This document discusses design challenges and solutions for energy efficiency in cyber-physical systems (CPS). It outlines key CPS challenges such as timing issues, miniaturization, and energy efficiency. It then describes approaches to optimize low power design at various layers, including low-energy VLSI techniques and low power communication methods. Two edge mining techniques called the Spanish Inquisition Protocol and Bare Necessities are introduced to reduce the number of sensing messages and achieve lower energy consumption. These techniques introduce state estimation and event detection at edge nodes to send aggregated data instead of raw sensor readings. This helps improve privacy by making it impossible to use the data for unintended purposes. Both techniques significantly reduce the number of data transmissions needed. The document

1. Cyber Physical Systems –
Solutions for Design Challenges
Part 1- Energy and Architecture
Sumanth Bhat
7th July 2015

2. Recap: Design Challenges for CPS
1. Abstraction issues
2. Timing issues
3. Architecture models
4. Miniaturization and Energy efficiency
5. Precision
6. Security & Privacy
7. Standardization

3. Low Power Designs for CPS
• Can be optimized at various layers
• Low energy VLSI design techniques - Near threshold Vdd operation

4. Low power communication
• “Communication is more expensive than computation”
• Edge mining techniques
1. Spanish Inquisition Protocol
2. Bare Necessities

5. Edge Mining
• “Data mining that takes place on the wireless, battery-
powered, smart-sensing devices that sit at the edge of
the IoT”
• Aim : To reduce number of sensing messages (packets) ,
thus achieving lower energy consumption and storage
area.

6. Data mining at the edge
• Instead of streaming raw data,
introduce state estimation and event
detection.
• Ex : In case of just streaming the data of
whether a new person has entered a
room, send out aggregated data such
as how many people are there in the
room etc.

7. Edge mining and privacy
• Due to introduction of states and event detection in edge nodes, raw
data is not stored anywhere.
• This makes it impossible to use available data for using it to any other
purpose than intended purpose.
• Example : Edge mining with GPS data may send out data such as “At
home”, “At work”, “In transit” rather than sending out raw GPS co-
ordinates. Thus, tracking your activities at minute level is not possible.

8. Introduction to SIP
• Spanish Inquisition Protocol
• Edge node transmits only that which the data sink (central
database server) does not expect
• Models can be fit in for the measured parameter, and hence only
the measured values that are not expected / outliers can be
transmitted.

9. Algorithm
1. Sensing : Obtain vector of sensor readings, and current time
2. Filtering : Estimation of new state using current sensor readings and old
state and time values
3. Prediction : Predict the sink state using old sink state and timing values,
and new timing value
4. Innovation Calculation : This is the difference between the new state
estimate and the predicted sink state
5. Conditional Transmission : Transmit new state and sequence number to
server if,
• innovation is greater than some threshold, or
• time since the last transmission exceeds a threshold
6. Acknowledgement: Post this stage, local copy of sink state and timing is
updated.

10. Performance
• Packet transmission reduced by around 95.5 %

11. Time-discounted Histogram Encoding (BN)
• Bare Necessities (or BN) is used for summarising relative
time spent in given states.
• Example, for determining how long is spent in a certain
modality (walking, driving, standing) in a given day.
• BN reduces the number of transmissions by 99.98%

12. Algorithm..
• If a sensed value is within a certain bin, then the bin count
B− is incremented
• A discount factor is also applied so that more recent states
are given more weight than older states.
• The counts are then converted to a normalised distribution

13. Architecture
• Needs to cater for heterogeneous
network performance
• Real Time Control
• Context-Aware Security
• Hard to come up with unified
CPS architecture!

14. 3-tier Architecture overview

15. Service Oriented Architecture