Comparison of General Multi-Carrier Schemes in Two Way Relaying Channels

In this paper multi-carrier transmission schemes applying general waveforms are discussed within two-phase two way relay channels. Here, two users communicate simultaneously on the same resources to an assisting relay. The relay has to cope with the superposition of both users, interferences of the channel and additional practical impairments like frequency and timing offsets. To be more robust against these impairments, Filter Bank Multi-Carrier (FBMC) systems with general waveforms are used. They offer better time-frequency properties by the cost of additional interference introduced by the waveforms than CP-OFDM applying rectangular waveform. The main contribution of this work is the performance analysis w.r.t. the sensitivity against phase differences of the user channels in FBMC with QAM and Offset-QAM (OQAM) modulation. BER performance analysis show that under realistic channel conditions QAM/FBMC outperforms OFDM as well as OQAM/FBMC with one antenna at the relay. If the relay use an additional antenna at the relay, the multi-carrier applying OQAM outperforms QAM modulation. Hence, the choice of OQAM or QAM depends on the number of antennas available at the relay.