Lesson 2

Lesson Objectives:

a. Explain how data transmission are sent and received.

b. List and describe the types of transmission media.

c. Describe the functions of a network interface card.

Understanding network

Networks enable people to share resources, including printers, hard disks, and applications, which can greatly reduce the costs of providing these resources to each person in a company. Networks are built around this idea, connecting shared sources resources to their consumers. Several terms are used to describe these network devices, including hosts, nodes, workstations, peers, servers, and clients. Any device capable of communicating on the network is also referred to generically as a node.

A typical network

How data transmission are send and received?

Data transmission and data reception (or, more broadly, data communication or digital communications) is the transfer and reception of data (a digital bitstream or a digitized analog signal[1]) over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.

Source: https://en.wikipedia.org/wiki/Data_transmission

Synchronous data transmission

Synchronous data transmission is a data transfer method in which a continuous stream of data signals is accompanied by timing signals (generated by an electronic clock) to ensure that the transmitter and the receiver are in step (synchronized) with one another. The data is sent in blocks (called frames or packets) spaced by fixed time intervals.

Asynchronous data transmission

In contrast, asynchronous transmission works in spurts and must insert a start bit before each data character and a stop bit at its termination to inform the receiver where it begins and ends.

The term asynchronous is used to describe the process where transmitted data is encoded with start and stop bits, specifying the beginning and end of each character.

Watch this video to understand fully the different kind of data transmission.

Network Adapter

Isa sa mga component ng isang computer ay ang pagkakaroon nila ng Network Adapter. Ang Network Adapter ay isang pyesa ng computer na kung saan ginagamit ito upang magkaroon ng komunikasyon sa bawat computer.

Transmission Media

1. Guided Media:

It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.

Features:

High Speed, Secure, Used for comparatively shorter distances

2. Unguided Media:

It is also referred to as Wireless or Unbounded transmission media.No physical medium is required for the transmission of electromagnetic signals.

Features:

The signal is broadcasted through air, Less Secure, Used for larger distances

Twisted pair cable

Fiber optic cable

Coaxial Cable

There are 3 major types of Guided Media:

(i) Twisted Pair Cable –

It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types:

Unshielded Twisted Pair (UTP):

This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.

Advantages:

Least expensive

Easy to install

High-speed capacity

Susceptible to external interference

Lower capacity and performance in comparison to STP

Short distance transmission due to attenuation

Shielded Twisted Pair (STP):

This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.

Advantages:

Better performance at a higher data rate in comparison to UTP

Eliminates crosstalk

Comparatively faster

Comparatively difficult to install and manufacture

More expensive

Bulky

(ii) Coaxial Cable –

It has an outer plastic covering containing 2 parallel conductors each having a separate insulated protection cover. The coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.

Advantages:

High Bandwidth

Better noise Immunity

Easy to install and expand

Inexpensive

Disadvantages:

Single cable failure can disrupt the entire network

(iii) Optical Fibre Cable –

It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for the transmission of large volumes of data.

The cable can be unidirectional or bidirectional. The WDM (Wavelength Division Multiplexer) supports two modes, namely unidirectional and bidirectional mode.

Advantages:

Increased capacity and bandwidth

Lightweight

Less signal attenuation

Immunity to electromagnetic interference

Resistance to corrosive materials

Disadvantages:

Difficult to install and maintain

High cost

Fragile

The electro magnetic spectrum

The radio waves are the electromagnetic waves which have the longest wavelengths in the electromagnetic spectrum, so long that if you were to look at the sky with a radio telescope, instead of point sources like stars and clouds, you can see entire regions that promote star formation, distant quasars and probable remnants of supernovas. These waves have low energy levels and low frequencies ranging from around 3 kHz to around 300 GHz.

Due to their wide range, they are mostly used in communication systems like broadcasting, communication satellites, computer networking systems, radar, and other kinds of navigation. How do you think FM/AM Radio works? Simply put, radio waves are generated and propagated by radio transmitters. These waves are then received by a radio receiver (tuned to a particular frequency/wavelength using a radio antenna) which then converts these into mechanical waves which are played through radios and different sounds.

Source: https://byjus.com/physics/electromagnetic-spectrum-radio-waves/

2. Unguided Media:

It is also referred to as Wireless or Unbounded transmission media.No physical medium is required for the transmission of electromagnetic signals.

Features:

The signal is broadcasted through air

Less Secure

Used for larger distances

There are 3 types of Signals transmitted through unguided media:

(i) Radiowaves –

These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and cordless phones use Radiowaves for transmission.

Further Categorized as (i) Terrestrial and (ii) Satellite.

(ii) Microwaves –

It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz. These are majorly used for mobile phone communication and television distribution.

(iii) Infrared –

Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz – 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.

source: https://www.geeksforgeeks.org/types-transmission-media/

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