A 4 x 4 MIMO Discrete Multitone Wireline Transceiver With Far-End Crosstalk Cancellation For ADC-Based High-Speed Serial Links

This paper presents an area- and energy-efficient 4-lane far-end crosstalk (FEXT) cancellation wireline transceiver (TRX) with a multiple-input multiple-output (MIMO) discrete multitone (DMT) modulation. The channel estimation (CHEST) is an essential block for DMT TRX to find the MIMO equalizer coefficients at the receiver (RX) side. However, due to the high computational complexity, the matrix inversion in CHEST hinders the generalization to larger MIMO, such as 4x4, considering circuit implementation. In this work, we show that CHEST can be effectively approximated to an element-wise reciprocal instead of an inversion when some properties of the wireline channels are used as constraints. This approximation also simplifies the MIMO equalizer circuit and realizes a decentralized MIMO. Simulation results demonstrated that the FEXT noise from adjacent lanes is sufficiently canceled out even with our approximated CHEST and MIMO equalizer, achieving a symbol error rate (SER) of 2E-4 for communicating over a channel exhibiting insertion loss (IL) of 16 dB and 17 dB of IL-to-crosstalk ratio at Nyquist, while showing SER of 1e-1 when the FEXT is not canceled.