1. A method of simulating a communications link using a link simulation tool implemented on computing equipment, wherein the communications link includes respective link subsystems and wherein the link subsystems in the communications link are represented by subsystem models in the link simulation tool, the method comprising: performing two-dimensional convolution operations on the subsystem models to determine link performance for the communications link using the link simulation tool, wherein the two-dimensional convolution comprises convolution on expressions that are a function of time and voltage, wherein the link subsystems comprise a transmitter subsystem that is represented by a transmitter subsystem model in the link simulation tool, and wherein performing the two-dimensional convolution operations comprises performing two-dimensional convolution operations with the transmitter subsystem model.