Far-End Crosstalk Cancellation With MIMO OFDM for >200 Gb/s ADC-Based Serial Links

This brief presents an area- and power-efficient far-end crosstalk (FEXT) cancellation scheme with multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) for an analog-to-digital converter (ADC)-based ultra-high-speed serial links. The frequency-domain per-sub-channel equalization nature of OFDM allows a simple FEXT cancellation with MIMO equalizer in its digital signal processor (DSP), unlike time-domain pulse amplitude modulation (PAM) that requires heavy parallel cross-lane filtering for FEXT cancellation. With architectural modeling of a $2\times 2$ MIMO OFDM wireline transceiver (TRX), simulation results show that the main and FEXT channels’ frequency responses are properly estimated using pilot symbols. With the estimated channel responses, simulation results also show that the FEXT can be effectively canceled out with per-sub-channel MIMO equalization, achieving an overall symbol error rate (SER) of $1.4\times 10^{\mathrm {-5}}$ at 224Gb/s/lane for a channel having 23dB loss at 40 GHz, while the SER is $4\times 10^{\mathrm {-1}}$ without FEXT cancellation.