Transmission Media

Transmission media, also known as communication channels, are the path through which data is transmitted in a computer network. Transmission media can be divided into two broad categories: guided and unguided.

Guided Media (Wired):

Guided media, also known as wired or bounded media, refers to the physical pathways or transmission media with a well-defined physical boundary through which signals are guided for communication in a computer network. Guided media is characterized by its physical structure and the fact that signals are confined within a specific pathway.

Guided media can be classified into various types, each with its own characteristics and applications.

Twisted Pair Cable:

Twisted pair consists of pairs of insulated copper wires twisted together. The twisting helps reduce electromagnetic interference from external sources and crosstalk between adjacent pairs, improving signal transmission. Common use of twisted pair cable: Ethernet networks, telephone lines.

There are two types of twisted-pair cables: UTP (unshielded twisted pair) and STP (shielded twisted pair). The main difference between both is STP uses an extra layer of coating on each pair. The additional layer of coating on each pair improves cable performance but increases the cost.

Unshielded Twisted Pair (UTP): UTP cable does not shield each pair individually. It uses only an outer cover to keep all pairs together. Since it uses only outer coating, it is much cheaper than STP. Due to low cost, flexibility, and good performance, it is mainly used in LAN networks. Almost all modern LAN networks use it to connect devices to the network. It can carry signals up to 100 meters.

UTP cables come in different categories, such as Cat5e, Cat6, Cat6a, and Cat7, each offering different levels of performance in terms of bandwidth and data transmission capabilities. UTP cables typically use modular connectors, such as RJ-45, for connecting to network devices.

UTP cables are extensively used in networking environments for connecting computers, routers, switches, and other network devices. They are also commonly used for telephone lines. UTP is versatile and can support a broad range of frequencies, making it suitable for transmitting both data and voice signals. It is the predominant medium for Ethernet networks.

UTP cables have become the standard for local area network (LAN) connections and are widely used in residential, commercial, and industrial settings. Their ability to handle both voice and data transmissions, coupled with their cost-effectiveness and ease of installation, has contributed to their widespread adoption in modern telecommunications and networking.

Shielded Twisted Pair (STP):  The outer insulated jacket protects the twisted-pair cable only from physical stress or damage. However, it does not protect the cable from electromagnetic interference (EMI). If the network premise contains many electrical appliances, UTP cables do not work. In such a situation, instead of UTP, STP cables are used to connect devices. STP cables are expensive but includes additional shielding to reduce electromagnetic interference, providing better performance in environments with high interference.

Advantages:

• Cost-effective
• widely available.
• Easy to install and terminate.

Disadvantages:

• Limited bandwidth compared to coaxial and fiber optic cables.
• Susceptible to electromagnetic interference.

Coaxial Cable:

Coaxial cable consists of a central copper conductor, surrounded by insulating material, a metallic shield, and an outer insulating layer. The metallic shield helps protect the signal from external interference. The central conductor and the shield share the same axis (hence the term “coaxial”).

Coaxial cables are often used for higher-frequency transmissions and have better shielding capabilities compared to twisted-pair cables. Common use of coaxial cable: cable television, Ethernet networks and other applications that require higher bandwidth.

There are two types of coaxial cables: thinnet and thicknet.

Thinnet (10BASE2): Thin and flexible coaxial cable, commonly used in older Ethernet networks. It can carry signals up to 200 meters. It offers a speed of 10 megabits per second. It also uses baseband transmission. In ethernet standards, it is specified as the 10Base5 (10 megabits per second Baseband transmission over 2 hundred meters) cable. In a network, it connects end devices such as PCs and printers to the network segment.

Thicknet (10BASE5): Thicker coaxial cable with a greater transmission distance. It can carry signals up to 500 meters. It offers a speed of 10 megabits per second. It uses baseband trasmission. Because of these properties, in ethernet standards, it is specified as the 10Base5 (10 megabits per second Baseband transmission over 5 hundred meters) cable. In a network, it is used as the backbone cable. It connects different network segments.

Advantages:

• Higher bandwidth compared to twisted pair cable.
• Better resistance to electromagnetic interference.
• Suitable for longer distances without signal degradation.

Disadvantages:

• More expensive and less flexible than twisted pair cable.
• More difficult to install and terminate
• Limited in terms of data transfer speed compared to fiber optics

Fiber Optic Cable:

Fiber optic cable is made up of glass or plastic and transmits signals in the form of light. They consist of a core made of glass or plastic fibers surrounded by a cladding layer that reflects light back into the core. The outer layer is a protective jacket.

Instead of copper Fiber optic cable use glass to carry signals. Since it uses glass to transport signals, electromagnetic interference (EMI) does not affect it. Common uses of fiber-optic cable: Long-distance telecommunications, high-speed internet.

It reflects light from one endpoint to another. Based on how many beams of light are transmitted at a given time, there are two types of fiber optical cable: SMF (Single-mode fiber) and MMF(multi-mode fiber).

Single-mode fiber (SMF): SMF carries only a single beam of light. It uses a laser as the light source and transmits 1300 or 1550 nano-meter wavelengths of light. It is more reliable and supports much higher bandwidth and longer distances than the MMF cable.

Multi-mode fiber (MMF): MMF carries multiple beams of light. Since it uses multiple beams, it can carry more data than the SMF cable. It uses an LED as the light source and transmits 850 or 1300 nano-meter wavelengths of light. It is used for shorter distances.

Advantages:

• High bandwidth and data transmission rates.
• Immune to electromagnetic interference.
• Capable of transmitting data over very long distances without signal degradation
• Lightweight and very low attenuation

Disadvantages:

• More expensive to install and maintain compared to copper cables
• Vulnerable to physical damage (e.g., bending or crushing of the cable)
• Requires specialized equipment for termination and maintenance.

Difference Between Twisted Pair Cable, Coaxial Cable and Fibre Optics Cable:

Twisted Pair Cable, Coaxial Cable, and Fiber Optic Cable are three different types of transmission media used in networking and telecommunications. Here are the differences between them:

Construction:

• Twisted Pair Cable: It consists of two insulated copper wires twisted together in a pair. Multiple pairs are then combined to form a cable.
• Coaxial Cable: It consists of a central conductor, surrounded by an insulating layer, a metallic shield, and an outer insulating layer.
• Fiber Optic Cable: It consists of thin strands of glass or plastic called optical fibers, which transmit data using light signals. The fibers are surrounded by protective layers.

Bandwidth and Data Rate:

• Twisted Pair Cable: It has lower bandwidth and data rate compared to coaxial and fiber optic cables. It is suitable for lower-speed applications.
• Coaxial Cable: It offers higher bandwidth and data rate than twisted pair cable, making it suitable for higher-speed applications.
• Fiber Optic Cable: It provides the highest bandwidth and data rate among the three, making it ideal for high-speed data transmission.

 Maximum Distance:

• Twisted Pair Cable: It has a limited transmission distance, typically up to a few hundred meters.
• Coaxial Cable: It has a longer transmission distance compared to twisted pair cable, typically up to several kilometers.
• Fiber Optic Cable: It has the longest transmission distance among the three, spanning several kilometers to tens of kilometers without requiring signal regeneration.

Immunity to Interference:

• Twisted Pair Cable: It offers moderate resistance to electromagnetic interference (EMI) due to the twisting of wire pairs.
• Coaxial Cable: It provides better resistance to EMI compared to twisted pair cable due to the shielding.
• Fiber Optic Cable: It is highly immune to EMI since it transmits data using light signals, which are not affected by electromagnetic interference.

Size and Flexibility:

• Twisted Pair Cable: It is thin, lightweight, and highly flexible, making it easy to install and maneuver.
• Coaxial Cable: It is thicker and less flexible compared to twisted pair cable.
• Fiber Optic Cable: It is thin and flexible, but more fragile than the other two cable types due to the delicate optical fibers.

Cost:

• Twisted Pair Cable: It is the most cost-effective option among the three cable types.
• Coaxial Cable: It is more expensive than twisted pair cable but less expensive than fiber optic cable.
• Fiber Optic Cable: It is the most expensive option due to the higher cost of materials and installation.

Unguided Media:

Unguided media, also known as unbounded or wireless media, refers to the transmission of data without the use of physical cables. Unguided media offer flexibility and mobility, allowing devices to communicate without being physically connected. However, they may be susceptible to environmental factors, interference, and have limitations in terms of range and data transfer rates compared to guided media (such as cables).

Radio Waves: The most common medium for wireless communication. These are used for multicast communication, such as radio and television. Wi-Fi, Bluetooth, and many other wireless technologies use radio waves for transmission.

Wi-Fi (Wireless Fidelity):

• Wi-Fi is a technology that enables wireless local area networking (WLAN) based on the IEEE 802.11 standards.
• It operates in the radio frequency bands, typically 2.4 GHz or 5 GHz, using radio waves to transmit data between Wi-Fi-enabled devices such as computers, smartphones, tablets, and routers.
• Wi-Fi is widely used for internet connectivity in homes, offices, public spaces, and other locations.

Bluetooth:

• Bluetooth is a short-range wireless communication technology that operates in the 2.4 GHz frequency range.
• It is designed for connecting devices over short distances, typically within a range of a few meters.
• Bluetooth is commonly used for wireless headphones, speakers, and for transferring data between smartphones.

Microwaves: These are used for unicast communication such as cellular telephones, satellite networks and wireless LANs. Higher frequency waves than radio waves, microwaves are often used in point-to-point communication for long-distance transmission, satellite communication.

Infrared: Infrared signals use light waves to transmit data. Infrared communication is often used in short-range applications, such as remote controls.

 

Difference between Guided and Unguided Media

Guided Media	Unguided Media
The guided media is also called wired or bounded media.	The unguided media is also called wireless or unbounded media.
In guided media, the signal energy communicates via wires.	In unguided media, the signal energy communicates through the air.
Physical cables provide a well-defined pathway.	No physical pathway; relies on wireless signals.
Limited mobility due to cable constraints.	Offers mobility and flexibility.
Less susceptible to interference and crosstalk.	More vulnerable to interference from obstacles and other electronic devices.
Capable of high-speed data transmission.	Slower data transmission compared to guided media.
Enhanced security due to the physical isolation of cables.	More susceptible to eavesdropping and unauthorized access.
It sends out a signal that indicates which way to go.	It does not indicate which way to travel.
Examples of guided media are twisted pair cables, coaxial cables, and optical fiber cables.	Examples of unguided media are microwave, radio waves and infrared light.