Beyond The Bits: Cooperative Packet Recovery Using Physical Layer Information

Abstract

Users increasingly depend on WLAN for business and entertainment. However, they occasionally experience dead spots and high loss rates. We show that these problems can be addressed by exposing information readily available at the physical layer. We make the physical layer convey its confidence that a particular bit is "0" or "1" to the higher layers. Access points that hear the same transmission communicate their confidence values over the wired Ethernet and combine their information to correct faulty bits in a corrupted packet. A single receiver may also combine the confidence estimates from multiple faulty retransmissions to obtain a correct packet. We implement our design and evaluate it using GNU software radios. The results show that our approach reduces loss rate by up to 10x in comparison with the current approach, and significantly outperforms prior packet combining proposals.