Rotationally Invariant Coded Modulation for physical layer network coding in two-way relay fading channel

We investigate a novel coded modulation scheme for physical layer network coding (PLNC) in the two-way relay (TWR) fading channel. Using an adaptive soft demodulator and independent decoding levels, the proposed scheme can eliminate the effect of fading on the TWR channel. To reduce system complexity at the relay, we also give a low-complexity two-demodulator scheme. Based on maximizing the mutual information between received signal and network coded symbol, the adaptive selection of the two demodulators is then optimized. The proposed simplified scheme exhibits advantages in terms of flexibility, complexity and performance.