2. What is the maximum data rate of Z-Wave communication technology?
a. 100 kbps
b. 250 kbps
c. 500 kbps
d. 1 Mbps
Correct Answer: (a)
3. Which device converts electromagnetic energy into electricity and vice versa?
a. Speaker
b. Antenna
c. Microphone
d. Strain gauge
Answer: (b)
Other Options and Their Energy Conversions:
1. a. Speaker
o
Converts electrical energy into sound energy.
2. c. Microphone
o
Converts sound energy into electrical energy.
3. d. Strain gauge
4. What does 'Range' indicate in a sensor?
a. The correctness of the output
b. The smallest change in input that can be detected
c. The difference between the standard value and the value produced by the sensor
d. The highest and the lowest value of the physical quantity within which the sensor
can
actually sense
Answer: (d)
5. Which coding scheme is used by the IEEE 802.15.4 standard for transmitting
information?
a. CSS
b. THSS
c. OFDM
d. DSSS
Answer: (d)
Explanation:
The IEEE 802.15.4 standard (used in Zigbee, Wireless Sensor Networks, and some
IoT devices) primarily uses DSSS (Direct Sequence Spread Spectrum) for transmitting
information.
Other Options Explained:
1. a. CSS (Chirp Spread Spectrum)
o
Used in LoRa (Long Range) technology, not IEEE 802.15.4.
o
Works by sweeping a signal over a wide frequency band.
2. b. THSS (Time Hopping Spread Spectrum)
o
Used in ultra-wideband (UWB) and military communications, not IEEE
802.15.4.
o
Transmits short bursts in different time slots.
3. c. OFDM (Orthogonal Frequency Division Multiplexing)
o
o
o
o
o
o
o
Used in Wi-Fi (802.11a/g/n/ac/ax), 4G/5G, and some other wireless
standards, but not in IEEE 802.15.4.
o
Splits data into multiple subcarriers for high-speed transmission.
6. What is the standard transmission range of IEEE 802.15.4?
a. 10 m to 75 m
b. 1 m to 9 m
c. 15 cm to 60 cm
d. 1 cm to 10 km
Answer: (a)
Explanation:
The IEEE 802.15.4 standard (used in Zigbee, Wireless Sensor Networks, and IoT
devices) typically has a transmission range of 10 to 75 meters, depending on:
Other Options & Why They Are Incorrect:
1. b. 1 m to 9 m
o
Too short for IEEE 802.15.4.
o
This range is more typical for NFC (Near Field Communication) or RFID.
2. c. 15 cm to 60 cm
o
Extremely short range, matching contactless smart cards (RFID/NFC).
o
IEEE 802.15.4 is designed for low-power, medium-range communication, not
ultra-short distances.
3. d. 1 cm to 10 km
o
Too broad and unrealistic for IEEE 802.15.4.
o
1 cm is impractical for wireless communication.
o
10 km is possible only with LoRa (Long Range) or cellular networks, not
standard 802.15.4
7. Which low power radio communication technology was designed as a simpler and
cheaper
alternative to Zigbee for small to medium range connectivity?
a. Bluetooth
b. Z-Wave
c. RFID
d. NFC
Answer: (b)
Explanation:
Z-Wave was designed as a simpler and cheaper alternative to Zigbee for small to
medium-range connectivity in smart home and IoT applications.
Key Features of Z-Wave:

Lower power consumption than Zigbee.

Sub-1 GHz frequency (reduces interference with Wi-Fi/Bluetooth).

Mesh networking (like Zigbee but with easier setup).

Standardized protocol for better interoperability.
Other Options & Why They Are Incorrect:
1. a. Bluetooth (especially Bluetooth Low Energy - BLE)
o
Used for short-range (up to 10–30 m) communication.
o
More suited for wearables, smartphones, and peripherals rather than largescale IoT networks.
2. c. RFID (Radio Frequency Identification)
o
Used for ultra-short-range (a few cm to meters) tracking and identification.
o
Not designed for two-way data communication like Zigbee/Z-Wave.
3. d. NFC (Near Field Communication)
o
Extremely short-range (<10 cm) technology.
o
Used for contactless payments, access control, and device pairing.
o
Not suitable for home automation or sensor networks.
8. Which organization has developed the ISA 100.11a standard?
a. Instrument Society of America
b. International Society of Automation
c. International Studies Association
d. International Solar Alliance
Answer: (b)
Explanation:
NFC (Near Field Communication) supports two main communication modes
between devices:
1. Active-Active Mode
o
Both devices generate their own RF fields (powered).
o
Example: Two smartphones exchanging data.
2. Active-Passive Mode
o
One device is active (generates RF field) and the other is passive (uses the
active device's field, like NFC tags).
o
Example: Smartphone (active) reading a passive NFC tag.
Why Other Options Are Incorrect:
a. Broadcast-Multicast

Not used in NFC.

Seen in Wi-Fi or Bluetooth for one-to-many communication.
b. Master-Slave

Used in Bluetooth, not NFC.

NFC uses peer-to-peer (in active-active) or initiator-target (in active-passive) roles.
d. All of these

Incorrect because NFC does not support broadcast-multicast or master-slave modes.
10. Which of the following is/are the drawbacks of proprietary non-IP-based
solutions?
a. Limited flexibility to end users
b. Interoperability
c. Limited last-mile connectivity
d. All of these
Answer: (d)
11. Which MQTT QoS Level is also known as “at most once” delivery?
a. QoS 0
b. QoS 1
c. QoS 2
d. None of these
Answer: (a)
Explanation of MQTT QoS Levels:
MQTT (Message Queuing Telemetry Transport) supports 3 Quality of Service (QoS) levels for
message delivery:
1. QoS 0 (At Most Once)
o
Fastest but least reliable.
o
Messages are delivered once (best effort) with no acknowledgment or
retries.
o
Used when minor data loss is acceptable (e.g., sensor data in non-critical
applications).
2. QoS 1 (At Least Once)
o
Guarantees delivery but may result in duplicates.
o
The sender retries until it receives an acknowledgment (PUBACK).
o
Used when data must not be lost (e.g., alarms, commands).
3. QoS 2 (Exactly Once)
o
Most reliable but slowest.
o
Ensures no duplicates and guaranteed delivery using a 4-step handshake.
o
Used for critical data where duplication is unacceptable (e.g., financial
transactions).
12. Fill in the blank. In CoRE the IoT client uses ________ for the discovery of IoT devices.
a. Lookup interface
b. Resource Directory
c. Registration Interface
d. None of these
Answer: (a)
Explanation:
In CoRE (Constrained RESTful Environments), which is part of the CoAP (Constrained
Application Protocol) framework:

The IoT client discovers IoT devices using a Resource Directory (RD).

The Resource Directory acts as a centralized registry where IoT devices register their
resources.

Clients can then query the RD to find available devices and services.
Why Other Options Are Incorrect:
1. a. Lookup Interface
o
Incorrect because the Lookup Interface is just one part of the Resource
Directory (used for querying resources).
o
The full discovery process relies on the RD, not just the Lookup Interface.
2. c. Registration Interface
o
Incorrect because the Registration Interface is used by devices to register
themselves with the Resource Directory.
o
It is not used for discovery by clients.
3. d. None of these
o
Incorrect because Resource Directory (b) is the correct answer.
13. Apart from MQTT, which IoT networking protocol supports the publish/subscribe
framework?
a. XMPP
b. AMQP
c. DDS RTPS
d. All of these
Answer: (d)
Explanation:
All the listed protocols (XMPP, AMQP, and DDS-RTPS) support the publish/subscribe
(pub/sub) messaging framework, similar to MQTT. Here's how each one works:
1. XMPP (Extensible Messaging and Presence Protocol)

Originally designed for instant messaging (chat) but extended for IoT.

Supports pub/sub via the XEP-0060 extension.

Used in smart home systems (e.g., lighting control).
2. AMQP (Advanced Message Queuing Protocol)

A robust, enterprise-grade messaging protocol.

Supports pub/sub with features like queues, exchanges, and routing keys.

Used in banking, cloud services, and industrial IoT.
3. DDS-RTPS (Data Distribution Service - Real-Time Publish Subscribe)

A real-time, high-performance pub/sub protocol.

Uses topics (like MQTT) but is faster and more scalable for real-time systems.

Used in autonomous vehicles, robotics, and defense systems.
14. Which of the following IoT protocols is based on the session layer of the OSI model?
a. MQTT
b. CoAP
c. AMQP
d. DTLS
Answer: (d)
Explanation:
The session layer (Layer 5) of the OSI model is responsible for managing communication
sessions, including authentication, encryption, and connection handshakes.

DTLS (Datagram Transport Layer Security) is a session-layer protocol that
provides secure communication for datagram-based applications (like CoAP).

It is derived from TLS (Transport Layer Security) but adapted for UDP (unlike TLS,
which runs over TCP).

Used in IoT for securing CoAP, VoIP, and VPNs.
Why Other Options Are Incorrect:
a. MQTT

Operates at the application layer (Layer 7).

Uses TCP for transport and does not handle session management independently.
b. CoAP

An application-layer protocol (like HTTP but for constrained devices).

Uses DTLS for security, but CoAP itself is not a session-layer protocol.
c. AMQP

An application-layer protocol for message-oriented middleware.

Runs over TCP/TLS but does not function at the session layer.
Key Difference:

MQTT, CoAP, AMQP are application-layer protocols.

DTLS is a session-layer security protocol (often paired with CoAP or UDP-based
systems).
Real-World Use Case:

CoAP + DTLS = Secure communication in smart meters or industrial sensors.
Conclusion:
Since DTLS operates at the session layer, the correct answer is (d) DTLS. ✅
15. Which of the following is not a component of RFID?
a. RFID Tag
b. RFID reader
c. Antenna
d. Router
Answer: (d)
Explanation:
RFID (Radio Frequency Identification) consists of three core components:
1. a. RFID Tag
o
Contains a microchip + antenna to store/transmit data.
o
Can be passive (powered by reader) or active (battery-powered).
2. b. RFID Reader
o
Sends RF signals to power passive tags and read/write data.
o
Connected to backend systems for processing.
3. c. Antenna
o
Integrated into both tags and readers for wireless communication.
o
Enables RF signal transmission/reception.
Why Router (d) is NOT part of RFID?

A router is a networking device used to forward data between IP networks (e.g., WiFi, Ethernet).

RFID systems do not require routers—communication happens directly between
tags and readers via RF waves.
Common Misconceptions:

Some confuse RFID with IoT networks (where routers may be used).

RFID operates at short ranges and does not rely on IP-based routing.
Real-World RFID Use Cases:

Inventory tracking (tags on products + handheld readers).

Access control (RFID cards + door readers).