Analysis of Cascaded Tomlinson-Harashima Precoding with Feedforward Equalizer for Pre-cursor Removal

In theory, a Tomlinson-Harashima precoding (THP) implemented in a wireline transmitter (TX) can compensate for all inter-symbol interference (ISI) present in the transmitted data regardless of the channel profile. However, to eliminate pre-cursors, a TX suffers from reduced output swing, resulting in an inferior noise margin. In this paper, we propose cascading a feedforward equalizer (FFE) to a THP and analyze its design merits: Vertical eye margin (VEM) and modulus of the modulo operation with different THP topologies are compared. Mathematical analysis and simulation results conclude that the cascade of a THP and an FFE outperforms a conventional THP for channels having a pre-cursor.