In this section you tell about how you intend to figure out what the sub-problems are and what approaches or theories you will use to solve them. This phase focuses on theory, analysis and conceptualization. If your project is a research project, then you will probably describe your scientific hypothesis here.
Most FYP advisors have their own expectations for the design section. You can ask yours directly, or you can check out the FYP Advisor Preferences page.
Your design section should be divided into several subsections (2.1.1, 2.1.2, etc.), and each design subsection usually maps back to one objective. However, you may have more than one design subsection related to a particular objective.
This section should also flow naturally from your Literature Survey, and it can include any data structures and message structures you may use.