Constellation Data Systems, Inc.
Constellation Data Systems, Inc.


Serial Port Forward Error Correction
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Overview

Forward Error Correction (FEC) is a technology which allows the receiver of a message to detect and correct most single bit errors, and many multi-bit errors ( error bursts) without referring to the transmitter of the message. While commonly implemented in hardware digital logic, FEC can also be implemented in either firmware (click here for more information on FEC implementations based in firmware) or software (such as a device driver) as described here.

Effect of Error Rate upon Throughput

In PC based communications, using simple protocol technologies such as SLIP / PPP / HDLC / SDLC / and most custom protocols, the data error rate has an effect upon data throughput. Simply put, the higher the error rate, the lower the throughput. This effect is vastly amplified by the connection's propagation delays. Simply put again, the larger the propagation delay, the reduction in data throughput can be HUGE.

In a typical case where 22mS of propagation latency exists due to geosynchronous satellite connection, a simple single or multi bit error can stall a link for periods far greater than the 44mS of retransmit propagation burden. This is often due to the additional burden imposed by detection of dropped packets being performed in a layer which is separated from the physical link layer, such as scenario where TCP is a remote layer from the serial port device. Stall times arising from single bit errors on SLIP (Serial Link IP), for example, of 1 to 5 seconds are not unusual.

Serial Port Forward Error Correct ("SP FEC") Technology

This all done in a fashion whereby the serial port appears as a standard serial port to Operating Systems, Routers, and Application software. Most common single bit and multi bit error burst no longer stall the link, resulting an improvement in throughput. Intangibly also, by eliminating data stalls when browsing content, can transform end user frustration into end user satisfaction.

Data Flow Diagram






Sales and Product Information:

White papers which describe this technology are available. Click here for more information, or for sales and licensing of this technology.