Transmission Media and Transmission Technologies
After Completing Unit 2, you should be able to demonstrate understanding concepts related to:
2.1The electrical interface
2.2 Metallic media
2.3 Optical fiber media
2.4 Wireless media (line-of-sight media)
2.5 Baseband and broadband transmission
2.6 Transmission bandwidth (Channel capacity)
2.7 Analog and digital signals
The electrical interface
What is network interface card (NIC)?
A hardware component, typically a circuit board or chip, which is installed on a computer so that it can connect to a network.
What is network interface card (NIC)?
A circuit board installed in a computer that provides a dedicated network connection to the computer. It is also called network interface controller, network adapter or LAN adapter.
Purpose of NIC
NIC allows both wired and wireless communications.
NIC is both a physical layer and a data link layer device
It provides the necessary hardware circuitry so that the physical layer processes and some data link layer processes can run on it.
Types of NIC Cards
In internal networks cards, motherboard has a slot for the network card where it can be inserted. It requires network cables to provide network access.
Internal network cards are of two types. Peripheral Component Interconnect (PCI) connection and Industry Standard Architecture (ISA).
External network cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the motherboard, however no network cable is required to connect to the network.
- Twisted Pair/Wire Pair
Twisted Pair – comprises two or more pairs of insulated wires twisted together, at six twists per inch.
Wire pairs are commonly used in local telephone communication and for short distance digital data communication
– (Shielded Twisted Pair, STP) ,or
– (Unshielded Twisted Pair, UTP).
Shielded twisted pair has a foil shield and copper braid surrounding the pairs of wires.
Types of UTP
Twisted pair come in various categories:
Cat 1 – 6. (Source: Ciscopress.com)
*Cat 7, Cat 10
The following summarizes the features of UTP cable:
Speed and throughput—10 to 1000 Mbps
Average cost per node—Least expensive
Media and connector size—Small
Maximum cable length—100 m (short)
Category 1—Used for telephone communications. Not suitable for transmitting data.
Category 2—Capable of transmitting data at speeds up to 4 megabits per second (Mbps).
Category 3—Used in 10BASE-T networks. Can transmit data at speeds up to 10 Mbps.
Category 4—Used in Token Ring networks. Can transmit data at speeds up to 16 Mbps.
Category 5—Can transmit data at speeds up to 100 Mbps.
Category 5e —Used in networks running at speeds up to 1000 Mbps (1 gigabit per second [Gbps]).
Category 6—Typically, Category 6 cable consists of four pairs of 24 American Wire Gauge (AWG) copper wires. Category 6 cable is currently the fastest standard for UTP.
A registered jack (RJ) is a standardized physical network interface for connecting telecommunications or data equipment. The physical connectors that registered jacks use are mainly of the modular connector and 50-pin miniature ribbon connector types
RJ45 is a standardized physical network interface for connecting telecommunications or data equipment.
- The “RJ” in RJ45 stands for “registered jack,” since it is a standardized networking interface.
- The “45” simply refers to the number of the interface standard.
- RJ45 is an 8P8C modular connector
8P8C = 8 position, 8 contact
- It looks similar to a telephone jack, but is slightly wider.
- Used with twisted pair cables,
- RJ45 connectors are most commonly seen with Ethernet cables and networks
Straight-thru Vrs Crossover Cables
Usually, straight through cables are primarily used for connecting unlike devices. And crossover cables are use for connecting alike devices.
Use straight through Ethernet cable for the following cabling:
Switch to router
Switch to PC or server
Hub to PC or server
Use crossover cables for the following cabling
Switch to switch
Switch to hub
Hub to hub
Router to router
Router Ethernet port to PC NIC
PC to PC
Uses of RJ 45 Connector
To provide internetworking between two systems.
In system to connect with network.
Cross connection for two system.
Connection of system with a hub or router.
Used for transmits digital signals between devices.
Advantage of RJ45
They are easy to install.
Connection speeds are higher ,100 Mbps for Fast Ethernet
Disadvantage of RJ45
It is only use for short distance network.
Require necessary wiring and equipment
Coaxial (Coax) Cables
Coaxial cable is groups of specially wrapped and insulated wires that are able to transfer data at higher rates.
They consist of a central copper wire surrounded by an insulation over which copper mesh is placed.
Coaxial cable is used for broadband and baseband communications networks (and for cable television), because the cable is usually free from external interference and permits high transmission rates over long distances.
Coaxial cable supports 10 to 100 Mbps and is relatively inexpensive, although it is more costly than UTP on a per-unit length.
Coaxial cable can be cabled over longer distances than twisted-pair cable. Ethernet can run approximately 100 meters using twisted-pair cabling. Using coaxial cable increases this distance to 500m
A transmission technology that sends pulses of light along specially manufactured optical fibres.
Fiber optic cable consists of a center glass core surrounded by several layers of protective materials. Signal transmission is achieved by total internal reflection of light through the glass core.
A fiber-optic cable is made up of incredibly thin strands of glass or plastic known as optical fibers; one cable can have as few as two strands or as many as several hundred.
Each strand is less than a tenth as thick as a human hair and can carry something like 25,000 telephone calls, so an entire fiber-optic cable can easily carry several million calls.
Light travels down a fiber-optic cable by bouncing repeatedly off the walls. Each tiny photon (particle of light) bounces down the pipe like a bobsleigh going down an ice run
Types of fiber-optic cables
- Single Mode and
- Multi Modes
The simplest type of optical fiber is called single-mode. It has a very thin core about 5-10 microns (millionths of a meter) in diameter.
Cable TV, Internet, and telephone signals are generally carried by single-mode fibers, wrapped together into a huge bundle. Cables like this can send information over 100 km (60 miles).
Each optical fiber in a multi-mode cable is about 10 times bigger than one in a single-mode cable.
Advantages of Fiber optics
Less attenuation: (signal loss) Information travels roughly 10 times further before it needs amplifying—which makes fiber networks simpler and cheaper to operate and maintain.
No interference: Unlike with copper cables, there’s no “crosstalk” (electromagnetic interference) between optical fibers, so they transmit information more reliably with better signal quality
Higher bandwidth: As we’ve already seen, fiber-optic cables can carry far more data than copper cables of the same diameter.
WIRELESS TRANSMISSION MEDIA
More convenient than installing cables. Wireless are installed in locations where it is impossible to install cables. Increased efficiency – remote connection Access and availability – ability to communicate while on the move. Flexibility – employees can work from home etc.
Types of wireless transmission media used in communications include
infrared (IR) is a wireless transmission medium that sends signals using infrared light waves.
Mobile computers and devices, such as a mouse, printer, and smart phone, often have an IrDA port that enables the transfer of data from one device to another using infrared light waves.
Broadcast radio is a wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home.
Cellular radio is a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones.
Microwaves are radio waves that provide a high-speed signal transmission.
Microwaves can transmit data at rates up to 4,500 times faster than a dial-up modem.
A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations.
Baseband and broadband transmission
Baseband transmission uses digital signals to send data through the media as a single channel. In broadband transmission, it is possible to send signals simultaneously over a range of different frequencies.
The difference between Baseband and Broadband Transmission is that in baseband transmission, one signal takes the entire bandwidth of the channel to send data while in broadband transmission, many signals with multiple frequencies send data through a single channel simultaneously.
Network bandwidth capacity
The term bandwidth sometimes defines the net bit rate ‘peak bit rate‘, ‘information rate,’ or physical layer ‘useful bit rate’, channel capacity, or the maximum throughput of a logical or physical communication path in a digital communication system.
DIGITAL AND ANALOG TRANSMISSION
In everyday communication:
A signal is a piece of information communicated by an action, gesture, or sign.
A Signal is information transmitted by means of a modulated current or an electromagnetic wave.
Signalling is the propagation of signals across a communication medium. Data is transmitted from one point to another point by means of electrical signals that may be in digital and analog form.
In analog signal the transmission power varies over a continuous range with respect to sound, light and radio waves.
On the other hand a digital signal may assume only discrete set of values within a given range.
Converting digital to analogue signals is called Modulation. Converting from analog to digital = Demodulation. A device that does the conversion is known as a Modem (MODulator – DEModulator). A modem or broadband modem is a hardware device that connects a computer or router to a broadband network.
Short for modulator/demodulator, a modem is a hardware device that allows a computer to send and receive information over telephone lines.
Converts analog signals to digital signals and vice versa
Congratulation! you have come to the end of unit 2.