The core difference between error detection and error correction code lies in their ability to handle errors: error detection identifies that an error has occurred, while error correction attempts to fix the error.
Error Detection Code
- Purpose: Error detection code is designed to detect errors that may occur during data transmission or storage. Its primary function is to signal the presence of an error.
- Mechanism: It works by adding redundant information to the original data. This redundant information allows the receiver to verify the integrity of the received data. If the check fails, an error is detected.
- Action on Detection: When an error is detected, the receiver typically requests retransmission of the data or simply discards the corrupted data. It does not attempt to reconstruct the original data.
- Examples: Common error detection codes include:
- Parity Bits: A simple method that adds an extra bit to make the total number of 1s either even (even parity) or odd (odd parity).
- Checksums: Calculate a value based on the data and transmit it alongside the data. The receiver recalculates the checksum and compares it to the received value.
- Cyclic Redundancy Check (CRC): A more sophisticated method that uses polynomial division to generate a checksum.
Error Correction Code
- Purpose: Error correction code goes a step further than error detection. Its purpose is not only to detect errors but also to automatically correct them without requiring retransmission.
- Mechanism: Similar to error detection, error correction also adds redundant information. However, the redundancy is designed to allow the receiver to identify the specific bit(s) that are in error and correct them.
- Action on Detection: When an error is detected, the receiver uses the redundant information to locate and correct the erroneous bit(s).
- Examples: Common error correction codes include:
- Hamming Code: Can detect and correct single-bit errors.
- Reed-Solomon Codes: Used in CDs, DVDs, and QR codes to correct burst errors (multiple consecutive errors).
Key Differences Summarized
| Feature | Error Detection Code | Error Correction Code |
|---|---|---|
| Purpose | Detect errors | Detect and correct errors |
| Action | Request retransmission or discard data | Correct errors automatically |
| Complexity | Generally simpler | Generally more complex |
| Overhead | Lower overhead | Higher overhead |
| Use Cases | Situations where retransmission is feasible | Situations where retransmission is not feasible |
In essence, error detection provides a flag that something went wrong, while error correction actively fixes the problem. The choice between them depends on the application's tolerance for errors, the cost of retransmission, and the complexity and overhead that can be tolerated.
