Write the problem statement and perhaps a separate system model section.

From "How to Write a Technical Paper: Structure and Style of the Epitome of your Research":

Problem Statement

Often, this section is merged with the system model.
State your problem clearly. Be as exact as possible into
stating what the question of the problem is. It reflects
poorly upon an author if he cannot describe or does not
know what problem his solution addresses. But most importantly, it will be easier for successive researchers to
classify your work.