An amplify-and-forward based opportunistic network coding scheme for two-way wireless relaying systems

The two-way relaying system is a promising research direction, for which there are two well-known amplify-and-forward (AF)-based protocols: analog network coding (ANC) and time division broadcast (TDBC). In this paper, we first compare the outage probability performance of these two protocols under the same conditions. It can be observed that ANC performs better under the low SNR circumstance, while TDBC is superior in the high. On this basis we put forward an opportunistic network coding scheme, which can choose the better transmission strategy according to instantaneous channel state. More optimal performance can be obtained by the help of the improved scheme. Furthermore, we derive a tight lower bound of the outage probability for the opportunistic network coding scheme, which is very close to the exact value for the whole SNR range. This is proved by simulation and numerical results.