  Cross-technology communication (CTC) was proposed in recent literature as a
way to exploit the opportunities of collaboration between heterogeneous
wireless technologies. This paper presents LtFi, a system which enables to
set-up a CTC between nodes of co-located LTE-U and WiFi networks. LtFi follows
a two-step approach: using the air-interface LTE-U BSs are broadcasting
connection and identification data to adjacent WiFi nodes, which is used to
create a bi-directional control channel over the wired Internet. This way LtFi
enables the development of advanced cross-technology interference and radio
resource management schemes between heterogeneous WiFi and LTE-U networks.
  LtFi is of low complexity and fully compliant with LTE-U technology and works
on WiFi side with COTS hardware. It was prototypically implemented and
evaluated. Experimental results reveal that LtFi is able to reliably decoded
the data transmitted over the LtFi air-interface in a crowded wireless
environment at even very low LTE-U receive power levels of -92dBm. Moreover,
results from system-level simulations show that LtFi is able to accurately
estimate the set of interfering LTE-U BSs in a typical LTE-U multi-cell
environment.
