A radio communication device is tested by forwarding relevant signal
characteristic data derived at the physical (PHY) layer to the media
access control (MAC) layer for processing, analysis and feedback to the
radio circuit to improve performance. The relevant signal characteristics
are forwarded to the MAC within (appended to) a data packet. Thus, the
relevant signal characteristic is forwarded to the MAC along an existing
data path (a path originally designed to transfer the receive frame only,
but now transfers the combined receive frame with the attached radio
characteristic). The radio characteristic may be used for testing and/or
tuning the radio circuit. In one embodiment, the radio characteristic is
a frequency domain representation of a received signal. The radio is
tuned based on a channel estimate derived from comparison of frequency
domain representations of transmitted and received signals.