Question

1. What are the three main multiplexing techniques used for bandwidth utilization? (Minimum 50 words)

2. Which of the three multiplexing techniques is (are) used to combine analog signals? Which of the three multiplexing techniques is (are) used to combine digital signals? (Minimum 50 words)

3. What are the two major categories of transmission media, explain (Minimum 50 words).

4. What is the purpose of cladding in an optical fiber?(Minimum 50 words)

5. What is the difference between omnidirectional waves and unidirectional waves? (Minimum 50 words)

6. What are the two approaches to packet switching? (Minimum 50 words)

7. List four major components of a packet switch and their functions.(Minimum 50 words) 8. Describe the need for switching and define a switch.(Minimum 50 words)

Answer 1

1.  Muxing (or) multiplexing is a way of transmitting various signals over a media or single line. A common kind of multiplexing merges a number of low-speed signals to send over an only high-speed link, or it is used to transmit a medium as well as its link with the number of devices. It provides both privacy & Efficiency. The entire process can be done using a device namely MUX or multiplexer, and the main function of this device is to unite n-input lines for generating a single output line. Thus MUX has many inputs & single output. A device is called DEMUX or demultiplexer is used at the receiving end which divides the signal into its component signals. So It has a single input and a number of outputs.

Multiplexing techniques are mainly used in communication, and these are classified into three types. The 3 types of multiplexing techniques include the following.

• Frequency Division Multiplexing (FDM)
• Wavelength Division Multiplexing (WDM)
• Time Division Multiplexing (TDM)

2. Out of frequency-division multiplexing, wavelength-division multiplexing, and time-division multiplexing. The first two are techniques designed for analog signals, the third, for digital signals.

Frequency Division Multiplexing is a technique which uses various frequencies to combine many streams of data for sending signals over a medium for communication purpose. It carries frequency to each data stream and later combines various modulated frequencies to transmission. Television Transmitters are the best example for FDM, which uses FDM to broadcast many channels at a time.

Wavelength Division Multiplexing (WDM) is an analog multiplexing technique and it modulates many data streams on the light spectrum. This multiplexing is used in optical fiber. It is an FDM optical equivalent. Various signals in WDM are optical signals that will be light and was transmitted through an optical fiber.WDM is similar to FDM as it mixes many signals of different frequencies into a single signal and transfers on one link. The wavelength of a wave is reciprocal to its frequency, if wavelength increases then frequency decreases. Several light waves from many sources are united to get a light signal which will be transmitted across the channel to a receiver.

TDM is one of the types of multiplexers that join data streams by allotting every stream a different time slot in a set. It frequently transfers or sends various time slots in order over one transmission channel. TDM attaches PCM data streams.

3. There are two types of transmission media, namely guided and unguided. Guided transmission media are cables like twisted pair cables, coaxial cables, and fiber optic cables. Unguided transmission media are wireless, such as infrared, radio waves, and microwaves.

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

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

4.  The function of the cladding is to provide a lower refractive index at the core interface in order to cause reflection within the core so that light waves are transmitted through the fiber.

Cladding in optical fibers is one or more layers of materials of lower refractive index, in intimate contact with a core material of higher refractive index. The cladding causes light to be confined to the core of the fiber by total internal reflection at the boundary between the two.

The most basic optical fiber consists of: An inner cylinder with a high refractive index called the core. A middle cylinder with a lower refractive index called the cladding. An outer protective polymer layer (usually polyurethane or PVC) called the jacket.

5.

Omnidirectional wave:

Omnidirectional in which wave travel in a different direction. On the other hand, we can say also that waves go in all directions like a circle.so omnidirectional devices broadcast and receive their singles from all the direction.

unidirectional waves:

unidirectional in which wave travels in one direction. Unidirectional devices only work in one direction and work best in a limited portion of the directions. This lets them direct signal more efficiently, but only in one direction so that has to be pointed.

Omnidirectional devices communicate or get their signs from all directions. Somebody who records sound impacts and needs a general perusing of an encompassing domain (like timber squeaking, rivulets prattling, and crickets tweeting in a backwoods, for instance) would locate an omnidirectional microphone. Cell phone antennas will (in principle, in any case — changing in unwavering quality relying upon carrier and scope) get signals from wherever around the gadget.

Unidirectional devices, then again, are more centered around getting or transmitting their signs in a single course. This is particularly useful in case you're in a region immersed with surrounding signals that you need to maintain a strategic distance from. Having a microphone that will give you and your subject full focus while overlooking the encompassing commotion and prattle is a profitable method for controlling the circumstance.

6.

The packet switching has two approaches: the Virtual Circuit approach and Datagram approach. WAN, ATM, frame relay, and telephone networks use connection oriented virtual circuit approach; whereas the internet relies on connectionless datagram based packet switching.

(i)  Virtual Circuit Packet Switching: In virtual circuit packet switching, a single route is chosen between the sender and receiver, and all the packets are sent through this route. Every packet contains the virtual circuit number. As in circuit switching, virtual-circuit needs call setup before actual transmission can be started. He routing is based on the virtual circuit number.

This approach preserves the relationship between all the packets belonging to a message. Just like circuit switching, the virtual-circuit approach has a setup, data transfer, and tear down phases. Resources can be allocated during the setup phase, as in circuit-switched networks or on-demand, as in a datagram network. All the packets of a message follow the same path established during the connection. A virtual circuit network is normally implemented in the data link layer, while a circuit-switched network is implemented in the physical layer and a datagram network in the network layer.

(ii)   Datagram Packet Switching: In datagram packet switching each packet is transmitted without any regard to other packets. Every packet contains a full packet of source and destination. Every packet is treated as an individual, independent transmission.

Even if a packet is a part of multi-packet transmission the network treats it as though it existed alone. Packets in this approach are called datagrams. Datagram switching is done at the network layer. The figure shows how a datagram approach is used to deliver four packets from station A to station D. All the four packets belong to the same message but they may travel via different paths to reach the destination i.e. station D.Datagram approach can cause the datagrams to arrive at their destination out of order with different delays between the packets. Packets may also be lost or dropped because of a lack of resources. The datagram networks are also referred to as connectionless networks. Here connectionless means that the switch does not keep information about the connection state. There is no connection establishment or tear down phases. The datagram can arrive at the destination with a different order from the order in which they were sent. The source and destination addresses are used by the routers to decide the route for packets. Internet use datagram approach at the network layer.

7. The four components of a package switch are:

1. Input ports – It presents the material and data connection meaning of the package switch.
2. Output ports- It presents the identical purpose as the input port, yet in the opposite sequence.
3. Routing processor- It presents the purpose of table research in the network layer.
4. Switching fabric- It presents the movement of the packet from the input row to the output row.

8. Switching provides a practical solution to the problem of connecting multiple devices in a network. It is more practical than using a bus topology; it is more efficient than using a star topology and a central hub. Switches are devices capable of creating temporary connections between two or more devices linked to the switch.

A switch is used in a wired network to connect to other devices using Ethernet cables. The switch allows each connected device to talk to the others. ... Switches allow you to connect dozens of devices. Switches keep traffic between two devices from getting in the way of your other devices on the same network.