  Hardware impairments in physical transceivers are known to have a deleterious
effect on communication systems; however, very few contributions have
investigated their impact on relaying. This paper quantifies the impact of
transceiver impairments in a two-way amplify-and-forward configuration. More
specifically, the effective signal-to-noise-and-distortion ratios at both
transmitter nodes are obtained. These are used to deduce exact and asymptotic
closed-form expressions for the outage probabilities (OPs), as well as
tractable formulations for the symbol error rates (SERs). It is explicitly
shown that non-zero lower bounds on the OP and SER exist in the high-power
regime---this stands in contrast to the special case of ideal hardware, where
the OP and SER go asymptotically to zero.
