  Error propagation and noise propagation at the relay node would highly
degrade system performance in two-way relay networks. In this paper, we
introduce DNF-AF selection two-way relaying scheme which aims to avoid error
propagation and mitigate noise propagation. If the relay successfully decodes
the exclusive or (XOR) of the messages sent by the two transceivers, it applies
denoise-and-forward (DNF). Otherwise, amplify-and-forward (AF) strategy will be
utilized. In this way, decoding error propagation is avoided at the relay.
Meanwhile, since the relay attempts to decode the XOR of the two messages
instead of explicitly decoding the two messages, the larger usable range of XOR
network coding can be obtained. As XOR network coding can avoid noise
propagation, DNF-AF would mitigate noise propagation. In addition, bit error
rate (BER) performance of DNF-AF selection scheme with BPSK modulation is
theoretically analyzed in this paper. Numerical results verify that the
proposed scheme has better BER performance than existing ones.
