The physical means by which data is transmitted from one geographic or electronic location to another is called transmission, or "communication" media. There are two categories of transmission media used in network communications.
- Bounded or guided media
- Unbounded or unguided media
Bounded Media
Bounded media are physical cables that signals travel through on a narrow path. Also known as guided media, bounded media are made up of an external conductor [usually copper] wrapped in a jacket made of nonconductive material. Bounded media are great for in-lab communications because they offer high speeds, are more secure than unbounded media and are low-cost. A downfall of bounded media are the distance constraints; one can only use bounded media as far as they can afford cable, and attenuation can prevent connections over longer distances.
Common Types
Three common types of bounded media are used in data transmission. These are:
- Coaxial Cable
- Twisted-Pair Cable
- Fiber Optic Cable
Coaxial cable
1. Coaxial Cable
Coaxial cable is a widely used type of transmission media. For example, a TV wire is usually coaxial.
Coaxial cable is named after the two conductors that run parallel to each other. The center conductor in the cable is usually copper, which is usually either a solid wire or stranded, twisted copper.
Outside this central conductor is a non-conductive material called a dielectric insulator. It is usually a white, plastic material used to separate the inner conductor from the outer conductor. The other conductor is a fine mesh made from braided copper. It is used to help shield the cable from electromagnetic interference, or EMI. Wrapped outside the copper mesh is the final non-conductive protective cover.
The actual data travels through the center conductor in the cable. EMI is "caught", or redirected, by the outer copper mesh. There are different types of coaxial cable that vary by gauge and impedance.
"Gauge" is the thickness of a given cable. It is measured by the radio guide measurement or RG number. The higher the RG number, the thinner the central core conductor. The lower the RG number, the thicker the core conductor.
The following are the most common coaxial standards:
- 50-Ohm RG-7 or RG-11: Used for thick Ethernet or "thicknet".
- 50-Ohm RG-58: Used for thin Ethernet, or "cheapernet".
- 75-Ohm RG-59: Used for cable television.
- 93-Ohm RG-62: Used for ARCNET.
Advantages
- low cost
- easy to install
- easy to expand
- up to 10 Mbps [megabits of data per second] capacity
- medium resistant to EMI
Disadvantages
- Single cable failure, also known as a single point of failure, can take down an entire network.
- Coaxial cable is an attenuating medium that results in a gradual weakening of transmission the further data gets from the point of origin.
What Is Crosstalk?
Crosstalk is the unintentional transfer of signals from one channel to another channel, creating interference.
STP
UTP
2. Twisted-Pair Cable
The most popular network cabling is twisted-pair cabling. It is light-weight, easy to install, inexpensive, and supports a variety of networks. In addition, it supports a data speed of up to 100 Mbps. Twisted-pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are to reduce vulnerability to EMI and crosstalk. The number of pairs in the cable depends on the type of cable.
The copper core is usually 22-AWG or 24-AWG, as measured by the American Wire Gauge standard. AWG is the U.S. measurement standard for the gauge of the conductive core in wiring. There are two types of twisted-pair cables:
- Unshielded twisted-pair [UTP]
- Shielded twisted-pair [STP]
2.1 Unshielded Twisted-Pair [UTP]
UTP wiring is more common than STP. UTP can be either voice-grade or data-grade. UTP cable normally has an impedance of 100 Ohms. UTP cost less than STP and is easily available due to its many uses. There are five levels of data cabling for UTP cabling:
- Category 1: These are used in telephone lines and low-speed data systems.
- Category 2: These cables can support up to 4 MPS implementation.
- Category 3: These cables support up to 16 MPS and are mostly used in 10 MPS environments.
- Category 4: These are used for larger distances and high speeds. It can support 20 MPS.
- Category 5: This is the highest rating for UTP cable and can support up to 100 MPS.
UTP cables consist of two or four pairs of twisted cable. Cable with two pairs uses RJ-11 connectors and four-pair cables use an RJ-45 connector.
Characteristics of UTP
- low cost
- easy to install
- high-speed capacity
- high attenuation
- effective to EMI
- 100-meter limit
Advantages
- easy installation
- capable of high speed for LAN
- low cost
Disadvantages
- short-range capability due to attenuation
2.2 Shielded Twisted-Pair [STP]
STP is similar to UTP but has a mesh shielding that protects transmissions from EMI. This allows for a faster transmission rate.
IBM has defined categories for STP cable:
- Type 1: STP features two pairs of 22-AWG.
- Type 2: This type includes type 1 with 4 telephone pairs.
- Type 6: This type features two pairs of standard shielded 26-AWG.
- Type 7: This type of STP consists of 1 pair of standard shielded 26-AWG.
- Type 9: This type consists of shielded 26-AWG wire.
Characteristics of STP
- medium cost
- easy to install
- higher capacity than UTP
- higher attenuation, but same as UTP
- medium immunity from EMI
- 100-meter limit
Advantages
- shielded
- faster than UTP and coaxial
Disadvantages
- more expensive than UTP and coaxial
- more difficult installation
- high attenuation rate
What Is Cladding?
Cladding is a layer or multiple layers of a material with a lower refractive index in contact with the core material of the transmission media to eliminate EMI and increase the speed of data transmission.
3. Fiber Optic Cable
Fiber optic cable uses light signals to transmit data. In fiber optics, light only moves in one direction, so for two-way communication to take place a second connection must be made between the two devices. To accomplish this, fiber optics are manufactured with two strands of cable running in parallel. Each strand is responsible for one direction of communication. A laser on one device sends pulses of light through this cable to the other device. These pulses translated into “1’s” and “0’s” at the other end. A response is sent from the receiving computer through the parallel cable.
In the center of fiber cable is a glass strand or core. The light from the laser moves through this glass to the other device. Around the internal core is a reflective material known as cladding. No light escapes the glass core because of this reflective cladding.
Fiber optic cable has a bandwidth of more than 2 Gbps [gigabytes per second].
Characteristics of Fiber Optic Cable
- expensive
- very hard to install
- capable of extremely high speed
- extremely low attenuation
- no EMI interference
Advantages
- fast
- low attenuation
- no EMI interference
Disadvantages
- very costly
- hard to install
As you can see, transmission media can seem complex but can really be broken down into neat categories. Please leaves questions or comments below regarding the transmission of data and media!
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Comments
kuma on June 29, 2019:
that cool
Lil j on February 26, 2019:
Good info
Bright on January 30, 2019:
please the authors details... i want to cite this article
gudmankinga on January 16, 2019:
Good Work
silly mshamu on January 12, 2019:
how about unguided
chandrakantraval9599@gmsil.com on January 06, 2019:
easy to understand.........and also very clear concept.thanks.
Fari on November 07, 2018:
Easy to understand
Thanks...
John ojwang on October 29, 2018:
smart notes
nikhil on October 14, 2018:
good notes
Ayushi on August 06, 2018:
Perfect answer
Vedansh on July 24, 2018:
Perfect explination
ria on July 09, 2018:
easy to understanding...thank you for the notes
manju on July 08, 2018:
Good
Adeel on July 05, 2018:
helpful
manas on June 29, 2018:
good explain..
Addis berhanu on June 11, 2018:
what about unbounded data transfer
harsh AWANA on June 05, 2018:
I need information about transmission media ,not their type. It is need to write more about transmission media. but other content are good .
percy st on May 31, 2018:
good notes
leo on May 22, 2018:
good explaining...
peter on May 16, 2018:
good
Aghdngth on April 28, 2018:
Awesome
Tuwee on April 23, 2018:
Awesome
kkkmm on April 21, 2018:
Really............
it is very help full
thank u very much............
it is very outstanding explanation............
sour candy on April 16, 2018:
nice notes they are helping
learner on April 07, 2018:
plz what does EMI stands for !!
jj on April 06, 2018:
nice
muthu on February 11, 2018:
Excellent
karkik on February 01, 2018:
awesome
jamshid on January 19, 2018:
nice note thanks
kk on January 04, 2018:
nice
timmo on October 04, 2017:
great site
ahmad on September 06, 2017:
where is unbounded media
A on September 05, 2017:
Nice
harshitabansal on September 03, 2017:
where is unbounded media define?
ken on June 22, 2017:
nice
Sharan Shrestha on April 30, 2017:
Great Answers,It was the best .And, I like it very much.
GASPER ANDREW BAKARI on April 25, 2017:
NICE ANSWER
swaggy on April 25, 2017:
Where is the defination of unbounded
radadiyagopi13@gmail.com on March 09, 2017:
nice to transmission media and very easy contain
radikhukhwane on March 08, 2017:
not bad all
Bedahn Niwampa on December 04, 2016:
its so nyc and it makes one understand much better,thx alot
baalagajakreedan on December 03, 2016:
Nice notes
blob:54B52A6A-3840-4DFE-A74F-9759EFDA8A16 on November 16, 2016:
nice
saruni on October 12, 2016:
cheers..simle and clear
ankita on October 07, 2016:
Simple n grt notes
Saniya memon on September 24, 2016:
Very nice explanation..
s samridha on September 02, 2016:
good explanation
Singh Sneha on August 03, 2016:
Nice answer! It is very easy to understand transmission media in networking..
Pradeep on July 28, 2016:
A good tute.. butr doesn't have unguided media as it mentioned in the topic
m dodo on July 22, 2016:
thanks
Levis Andrew sui on July 21, 2016:
Thanks finding very useful,,, but information about Unbounded is not being added
bbvines on June 28, 2016:
thank u
piyush singh on June 09, 2016:
It is good but give full information
killer982839429994392293939920993939 on February 22, 2016:
thnx
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cinna on July 23, 2015:
it was good in terms of understanding but u seriously need to work on ur english
mark on June 15, 2015:
nice
Ibtu on February 07, 2015:
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nikhitha on October 19, 2014:
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21 months ago
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Easy to understand
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Exellent theory
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wah.... ye notes to mere kapdo ki trah bhut kam h...
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nik sharma on March 30, 2013:
gud, but not full information....
Basharat Toori on March 27, 2013:
Its too much easy to understand Trasmission Media , but it will be more fabulous if Unbounded Media notes were also posted.