Internet of Things (CS-801) - Unit 3 Short Notes

How unit 3 is examined

This unit covers the IoT network stack from service architecture and low-power link protocols (6LoWPAN, IEEE 802.15.4, ZigBee) to short-range technologies (RFID, NFC, Bluetooth) and WSN. RFID carries the most marks; SOA, 6LoWPAN, 802.15.4, ZigBee, NFC and WSN follow.

Basics of IoT Networking

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>IoT networking is the set of protocols and links that let constrained, low-power devices with sensors and actuators exchange data with each other, with gateways and with the Internet.</mark>

Key points.

1. Devices connect through short-range links (RFID, NFC, Bluetooth, ZigBee) or long-range links (cellular, LoRa) chosen by range, data rate and power.
2. A gateway translates between low-power local protocols and IP networks such as the Internet.
3. Constrained devices need lightweight protocols with small headers, low energy use and low cost.
4. Data flows device to gateway to cloud, and commands flow back the same way.

IoT Components

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>IoT components are the building blocks of an IoT system: sensors and actuators, connectivity, data processing and a user interface.</mark>

Key points.

1. Sensors and actuators sense the physical world and act on it.
2. Connectivity (Wi-Fi, ZigBee, Bluetooth, cellular) carries the data through a gateway.
3. Data processing at the edge or in the cloud analyses the readings and stores them.
4. The user interface (mobile app or dashboard) shows results and sends control commands.

Functional components of IoT

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Functional components are the functional blocks of an IoT system: devices, communication, services, management, security and application.</mark>

Key points.

1. The device block holds sensing, actuation, monitoring and identification.
2. The communication block handles the protocols between device, gateway and cloud.
3. The service block provides device modelling, data analytics and device control.
4. The management block configures devices and handles their faults, while the security block gives authentication, authorisation and data integrity.
5. The application block gives users an interface to monitor and control the system.

IoT service oriented architecture

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>IoT service oriented architecture (SOA) exposes every IoT function (sensing, data, control, analytics) as a loosely coupled, reusable service reached through web-service interfaces or APIs.</mark>

Diagram.

<figure class="ds-fig" style="margin:1.4rem 0;overflow-x:auto"><svg xmlns="http://www.w3.org/2000/svg" id="dsfig-u3-01" viewBox="0 0 603 80" width="603" height="80" role="img" aria-label="Layers of IoT SOA. App = application layer, Comp = service composition layer, Svc = service management layer (discovery, registry), Net = network layer, Sen = sensing (device) layer"><style>#dsfig-u3-01 .e{stroke:#454C5A;stroke-width:1.4;fill:none}#dsfig-u3-01 .e.hi{stroke:#2340B8;stroke-width:2.6}#dsfig-u3-01 .n{fill:#FFFFFF;stroke:#16181D;stroke-width:1.4}#dsfig-u3-01 .n.hi{fill:#E3E9FC;stroke:#2340B8;stroke-width:2.2}#dsfig-u3-01 .n.rb-b{fill:#16181D;stroke:#16181D}#dsfig-u3-01 .n.rb-r{fill:#BD3227;stroke:#BD3227}#dsfig-u3-01 text{font-family:"JetBrains Mono",ui-monospace,Menlo,Consolas,monospace;font-size:13px}#dsfig-u3-01 .t{fill:#16181D;font-weight:500}#dsfig-u3-01 .t.inv{fill:#FFFFFF;font-weight:700}#dsfig-u3-01 .kd{stroke:#16181D;stroke-width:1.2}#dsfig-u3-01 .dot{fill:#16181D}#dsfig-u3-01 .ann{fill:#2340B8;font-size:11px;font-weight:700}#dsfig-u3-01 .lbl{fill:#6F7787;font-family:system-ui,-apple-system,sans-serif;font-size:12px;font-weight:700}#dsfig-u3-01 .ptr{fill:#2340B8;font-size:12px;font-weight:700}#dsfig-u3-01 .ah{fill:#454C5A}#dsfig-u3-01 .ah.hi{fill:#2340B8}#dsfig-u3-01 .wl rect{fill:#FFFFFF;stroke:#DCE0E7}#dsfig-u3-01 .wl .t{font-size:12px;font-weight:700}#dsfig-u3-01 .wl.hi rect{fill:#2340B8;stroke:#2340B8}#dsfig-u3-01 .wl.hi .t{fill:#FFFFFF}html.dark #dsfig-u3-01 .e{stroke:#B1B7C3}html.dark #dsfig-u3-01 .e.hi{stroke:#8FA3FF}html.dark #dsfig-u3-01 .n{fill:#161920;stroke:#E6E8ED}html.dark #dsfig-u3-01 .n.hi{fill:#1E2748;stroke:#8FA3FF}html.dark #dsfig-u3-01 .n.rb-b{fill:#E6E8ED;stroke:#E6E8ED}html.dark #dsfig-u3-01 .n.rb-r{fill:#FF7E71;stroke:#FF7E71}html.dark #dsfig-u3-01 .t{fill:#E6E8ED}html.dark #dsfig-u3-01 .t.inv{fill:#0F1115}html.dark #dsfig-u3-01 .kd{stroke:#E6E8ED}html.dark #dsfig-u3-01 .dot{fill:#E6E8ED}html.dark #dsfig-u3-01 .ann{fill:#8FA3FF}html.dark #dsfig-u3-01 .lbl{fill:#858D9C}html.dark #dsfig-u3-01 .ptr{fill:#8FA3FF}html.dark #dsfig-u3-01 .ah{fill:#B1B7C3}html.dark #dsfig-u3-01 .ah.hi{fill:#8FA3FF}html.dark #dsfig-u3-01 .wl rect{fill:#161920;stroke:#2A2E37}html.dark #dsfig-u3-01 .wl.hi rect{fill:#8FA3FF;stroke:#8FA3FF}html.dark #dsfig-u3-01 .wl.hi .t{fill:#0F1115}</style><defs><marker id="ah11" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path class="ah" d="M0,1 L9,5 L0,9 z"/></marker><marker id="ahh11" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path class="ah hi" d="M0,1 L9,5 L0,9 z"/></marker></defs><path class="e" d="M59,40 L141,40" marker-end="url(#ah11)"/><path class="e" d="M195,40 L277,40" marker-end="url(#ah11)"/><path class="e" d="M317,40 L406,40" marker-end="url(#ah11)"/><path class="e" d="M446,40 L535,40" marker-end="url(#ah11)"/><circle class="n" cx="40" cy="40" r="18"/><text class="t" x="40" y="40" dy=".35em" text-anchor="middle">App</text><rect class="n" x="144" y="25" width="50" height="30" rx="15"/><text class="t" x="169" y="40" dy=".35em" text-anchor="middle">Comp</text><circle class="n" cx="298" cy="40" r="18"/><text class="t" x="298" y="40" dy=".35em" text-anchor="middle">Svc</text><circle class="n" cx="427" cy="40" r="18"/><text class="t" x="427" y="40" dy=".35em" text-anchor="middle">Net</text><circle class="n" cx="556" cy="40" r="18"/><text class="t" x="556" y="40" dy=".35em" text-anchor="middle">Sen</text></svg><figcaption style="font-size:.82em;opacity:.72;margin-top:.45rem">Layers of IoT SOA. App = application layer, Comp = service composition layer, Svc = service management layer (discovery, registry), Net = network layer, Sen = sensing (device) layer</figcaption></figure>

Key points.

1. The sensing layer holds sensors, actuators and tags, and offers services such as reading a value or switching a device.
2. The network layer carries data through gateways and networks such as ZigBee, Wi-Fi and cellular.
3. The service layer registers, discovers and manages the atomic services, and keeps their QoS.
4. The composition layer combines atomic services into a bigger service, for example temperature service plus alert service gives a fire-alarm service.
5. The application layer offers the final services to users, such as a smart home or smart city app.
6. Services are loosely coupled, reusable and interoperable, so devices from different vendors work together.
7. Challenges are device heterogeneity, QoS management, service discovery in large deployments, and security and reliability of composed services.

Answer frame. Open with the definition; draw the five-layer diagram with the services listed beside each layer; develop points 1-5 bottom-up, then the service interaction (application calls composition, which calls atomic services); close with point 7 as the challenges and the significance for interoperability.

Asked: [7 marks] (May 2023, Dec 2024, May 2026) Explain services of IoT oriented architecture with neat diagram. Explain IoT SOA and challenges. Explain IoT SOA and discuss its significance in connected communication systems.

IoT challenges

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Low weight</span>

Definition. <mark>An IoT device is a constrained node, so its challenges are limited power, memory and processing, plus security, interoperability and scalability.</mark>

Key points.

1. Power is limited because most devices run on batteries, so radios must sleep most of the time.
2. Security is weak because small devices cannot run heavy cryptography and are exposed to attacks.
3. Interoperability is hard because vendors use different protocols and data formats.
4. Scalability is a problem because billions of devices need addressing, management and updates.
5. Requirements are sensing, connectivity, processing and energy efficiency, so design must be low-cost and low-power.

Asked: [7 marks] (Jun 2025) Explain challenges and requirements of IoT device.

6LowPAN

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>6LoWPAN (IPv6 over Low-power Wireless Personal Area Networks) is an adaptation layer that lets IPv6 packets run over IEEE 802.15.4 links by compressing headers and fragmenting packets.</mark>

Key points.

1. It is needed because IPv4 has only $2^{32}$ addresses, while IPv6 has $2^{128}$ addresses, enough for billions of IoT devices.
2. IPv6 needs a minimum MTU of 1280 bytes but an 802.15.4 frame is only 127 bytes, so 6LoWPAN fragments and reassembles packets.
3. Header compression shrinks the 40-byte IPv6 header (and UDP header) to a few bytes by using link-layer addresses.
4. It supports mesh routing, so packets hop through multiple nodes to extend the range.
5. IPv6 gives stateless auto-configuration, built-in security (IPsec), a simpler header and better QoS with the flow label.
6. Migration challenges are cost, dual-stack management and heavier processing for constrained devices.

Answer frame. For the role question: define 6LoWPAN, draw the stack (application, UDP, IPv6, 6LoWPAN adaptation, 802.15.4), give points 2-4, then the table, and close with use cases (smart home, smart meters). For the IPv6 impact question: open with address space, develop points 1 and 5 as benefits for scalability, and close with point 6.

Asked: [7 marks] (May 2022) How might Internet Address (IPv6) affect the development and implementation of the Internet of Things? Asked: [7 marks] (Jun 2025) What is the role of 6LoWPAN in IoT? How does 6LoWPAN differ from IPv4 or IPv6?

IEEE 802.15.4

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>IEEE 802.15.4 is the standard for the physical and MAC layers of low-rate, low-power, low-cost wireless personal area networks (LR-WPAN).</mark>

Key points.

1. The physical layer works in the 868 MHz band (20 kbps), 915 MHz band (40 kbps) and 2.4 GHz band (250 kbps), and handles channel selection, energy detection and link quality.
2. The MAC layer handles frame delivery, beacons, channel access with CSMA/CA, and optional guaranteed time slots.
3. Maximum frame size is 127 bytes, and nodes use 16-bit short or 64-bit extended addresses.
4. Two device types exist: the full-function device (FFD) can coordinate and route, while the reduced-function device (RFD) is a simple end node.
5. Topologies are star, peer-to-peer and cluster tree, and range is about 10-100 m.
6. Relation to IoT: it is the link layer beneath ZigBee and 6LoWPAN, and its low power use suits battery-run sensor nodes.

Answer frame. Open with the definition; draw a star and mesh topology with PAN coordinator, FFD and RFD; develop points 1-5, then point 6; close with "802.15.4 is the base of ZigBee and 6LoWPAN".

Asked: [7 marks] (May 2022, May 2024, Jun 2025) What is IEEE 802.15.4 protocol? How is it related to IoT?

ZigBee and its types

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>ZigBee is a low-power, low-data-rate wireless mesh standard built on IEEE 802.15.4, used for monitoring and control in IoT.</mark>

Diagram.

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Key points.

1. The PHY and MAC layers come from 802.15.4, the network layer does addressing, routing and mesh formation, and the application layer holds the application support sub-layer and ZigBee device object.
2. The ZigBee coordinator (ZC) starts the network, selects the channel and stores security keys; there is exactly one per network.
3. The ZigBee router (ZR) relays data and extends the range, and it must stay powered.
4. The ZigBee end device (ZED) only senses or acts, sleeps to save battery and talks through its parent.
5. Topologies are star, tree and mesh; mesh gives self-healing routes.
6. It works at 2.4 GHz with 250 kbps, range of 10-100 m, and supports up to about 65,000 nodes.
7. Advantages are low power, low cost, large networks and secure AES-128 encryption; limitations are low bandwidth, short range, interference with Wi-Fi and Bluetooth in 2.4 GHz, and weak IP integration.

Answer frame. For the architecture question: define ZigBee, draw the stack and a mesh with ZC, ZR and ZED, explain the three roles, and close with applications (smart home, industrial control) and advantages. For the critical-examine question: one line on each technology, the table, then advantages and limitations.

Asked: [7 marks] (Jun 2025) What is ZigBee? Draw and explain about ZigBee architecture in detail. Asked: [7 marks] (May 2026) Critically examine the advantages and limitations of ZigBee, 6LoWPAN and IEEE 802.15.4 communication technologies.

RFID Features

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>RFID (Radio Frequency Identification) identifies and tracks objects automatically using radio waves between a tag and a reader.</mark>

Key points.

1. No line of sight is needed, so many tags can be read at once through packaging.
2. Passive tags need no battery, are cheap and work at short range, while active tags have a battery and reach 100 m or more.
3. Tags can store a unique ID and, in some types, rewritable data.
4. Frequency bands are low (125 kHz), high (13.56 MHz) and ultra-high (860-960 MHz).

RFID working principle and applications

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">High weight</span>

Definition. <mark>RFID is a technology in which a reader sends radio waves to a tag attached to an object, and the tag replies with its stored identity, so the object is identified and tracked without contact or line of sight.</mark>

Diagram.

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Key points.

1. A tag has a microchip that stores the ID and an antenna; a reader has a transmitter, receiver and antenna; the back-end database or middleware links the reader to the network.
2. Principle: the reader sends a radio field, the tag antenna takes energy from it, the chip wakes up and sends back its ID by modulating the reflected signal.
3. Coupling: low and high frequency tags use inductive (near-field) coupling with a range of a few centimetres to about 1 m, while UHF tags use backscatter (far-field) coupling with a range of several metres.
4. Types of tag: passive (no battery, powered by the reader), active (own battery, long range) and semi-passive (battery for the chip, reader field for communication).
5. Frequencies are LF 125-134 kHz, HF 13.56 MHz, UHF 860-960 MHz and microwave 2.45 GHz.
6. Working steps: the reader emits the field, the tag powers up, the tag sends its ID, the reader decodes and passes it to the middleware, and the database returns the details of the object.
7. RFID and IoT link: tags give every physical object a unique identity, readers connect to the network through gateways, and the cloud uses the data for real-time tracking, so objects become smart things.
8. Applications are inventory and supply chain management, toll collection, access control and ID cards, livestock and pet tracking, library books, and contactless payment.

Example. A warehouse tags each carton with a passive UHF tag. A reader at the dock door reads all cartons on the pallet at once and sends the IDs to the cloud, and stock is updated in real time.

Answer frame. Open with the definition; draw the tag, reader and middleware diagram; develop points 1-6 in order (parts, principle, coupling, types, frequency, steps); then point 7 for the IoT link; close with applications from point 8 and the example.

Pitfall: Do not say RFID needs line of sight or that all tags carry a battery; that is barcode behaviour and active tags only.

Asked: [7 marks] (May 2022, Dec 2024, May 2024, May 2026) Explain principles of RFID. How are RFID and the Internet of Things linked? How RFID and IoT implemented smart things? Explain the concepts and terminology of RFID application. Analyze RFID features, working principles and applications with suitable examples.

NFC (Near Field communication)

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>NFC is a short-range wireless technology working at 13.56 MHz that exchanges data between two devices placed within about 4 cm using magnetic inductive coupling.</mark>

Key points.

1. It is built on HF RFID (ISO 14443 and ISO 18092), and one device generates the field while the other is powered by it or has its own power.
2. Reader/writer mode reads or writes NFC tags, such as a smart poster.
3. Peer-to-peer mode exchanges data between two active devices, such as sharing a file or a contact.
4. Card emulation mode makes the phone behave like a contactless card, used in payments and ticketing.
5. Range is up to about 4 cm (at most 10 cm) and data rate is 106, 212 or 424 kbps, so it is slow but very secure because of the tiny range.
6. Applications are contactless payments, transport passes, access control, device pairing (for Bluetooth or Wi-Fi setup) and smart tags in IoT.

Answer frame. Open with the definition and the inductive coupling principle; draw two devices with overlapping fields; develop points 1-6 with the three modes as a list; close with applications. For the short-range question: add a row comparing NFC, Bluetooth and WSN on range, rate and power (see the next two topics).

Asked: [7 marks] (May 2022, May 2023) Define Near Field Communication technologies and their applications. Explain Near Field Communication (NFC). Asked: [7 marks] (May 2026) Examine the role of NFC, Bluetooth and Wireless Sensor Networks in short range IoT communication systems.

Bluetooth

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Bluetooth is a short-range wireless standard in the 2.4 GHz band that connects nearby devices in small networks called piconets.</mark>

Key points.

1. Classic Bluetooth gives 1-3 Mbps and a range of about 10 m (up to 100 m for class 1).
2. A piconet has one master and up to seven active slaves; linked piconets form a scatternet.
3. Bluetooth Low Energy (BLE) uses very little power and suits coin-cell sensors and wearables.
4. It uses frequency hopping over 79 channels to reduce interference.

Wireless Sensor Networks and its Applications

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>A Wireless Sensor Network (WSN) is a network of many spatially distributed, autonomous, battery-powered sensor nodes that cooperatively monitor physical or environmental conditions and send the data to a base station.</mark>

Key points.

1. A sensor node has four parts: a sensing unit (sensor and ADC), a processing unit (microcontroller and memory), a transceiver, and a power unit (battery).
2. The base station or sink collects the data and passes it to the user or the Internet.
3. Characteristics are self-organisation, multi-hop communication, limited power, large scale and data fusion.
4. Applications are environmental monitoring, health monitoring, military surveillance, precision agriculture and smart buildings.
5. WSN and IoT: a WSN is the sensing subsystem of IoT, and IoT adds Internet integration, cloud analytics and wider scope beyond one local network.
6. Example: soil-moisture nodes in a farm send readings by multi-hop to a gateway, which uploads them to the cloud so the IoT app switches irrigation on.

Answer frame. Open with the definition; draw the node block diagram (sensor, processor, transceiver, power) and the multi-hop network to a sink; develop points 1-4; close with applications. For the relation question: definition of both, point 5, the table and the example in point 6.

Asked: [7 marks] (May 2023, Dec 2024) What is a Wireless Sensor Network? Mention the applications of it. Explain Wireless Sensor Networks and its applications. Asked: [7 marks] (May 2024) What is relation between WSN and IoT? Explain with example.

Last-minute revision

• IEEE 802.15.4: PHY and MAC for LR-WPAN; 250 kbps at 2.4 GHz, 40 kbps at 915 MHz, 20 kbps at 868 MHz; frame 127 bytes.
• 6LoWPAN: IPv6 over 802.15.4 with header compression and fragmentation; IPv4 32 bit, IPv6 128 bit; IPv6 minimum MTU 1280 bytes.
• ZigBee roles: coordinator, router, end device; 250 kbps, 10-100 m, about 65,000 nodes, AES-128.
• ZigBee stack: PHY, MAC (802.15.4), network, application.
• SOA layers: sensing, network, service, composition, application.
• RFID: tag plus reader plus middleware; LF 125 kHz, HF 13.56 MHz, UHF 860-960 MHz.
• RFID tags: passive (no battery), active (battery), semi-passive.
• NFC: 13.56 MHz, about 4 cm, 106/212/424 kbps, three modes.
• Bluetooth: 2.4 GHz, piconet of 1 master plus 7 active slaves, BLE for low power.
• WSN node: sensing, processing, transceiver, power unit; multi-hop to sink.

Memory hooks

• ZigBee roles: "C-R-E", Coordinator starts, Router relays, End device sleeps.
• SOA layers bottom-up: "Sensors Need Services, Composed for Apps".
• RFID types: Passive is Poor (no battery), Active has Amps.
• NFC modes: "R-P-C", Reader, Peer, Card.
• 6LoWPAN fixes two things: too big headers and too big packets (compress and fragment).

Coverage checklist

• Basics of IoT Networking: no past questions.
• IoT Components: no past questions.
• Functional components of IoT: no past questions.
• IoT service oriented architecture: Q5 (May 2023, Dec 2024, May 2026).
• IoT challenges: Q4 (Jun 2025).
• 6LowPAN: Q1 (May 2022), Q2 (Jun 2025).
• IEEE 802.15.4: Q3 (May 2022, May 2024, Jun 2025).
• ZigBee and its types: Q11 (Jun 2025), Q12 (May 2026).
• RFID Features: no past questions.
• RFID working principle and applications: Q8 (May 2022, Dec 2024, May 2024, May 2026).
• NFC (Near Field communication): Q6 (May 2022, May 2023), Q7 (May 2026).
• Bluetooth: no past questions (used in Q7).
• Wireless Sensor Networks and its Applications: Q9 (May 2023, Dec 2024), Q10 (May 2024).