Transmission Modes in Computer Networks (Simplex, Half-Duplex and Full-Duplex)

Transmission modes also known as communication modes, define how data is transferred between devices in a network or bus system. They are classified into three types: Simplex Mode, Half-Duplex Mode, and Full-Duplex Mode.

Note: It is also known as a communication mode. Buses and networks are designed to allow communication to occur between individual devices that are interconnected

Simplex Mode

In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit, the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one direction. 

Example: Keyboard and traditional monitors. The keyboard can only introduce input, the monitor can only give the output. 

Pros of Simplex Mode

• It is the most cost-effective mode, as it only requires one communication channel.
• There is no need for coordination between the transmitting and receiving devices, which simplifies the communication process.
• Simplex mode is particularly useful in situations where feedback or response is not required, such as broadcasting or surveillance.

Cons of Simplex Mode

• Only one-way communication is possible.
• There is no way to verify if the transmitted data has been received correctly.
• Simplex mode is not suitable for applications that require bidirectional communication.

Half-Duplex Mode

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is used in cases where there is no need for communication in both directions at the same time. The entire capacity of the channel can be utilized for each direction. 

\text{Channel capacity = Bandwidth * Propagation Delay}

Example: Walkie-talkie in which message is sent one at a time and messages are sent in both directions. 

Full-Duplex Mode

In full-duplex mode, both stations can transmit and receive simultaneously. It is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions. Here, signals going in one direction share the capacity of the link with signals going in another direction, this sharing can occur in two ways: 

• Either the link must contain two physically separate transmission paths, one for sending and the other for receiving.
• Or the capacity is divided between signals traveling in both directions. 

\text{Channel Capacity = 2 * Bandwidth * propagation Delay}

Example: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time. 

Pros of Full-Duplex Mode

• Ideal for real-time applications such as video conferencing or online gaming.
• Provides a high level of reliability and accuracy, as there is no need for error correction mechanisms.

Cons of Full-Duplex Mode

• It's the most expensive mode, as it requires two communication channels.
• It is more complex than simplex and half-duplex modes, as it requires two physically separate transmission paths or a division of channel capacity.
• Full-duplex mode may not be suitable for all applications, as it requires a high level of bandwidth and may not be necessary for some types of communication.