with cable modems


Additional sites
Additional Sites Kbps)

  • www.cablemodemdatacom.com

    • Extensive information with good graphics


Modulation and demodulation frequencies
Modulation and Demodulation Frequencies Kbps)

Source: http://www.cable-modems.org/tutorial/01.htm


Speed and bandwidth
Speed and Bandwidth Kbps)

  • Shannon’s Law

    • Speed is proportional to bandwidth

  • In most cases, downstream speed is higher than upstream speed

  • Higher upstream speed is desired in certain cases

    • Hosting of a web server

  • Symmetric streams are desired for video conferencing


Maximum bandwidth
Maximum Bandwidth Kbps)

  • Upstream

    • Lower frequencies are used

    • Up to 3Mbps

  • Downstream

    • Higher frequencies are used

    • Between 27-56 Mbps

  • Note that communication speed is proportional to available bandwidth


Downstream communication characteristics
Downstream Communication Characteristics Kbps)

Source: http://www.cable-modems.org/tutorial/08.htm


Upstream communication characteristics
Upstream Communication Characteristics Kbps)

Source: http://www.cable-modems.org/tutorial/09.htm


Osi iso reference model and cable modem communication
OSI-ISO Reference Model and Cable Modem Communication Kbps)

Source: http://www.cable-modems.org/tutorial/02.htm


Sample cable modem companies
Sample Cable Modem Companies Kbps)

  • 3Com

  • CISCO Systems

  • Toshiba

  • Sony

  • More DOCSIS compatible Cable Modems

    • A gallery of selected cable modems from cable-modems.org



Sample product demonstration
Sample Product Demonstration Kbps)

  • 3Com Cable Modem CMX product demonstration

    • Explore the purpose of the different status lights on the modem

    • Try this to see the product feature and rotate the modem to view the different sides of the modem


Possible downside
Possible Downside Kbps)

  • Potential downsides to the cable modem are discussed in this ZDnet article


Advantages and disadvantages
Advantages and Disadvantages Kbps)

  • Advantages

    • Higher speeds compared to analog connections

    • The connection is always on

    • Possible assignment of static IP addresses

  • Disadvantages

    • Speed drops with an increase in the number of customers on a cable drop

    • Higher costs compared to analog connections


FAQs Kbps)

  • A collection of 100 FAQs from cable-modems.org

    • Includes FAQs for DSL as well


Other cable modem links
Other Cable Modem Links Kbps)

  • ZDnet home page on cable modem

  • Cable modem help web site

  • Cable modem net information site

  • Tom Higgins’ cable modem site

    • Recommended

  • Cable modem books

    • A listing of selected books from cable-modems.org



Module9

MODULE Kbps)

DSL Modems


Dsl modem
DSL Modem Kbps)

  • A modem that is used for connecting a computer to the Digital Subscriber Line (DSL)

  • The purpose is to facilitate high speed access to the Internet

  • DSL modem is a broadband technology device

    • The regular telephone line carries the DSL line as well

    • Therefore, there are multiple channels present on the POTS line delivering the DSL connection


Simple dsl line drop
Simple DSL Line Drop Kbps)

Source: xDSL Technology Web Site


Another xdsl line drop
Another xDSL Line Drop Kbps)

Soource: XDSL


Typical dsl modem connection single ip address
Typical DSL Modem Connection Kbps)(Single IP Address)

POTS line

DSL

Modem

UTP (Cat 3 – 5)

10/100 Mbps

(*Cat 5 is recommended)

Computer

NIC





Dsl modem lan connection multiple ip addresses
DSL Modem LAN Connection Kbps)(Multiple IP Addresses)

Source: xDSL


Source: Kbps)DSL Reports


Dsl resources
DSL Resources Kbps)

  • DSL Reports itself is a good DSL web site

  • A good reference to DSL Resources from DSL reports

  • A good page that shows graphically the speed comparison of DSL with other technologies


Typical adsl connection
Typical ADSL Connection Kbps)

Source: ADSL Tutorial from adsl.com


Cable modem limitation1
Cable Modem Limitation Kbps)

  • Each cable drop is shared by a number of customers

  • As the number of customers increase in a trunk the bandwidth available per customer decreases


Asdl modem types
ASDL Modem Types Kbps)

  • Internal Modems

    • Installed into a PC’s modem

  • External Modems

    • An external box connected to the computer’s NIC


Cable modem standards1
Cable Modem Standards Kbps)

  • The current versions are known as the second generation modems

  • US Standards

    • MCNS/DOCSIS 1.0/1.1

    • A de facto standard

    • IEEE is yet to propose or approve a standard

  • European

    • DVB/DAVIC 1.3/1.4/1.5


The tutorial for cable modems1
The Tutorial for Cable Modems Kbps)

  • www.cable-modems.org

    • Contains useful information on cable modems

  • Access to the tutorial

    • http://www.cable-modems.org/tutorial/

  • Access to Q and A

    • http://www.cable-modems.org/Q&A/

  • Appreciation and credit

    • Some of the slides used in this chapter are from the above web site as acknowledged in the appropriate slides

    • Also, visit the site for a description of some of the technical terms associated with cable modems


Modulation and demodulation frequencies1
Modulation and Demodulation Frequencies Kbps)

Source: http://www.cable-modems.org/tutorial/01.htm


Maximum bandwidth1
Maximum Bandwidth Kbps)

  • Upstream

    • Lower frequencies are used

    • Up to 3Mbps

  • Downstream

    • Higher frequencies are used

    • Between 27-56 Mbps

  • Note that communication speed is proportional to available bandwidth


Downstream communication characteristics1
Downstream Communication Characteristics Kbps)

Source: http://www.cable-modems.org/tutorial/08.htm


Upstream communication characteristics1
Upstream Communication Characteristics Kbps)

Source: http://www.cable-modems.org/tutorial/09.htm


Osi iso reference model and cable modem communication1
OSI-ISO Reference Model and Cable Modem Communication Kbps)

Source: http://www.cable-modems.org/tutorial/02.htm


Sample dsl modem companies
Sample DSL Modem Companies Kbps)

  • 3Com

  • CISCO Systems

  • Alcatel


Sample cable modem1
Sample Cable Modem Kbps)

Source: 3Com Modem


Sample product specifications
Sample Product Specifications Kbps)

Source: 3Com


Sample product demonstration1
Sample Product Demonstration Kbps)

  • 3Com ADSL Modem Demonstration

    • http://www.3com.com/client/pcd/homeconnect/dsl/images/prod_sidenav.gif

    • Explore the purpose of the different status lights on the modem

    • Try this to see the product feature and rotate the modem to view the different sides of the modem


Possible downside1
Possible Downside Kbps)

  • Potential downsides to ADSL


Advantages and disadvantages1
Advantages and Disadvantages Kbps)

  • Advantages

    • Higher speeds compared to analog connections

    • The connection is always on

    • Possible assignment of static IP addresses

    • Existing POTS line can be used

  • Disadvantages

    • Higher costs compared to analog connections

    • May not be available at all locations


Other dsl links
Other DSL Links Kbps)

  • DSL Reports web site contains a good collection of selected links


End of module end of chapter
END OF MODULE Kbps)END OF CHAPTER


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