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Quiz-1 paper solution

Quiz-1 paper solution
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Internet of Things (ELEC4740)

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ELEC4740 Internet of Things

Quiz-1 (Sample Answer)

2020

Answer all questions:

  1. Discuss three main requirements of an IoT network. Explain how the Bluetooth network standard support above requirements.

[5]

Main five requirements are given in the following table, any three can be used for the answer.

IoT Network Requirements Bluetooth Network Features Mostly generate and transmit short data bursts; mainly machine generated sensor data

The standard support small to medium size payload in data packets. Payload size depends on the connection type. The standard also support longer data burst transmissions using the L2CAP protocol. The L2CAP protocol support the segmentation and reassembly property to send larger payloads over the Bluetooth links. Data generation rate can be periodic, aperiodic or random, i. data/packet interarrival time could be variable

Bluetooth network can support variable packet scheduling policy. The cluster head can adjust the POLL messaging frequency to transmit packets arriving with different interarrival time. Generally the aperiodic or random traffic is supported using the ACL links. It can also support synchronous/periodic traffic such as voice using the SCO connections Low power consumption for prolonged battery life.

Three class of devices supported with different maximum transmission power. In addition, power control algorithm is used. Power consumption is also controlled by regulating the duty cycle of a Bluetooth device. Different quality of service (QoS) requirement needs to be supported. QoS is generally defined by the throughput, packet delay, packet loss and delay jitter.

Generally the QoS is determined by the throughput and delay values. Different QoS requirements can be met by controlling polling frequency. Also choice of connection type such as ACL, SCO and eSCO, as well as retransmission and channel coding techniques are used to support different QoS requirements. Support short to longer transmission distances as well as indoor/outdoor deployments supporting different node

Bluetooth supports both short and longer distance transmissions. In addition, different node densities are managed by using the Piconet and the Scatternet architecture. Piconet can support a smaller operating area whereas the scatternet architecture support longer transmission ranges.

  1. Consider an IoT system used for an environmental monitoring task in a city park. Assume that 4 sensor nodes are placed in the park that are connected to an Edge server. Each sensor node is connected to three on board sensors. Sensor nodes 1 and 2 generates data at a 10 sec frequency while other nodes data generation frequency is 70 sec. All sensor nodes accumulate data at every 5 minute and transmit the payload to the edge server. Sensor nodes (SN) 1 and 2 use 24 bit ADCs (Analog to Digital Converter) while other nodes use 12 bit ADCs. All sensor nodes transmit data to the edge server using the Bluetooth DH3 ACL links. Necessary DH3 connection features are listed below.

DH3 connection parameters: Payload: 0-183 byte, slot size: 625 μsec.

a. Calculate the payload size used by sensor nodes 1 and 2. b. Data transmission delay to the edge server from SN 1 to S4. c. Suggest a technique that can be implemented on these sensor nodes to reduce power consumption.

[3+3+6 =12]

Sensor node 1 (SN1) and 2 (SN2) generates data every 10 sec. SN3 and SN4 generates data every 70 sec.

Payload of SN1 and SN2:

a. Payload of a sensor node 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃=𝑛𝑛𝑠𝑠×𝑁𝑁𝑠𝑠×𝑁𝑁𝑇𝑇 where 𝑛𝑛𝑠𝑠𝑖𝑖𝑖𝑖 𝑡𝑡ℎ𝑒𝑒 𝑛𝑛𝑃𝑃.𝑃𝑃𝑜𝑜𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑏𝑏𝑏𝑏𝑏𝑏𝑠𝑠 ,𝑁𝑁𝑠𝑠 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑒𝑒𝑛𝑛 𝑃𝑃𝑜𝑜 𝑖𝑖𝑃𝑃𝑛𝑛𝑠𝑠𝑃𝑃𝑒𝑒 𝑖𝑖𝑛𝑛 𝑃𝑃 𝑡𝑡𝑖𝑖𝑛𝑛𝑒𝑒 𝑛𝑛𝑛𝑛𝑖𝑖𝑡𝑡 𝑃𝑃𝑛𝑛𝑃𝑃 𝑁𝑁𝑇𝑇𝑖𝑖𝑖𝑖 𝑡𝑡ℎ𝑒𝑒 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑒𝑒𝑛𝑛 𝑃𝑃𝑜𝑜 𝑡𝑡𝑒𝑒𝑛𝑛𝑛𝑛𝑖𝑖𝑛𝑛𝑃𝑃𝑃𝑃𝑖𝑖.

⇒ 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃= 24 ×

60

10

× 3 = 432 𝑛𝑛𝑖𝑖𝑡𝑡𝑖𝑖/ min= 2160 𝑛𝑛𝑖𝑖𝑡𝑡𝑖𝑖/5min= 270 𝐵𝐵𝑃𝑃𝑡𝑡𝑒𝑒/5𝑛𝑛𝑖𝑖𝑛𝑛

b. This question had a typo; the question should be “ Data transmission delays to the edge server from SN1 and SN2.”

Payload of SN1 is already worked out in (a). This payload will be transmitted in two DH3 slots. For each DH3 transmission slot a poll slot is necessary. Hence, to transmit data using two DH3 slots total four slots will be necessary.

Data transmission time from SN1, 𝑇𝑇𝐷𝐷= 4∗ 625 × 10 −6= 2 × 10 −3sec= 2 𝑛𝑛𝑖𝑖

Repeatability error is caused by the inability of a sensor to represent the same value under identical conditions. Above system has 12 cycles per day hence, the sensor will have same input several times day. Under this condition if the sensor is unable to produce the same output, then a wrong actuator could be activated. So, all three sensor parameters could trigger wrong actuator if the average value of above parameters are high.

  1. Explain how the superframe structure of the IEEE802.15 MAC standard support transmission of packets from sensor nodes with different Quality of Service (QoS) requirements for different applications. Consider two type of applications. One type of application generate data in asynchronous manner and has relaxed packet transmission delay, while the other data is generated in a synchronous manner that requires data to be transmitted within a fixed delay.

[8]

The IEEE802.15 superframe structure is shown in the following figure. The superframe duration is divided in to active and inactive parts. Active part is used for packet transmissions, which is again divided in to CAP (Contention Access Period) and CFP (Contention Free Period) periods. In the CAP period packets are transmitted using the Slotted CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol. This is a contention based protocol where a transmission could result in success or failure due to packet collisions. The GTS period contains several time slots where transmitters can transmit packets in a reserved mode i. contention free mode. However, to obtain a reserved slot, a terminal need to send its request via one of the CAP slots. Once the cluster head receive the slot request then the requested terminal can get a reserved slot for a certain duration.

The CAP slots will introduce variable packet transmission delay and throughput. However, it offers a benefit of transmitting packets whenever information packet is generated. For asynchronous data with relaxed packet transmission delay the CAP slots will be suitable because no prior reservation is necessary and the application can attempt to transmit packets whenever any information is generated. For synchronous traffic with fixed delay requirement, the GTS slots will be more useful because this connection will offer guaranteed fixed delay values. If the GTS slots are synchronised with the application information generation rate then packets can be transmitted with minimum delay.

  1. Consider a sensor node is used to measure distance using the time difference between a transmitted and its reflected pulses. The system activate a timer on its processor and stop the timer when the reflected pulse is received. Assume that the timer increments its time step using the system clock. Assume that the system use a 100 MHz clock. Calculate the minimum distance that can be measured when a) an ultrasonic sensor used b) an Infra red LED (Light Emitting Diode) used.

[7]

System clock is 100 MHz, hence the clock cycle is 𝑇𝑇𝐶𝐶=

1 𝑓𝑓=

1 100 × 106 = 1 × 10

−8𝑖𝑖𝑒𝑒𝑠𝑠

Minimum distance traversed in one clock cycle, i. the time difference between the transmitted and the reflected pulse timings.

a. We need to calculate the minimum return distance traversed in one clock cycle. The speed of sound for ultrasonic sensor is 330 m/sec.

𝑇𝑇𝑐𝑐=

2 𝑃𝑃

𝑖𝑖

⇒ 𝑃𝑃=

𝑖𝑖𝑇𝑇𝑐𝑐

2

=

330 × 1 × 10 −

2

= 1. 65 × 10 −6𝑛𝑛= 1. 65 𝜇𝜇𝑛𝑛

b. For the LED the propagation velocity of light is 3x10 8 m/sec

𝑇𝑇𝑐𝑐=

3 × 108 × 1 × 10 −

2

= 1 𝑛𝑛

  1. Assume that a Bluetooth sensor node transferring data over an ACL link using the DH connection. The application layer is sending 14 KB data block at every minute. Assume the node reserve three DH5 time slots to transmit the data block. Calculate the data block transfer delay. Assume that the node remain in the sleep state when not transmitting data. Show inactive (sleep) and active state sequences of the node for a 5 minute operational cycle. Calculate the timing of inactive and active periods. DH5 connection features are listed below.

DH5 connection parameters: Payload: 0 - 339 byte, time slot size: 625 μsec. [5+5=10]

Data Block = 14 𝐾𝐾𝐵𝐵= 14 × 1024 = 14 ,336 𝐵𝐵𝑃𝑃𝑡𝑡𝑒𝑒

Number of DH5 packets to transmit, 𝑁𝑁𝑃𝑃𝑠𝑠𝑐𝑐𝑃𝑃=

14336

339 = 42.

So, it is necessary to transmit 43 packets, 42 full packets and one partial packet.

In this case the terminal use 3 slots per transmission, hence for each transmission four

time slots will be necessary one for poll and three for data.

Total delay is given by 𝑇𝑇𝑏𝑏𝑡𝑡𝑏𝑏=𝑇𝑇𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏×𝑛𝑛𝑃𝑃.𝑃𝑃𝑜𝑜

𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏𝑠𝑠

𝑟𝑟𝑠𝑠𝑠𝑠𝑠𝑠𝑟𝑟𝑟𝑟𝑠𝑠𝑏𝑏𝑏𝑏𝑡𝑡𝑟𝑟×𝑛𝑛𝑃𝑃.𝑃𝑃𝑜𝑜 𝑛𝑛𝑒𝑒𝑖𝑖𝑒𝑒𝑛𝑛𝑟𝑟𝑃𝑃𝑡𝑡𝑖𝑖𝑃𝑃𝑛𝑛+ 𝑇𝑇𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏× 2

=𝑇𝑇𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏× 4 × 14 +𝑇𝑇𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏× 2 =𝑇𝑇𝑠𝑠𝑠𝑠𝑡𝑡𝑏𝑏( 56 + 2)= 58 × 625 × 10 −

= 0. 03625 sec = 36 .25 𝑛𝑛𝑖𝑖

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Quiz-1 paper solution

Course: Internet of Things (ELEC4740)

15 Documents
Students shared 15 documents in this course

University: University of Newcastle (Australia)

Was this document helpful?
ELEC4740 Internet of Things
Quiz-1 (Sample Answer)
2020
Answer all questions:
1. Discuss three main requirements of an IoT network. Explain how the Bluetooth network standard
support above requirements.
[5]
Main five requirements are given in the following table, any three can be used for the answer.
IoT Network Requirements
Bluetooth Network Features
Mostly generate and transmit
short data bursts; mainly
machine generated sensor data
The standard support small to medium size payload in data
packets. Payload size depends on the connection type. The
standard
also support longer data burst transmissions
using the L2CAP protocol. The L2CAP protocol support the
segmentation and reassembly
property to send larger
payloads over the Bluetooth links.
Data generation rate can be
periodic, aperiodic or random,
i.e. data/packet interarrival time
could be variable
Bluetooth network can support variable packet scheduling
policy. The cluster head can adjust the POLL messaging
frequency to transmit packets arriving
with different
interarrival time. Generally the aperiodic or random traffic is
supported using the ACL links. It can also support
synchronous/periodic traffic such as voice using the SCO
connections
Low power consumption for
prolonged battery life.
Three class of devices supported with different maximum
transmission power. In addition, power control algorithm is
used. Power consumption is also controlled by regulating
the duty cycle of a Bluetooth device.
Different quality of service (QoS)
requirement nee
ds to be
supported. QoS is generally
defined by the throughput,
packet delay, packet
loss and
delay jitter.
Generally the QoS is determined by the throughput and
delay values.
Different QoS requirements can be met by
controlling polling frequency. Also cho
ice of connection
type such as ACL, SCO and eSCO, as well as
retransmission and channel coding techniques are used to
support different QoS requirements.
Support short to longer
transmission distances as well
as indoor/outdoor deployments
supporting different node
Bluetooth supports both short and longer distance
transmissions. In addition, differe
nt node densities are
managed by using the Piconet and the Scatternet
architecture. Piconet can support a smaller operating area
whereas the scatternet architecture supp
ort longer
transmission ranges.

Students also viewed

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