Abstract: Natural radio environments are virtualized to test radio devices. In one example, this is done by extracting signals and messages recorded in the field and injecting them in the operation of a protocol tester. In another example, the radio environment is reproduced by generating channel impulse responses in a ray-tracer, then interpolating them in a channel emulator and supporting the interpolation by means of post-processing. In another example, the radio environment is recorded using a mobile terminal in the field. In another example, natural radio environments are produced by reconstructing realistic cell loads and, as a consequence, intra-cell interference for a given device under test.