In which mode both communicating parties can send and receive at the same time?

Based on the direction of data from sender to receiver, there can be 3 types of transmission modes which are as follows

1. Simplex
2. Half-duplex
3. Duplex

Simplex:

In simplex mode, among the two devices which are communicating with each other, one device can only be a sender and the other can only be a receiver. Thus the sender device will not receive data but will transmit data, and the receiver device will only receive data but will not transmit or send any data. This transmission is unidirectional.

Examples: Keyboards and monitors or displays, traditional FM radios etc. Traditional FM radios only output broadcasted or transmitted audio from stations, but does not communicate back.

Advantage

1. The sender can use the full capacity of the medium to transmit data, so more data is transmitted at a time.

Disadvantage

1. One way connection, so no inter-communication between devices.  

Half-Duplex

In half-duplex, both devices which are communicating with each other can send and receive data, but not at the same time, that is, when one device is sending data then another device can only receive that data but can’t send data back. This is like a narrow bridge where vehicles from both end of the bridge can cross the bridge but not at the same time.  

Examples: walkie-talkie, CB radios etc.

Advantage

1. In half-duplex, both devices can send and receive data and also entire capacity of the transmission medium is used when transmitting data.

Disadvantage

1. As when one device is sending data then another one must wait, this can cause delay in sending the data at the right time.

Full-Duplex

In full-duplex or duplex mode, both devices can send and receive data at the same time. Here is this transmission mode, data going in a direction will share the capacity of the transmission medium with the data going in another direction. This sharing can be obtained by two ways, such as, by sharing the capacity of the medium, or having two physically separated transmission paths.

• 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:

• Simplex mode
• Half-duplex mode
• Full-duplex mode

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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.
• This transmission mode is not very popular as mainly communications require the two-way exchange of data. The simplex mode is used in the business field as in sales that do not require any corresponding reply.
• 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.
• The main advantage of the simplex mode is that the full capacity of the communication channel can be utilized during transmission.

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.

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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.
• A 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.

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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.
• The Full-duplex mode is the fastest mode of communication between devices.
• 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.

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.

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

Basis for comparisonSimplex modeHalf-duplex modeFull-duplex modeDirection 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.

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Which mode of communication can send and receive data simultaneously?

In which communication mode each station can both transmit and receive but not at the same time?