Transmission media
A transmission medium is something that can mediate the propagation of signals for the purposes of telecommunication. Signals are typically imposed on a wave of some kind suitable for the chosen medium.
Transmission media is a communication channel that carries the information from the sender to the receiver. Data is transmitted through the electromagnetic signals.
The main functionality of the transmission media is to carry the information in the form of bits through LAN(Local Area Network).
It is a physical path between transmitter and receiver in data communication.
In a copper-based network, the bits in the form of electrical signals.
In a fibre based network, the bits in the form of light pulses.
In OSI(Open System Interconnection) phase, transmission media supports the Layer 1. Therefore, it is considered to be as a Layer 1 component.
The electrical signals can be sent through the copper wire, fibre optics, atmosphere, water, and vacuum.
The characteristics and quality of data transmission are determined by the characteristics of medium and signal.
Transmission media is of two types are wired media and wireless media. In wired media, medium characteristics are more important whereas, in wireless media, signal characteristics are more important.
Different transmission media have different properties such as bandwidth, delay, cost and ease of installation and maintenance.
The transmission media is available in the lowest layer of the OSI reference model, i.e., Physical layer.
Some factors need to be considered for designing the transmission media:
Bandwidth: All the factors are remaining constant, the greater the bandwidth of a medium, the higher the data transmission rate of a signal.
Transmission impairment: When the received signal is not identical to the transmitted one due to the transmission impairment. The quality of the signals will get destroyed due to transmission impairment.
Interference: An interference is defined as the process of disrupting a signal when it travels over a communication medium on the addition of some unwanted signal.
Guided Media
It is defined as the physical medium through which the signals are transmitted. It is also known as Bounded media.
Types Of Guided media:
Twisted pair:
Twisted pair is a physical media made up of a pair of cables twisted with each other. A twisted pair cable is cheap as compared to other transmission media. Installation of the twisted pair cable is easy, and it is a lightweight cable. The frequency range for twisted pair cable is from 0 to 3.5KHz.
A twisted pair consists of two insulated copper wires arranged in a regular spiral pattern.
The degree of reduction in noise interference is determined by the number of turns per foot. Increasing the number of turns per foot decreases noise interference.
Unshielded Twisted Pair:
An unshielded twisted pair is widely used in telecommunication. Following are the categories of the unshielded twisted pair cable:
Category 1: Category 1 is used for telephone lines that have low-speed data.
Category 2: It can support upto 4Mbps.
Category 3: It can support upto 16Mbps.
Category 4: It can support upto 20Mbps. Therefore, it can be used for long-distance communication.
Category 5: It can support upto 200Mbps.
Advantages Of Unshielded Twisted Pair:
It is cheap.
Installation of the unshielded twisted pair is easy.
It can be used for high-speed LAN.
Disadvantage:
This cable can only be used for shorter distances because of attenuation
Shielded Twisted Pair
A shielded twisted pair is a cable that contains the mesh surrounding the wire that allows the higher transmission rate.
Characteristics Of Shielded Twisted Pair:
The cost of the shielded twisted pair cable is not very high and not very low.
An installation of STP is easy.
It has higher capacity as compared to unshielded twisted pair cable.
It has a higher attenuation.
It is shielded that provides the higher data transmission rate.
Disadvantages
It is more expensive as compared to UTP and coaxial cable.
It has a higher attenuation rate.
Coaxial Cable
Coaxial cable is very commonly used transmission media, for example, TV wire is usually a coaxial cable.
The name of the cable is coaxial as it contains two conductors parallel to each other.
It has a higher frequency as compared to Twisted pair cable.
The inner conductor of the coaxial cable is made up of copper, and the outer conductor is made up of copper mesh. The middle core is made up of non-conductive cover that separates the inner conductor from the outer conductor.
The middle core is responsible for the data transferring whereas the copper mesh prevents from the EMI(Electromagnetic interference).
Coaxial cable is of two types:
Baseband transmission: It is defined as the process of transmitting a single signal at high speed.
Broadband transmission: It is defined as the process of transmitting multiple signals simultaneously.
Advantages Of Coaxial cable:
The data can be transmitted at high speed.
It has better shielding as compared to twisted pair cable.
It provides higher bandwidth.
Disadvantages Of Coaxial cable:
It is more expensive as compared to twisted pair cable.
If any fault occurs in the cable causes the failure in the entire network.
Fiber Optic
Fiber optic cable is a cable that uses electrical signals for communication.
Fiber optic is a cable that holds the optical fibers coated in plastic that are used to send the data by pulses of light.
The plastic coating protects the optical fibers from heat, cold, electromagnetic interference from other types of wiring.
Fiber optics provide faster data transmission than copper wires
Basic elements of Fibre optic cable:
Core: The optical fibre consists of a narrow strand of glass or plastic known as a core. A core is a light transmission area of the fibre. The more the area of the core, the more light will be transmitted into the fibre.
Cladding: The concentric layer of glass is known as cladding. The main functionality of the cladding is to provide the lower refractive index at the core interface as to cause the reflection within the core so that the light waves are transmitted through the fibre.
Jacket: The protective coating consisting of plastic is known as a jacket. The main purpose of a jacket is to preserve the fibre strength, absorb shock and extra fibre protection.
Following are the advantages of fiber optic cable over copper:
Greater Bandwidth: The fiber optic cable provides more bandwidth as compared copper. Therefore, the fiber optic carries more data as compared to copper cable.
Faster speed: Fiber optic cable carries the data in the form of light. This allows the fiber optic cable to carry the signals at a higher speed.
Longer distances: The fiber optic cable carries the data at a longer distance as compared to copper cable.
Better reliability: The fiber optic cable is more reliable than the copper cable as it is immune to any temperature changes while it can cause obstruct in the connectivity of copper cable.
Thinner and Sturdier: Fiber optic cable is thinner and lighter in weight so it can withstand more pull pressure than copper cable
Unguided transmission media are methods that allow the transmission of data without the use of physical means to define the path it takes. Examples of this include microwave, radio or infrared.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz)
Radio waves are generated artificially by transmitters and received by radio receivers, using antennas. Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) wavelengths, but relatively short for radio waves. Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz).
Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy,
•Infrared transmission refers to energy in the region of the electromagnetic radiation spectrum at wavelengths longer than those of visible light, but shorter than those of radio waves. Correspondingly, infrared frequencies are higher than those of microwaves, but lower than those of visible light.
•Infrared waves are those between the frequencies 300GHz and 400THz in the electromagnetic spectrum.
Applications of Infrared Waves in Communications
•Remote controls for television, stereos and other home appliances.
•Wireless LANs
•Wireless modem, keyboard, mouse, printer etc
•Fire detectors
•Night vision systems
•Intrusion detection systems
•Motion detectors
Difference between Radio wave, Microwave and Infrared waves
1. Radiowave Transmission :
The radio waves have frequency range from 3 KHz to 1 GHz. These waves are easy to generate and these can travel along long distances. These waves are omni directional in nature which means that they can travel in all the directions. They are widely used for the communication between both indoor and outdoor because they have the property that they can penetrate through the walls very easily. These waves are usually used for AM and FM radio, television, cellular phones and wireless LAN
2. Microwave Transmission :
Microwaves are electromagnetic waves which have frequency range between 1 GHz to 300 GHz. These can travel along long distances. These are unidirectional in nature which means that they can travel only in straight line. At very high frequency that cannot penetrate into walls. These waves are usually used for one to one communication between sender and receiver, cellular phones, satellite networks, and wireless LAN.
3. Infrared Waves :
Infrared Waves are electromagnetic waves that have frequency range between 300 GHz to 400 GHz. These cannot travel along long distances. These waves are used for short range communication and they also use line-of-sight of propagation. These waves cannot pass through solid objects like walls etc. These also not penetrate through walls. The most common application of the IR waves is remote controls that are used for TV, DVD players, and stereo system.