THE UNIVERSITY OF SYDNEY © MAHYAR SHIRVANIMOGHADDAM 1
Tutorial 4: Exam Preparation ELEC5518: IoT for Critical Infrastructure
EXAMPLES 1
The personal area network (PAN) is used to gather periodical information on the average temperature of a given area. N motes are geared with temperature sensors. Consider the following two scenarios:
1) The sensors periodically report their measures to the PAN Coordinator which then relays each report to the information sink which performs the average operation.
2) The sensors periodically report their measures to the PAN Coordinator which performs the average operation and then sends one averaged sample to the information sink.
Sensor
PAN Coordinator Sink node
rD
d
Sensor
Assuming that:
• The length of each packet containing the temperature samples and the averaged temperature is b=100
[bits].
• The energy for operating TX/RX circuitry is Ec = 50[nJ/bit];
• the energy required to support sufficient transmission output power Etx(d) = kd2[nJ/bit], being
k = 1[nJ/bit/m2];
• the energy required to perform the average operation is Ep = 4[nJ] for each temperature measure;
• the energy consumption at the sink node is negligible.
i) Write the overall energy consumption to get one averaged temperature value at the sink in the two aforementioned scenario.
ii) Assuming that D = 10m, d = 5m, and r = 1m, wich scenario is more energy efficient?
iii) What is the optimal value of r to minimize the overal energy concumption in Scenario 1 and Scenario
2.
THE UNIVERSITY OF SYDNEY
© MAHYAR SHIRVANIMOGHADDAM 2
EXAMPLAE 2
Consider a wireless sensor network consisting of two sensors and one access point. Each sensor measures the temperature and sends it to the access point via the slotted ALOHA scheme and access probability p = 0.5. Determine the average total energy consumption to get at least one measurement at the access
point.
Assume that Esensing = 1μJ, Ecircuit = 1μJ/bit , Etx = d2μJ/bit , and each measurement is a packet
of length b = 100 bits .The total energy is the sum of the energy consumed at Sensor 1, Sensor 2, and Access Point.
EXAMPLES 3
Consider the following data set which represents some sample pies that Johnny likes. We are using decision tree to classify this data set.
No.
Crust size
Shape
Filling size
Class
1
big
circle
small
pos
2
small
circle
small
pos
3
big
square
small
neg
4
big
circle
small
neg
5
big
square
big
pos
6
small
square
small
neg
7
small
square
big
pos
8
big
circle
big
pos
i) What is the most informative attribute and what is the respective information gain to start partitioning the data?
ii) Draw the optimal decision tree for this data set.