Energy Efficiency, Arithmetics and Design Effort on FPGAs

1. Energy Efficiency, Arithmetics and Design Effort on FPGAs Case study: Reconfigurable Miniature Sensor Nodes for Condition Monitoring Teemu Nyländen, Jani Boutellier, Karri Nikunen, Jari Hannuksela, Olli Silvén

2. Introduction • WSNs for condition monitoring • Wide range of algorithms with very different processing needs • Need to adapt to prevailing energy conditions • Cheap and low power • Fixed design out of question • Floating point vs Fixed point • Typically fixed point preferred in embedded designs • Floating point designs do not necessarily carry energy efficiency penalty • The design time and effort speaks for floating point designs • FPGAs vs ASICs • ASICs usually targeted to a larger spectrum of users and applications • FPGA based implementations can be made more specific

3. Our TTA mote • Flash FPGAs help to avoid overprovisioning and provide for energy efficient implementations that rival off-the-shelf SoCs for sensor node designs • Floating point implementations rival fixed point designs • Transport triggered architecture (TTA) is an attractive framework for designs • Instruction level parallelism at low programmability overheads

4. Why wireless? • Wouldn’t it be much easier to use wired solutions? • Connections break easily • Maintenance a major expenditure • Wired solutions cannot be used everywhere • Wireless is simply easier, cheaper and enables condition monitoring in places formerly impossible http://www.hub-4.com/news/s1/5000/compact-online-sensor-monitors-condition-of-vibrating-screens-pumps-and-motors

5. Why energy autonomous? • There is plenty of energy available in the industrial environment. Why do you need energy harvesting? • Energy harvesting enables wireless solutions • Batteries cannot always be replaced • Currently battery/super condensator needed http://vibpower.w3.kanazawa-u.ac.jp/about-e.html

6. Why not just use off-the-shelf WSN solutions or ASICs? • Off-the-shelf solutions are often compromises • Target as wide spectrum of users as possible • Low power consumption • Low power consumption but poor performance or vice versa • ASICs • Very low power, very energy effiecient • Long design and testing times • Fixed

7. Flash vs SRAM FPGA Altera Cyclone III + Embedded multipliers + Unlimited reprogrammability + Logic element composition (4LUT) - Higher static and therefore total power consumption Actel Igloo + Designed for energy efficiency + Very low static power consumption - Limited reprogrammability - Logic element composition (3LUT) - No embedded multipliers - 130 nm technology

8. Power dissipation

9. Our TTA mote • 32-bit,16-bit floating point and 16-bit fixed point More about TTAs: http://tce.cs.tut.fi

10. Bearing fault monitoring • Time and frequency based analysis • Time: RMS, Kurtosis,... • Frequency: Spectrum analysis • Processing needs vary greatly • Analysis based on the energy state

11. Floating point vs Fixed point

12. Floating point vs Fixed point

13. TTA mote vs off-the-shelf solutions

14. TTA mote vs TelosB

15. THANK YOU!