Bringing Cross-Layer MIMO to Today’s Wireless LANs

Recent years have seen major innovations in cross-layer wireless designs. Despite demonstrating significant throughput gains, hardly any of these technologies have made it into real networks. Deploy-ing cross-layer innovations requires adoption from Wi-Fi chip man-ufacturers. Yet, manufacturers hesitate to undertake major invest-ments without a better understanding of how these designs interact with real networks and applications. This paper presents the first step towards breaking this stalemate, by enabling the adoption of cross-layer designs in today’s networks with commodity Wi-Fi cards and actual applications. We present OpenRF, a cross-layer architecture for managing MIMO signal pro-cessing. OpenRF enables access points on the same channel to cancel their interference at each other’s clients, while beamform-ing their signal to their own clients. OpenRF is self-configuring, so that network administrators need not understand MIMO or physical layer techniques. We patch the iwlwifi driver to support OpenRF on off-the-shelf Intel cards. We deploy OpenRF on a 20-node network, showing how it manages the complex interaction of cross-layer design with a real network stack, TCP, bursty traffic, and real applications. Our results demonstrate an average gain of 1.6 × for TCP traffic and a significant reduction in response time for real-time applications, like remote desktop