Data Transmission. from one person or place to another. person or place to another of passing something

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Data Transmission

Transmission: the process of passing something from one person or place to another of passing something

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Data Transmission

• _{Main types of Transmission} • _{Dual use of Voice and Data}

• _{Wireless communication methods} • _{Connections to the Internet}

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Types of Transmission

• _Unicast

– Data is sent to only one recipient

• _Multicast

– Same data sent to a group of people

• _Broadcast

– _{Data is sent to everyone who wishes to receive}

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Voice and Data Transmission

Both Local Area Networks and Wide Area

Network cables or Wireless links can be used to transfer computer data and voice messages at the same time.

This can save a company money as it only need one set of cables for an internal phone system or can use the Internet for Phone calls

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LAN Voice and Data

• _{The cables on a LAN can also be used to}

provide a internal telephone network

– _{Saves money and disruption as only 1 set of}

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WAN Voice and Data

• _{WAN computers use the public telephone lines to}

transfer data

• Can be set up to carry either:

– Voice OR data signal (standard dial up)

or

– Voice AND data (Broadband, ADSL, ISDN)

The cables that form the backbone of the Internet are

complex enough that they can carry

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Wireless Communications

Transmission of data around a network WITHOUT cables

• _{Easier to change the network layout as}

there are NO cables to install

• _{More flexible work place}

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Types of wireless networking

• _{WPAN - Wireless Personal Area Network}

– network operates over a small area e.g. between a laptop, portable printer and PDA (‘Bluetooth networks <30m)

– Usually one or two users at most at anyone time

• _{WLAN – Wireless Local Area Network}

– Multiple users

– Usually a single office or building

– Uses infrared or radiowaves

• WWAN – Wireless Wide Area Network

– Operates over a very wide area

– Often need ‘line of site’

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Connecting to the Internet

Different ways of connecting:

• _{Dial-up modem} • _ADSL

• _ISDN

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Dial up

• _{Requires a MODEM}

– (MODulator/DEModulator) A piece of hardware to transfer the computer signal to the telephone network and vice versa.

• _{Digital computer signal is converted to an}

analogue signal for transfer on the telephone lines.

• Slowest way of connecting to the Internet

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ADSL

• _{Asynchronous Digital Subscriber Line}

• _{Uses a telephone line and an ADSL modem} • _{Telephone line can be used at the same time}

as data transfer

• _{Some areas do not have ADSL coverage}

• _{Commonly known as BROADBAND}

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ISDN

• _{Integrated Services Digital Network}

• _{Voice and Data can be sent on the same}

telephone line

• _{Different speeds are available}

• _{Faster than dialup but not usually as fast as}

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Cable Modem

• _{Uses Cable television cables to transfer data}

• _{Requires a Cable MODEM}

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Leased Line

• _{A dedicated telephone line which is rented}

by an organisation

• _{Permanent data connection between two}

locations

• _{Data can be kept very secure} • _{Fixed monthly fee}

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Broadband

Broadband is a general term that is used to describe an Internet connection that is faster than Dialup

• _{Most commonly used for ADSL or CABLE}

Modem connections

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Advantages and disadvantages

•Limited availability

•Speed can vary

•Affordable

•Shares telephone

line

•Wide variety of

speeds and prices

•Choice of providers

ADSL

•Slow

•Connection not

‘always on’

•Using modem ties

up the phone line

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•Limited availability In UK

•Sharing with

neighbours poses a security risk

•Usually for home

users •Relatively inexpensive Cable Modem •Can be difficult to set up

•Not practical for

more than 10 computers

•Does not tie up

phone line

•Usually faster than

56k

ISDN

Disadvantage Advantage

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