5 Data Transmission Modes in Computer Networks You Should Know

Pohan Lin
Published 03/03/2023
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Five Data Transmission ModesData transmission is something that happens every day. Even before modern interconnected computer networks, we were sending analog signals like radio transmissions. Now, with millions of digital devices in use globally, data transmission happens more than ever before.

Data Transmission in Computer Networks Explained

When we say data transmission, we’re talking about the flow of information in a network. The three basic data transmission types tell us in what direction the data flows. These subtypes tell us how that data is transmitted.

In a computer network, the physical layer handles data transmission. That means physical infrastructure like fiber-optic cables or electromagnetic signals broadcast by wireless network transmitters.

What are the Three Basic Types of Data Transmission?

The basic data transmission types tell us which direction data moves between sender and receiver. These are:

  • Simplex Data Transmission
  • Half-Duplex Data Transmission
  • Full-Duplex Data Transmission



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In a simplex transmission, data is only sent in one direction from sender to receiver. Half-duplex connections can transmit both ways, but not simultaneously. Full-duplex connections transmit data both ways at the same time, this is the most common type found in computer networks.

What are Serial and Parallel Transmission?

There are two ways of grouping bits of data and sending them across a network. Serial transmission means bits are sent sequentially, whereas parallel transmission sends data packets simultaneously.

Parallel Transmission

In parallel transmission, binary data is grouped into bits. The number of groups corresponds to the number of threads between the sender and receiver, and the groups are transmitted simultaneously.


This method allows for groups of bits (bytes) to be transmitted faster than serial transmission. However, because separate lines are required for each bit, building infrastructure this way would be costly.

That’s why we mostly see parallel transmission within devices, like computer processors, for example. The communication between an API like RDD and the Spark codebase is another example of parallel transmission.

Serial Data Transmission

In serial data transmission, each bit is sent one after the other in sequence. This is the type of data transmission method devices use to communicate over a network.

Since the sending or receiving devices will use parallel transmission internally, converters (serial to parallel and parallel to serial) are used at the interface point between the device and the line.


Parallel transmission always happens in synchronicity with the system clock. Serial transmission, though, can be subdivided into three further groups based on the synchronization of the sending and receiving device.

What are Synchronous and Asynchronous Transmission?

When data is sent at a synchronized rhythm, defined by the system clock, we call it synchronous transmission. Some types of data, like live video streams, need highly synchronized data feeds that arrive constantly. Other types can be sent asynchronously.


In synchronous transmissions, data is sent in frames. These are long continuous strings of uninterrupted binary data. The receiving device counts the bits of binary data, using the synchronicity between devices (defined in the data layer) to count the length of a byte.

Since data is sent as a constant stream, synchronous transmission allows for high transfer speeds. This kind of transmission is used for high-speed connections between modern computer networks.



This method sends bytes with an additional “start” and “stop” bit at the beginning and end. That means the receiving device knows the length of a byte without synchronizing with the transmitter.

By counting the start and stop bits, the receiver can resynchronize the data stream at the byte level each time a new signal is received. This method is often used for low-speed transmissions, such as the input data from your keyboard or sporadic data from business microservices.



When an image or audio signal needs to be broadcast at a specific frame rate, uninterrupted, then synchronous and asynchronous transmission both fall short. The entire bit stream needs to be synchronized and sent at a constant rate with no gaps between frames.

This is where Isochronous transmission is used. You might see this in a digital TV broadcast signal, or a live streaming service.

Transmission Modes Summarized

So when it comes to data transmission in computer networks, we define modes by the direction of data flow, the number of simultaneous bits being sent, and the synchronicity of devices.

Direction – Simplex, Half-duplex, Full duplex

Number of simultaneous bits – Serial or Parallel

Synchronicity – Synchronous, Asynchronous, Isochronous

Each method has its uses. A network and each of its parts could use every kind of transmission at some stage. Whether you’re Ad Hoc testing with remote developers or crunching numbers on your desktop, data transmission never stops.

About the Writer

Pohan LinPohan Lin is the Senior Web Marketing and Localizations Manager at Databricks, a global Data and AI provider connecting the features of data warehouses and data lakes to create lakehouse architecture. With over 18 years of experience in web marketing, online SaaS business, and ecommerce growth. Pohan is passionate about innovation and is dedicated to communicating the significant impact data has in marketing. Pohan Lin also published articles for domains such as Pics.io.