Investigation on Gaussian Waveforms to Improve Robustness in Physical Layer Network Coding

In this paper, two-way relaying networks using physical layer network coding under practical constraints are considered. In the multiple access phase, both users transmit their messages simultaneously on the same resources. At the relay a superposition of both massages is received containing the influence of the channel as well as the impact of Carrier Frequency Offsets (CFOs) and Timing Offsets (TOs), respectively. To be more robust against these impacts, a combination of a generalized Frequency Division Multiplexing (FDM) system, which uses Gaussian waveforms is analyzed in comparison to classical Orthogonal Frequency Division Multiplexing (OFDM). The additional interference introduced by the non-orthogonal impulse shape is treated by an additional linear equalizer. The overall system performance of the classical OFDM system and non-orthogonal waveforms is compared for Physical-Layer Network Coding (PLNC) with respect to the Signal to Interference and Noise Ratio (SINR) and the achievable mutual information in the PLNC system. The obtained simulation results show that a well designed Gaussian waveform outperforms the classical OFDM system with guard interval.

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