Forward Error Correction (FEC)
FEC is a technique used to detect and correct errors in transmitted data without the need for retransmission. FEC involves adding redundant information (parity bits or error-correcting codes) to the transmitted data. This redundant information allows the receiver to detect and correct errors without requiring the sender to resend the data.
FEC is efficient in scenarios where the round-trip delay or retransmission overhead is high, as it can correct errors on the fly without the need for additional communication between the sender and receiver. While FEC can effectively correct errors, it comes with the overhead of adding redundant data to the transmitted stream, which increases bandwidth utilization.
Reed-Solomon codes and convolutional codes are examples of FEC techniques used in various communication systems, such as satellite communication and digital broadcasting.
Automatic Repeat reQuest (ARQ)
ARQ is a technique used to ensure data integrity by requesting retransmission of lost or corrupted packets. In ARQ, the receiver detects errors in the received data and sends a request to the sender to retransmit the corrupted or missing packets.
ARQ is efficient in scenarios where the error rate is relatively low or when the round-trip delay is acceptable. It ensures data integrity by requesting retransmission only when errors occur. ARQ introduces additional communication overhead due to the need for retransmission requests and acknowledgments, which can impact overall system efficiency.
Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ are examples of ARQ protocols used in various communication systems, including wireless networks and the Internet.
FEC vs ARQ: Key Takeaway
| Basis | Forward Error Correction (FEC) | Automatic Repeat reQuest (ARQ) |
| Operation | Adds redundant information to the transmitted data for error detection and correction. | Detects errors in received data and requests retransmission of corrupted or missing packets. |
| Efficiency | Efficient in scenarios with high error rates or significant round-trip delays. | Efficient when the error rate is low or when latency is acceptable. |
| Latency | Minimal latency, as errors are corrected on the fly. | May introduce additional latency due to retransmission requests and acknowledgments. |
| Complexity | Generally simpler to implement, as it does not require coordination between sender and receiver for error recovery. | Can be more complex to implement due to the need for sender-receiver coordination for retransmissions. |
| Overhead | Increases bandwidth utilization due to the addition of redundant data. | Introduces additional communication overhead due to retransmission requests and acknowledgments. |
| Examples | Reed-Solomon codes, Convolutional codes. | Stop-and-Wait ARQ, Go-Back-N ARQ, Selective Repeat ARQ. |