Transmission Medium

From the observation of “Network+ Guide to the Network” (pg75) transmission medium is a material medium that can transfer energy waves. Examples, sound use air and liquids particle as a transmission to travels. In ancient time, people transmitted information across distance by using animal, smoke, fire etc. These days, transmission medium allows the data travels through a network. With a single click, you can send the data to your destination in a short period. Transmission medium play an important role in the internet world. Data transmission can be transmitting via two type of signaling method there are analog signal and digital signal. Analog signal is continuous signal represent varying quantity which the time varying feature (variable) of the signal, the signal easy get noise interfere.

Analog signal depend the result in random medication that degrade signal quality, and can cause errors. Digital signal is physical signal that represent sequence value positive voltage present a 1 and negative voltage present a 0, the signal cannot interfere by the noise. Digital signal depends on the result in bit error (Dean, 2010). (http://www.dia.unisa.it) Chapter4 transmission medium explain that transmission media basically split into two types: bounded (guided) and unbounded (unguided) media. Bounded (guided) media given a physical path (cable) to the signal to transmit, these include twisted pair, coaxial cable and optical fibre. Unbounded (unguided) media does not have physical path or medium to control or contain signals. Therefore, no boundaries present, these include microwave, satellite, radio etc. This topic mainly explains 3 bounded (guided) and 3 unbounded (unguided) media about the performance, applications, advantages and disadvantages. (Anon., n.d., p. 75)

Bounded (guided) media

Twisted Pair (TP)
From the (http://en.wikipedia.org/wiki/Twisted_pair) Twisted Pair article explain that the twisted pair is a copper wire with color- coded. Twisted pair often “bounded” into the cable. Twisted pair consist 4 pair of copper wire each pair was twisted together for the purposes of preventing unwanted electrical coupling of two copper and crosstalk. Twisted pair divides into two types: shielded and unshielded TP. UTP contain 4 pair insulated copper wire encased in a plastic sheath. In other word, UTP does not have any additional shield to protect the wire to prevent the electromagnetic interfere. However, STP is shielded by metallic substance such as foil; even some are shielded by braided copper. As a result, STP capable of noise resistant, not only that it also increase the data rate and bandwidth. (Anon., n.d.)

Image of UTP

Image of ST
Application
William Stallings Data and Computer Communication 7th Edition explain twisted pair commonly use by most ISP as a medium for Ethernet. It connected with telephone network between house and local exchange for subscriber loop. Twisted pair commonly use to LAN network for short distance data transmits. The range will not excess within a building. Twisted pair carry analog signal, its need a modem of modulate analog signal to digital signal. Amplifiers needed every 5 or 6 km until the signal reach the destination. The speed will slow down when exceed range limited. (Dean, 2010)

Performance
I learn that TIA/EIA designed seven type of cabling system to standardize twisted pair on modern network. (Dean, 2010) -Cat 3 (Category3)
-Cat 4 (category4)
-Cat 5 (category4)
-Cat 5e (Enhanced category 5)
-Cat 6 (category 6)
-Cat 6e (Enhanced category 6)
-Cat 7 (category 7)
Each cabling system each has difference speed and unique function.

Cat 3- A UTP contains four wire pair and 10-Mbps for maximum speed with 16 MHz bandwidth. Cat3 commonly use in 10-Mbps Ethernet or 4-Mbps token ring network. These day, Cat3 have been replace by Cat5 due to better cabling accommodate higher throughput. Cat 4- UTP contains four wire pair up to 16-Mbps maximum throughput. Now days, Cat4 unpopular install in network, they might be found in older generation 16-Mbps token ring. Signal is trusted at maximum 20 MHz and high resistant crosstalk and attenuation than Cat3. Cat 5- Four wire pair form of UTP provides 1000Mbps throughput with 100-bandwidth. Some of Cat5 are STP. Punch down blocks and modular connectors commonly using Cat5 cabling system. Cat 5e- An upgraded-version of Cat5 wiring. Cat5e provides high-quality copper, high twist ratio, and resistant crosstalk. It’s get a triple signalling rate as 350 MHz compared original Cat5. Cat 6- 4 pair of wire in UTP covers with foil insulation. The foil insulation help provide higher crosstalk resistant compared to Cat4, Cat5 and Cat5e. It also support 250-MHz signaling rate.

Additional foil cover consist two layers, the first layer bundle with wire pair as protection; the second layer provides fire resistant. Cat6 performance suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), 1000BASE-T/1000BASE-TX (Gigabit Ethernet) and 10GBASE-T (10-Gigabit Ethernet). Cat 6 e-High-grade version of Cat 6. Compared to Cat 6 it has a better resistant crosstalk and reduces attenuation; allow the limits exceeding traditional network segment network. Cat 6e’s performance up to 550 MHz signal rate reliable transmits data at multi-Gigabit per second rate. Cat 7- Also known as Ultra fast Ethernet, contain multiple wire pair “specifics general-purpose telecommunication cabling system (structure cabling) that are suitable for a wide range of application. The cable is covered by shielding. Although standards not yet finalized for Cat7, some companies are selling it, and some organization are installing it. Cat 7 provides the highest signal rate up to 1 GHz. But sadly Cat 7 need a different connector than other version of UTP due to the twisted pair more isolated from each other to prevent cross talk.

Advantage
From the (http://wiki.answers.com) Wiki Answer Explain the advantage and disadvantage of twisted pair. (Anon., n.d.) Easy installation
Due to the flexibility and thin wire it is easy to bend and string between walls. Wiring ducts allow multiple lines running through. Inexpensive cost

UTP is the cheapest costs per meter/inch than any type cable. High availability
Most of the telephone subscriber based on twisted pair to connect. Twisted pair available as long there are telephone line.

Disadvantage
Limited frequency
The maximum of usable frequency id about 1MHz the lowest compared to others transmission media. Limited range transmission
The data transfer rate will slow down if the range getting higher. The data rate will drop to 2Mbps or less every 5 or 6 km. That’s why it needs amplifiers or repeater every 5 or 6 km.

Coaxial cable
From (http://en.wikipedia.org/wiki/Coaxial_cable) “Coaxial cable” I learn coaxial cable is type of wire that are cover by insulation on the inner layer and the grounded shield of braided wire on the middle layer lastly the sheath or jacket on the outer layer . Shield is use for noise resistance and radio frequency interference. Coaxial cable can carry the signal father than twisted before amplifier required, but it’s more expensive over twisted pair per meter/inch. Back in 1880 A English engineer and mathematician Oliver Heaviside who invented the coaxial cable. Now days coaxial cable commonly used by television industry and Ethernet. Although it is more expensive than twisted pair, it got more noise resistance and higher signal rate. (Anon., n.d.)

Image of coaxial cable

Application
(http://en.wikipedia.org/wiki/Coaxial_cable#Applications) Coaxial cable mainly explain the reason coaxial cable is commonly use as cable TV (ex.astro) and Ethernet is because it used frequency signals as a transmission line. The feedlines connecting receivers with their antennas homes and businesses are including in its application. The reason coaxial cable is better than other types radio transmission line is that the cable only carry signal that exist in the space between inner and outer conductors. “This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines” (http://en.wikipedia.org/wiki/Coaxial_cable#Applications). (Anon., n.d.) Performance

(http://en.wikipedia.org/wiki/RG-6),( http://en.wikipedia.org/wiki/RG-59) Coaxial cable(RG) say that when talk about the performance, we have to refer to the American Wire Gauge (AWG). The smaller the diameter of the wire the larger the AWG . RG come with 4 sizes (Anon., n.d.) – (RG-6)

– (RG-8)
– (RG-58)
– (RG-59)
RG-6: they are made of solid copper with 75 ohm characteristic impedance and 18 AWG conducting core. RG-6 has two functions, provides broadband cable internet service and cable TV. RG-6 is commonly recognized breed of cable television (CTV) distribution coax, used to within the house it used router cable television signal. RG-8: A type of coaxial cable support 50-ohm characteristic impedance and 10 AWG central cores. The first medium of Ethernet’s network was provided by RG-8 whit the now-obsolete 10Base-5 standard. 10Base-5 with maximum 10 Mbps throughput and segment length 500m. Thicknet is another name of 10Base-5. Although thicknet was used in the older generation of network, thicknet was never found in the modern network. RG-58: A type of coaxial cable with 50 ohm characteristic impedance and 18 AWG conducting core. Back in 1980s, RG-58 was commonly use for Ethernet LANs. Compared to RG-8, RG-58 has a smaller diameter, more flexible and easier to handle and install.RG-58 followed the 10Base-2 standard- 10 baseband transmission (Mbps) with segment length 200m. It also known as thinnet because thinner than the thicknet. Thinnet share the same fate of thicknet never seen in modern network, you only encounter thinnet back in 1980s.

RG-59: A type of coaxial cable with 75 ohm characteristic impedance and 20 or 22 AWG central core. RG-59 commonly used at baseband video frequencies, like composite video. Although RG-59 can be used for broadcast frequencies, it suffer the risk of high-frenquency losses when use over long distance. Compared to RG-6, RG-59 has a greater attenuation.

Advantage
Present of broadband system
Coaxial cable send and receive data at the has a ample frequency range to support multiple channels, which allow a greater performance. Good bandwidth
Coaxial cable provides greater bandwidth systemwide for every channel. As a result, it can provides a mixed range services. The things that benefit from enhanced capacity are video, data, voice and multimedia. Longer spacing between amplifiers

Noise and crosstalk is reduces by the coaxial cable’s shielding, that’s mean the space between amplifiers longer than twisted pair. Lower error rate

Because the second shielding layer has greater noise resistant and reducing crosstalk, the performance is slightly better than the twisted pair.

Disadvantage
Expensive costs
The costs of installation and the cable per inch/meter are high. Risk to damage from lightning strikes
Coaxial cable easy get damage from lightning strikes due to lightning is conducted by a coax.

Fiber-optic
From Network+ Guide to Network Chapter3, pg105 I learn that fiber-optic is a type of cable that made of plastic or glass (silex), allow the light travel through the fiber-optic cable. Data can sent through with very high speed because of fiber-optic is light-based. Fiber-optic are high noise resistant and less interference than other transmission medium because it based on beams of light. Because fiber-optic given the transmission over long distance and greater bandwidths than other transmission medium such as twisted pair and coaxial cable, it is widely used in communication. The idea of fiber-optic using glass/plastic as a core of transmission is to prevent the signal when travel and resistance to electromagnetic interference. However, the cost of installation is expensive and the cable usually hide underground due to the core is weak easy to broke. Image of bundle fiber-optic

Image of encased fiber-optic

Application
(http://en.wikipedia.org/wiki/Optical_fiber) “Application of fiber-optic” say that because fiber-optic flexible, high speed transmission and can use as cable it is widely use medium of telecommunication and computer networking. It’s great for distance communication because it is light-based communication, reduce the number of amplifiers needed. When come to short distance, fber-optic (LAN/MAN) capable carry massive data compared to electrical cable. Data will transmit to the destination in secure.

Performance
All fiber-optic’s mutation split into two categories:
* (single-mode)
* (multimode)

Single-mode (SMF): From (http://en.wikipedia.org/wiki/Single-mode_optical_fiber) Single-mode article I knew that SMF is a type of optic used a very narrow core (almost near to hair thickness). The narrow core cause the light signal travel through one path with little reflecting. Because of the narrow reflecting, the light did not distribute signal while travel through fiber. As result, SMF has the greatest bandwidth and distant of all network transmission media. That is why SMF is widely use for distance communication. Because of the costs of installation is too high, it is uncommonly use for short distance network (LAN/WAN).

Multimode (MMF): (http://en.wikipedia.org/wiki/Multi-mode_optical_fiber) Multimode fiber-optic’s article Explain MMF is a type of cable that use a wider core between 15 and 115 micro diameter. Because the core is wider, the transmit speed is slower than SMF because it travel multiple path. MMF has a very high noise resistant and prevent crosstalk. MMF can be split to two types: graded-index and step-index. We use the refraction index between core and cladding. Graded index change the index between core and cladding. Step index straight forward reflection.

Advantage
Massive bandwidth
When it comes to bandwidth, no one can better than fiber-optic. High resistance noise
Fiber has very high noise resistant because fiber has a very low rate of bit error (10 EXP-13). Disadvantage
High cost
Fiber costs the most in transmission media. Although the price of installation drop almost 60% per year, it still costly.

Test equipment require
Sometimes special test equipment required to test the fiber networking system.

Unbounded (unguided) media
Microwave
From(http://en.wikipedia.org/wiki/Microwave) “Microwaves article” Microwave are radio waves with the range between one meter and one millimeter, frequencies between 0.3 GHz and 300GHz. Microwaves are generate by high- power vacuum tube. Same as light wave, microwaves travel in straight lines.

With the range one meter, the receiver must be close to the microwave tower. Microwaves send analog signal through atmosphere and the receiver receive data and modulate to digital signal. Image of microwaves

Name| Wavelenght| Frequency| Photon Energy|
Microwave| 1mm-100,000km| 300 Ghz-3 Hz| 1.24 meV-12.4 feV|

Application
Microwaves tower sending television signal, telephone, and data transmit between the earth satellites. Military use microwaves the locate ships and planes because the beans are short pulses. Not only that, it also can measure the speed of a moving objects. Sometimes when microwave might encounter some metal object reflect them to another direction cause the signal interfere. The range from one microwave tower to another must be line of sight due to the short range and straight line transmission. (Anon., n.d.)

Performance
The electromagnetic energy ranging from 1GHz to 100GHz frequency defined as the microwave spectrum. Most common application within 1 to 40 GHz range.
Table of frequency band
L band| 1-2 GHz|
S band| 2-4 GHz|
C band| 4-8 GHz|
X band| 8-12 GHz|
Ku band| 12-18GHz|
K band| 18-26.5 GHz|
Ka band| 26.5-40 GHz|
Q band| 33- 50 GHz|

Microwave and millimeter wave power can amplification with watt power range from 50 to 200. It’s high amplification from S band through Q band. It driven the transmission speed to another level. (Anon., n.d.) Advantage

Absent of cable
Cable does not needed for microwave no installation required. Multiple channels available
Microwave can transmit through many channels at the same time, allow transmission speed faster. Large Bandwidth
Provides wide bandwidth for the user preventing “traffic jam”.

Disadvantage
Line of sight interfere
Some transmission interfere like tall building in the way might cause signal loss. (Anon., n.d.)

Weather interfere
Bad weather like raining will cause the signal loss.
High cost equipment
Equipment like microwave tower is costly to build

Satellite
From (http://en.wikipedia.org/wiki/Satellite) Satellite also known as transponder that accepts signal from the earth. User’s receiver like smart phone communicate and request data from the satellite; earth stations communicate by sending signals on an uplink, then on the downlink satellite repeats those signal. Satellite change the signal to another frequency then amplifies signal and send back to earth station. Because of the sending path distance, satellites needs large amount of power to transmit the data. Image of satellite

Application
Satellite is widely use in television distribution, direct broadcast satellite (DBS) allows the program like football match broadcast to any place at the same time. Satellite also has a network that provides provides programming from a central location. Satellite also widely use for long distance communication (oversea), commonly use by international trunks for transporting trunks to another country.

Performance
The performance fall into three types
* Geosynchronous earth orbit (GEO)
* Middle earth orbit (MEO)
* Low earth orbit (LEO)

Geosynchronous earth orbit (GEO): A type of satellites with 22, 300miles above the ground with delay 0.25/leg. Because of the distance, it requires the most power for signal transmit. GEO follow the rotation of earth and the speed almost same as the earth. As result, GEO keep stick in one place. Each satellites cover 33.333% of the earth, total up 3 satellites can cover up the earth. Middle earth orbit (MEO): A type of satellites between 6,200 and 9,400 miles above the earth with delay 0.05/leg. Now days widely use for GPS, low-speed data and mobile voice. Because it got smaller footprint, MEO required 10-15 satellites to cover the earth. Low earth orbit (LEO): A type of satellites that closest to earth (400-1,000 miles above earth). Because LEO closest to the earth, it has the least amount of delay 0.025 second/leg. LEO only needs less amount of energy to transmit data. It also has the smallest footprint requires 60 satellites to cover earth.

Advantages
Access to remote areas
As long as the signal is available satellites can be access any time.
Cover large geographies
Satellites allow the user connect at any place.
High bandwidth
Allow users have a smmonths connection.
Disadvantage
High initial cost
Costly to build a satellites

Radio
From(http://en.wikipedia.org/wiki/Radio) Radio wave is similar to Microwave while radio is omnidirectional and microwave is directional. A common radio standard often use to surround frequencies in the range of 3 kHz to 300 GHz. Most common application use radio wave is mobile telephony
(telecommunication). Radio wave transmit through free space by electromagnetic wave with lower frequency than visible light.

Application
Back in 1950s, AM radio uses amplitube modulation to modulate the sound into frequency signal and send to the hi-fi receiver. A Fisher 500 AM/FM hi-fi receiver from 1959.

Cell phone connect to the PSTN transmit to local cell site (receiver/transmitter). Mobile telephony occupies several frequency bands hust under 1 GHz.

Performance
Radio waves can travel as fast as light in a vacuum. However, if electrically conductive objrct of any size strike by radio wave, they will be slow down depend that object permeability and permittivity. The one ‘peak’ of magnetic flux to the next measure radio’s wavelength. In vacuum radio can travel 299,792,458 meters in 1second which is the wavelength of 1 hertz radio signal. A wavelength of 299 meters has 1megahertz of radio signal. Advantage

Cost saving
Radio transmission cost cheaper compared to other transmission media Less sensitive to environmental
Low rick of getting environment interfere
Disadvantage
Requires line-of-sight
Line of sight required because of signal transmit in straight way.

Conclusion
Based on all transmission media I overview, I personal prefer fiber-optic is my first choice. Although the installation is costly, the performance, application is the best compared to others transmission media. If price is the first consideration, I would prefer twisted. Because it is cheaper and has a stable speed, performance and application.