Modem Technologies
ADSL Modem
Outline of the Presentation
Modem Technologies.
DSL
ADSL Modem
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Upstream/Downstream Bands and Frequency
Bandwidth notation
Setup Properties of ADSL Modem
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Routing and Security
Wireless ADSL
Cable Modem
Comparison of ADSL and Cable Modem
What does modem mean?
The word "modem" comes from
"modulator-demodulator“
Modulation: digital information to
analog signals
Demodulation: analog signals back
into useful digital information
Settled device for computers.
Allows 2 computers to communicate
over standard phone lines.
They have many different shapes
and sizes to correspond all kind of
needs.
Conversion of Digital Information
to Analog Information
What is DSL?
Digital Subscriber Line.
New modem technology.
Data transmission is based on digital encoding (digital).
Uses phone line so for the customer wiring (subscribers’
line).
Use digital coding techniques to provide more capacity.
Allows high-speed Internet access over existing twisted-
pair and ordinary copper telephone wires.
What is DSL?
Provides "always-on" connection.
To transport high-bandwidth data.
A special hardware attached to both the user and switch
ends of line.
Advantages of DSL
High-speed.
Secure connection.
No dial-up, waiting or dropped connections.
It's always on connection.
Saves both money and time.
Provides large file transfers.
Multiple workers on a network can connect to a single
DSL.
What is ADSL?
Asymmetric Digital Subscriber Line.
Is a form of DSL.
A high-speed Internet access service.
Speed depends on the length and the diameter of the
cable and the type of the mode
Requires a special ADSL modem and an Internet
service provider (ISP) .
What is ADSL?
It is asymmetric since the data coming to your computer
from the Internet (download) is faster than the data
traveling from your computer to the Internet (upload).
Uses standard telephone lines.
Telephone can be used normally, even when surfing in
the Web with ADSL service.
An "always on" service.
Not available to everyone.
How does ADSL work?
ADSL Splitter separates the analogue voice (phone)
traffic from data (adsl) traffic.
ADSL Modem converts digital signals from your PC into
analog signals that can be transmitted over telephone
cable in the local loop.
Local Loop is the path your telephone line will take from
your house to the local exchange.
Service Provider.
The cable consists of a "copper pair" .
How does ADSL work?
How does ADSL work?
How does ADSL work?
•DSLAM - DSL Access Multiplexer
•BRAS – Broadband Remote Access Server
•ISP - Internet Service Provider
How does ADSL work?
The DSLAM associates a
number of ADSL user
connections as many as
several hundred into a single
fiber connection.
This fiber will normally be
connected to a Broadband
Remote Access Server or
BRAS.
How does ADSL work?
BRAS routes traffic to and from
the digital subscriber line access
multiplexers (DSLAM) on an
Internet service provider’s (ISP)
network.
A single BRAS will probably
handle connections from several
DSLAMs.
How does ADSL work?
This is the place where your
connection to the Internet is
made.
The ISP usually provides other
services like mail and news
servers, and frequently-used
pages from the Internet so that
you can access them more
quickly.
How does ADSL work?
ISP
Internet Service Provider
ISP
A company.
Access to the internet.
Monthly fee.
Software package.
User name, password and access phone
number.
Modem.
Log-on.
ISP
Individuals and large companies.
Connected to one another through Network
Access Points (NAPs).
Examples:
Superonline
E-kolay.
Atlas On-Line.
Tr-Net.
ADVANTAGES of ADSL
Quick connection.
Fast.
Use phone connection when connected to the internet.
No need for second phone line.
No dropped connections.
Always on connection.
Ability to download large files.
Save time.
Cost efficiency.
Upstream/Downstream Bands and
Frequency
ADSL Communication is Full Duplex.
Full duplex ADSL communication is usually providing
with a wire pair by either frequency division multiplex
(FDM).
FDM uses two separate frequency bands, these are
the upstream and downstream bands.
Upstream/Downstream Bands and
Frequency
Downstream data.
Upstream data.
ADSL transmit upstream and downstream data on a
digital frequency
Upstream/Downstream Bands and
Frequency
PSTN
(Plain Old
Telephone
Service )
UPSTREAM
DOWNSTREAM
Frequency plan for ADSL. The red area is the frequency
range used by normal voice telephony (PSTN), the green
(upstream) and blue (downstream) areas are used for ADSL.
BANWIDTH NOTATION
Monthly quota of data.
Upload/download.
Monthly bandwidth allowance will be measured in
Megabytes or Gigabytes.
The amount of bandwidth you need depends on how
frequently use the internet.
SETUP PROPERTIES of ADSL
Physical connections.
Modem synchronization.
Computer network
configurations.
Modem Configuration.
Ip Control.
Connection Control
ROUTING and SECURITY
ROUTING
Device.
A router allows you to connect one
or more computers or one or more
networks onto the ADSL service.
Many routers have built in
switches that allow you to plug
your computer directly into them
Sharing an Internet connection.
ROUTING and SECURITY
SECURITY
Change the user name and password after first
configuration.
Change the port which is used for access to modem
settings.
Activate the firewall applications.
Use Ethernet+Router+USB Adsl modems.
Do not use USB Adsl modems.
Use antivirus software programs.
Update the antivirus programs.
WIRELESS ADSL
Without any cable it provides broadband data transfer.
This service using at hotspots such as airports, hotels,
shopping centers, universities, conference halls etc.
If you have WLAN technology in your laptop, phone or
etc. You can use this service.
If you don not have this technology in your pc you can
take a card that has the wi-fi (wireless fidelity ) capability
and fix it to your pc than you can use this service.
Uses access point which is a wireless access device to
spread the adsl connections.
VDSL
Very high bit-rate Digital Line Subscriber.
Next generation DSL.
Entire home-entertainment package .
Very high bandwidth.
Shorter distance, faster connection.
Coding based on Discrete Multitone (DMT) and
Quadature Amplitude Modulation (QAM).
Is not literally deployed yet
CABLE MODEM
CMTS: Cable Modem Termination System
CATV: Community Antenna Television or Cable TV system. Can be
all coaxial or HFC (Hybrid Fiber Coax) based.
CABLE MODEM
Provides high-speed Internet access through a cable
television network.
TV cables provide much higher bandwidth.
Upstream/downstream.
Asymmetric.
Coaxial cable line.
It can be external devices nearly computer or integrated
within a computer .
“Always on” connection.
ADSL vs CABLE MODEM
Speed.
Availability.
Bandwidth.
Time for getting the service.
Installation.
Service.
Cost.
Hardware requirements.
Security.
WAP/GPRS
WAP (Wireless Application Protocol ).
Allows users to access information instantly with
handheld wireless devices.
Internet content in special text format.
Low-bandwidth.
Uses WML format for small screens and one-hand
navigation without a keyboard .
GPRS
GPRS (General Packet Radio Service).
Uses existing GSM network.
Transmit and receive data from GPRS mobile devices.
Runs at speeds up to 115 kilobits per second.
Supports a wide range of bandwidths.
Efficient use of limited bandwidth.
Provides “always online” connection.
GPRS
Thank you for Listening.
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