  This paper presents OpenAirLink(OAL), an open-source channel emulator for
reproducible testing of wireless scenarios. OAL is implemented on off-the-shelf
software-defined radios (SDR) and presents a smaller-scale alternative to
expensive commercially available channel emulators. Path loss and propagation
delay are the fundamental aspects of emulating a wireless channel. OAL provides
a simple method to change these aspects in real-time. The emulator is
implemented using a finite impulse response (FIR) filter. The FIR filter is
written in Verilog and flashed on the SDRs Field Programmable Gate Array
(FPGA). Most processing transpires on the FPGA, so OAL does not require
high-performance computing hardware and SDRs. We validate the performance of
OAL and demonstrate the utility of such a channel emulation tool using two
examples. We believe that open-source channel emulators such as OAL can make
reproducible wireless experiments accessible to many researchers in the
scientific community.
