SDI Seminar

Speaker: David Eckhardt, CMU

A Case for Adaptive Error Correction in a Wireless Local Area Network

Date: April 3, 1997

Abstract:

Wireless transmissions are highly susceptible to noise and interference. As a result, the error characteristics of a wireless link may vary widely depending on environmental factors such as locations of the communicating systems and activity of competing radiation sources. Strategies such as retransmission and Forward Error Correction (FEC) can greatly increase the usability of even the noisiest links. However, the strong FEC employed in poor conditions requires so much bandwidth that it is undesirable when link errors are rare.

In this paper we propose the use of adaptive error correction in a wireless LAN environment. We observe that dynamically adapting the degree of error correction to the error environment is practical because changes in the error environment are often caused by human actions such as the motion of a cordless phone, which take place over seconds, whereas adaptation protocols can respond in tens or hundreds of milliseconds.

Based on low-level packet traces, we determine that observed changes in the error environment support the use of varying error correction strategies, that FEC is effective in recovering from bit corruptions, and that packet length adjustments can reduce packet truncation.