Second Chapter Lesson-3: Data transmission mode.

At the end of this lesson-

  • 1. You will be able to explain the concept of data transmission mode.
  • 2. You will be able to classify the data transmission mode.

 

The direction of transmitting data from source to one or more destination is called data transmission mode. or The way in which data is transmitted from one device to another device is known as transmission mode. The transmission mode is also known as the communication mode. Each communication channel has a direction associated with it, and transmission media provide the direction. Therefore, the transmission mode is also known as a directional mode. The transmission mode is defined in the physical layer.

The Transmission mode is divided into three categories based on the direction of data flow:

Transmission modes

 

Simplex mode: In Simplex mode, the communication is unidirectional, i.e., the data flow in one direction. A device can only send the data but cannot receive it or it can receive the data but cannot send the data.

Transmission modes

The radio station is a simplex channel as it transmits the signal to the listeners but never allows them to transmit back. Keyboard and Monitor are the examples of the simplex mode as a keyboard can only accept the data from the user and monitor can only be used to display the data on the screen.

Advantage of Simplex mode:

  • In simplex mode, the station can utilize the entire bandwidth of the communication channel, so that more data can be transmitted at a time.

Disadvantage of Simplex mode:

  • Communication is unidirectional, so it has no inter-communication between devices.

 

Half-Duplex mode: In a Half-duplex channel, direction can be reversed, i.e., the station can transmit and receive the data as well. Messages flow in both the directions, but not at the same time. The entire bandwidth of the communication channel is utilized in one direction at a time. In half-duplex mode, it is possible to perform the error detection, and if any error occurs, then the receiver requests the sender to retransmit the data.

Transmission modes

Walkie-talkie is an example of the Half-duplex mode. In Walkie-talkie, one party speaks, and another party listens. After a pause, the other speaks and first party listens. Speaking simultaneously will create the distorted sound which cannot be understood.

Advantage of Half-duplex mode:

  • In half-duplex mode, both the devices can send and receive the data and also can utilize the entire bandwidth of the communication channel during the transmission of data.

Disadvantage of Half-Duplex mode:

  • In half-duplex mode, when one device is sending the data, then another has to wait, this causes the delay in sending the data at the right time.

 

Full-duplex mode: In Full duplex mode, the communication is bi-directional, i.e., the data flow in both the directions. Both the stations can send and receive the message simultaneously. Full-duplex mode has two simplex channels. One channel has traffic moving in one direction, and another channel has traffic flowing in the opposite direction.

Transmission modes

The most common example of the full-duplex mode is a telephone network. When two people are communicating with each other by a telephone line, both can talk and listen at the same time.

Advantage of Full-duplex mode:

  • Both the stations can send and receive the data at the same time.
  • The Full-duplex mode is the fastest mode of communication between devices.

Disadvantage of Full-duplex mode:

  • If there is no dedicated path exists between the devices, then the capacity of the communication channel is divided into two parts.

 

Differences b/w Simplex, Half-duplex and Full-duplex mode:

Basis for comparisonSimplex modeHalf-duplex modeFull-duplex mode
Direction of communicationIn simplex mode, the communication is unidirectional.In half-duplex mode, the communication is bidirectional, but one at a time.In full-duplex mode, the communication is bidirectional.
Send/ReceiveA device can only send the data but cannot receive it or it can only receive the data but cannot send it.Both the devices can send and receive the data, but one at a time.Both the devices can send and receive the data simultaneously.
PerformanceThe performance of half-duplex mode is better than the simplex mode.The performance of full-duplex mode is better than the half-duplex mode.The Full-duplex mode has better performance among simplex and half-duplex mode as it doubles the utilization of the capacity of the communication channel.
ExampleExamples of Simplex mode are radio, keyboard, and monitor.Example of half-duplex is Walkie-Talkies.Example of the Full-duplex mode is a telephone network.

Again, There are three types of data transmission mode based on the number of receivers. Such as:

  1. Unicast
  2. Broadcast
  3. Multicast

Unicast: Unicast is a point-to-point or one-to-one transmission mode. Data is transmitted from one sender node to only one receiver node in simplex, half duplex or full duplex. This type of information transfer is useful when there is a participation of single sender and single recipient.

For example, a device having IP address 10.1.2.0 in a network wants to send the traffic stream(data packets) to the device with IP address 20.12.4.2 in the other network,then unicast comes into picture. This is the most common form of data transfer over the networks. The devices such as switch uses unicast mode of transmission.

Broadcast: Broadcast is a point to multipoint or one-to-all transmission mode. Data is transmitted from one node to all other nodes in the network in simplex.

This is useful when a device in one network wants to transfer packet stream to all the devices over the other network. This mode is mainly utilized by television networks for video and audio distribution. The devices such as bridge uses this.

Multicast: Multicast is a point to selected multipoint or one to selected group of members transmission mode. Data is transmitted from one node to Selected or authorized nodes in the network in simplex. The protocols such as IGMP, MPLS (uses labels instead of addresses) uses multicast transmission concept.

 

Lesson Evaluation-

Knowledge Based Questions:

  • a. What is data transmission mode?
  • a. What is simplex/half-duplex/full-duplex mode?
  • a. What is unicast/ broadcast/multicast mode?

Comprehension Based Questions:

  • b. Explain data transmission mode of mobile phone.
  • b. Explain data transmission mode of keyboard.
  • b. Explain data transmission mode of radio/television.
  • b. Explain data transmission mode of walkie-talkie.
  • b. Explain point-to-point data transmission mode.
  • b. Explain point-to-multipoint data transmission mode.
  • b. Explain point-to-selected multipoint data transmission mode.

Creative Questions:

Multiple Choice Questions:

 


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