Nonlinear Equalization Approaches for Physical Layer Network Coding
Abstract: way relaying system employing physical layer network coding We consider a two-way in channels suffering from frequency-selective frequency selective fading. We study decision decisionfeedback equalization (DFE), a technique based on delayed decision-feedback decision sequence estimation (DDFSE), and Tomlinson Tomlinson-Harashima Harashima precoding (THP) approaches for mitigating the distortions introduced by the channel. For DFE, we introduce transmit filtering schemes that generate identical identical overall source-tosource relay channel impulse responses for both source nodes, while achieving the maximum signal-to-noise noise ratio after equalization for the zero zero-forcing and the minimum mean-squared squared error criterion, respectively. The advocated DDFSE approach oach also relies on transmit filtering at the source nodes. For the THP scheme, we derive the optimal precoding filters that guarantee an intersymbol interference free source source-to-relay relay transmission. In order to obtain a two-way two relaying system, which uses the the same equalization techniques in both transmission directions, we design a THP-based THP based compromise precoding scheme for the relay-to-destination destination transmission. The performance of the proposed techniques is compared with that of benchmark schemes with simpler filtering/precoding, where identical overall source-to-relay source relay channel impulse responses are enforced by straightforward but suboptimum choices for the transmit filters. Our results reveal that the developed schemes enable significant gains compared with thee benchmark schemes.