HARQ, or Hybrid Automatic Repeat Request, is a method of error correction used in data transmission. It combines two different methods, Forward Error Correction (FEC) and Automatic Repeat Request (ARQ), providing better performance than either method alone.
How does HARQ work?
In standard ARQ, redundant bits are added to transmitted data, and a receiver who detects an error requests a retransmission of the message. In HARQ, the original data is encoded with an FEC code, which adds parity bits to the message. These parity bits are either sent immediately, along with the message, or transmitted on demand if the receiver detects a corrupted message.
HARQ can also work without an Error-Detection (ED) code, making it possible to perform both FEC and ED using techniques such as Reed-Solomon code. It provides a more efficient use of bandwidth while maintaining the accuracy of transmission.
What are the benefits of HARQ?
HARQ provides several benefits over other error-correction techniques:
- Reduced latency: HARQ allows the receiver to correct errors without waiting for retransmissions
- Improved reliability: HARQ provides better transmission accuracy than FEC or ARQ alone
- Increased efficiency: HARQ can transmit more data per unit of time than other error-correction techniques
How is HARQ different from ARQ?
ARQ only uses redundancy to correct errors, and if an error occurs, it requests a retransmission of the entire message. HARQ combines FEC and ARQ into a single protocol, which can correct errors using the parity bits while maintaining the reliability of ARQ.
Can HARQ be used in wireless networks?
Yes, HARQ is suitable for wireless transmission, where errors are more frequent due to interference, noise, and signal attenuation. The use of HARQ in wireless networks helps to improve their data transmission performance and robustness.
Is HARQ widely used in modern communication standards?
Yes, HARQ is used in many modern communication standards, including LTE, WiMAX, and 5G. It is an essential component of Error Control Procedures in these standards and plays a crucial role in improving the reliability and efficiency of wireless data networks.
HARQ is a valuable technology that can improve the reliability, efficiency, and latency of data transmission. Its combination of FEC and ARQ techniques enables it to provide better performance than either method on its own. This technology has become an essential part of modern communication standards, helping wireless networks to deliver high-quality data services to millions of people worldwide.