A System Level Performance Study on Symbol-Wise XOR Based Bi-Directional Relaying

In this paper, we investigate the system performance on decode and forward based bi-directional relaying based on symbol-wise XOR operation. This technique gives more freedom of selecting modulation and coding scheme at relay station, and significantly relaxes its transmission bottom neck. However, the performance degradation occurs when the modulation orders of both links differ from each other. To mitigate such an impact, we exploit a repetition coding scheme in conjunction with a redundant modulation code scheme by overlapping MCS levels. To this end, a system level simulation proves that the proposed scheme achieves about 40% capacity gain over bit-wise XOR based bi-directional relaying and gives additional 7% gain over symbol-wise XOR based bi-directional relaying.