Analytical method for joint optimization of FFE and DFE
equalizations for multi-level signals

Nana Dikhaminjia – Mikheil Tsiklauri – Zurab Kiguradze – Jiayi He
– Arun Chada – Bhyrav Mutnury – James L. Drewniak

   Channel equalization is the efficient method for recovering distorted signal and correspondingly reducing bit error rate (BER). Different type of equalizations, like feed forward equalization (FFE) and decision feedback equalization (DFE) are canceling channel effect and recovering channel response. Separate optimization of tap coefficients for FFE and DFE does not give optimal result. In this case FFE and DFE tap coefficients are found separately and they are not collaborating. Therefore, the final equalization result is not global optimal. In the present paper new analytical method for finding best tap coefficients for FFE and DFE joint equalization is introduced. The proposed method can be used for both NRZ and PAM4 signals. The idea of the methodology is to combine FFE and DFE tap coefficients into one optimization problem and allow them to collaborate and lead to the global optimal solution. The proposed joint optimization method is fast, easy to implement and efficient. The method has been tested for several measured channels and the analysis of the results are discussed.

Keywords: bit error rate, channel equalization, channel response, DFE, FFE, joint optimization, PAM4, tap coefficients

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