Cascading S-parameters, Segmented Analysis

F. de Paulis, Y. Zhang and J. Fan, "Signal/Power Integrity Analysis for Multilayer Printed Circuit Boards Using Cascaded S-Parameters," in IEEE Transactions on Electromagnetic Compatibility, vol. 52, no. 4, pp. 1008-1018, Nov. 2010.

T. Reuschel, S. Müller and C. Schuster, "Segmented Physics-Based Modeling of Multilayer Printed Circuit Boards Using Stripline Ports," in IEEE Transactions on Electromagnetic Compatibility, vol. 58, no. 1, pp. 197-206, Feb. 2016.

L. Ren et al., "A Hybrid Method for Signal Integrity Analysis of Traces and Vias in an Infinitely Large Plate Pair," in IEEE Transactions on Electromagnetic Compatibility, vol. 57, no. 4, pp. 885-893, Aug. 2015.

Ok, I really didn't read all of these papers but they seem to promote the approach to finding segment s-parameters and then cascading them together.