Transmission Media TaxonomyA transmission medium is a process of how the transmission of signals is undertaken. The OSI layer is passive and structured as shown below
Transmission Media Taxonomy
1. Unshielded Twisted Pairs (UTP)
It is composed of a conductor/ copper wire covered by a color coded insulator with 4 pairs of twisted cables that prevents crosstalk and attenuation. The PVC is also covered with a jacket.
Courtesy: unshielded twisted pairAdvantages of Unshielded Twisted Pairs
- Inexpensive connections and cables
- Easy to install cabling
- Easy to connect cable ends to devices
- There is possible interference of Electromagnetic
- Prone to interference to Temperature and humidity
- Limited segment length depending on the standard of the cable
- Posse a limited bandwidth.
2. STP (Shielded Twisted Pair)
- In addition, a UTP structure, STPs are all known to have each pair wrapped in an aluminum foil/ copper braid
- To prevent or reduce interference, the metal braid is earthed/ connected to earth
- They are capable of reducing large scale interference to a large extend but are known to be very expensive
Courtesy: Unshielded twisted pair
Categories We have several categories that depends on the transmission capacity and transmission frequency in mbps.
|For telephone or voice only
|For slow token ring
|For fast token ring application
|For fast Ethernet
|: LAN for ATM
|For LAN and ATM
|For LAN and ATM
Thin Coaxial Cable
Coaxial cables, with similarities to TV cable have a copper core or conductor covered by a flexible insulation of a copper braid that acts as a conductor and reduces EMIs. It is also covered with a plastic case covering commonly known as PVC.
- It is used in mainly in backbone topologies
- They use British naval connector terminators or BNC
- They transmit data over long distances and are strong.
- They support higher bandwidth transmissions
- They are easier to install
- They are expensive, and are incompatible with telephone cables unless with use of convertors
- They are greatly affected with interferences.
Courtesy: Thin coaxial cableA 10 base2 a segment length of maximum 185m, 50impedance and a 10mbps speed with a minimum 15cm physical bend radius. The cable can be trimmed at the terminator point.
Thick coaxial cableOne has to drill at the point where a terminator happens because it is big. E.g. standard, Thicknet and 10Base5
- An added layer of aluminum tape
- Has extra layer of copper braid
- It covers 500m length segment
- It has a 60cm bend radius
Courtesy: Image of Transmission application demonstrated
- Fiber optic cables consists of flexible plastic or glass core surrounded by coat or glass cladding that is covered by a light proof PVC sleeve which is slightly thicker than human being hair.
- The flexible plastic or glass core should be of a high density when compared to the glass cladding one.
- Should have straight tip (ST) by AT&T or subscriber connector (SC) new version that is capable to allow the push and pull insertion for simple connections.
Courtesy: Fiber optic cable
Fiber optics transmissionIn Fiber Optics transmissions, the source of light is projected into the cable by quickly switching on and off by:
High intensity LED- photo diode projections
- Low on power
- Low on cost
- Covers short distances
- Uses transmission speeds of up to 200mbps
- Do cover longer distances
- Has much more longer transmission speeds of 1 to 2 gbts
- Light reflects off the glass fiber sleeve during transmission because of high refractive index of glass thread as a result of internal reflection. The optic sensor or photo receptor receives pulses on the receiving end.
Categories of transmission media
- It carries single rays of light that are emitted from laser projections.
- Can transmit pulses over a long distance and light is unidirectional from the center of the fiber.
- Supports very high transmission rates and thus is expensive
Courtesy: monomode laser projection
MultimodeThe wavelength of light assumes modal dispersion or multiple paths therefore the path at the receiving end is more blurred than is the case with monomode
Courtesy: multimode laser projectionAdvantages
- There is no impedance because it is 10 to 100 times very fast than the wire systems.
- It covers far more greater distances with no signal degradation
- It uses light waves hence it is immune to electromagnetic radiation
- It cannot electrocute and hence safe.
- It uses photons and therefore more secure in most conditions
- It doesn’t support crosstalk because it is electrically isolated
- Has no known good set intentional standards
- Due to lack of knowledge, there is scarcity of technicians hence expensive to hire the few with the expert knowledge.
- It is an expensive media type
- Is difficult to install because it can easily shatter in transit or when bent around the corner edges.
Wireless mediaWireless media is a mode where transmission of signals is through the space.
Types of wireless mediaThe type of wireless media depends on the ranges of frequencies defining the various types of wireless transmission
InfraredIt covers a range of approximately 3×1011 to 2×1014 Hz and therefore a very short wavelength that have weak penetration ability. It cannot pass through obstacles. Uses only line-of sight transmission and support local point to point and multipoint applications within a given area like in a room.
MicrowavesIt ranges from 1 GHz to 40GHz, has a longer and stronger wavelength as compared to infrared waves weaker than radio wave. They work with a line of site transmission. They are suitable for point-to-point transmission because of their high directional beams Are used in both terrestrial and satellite communication radio waves because they use frequencies ranging from 30MHz to 1HGz that correspond well to long wavelengths. Are suitable for omni directional transmissions and where you cannot avoid obstacles, hence expensive. Example is a Wi-Fi in wireless Local Area Network (LAN) environment.Examples
1. Wireless Personal Area (WPAN)Used to exchange and connect information between devices in a short-range radio transmission frequency without connecting to elaborate network connectivity. For example, the radio connection between mobile phones, laptops, video consoles e.t.c.
2. Wireless Fidelity (Wi-Fi)This connection connects within wireless Local area network WLAN e.g Ethernet for a fast and secure better range connection
3. World interoperability for microwave access WiMAXIt employs the mode of point to a multiple point topology to give a broadband access transmission.
4. Global system for mobile communications (GSM)It allows for roaming and switching between different carriers without switching phones for voice calls and sms services.
Versions of a GSM CommunicationGPRS (General packet radio services) – they use WAP (wireless application protocol) for a high speed transmission of data and MMS (multimedia messaging services) CDMA (code division multiple access) It is limited transmission to certain regions that uses shared codes for high data bandwidth.
- Wireless media transmissions have no physical connection points.
- They are expensive.
- They are used in more complex structures.
- They are easily affected by external interference including interference from other devices, fluorescent tubes etc.
- Wireless media transmission is less secure.
- Wireless media transmissions have 3 to 4 ports on their hubs.
- For internet, can connect wireless to telephone line.
- Can act as transmitter/ receiver access point.
Courtesy: Image of an electromagnetic spectrum
Factors to Consider when choosing a Medium
- Distance it can cover and its expansibility.
- The conditions of environment like weather, noise conditions.
- The layout infrastructural costs.
- The transmission speeds.
- The media security.
About the Author:
Fadhil Kennedy is a 3rd year student doing
Business Management and Information Technology at the prestigious
Kabarak University, Nakuru, Kenya.