System Design I: Functional Decomposition

1. ECE/BENG-492 SENIOR ADVANCED DESIGN PROJECT Meeting #4 10 Aug 2010

2. ECE-492 Meeting#4 Q1: Which teams have a written draft of Requirements Specification? Q2: Which teams run a Conceptual Design session? Q3: Who read assigned chapters from the textbook?

3. System Design I:Functional Decomposition “At Sony, we assume all products of our competitors will have basically the same technology, price, performance, and features. Design is the one thing that differentiates one product from another in the marketplace” Norio Ohgo, Chairman and CEO, Sony • You take what you have done for Concept Sketching and refine into greater details, in a more systematic way • Look at Concept Sketching as ‘a proposition’ • Now refine your ‘proposition’ into a system architecture • Later follow deeper into a blueprint (‘Production Documentation’) in order to build/implement your system

4. Design DirectionBottom-Up vs. Top-Down • Bottom-up • The designer starts with basic components and synthesizes them to create the overall system • Consider designing a car from many parts – Will the final product meet requirements? • Pros: Leads to efficient subsystem • Cons: Difficult to meet requirement; Complexity difficult to manage; Difficult redesign • Top-down • The designer has an overall vision of what the final system must do, and the problem is partitioned into components, or subsystems that work together to achieve the goal • Pros: Highly predictable design cycle; Full utilization of requirements; Efficient development of large systems • Cons: More time spent in planning; May limit creativity

5. Black-Box Design and White-Box Design • Black-Box design – this is your first design step • You look at a system as a box, without knowing what is inside • Refer to requirements specification all the time • This step helps to: • Define interfacing methods with environment, other systems, and people • Define protocols of operating your system • Fine refine top-level functions /operations for the system • Let’s call this Level-0 design Operator/User Top-Level Functionality Description Inputs Outputs Environment

6. CASE STUDY#1< Level-0 Design >

7. After Black-Box design follow with White-Box Design • White-Box design – this is your second design step • Apply it only after Black-box design • You design a system with an understanding what are internal processes, modules/subsystems, and connections between them • Functional decomposition is probably the most pervasive design technique at this stage

8. Functional Decomposition • Functional Analysis • Identify top level functions (actions/objectives) the system must perform • Functions may ultimately be accomplished through the actions of the equipment, software, people • Specify “whats” (not “hows”) • Iteratively keep decomposing functions onto a lower-level functions • Functional Flow Block Diagram • End product of functional decomposition – shows sequence of system activities • Used to illustrate system organization and major interfaces • Functional Allocation • Combine or group similar functions into logical subdivisions, identifying major groups • Conversion of the “whats” into “hows” – system broken down into components

9. Level-0 Functionality Top-level functions Level-1 Function A Function B Function C Function D Function E Function F Second-level functions Level-2 E.2 E.4 E.5 E.1 E.3 E.3 E.6 Figure: System functional breakdown

10. Component-1 Component-2 Component-3 Function A Function B Function C Function D Component-4 Function E Function F Figure: Functional allocation

11. Levels in Functional Decomposition • Level-0 • This is where you start –the highest level involving one block only, i.e. a black-box corresponding to your system • Define inputs, outputs and system functionality • Level-1 • Typically referred as main system architecture • Architecture means the organization and interconnection between modules. Describe the operation – how modules work together. • Define functional requirements for each module. • Level-2 • Typically shows the organization of components within a single module

12. Decomposition process continues until you reach Detail Design • This is where the problem can be decomposed no further and you identify all available components • Number of levels can vary – your design should have Level-0, Level-1 and Level-2, at minimum • Proposal requires to include Level-0 and Level-1 design • Design Document requires all levels

13. Example: Audio Power Amplifier(Chapter 5.4) Level-0 Level-1

14. Example: Thermometer Design Level-0 Level-1

15. CASE STUDY#1< Level-1 Design >

16. Proposal • Each team needs to prepare and defend a project proposal • Proposal is a formal document explaining: • The need • Proposed technological solution (Technical section) • Team capability and plan to undertake the effort (Administrative section) • Proposal defense is a formal presentation • Educate yourself on: • Technical solution you propose • Top-down design process, system architecture • Systems engineering practice (project management)

17. Proposal Preparation • Your proposal is a formal document representing you ! • Don’t forget about nice printout, cover, etc. • Included drawings must be nice, clean, and readable • Look from a perspective that you compete for a limited pool of money • It means, the best proposals win and get funded • You have to attract a reader to your proposed work ! • Be realistic • Say something about the team and your skills (any exceptional issues?) • Write very well in a narrative form – get English checked • Particularly, pay attention to the Executive Summary

18. Proposal Format • Cover page • Executive summary (1/2 – 1 page) • Problem statement as an “Identification of Need”, Objectives, Motivation, etc. (1-2 pages) • Approach (2-4 pages) • Include problem analysis and requirements definition/analysis • Mention briefly about alternative approaches and why you have chosen the proposed one • Preliminary design (2-5 pages) • Preliminary experimentation plan (1-2 pages)

19. Preliminary list and brief description of major tasks and allocation of responsibilities (1-2 pages) • References • Literature references • Web URLs, etc. • People contacted

20. For the Next Meeting • Read textbook – Chapters 5 • Apply black-box and white-box designs to your problem • Teams - bring a diagram showing a draft of your system architecture • Have questions about proposal preparation and presentation • Next meeting: • System design II; Early prototyping; Proposal presentation