Automatic Repeat reQuest

Definition of Automatic Repeat reQuest

Automatic Repeat reQuest (ARQ) is a communication protocol used in data transmission systems to ensure error-free data transfer. It works by having the receiver automatically request retransmission of data packets when they are detected as being corrupted or lost. This error detection and correction process continues until the correct data is received, enhancing the reliability of the data transfer.


The phonetic representation of “Automatic Repeat reQuest” using the International Phonetic Alphabet (IPA) is: /ɔːˈtəʊmætɪk rɪˈpi:t rɪˈkwɛst/

Key Takeaways

  1. Automatic Repeat reQuest (ARQ) is an error control method to ensure reliable data transmission in communication systems by detecting and retransmitting corrupted or lost data packets.
  2. There are three main ARQ techniques: Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. Each technique varies in efficiency, complexity, and resource allocation for managing transmission errors.
  3. ARQ is particularly useful in wireless and noisy communication channels where the probability of data corruption is high. It helps to achieve reliable data transmission by minimizing the need for manual error correction and reducing the overall system latency.

Importance of Automatic Repeat reQuest

The technology term Automatic Repeat reQuest (ARQ) is important because it plays a vital role in ensuring reliable data transmission across communication systems.

In the digital world, information is often sent in the form of packets or blocks of data.

ARQ is an error control technique that checks the integrity of the received packets by utilizing error-detection codes, like checksums or CRC, and retransmits them when necessary to prevent data loss or corruption due to factors like noise, interference, or distortion.

As a result, ARQ contributes to efficient and accurate communication by maintaining the quality standards and reliability of the transmitted data, which translates into improved network performance and user experience.


Automatic Repeat reQuest (ARQ) serves a vital purpose in ensuring reliable and accurate data transmission in digital communication systems. Its primary function is to maintain the integrity of the information being exchanged over different mediums, such as wireless, wired, or optical networks.

To achieve this, ARQ uses an error detection and correction mechanism wherein the receiver automatically requests retransmission of a data packet in case it determines an error or damaged data upon reception. Utilizing this strategy, ARQ greatly reduces the probability of corrupted data or information loss during the communication process, meeting the ever-growing demand for high-quality and uninterrupted data exchanges, particularly in high-speed networks and other critical applications.

Various ARQ protocols are utilized to satisfy different specifications of communication systems, including Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. Commonly used in digital communication, like computer networks and satellite communications, the ARQ enables efficient management of data flow control, enhances transmission performance, and ensures data consistency even in environments with high signal interference or weak signal strengths.

For instance, its applications in satellite communications prove essential in mitigating the adverse effects of long propagation delays and high bit error rates. By incorporating ARQ into digital communication systems, users can enjoy smoother connectivity, fewer interruptions, and a significantly improved experience in transferring data, audio, and video content alike.

Examples of Automatic Repeat reQuest

Automatic Repeat reQuest (ARQ) is a crucial error-correcting technique used in data communication and networks to ensure the accuracy and reliability of data transfer. It works by detecting errors in data transmission and automatically requesting the data to be retransmitted until it is error-free. Here are three real-world examples of this technology:

WiFi Networks: ARQ plays an essential role in WiFi networks’ functionality by ensuring reliable and accurate data transfer. When a device connects to a WiFi network and sends data packets, if any corruption or errors are detected, the receiving device sends an acknowledgment indicating an error has occurred. The transmitting device then resends the affected data packet until an error-free transmission is confirmed.

Mobile Networks: Telecommunication networks, like 4G and 5G, rely on ARQ to maintain the quality of voice and data connections. When a mobile phone communicates with a cell tower, ARQ mechanisms detect and correct errors in data transmission by requesting retransmission of erroneous data packets. This ensures a clear and uninterrupted connection, even in circumstances with a weak signal or interference.

Satellite Communication: In satellite communication, data transmission occurs over long distances and can be affected by various factors such as interference, noise, and signal attenuation. ARQ helps secure accurate and error-free communication between satellites and ground stations by identifying missing or corrupted data packets and requesting their retransmission until they are successfully received and acknowledged.

Automatic Repeat reQuest: Frequently Asked Questions

What is Automatic Repeat reQuest (ARQ)?

Automatic Repeat reQuest (ARQ) is an error control protocol used in data communication systems to ensure reliable data transfer. It involves the detection and retransmission of missing or corrupted data packets by either the sender or the receiver, without any manual intervention.

How does ARQ work?

ARQ works by using acknowledgements (ACKs) and negative acknowledgements (NAKs) sent by the receiver to the sender. When the receiver successfully receives a data packet, it sends an ACK back to the sender. If the packet is missing or corrupted, the receiver sends a NAK back to the sender, requesting the retransmission of that particular packet. The sender then resends the packet until it is received correctly or a set number of attempts have been made.

What are the different types of ARQ?

There are three main types of ARQ: Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. Each type has its own approach to handling missing or corrupted data packets and is suited for different communication scenarios.

What are the advantages of using ARQ?

ARQ provides improved data reliability, as it ensures that all the transmitted data packets are received and processed correctly by the receiver, minimizing the impact of errors in the communication channel. This can be especially important in applications where data integrity is critical, such as in banking transactions or in communication between aircraft and ground control.

What are the disadvantages of using ARQ?

While ARQ improves data reliability, it also increases the transmission time and overhead, as the system waits for acknowledgements and potentially retransmits data packets. This can reduce the overall throughput of the communication system. In addition, ARQ may not be suitable for real-time applications, where delays caused by retransmissions can be detrimental to the quality of service.

Related Technology Terms

  • Error detection
  • Packet retransmission
  • ACK and NAK signals
  • Reliable data transfer
  • Flow control

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