Locora: Practical Wi-Fi Packet Loss Diagnosis With Only Local Observations

In a Wi-Fi network, packet loss may occur due to bad channel, collision, or hidden terminal. The Wi-Fi protocol however cannot identify the causes of the loss, and may lead the nodes to take unnecessary or even incorrect actions. In this paper, we propose Loss Cause Oracle (Locora), which can diagnose the actual cause of the packet loss and make correct responses with only local observations. Locora is a comprehensive set of solutions that can estimate the collision probability, detect various kinds of hidden terminals, and interact with the rate selection algorithm and assist it to converge to the best data rate. Locora advances Wi-Fi packet loss diagnosis because it can handle all three types of packet loss while modifying only the packet sender and does not depend on any assumptions on the user traffic. We implement Locora in assembly language in the firmware of the BCM4306 wireless card on the OpenFWWF platform and our experiments show that Lococa achieves significant gains over existing schemes.