  We propose WiPLUS -- a system that enables WiFi to deal with the stealthy
invasion of LTE-U into the frequency bands used by WiFi. Using solely MAC layer
information extracted passively, during runtime, out of the hardware registers
of the WiFi NIC at the WiFi access point, WiPLUS is able to: i) detect
interfering LTE-U signals, ii) compute their duty-cycles, and iii) derive the
effective medium airtime available for each WiFi link in a WiFi Basic Service
Set (BSS). Moreover WiPLUS provides accurate timing information about the
detected LTE-U ON and OFF phases enabling advanced interference mitigation
strategies such as interference-aware scheduling of packet transmissions, rate
adaptation and adaptive channel bonding.
  WiPLUS does not require any modifications to the WiFi client stations and
works with commodity WiFi APs where it has a simple software installation
process.
  We present the design, the implementation details and the evaluation of the
WiPLUS approach. Evaluation results reveal that it is able to accurately
estimate the effective available medium airtime for each link in a WiFi BSS
under a wide range of LTE-U signal strengths with a root-mean-square error of
less than 3% for the downlink and less 10% for the uplink.
