Transmission Media Prepared by: Engr. Maria Diorella A. Paguio.
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Transcript of Transmission Media Prepared by: Engr. Maria Diorella A. Paguio.
Transmission MediaPrepared by: Engr. Maria Diorella A. Paguio
The Basic Idea
Encode data as energy and transmit energy
Decode energy at destination back into data
Energy can be electrical, light, radio, sound, ...
Each form of energy has different properties and requirements for transmission
Data Transmission
Simplex transmission Refers to one way transmission where
one party is the transmitter and the other is the receiver
Example: simple radio
Data Transmission
Half duplex transmission Refers to two way communications
where only one party can transmit at a time
Example: walkie-talkie
Data Transmission
Full duplex transmission Refers to the transmission of data in
two directions simultaneously Example: telephone is a full duplex
device because both parties can talk at once
Transmission Methods
• Data is presented by binary digits, 1 and 0, also called bits. Serial transmission
In serial transmission, bits are sent sequentially on the same channel (wire) which reduces costs for wire but also slows the speed of transmission.
Examples of serial mode transmission include connections between a computer and a modem using the RS-232 protocol.
Transmission Methods
Parallel Transmission In parallel transmission, multiple bits (usually
8 bits or a byte/character) are sent simultaneouslyon different channels (wires,frequency channels) within the same cable,or radio path, and synchronized to a clock.
Examples of parallel mode transmission include connections between a computer and a printer (parallel printer port and cable).
Transmission Media
WIRED TRANSMISSION MEDIA Physical channels or paths that carry
the signal or message from the sender to the receiver
Example: copper wires, twisted pair wires and coaxial cables
Transmission Media
Copper Wires Preferred due to
its low resistance to electric current, which enables signals to travel faster
Transmission Media
To minimize interference, networks use one of two basic wiring types:
Twisted pair Coaxial cable
Transmission Media
Twisted pair wire The most common
form of cable today Used to connect
telephone subscribers to exchanges (switching enters) and wire building)
Used to interconnect PC’s on a Local Area Network (LAN)
Transmission Media
Twisted pair wire Each twisted pair wire is actually two
insulated copper wires twisted around each other.
They are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs.
Transmission Media
Twisted pair wire Other services which makes use of twisted pair
wires: POTS
Public Old Telephone Service Permits voice conversations and digital transmissions with the aid
of a modem Also referred to as PSTN or Public Switched Telephone Network
ISDN Integrated Services Digital Network A digital service
ADSL Asymmetric Digital Subscriber Line Receive data over POTS lines at 1.5 to 9 Mbps
Transmission Media
Twisted pair wire Two forms of twisted pair: Unshielded
and Shielded Twisted PairUTP (unshielded twisted pair) Cable which has no ground shield Two conductors are coated with a plastic
sheath then twisted around each other
Transmission Media
UTP (unshielded twisted pair) Advantages:
High installed base Inexpensive to install Easy to terminate
Disadvantages: Very noisy Limited in distance – 100m Suffer from interference
Transmission Media
STP (Shielded twisted pair)
Shielded twisted pair is a special kind of copper telephone wiring used in some business installations.
An outer covering or shield is added to the ordinary twisted pair telephone wires; the shield functions as a ground.
Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company.
Maximum Length – 100m
Transmission Media
Coaxial Cable More commonly known as the wiring used for cable
TV Permits high speed data transmission with a
minimum of signal distortion because it provides greater protection from interference than twisted pair
Consists of a single wire surrounded by heavier metal shield which surrounds the center wire uniformly on all sides, making it a more effective barrier to electromagnetic radiation
Maximum length: 200 meters – thin 500 meters - thick
Transmission Media
Coaxial Cable Advantages:
Inexpensive to install
Conforms to standards
Widely used Greater capacity
than UTP
Disadvantages: Limited in distance Limited in number of
connections Costly compared to
twisted pair wires and copper wires
Terminations and connections must be done properly
Utilizes air as channel for carrying the signals in waveform
Utilizes signal generation devices from source and destination endpoints
Transmission Media
WIRELESS TRANSMISSION MEDIA Utilizes air as its channel for carrying
the signals in waveform Utilizes signal generation devices from
the source and destination endpoints
Transmission Media
Microwave System
The transmission of these signals is line of sight, meaning there should be no physical obstacles between the sending and receiving devices
Transmission Media
Microwave System Advantages:
Medium capacity Medium cost Can go long distances
Disadvantages: Noise interference Geographical problems due to line of
sight requirements
Transmission Media
Orbital satellite transmission
Satellite systems are comprised of ground based transmitter and receiver dishes, with an orbital satellite circuit (called a transponder)
Signal are transmitted to the orbiting satellite, which relays it back to another ground station
Transmission Media
Orbital satellite transmission Advantages:
Low cost per user (for PAY TV) High capacity Very large coverage
Disadvantages: High install cost in launching a satellite Receive dishes and decoders required Delays involved in the reception of the
signal
Transmission Media
Very Small Aperture Terminal (VSAT)
An earthbound station used in satellite communications of data, voice and video signals, excluding broadcast television
Can handle up to 56Kbps
Transmission Media
Very Small Aperture Terminal (VSAT)
Consists of two parts: Transceiver: placed
outdoors in direct line of sight to the satellite
Device: placed indoors to interface the transceiver with the end user’s communications device, such as PC
Transmission Media
HIGH SPEED WIRELESS COMMUNICATION T-carrier system Introduced by the Bell System in the U.S. in
the 1960’s First successful system that supported
digitized voice transmission Entirely digital, using pulse code modulation
and time division multiplexing Uses four wires and provides duplex capability
(two wires for receiving and two for sending at the same time)
Transmission Media
T1-carrier system Dedicated phone connection support data
rates of 1.544Mbits per second Consists of 24 individual channels, each
of which supports 64Kbits per second Popular leased line option for business
connecting to the internet and for internet service providers (ISPs) connecting to the internet backbone
Sometimes referred to as DS1 lines
Transmission Media
E1 The European format for digital
transmission Carries signals at 2Mbps (32
channels at 64Kbps)
Transmission Media
Digital signal X Term for the series of standard
digital transmission rates or levels based on DS0, a transmission rate of 64 Kbps, the bandwidth normally used for one telephone voice channel
Transmission Media
Wireless connections Wireless transceiver provides an
alternative to running a permanent physical line
Used to link these devices: Desktop PC and laptop PC PC and local area network (LAN) PC and mainframe computer Terminal and multiplexer Laptop PC and large printer
Transmission Media
GLASS-BASED TRANSMISSION MEDIA
Fiber optic cable: light pulse Used to transport data as laser generated
pulse of light A single fiber can carry over 32,000 voice
and data transmission, the equivalent of 2.5 billion bits per second
More secure than electronic signals over a wire
Transmission Media
Fiber optic cable: light pulse
Advantages: High capacity Immune to
interference Can go long
distance Disadvantages:
Costly Difficult to join
Transmission Media
Fiber optic cable: light pulse
COMMON CARRIERS: DEDICATED LINE OR DIAL UP LINE
Dedicated Line A telecommunications
path between two points that is available 24 hours a day for use by a designated user
Physical path owned by the user or rented from a telephone company, in which case it is called a leased line.
Dial - up Line Sometimes called
switched line Telephone connection
in a system of many lines shared by many users
Established and maintained for a limited time duration
-END OF PRESENTATION-