Low-complexity echo and NEXT cancellers for high-speed ethernet transceivers

Gigabit and multigigabit transceivers require very long adaptive filters for echo and near-end crosstalk (NEXT) cancellation. Implementation of these filters not only occupies large silicon area but also consumes significant power. These problems become even worse when the Tomlinson-Harashima precoding (THP) technique is used in applications such as 10-Gigabit Ethernet over Copper (10GBASE-T) as the input to the echo and NEXT cancellers is no longer a simple PAM-M signal. To reduce the complexity of these cancellers, in this paper, a novel method based on word-length reduction technique is proposed. The proposed design is derived by replacing the original input to the echo and NEXT cancellers with a finite-level signal, which is the sum of the input to the TH precoder and a finite-level compensation signal. Then, this modified input signal is recoded to have shorter word-length compared with the original input. Hence, the overall complexity can be reduced by using the proposed method. To further reduce the complexity of these cancellers, an improved design is proposed by exploiting the property of the compensation signal. Compared with the traditional design, the proposed echo and NEXT cancellers have exact input and do not suffer from the quantization problem, and thus they are more suitable for VLSI implementation. The proposed method can also be applied to design adaptive echo and NEXT cancellers with little modification. The performance evaluation is performed by simulations to verify the proposed design. It is shown that, by applying the proposed method to a 10GBASE-T ethernet system, the hardware complexity of echo and NEXT cancellers can be reduced by about 10.82% without performance loss, compared with the traditional design.