Efficient Software Partial Packet Recovery in 802.11 Wireless LANs

In 802.11 wireless LANs, partial packets are often received which usually contain only a few errors. According to the current 802.11 standard, such packets have to be retransmitted. Much effort has been invested recently in repairing such packets without retransmitting the entire packet, e.g., by using error correction (EC) code or retransmitting only the corrupted blocks. In this paper, we study the software partial packet recovery and propose a comprehensive scheme called UNITE with the following key features. First, UNITE supports both the EC-based and block-based methods, because they are suited for different scenarios and can complement each other to achieve higher performance. Second, UNITE employ AMPS, an error estimator designed by us, which is capable of estimating the error condition in each individual partial packet and providing key information for repairing the packet. Third, UNITE selects the repair method for each packet to optimize the link performance under configurable system resource constraint, such as CPU or power. We implement UNITE on the Madwifi open-source driver. Our experiments show that UNITE outperforms other recovery schemes while not over-consuming the system resources.