Internet of Things (AD-604 (A)) - Unit 3 Short Notes

How unit 3 is examined

This unit covers IoT functional blocks, service-oriented architecture and challenges, IEEE 802.15.4 with 6LoWPAN and ZigBee, and short-range technologies (RFID, NFC, Bluetooth, WSN); the RFID/NFC/WSN topic carries most marks.

Basics of IoT Networking, IoT Components, Functional components of IoT

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Definition. <mark>An IoT system is made of six functional blocks (device, communication, services, management, security and application) that together sense, connect, process, control and protect the connected things.</mark>

Diagram.

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Key points.

1. The communication block handles all networking: it links devices to each other and to the cloud using protocols at the link layer (802.15.4, Wi-Fi), network layer (IPv4/IPv6, 6LoWPAN), transport layer (TCP/UDP) and application layer (HTTP, CoAP, MQTT).
2. The device block holds the sensors, actuators and microcontroller that sense the surroundings, act on them and give the thing its identity.
3. The services block provides device monitoring, control, data publishing and device discovery.
4. The management block configures the system, monitors it and manages its faults, settings and performance.
5. The security block provides authentication, authorisation, message and content integrity, and data security.
6. The application block gives the user an interface (web, mobile or dashboard) to view status and control the system.

Asked: [7 marks] (May 2023) What is the function of communication functional block in an IoT system? What are the other components of a complete IoT system? Explain with diagram.

IoT service oriented architecture, IoT challenges

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Definition. <mark>IoT service oriented architecture (SOA) builds an IoT system as loosely coupled, reusable services that are discovered and composed through standard interfaces.</mark>

Key points.

1. It has four layers: sensing (devices and data), network (connectivity), service (discovery, composition and management of services) and interface (applications and users).
2. Each device capability is exposed as a service, so heterogeneous hardware can be combined without depending on its make.
3. The main challenges are security and privacy, interoperability between vendors, limited power and memory on constrained devices, scalability with billions of devices, and reliable connectivity.

6LowPAN, IEEE 802.15.4, ZigBee and its types

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

Key points.

1. It gives low data rates: 250 kbps at 2.4 GHz, 40 kbps at 915 MHz and 20 kbps at 868 MHz, with a range of about 10 to 100 m.
2. It uses very little power, since devices sleep most of the time and use CSMA/CA with an optional beacon-enabled superframe.
3. It supports star and peer-to-peer topologies, with full-function devices (FFD) that can coordinate and reduced-function devices (RFD) that are simple end nodes.
4. Its maximum PHY packet is 127 bytes, which is why IPv6 needs 6LoWPAN to compress and fragment headers on it.
5. It is related to IoT as the radio base for ZigBee (which adds network and application layers) and for 6LoWPAN (which carries IPv6), so it suits constrained IoT nodes.
6. ZigBee devices are of three types: Coordinator (forms and manages the network), Router (relays data) and End device (senses and sleeps).

Asked: [7 marks] (May 2023) What is IEEE 802.15.4 protocol? How it is related to IoT?

RFID Features, RFID working principle and applications, NFC (Near Field communication), Bluetooth, 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>

RFID definition. <mark>RFID (Radio Frequency Identification) uses radio waves for a reader to identify and read data from a tag attached to an object, without contact or line of sight.</mark>

RFID components. A tag (chip plus antenna, passive or active) stores a unique ID; a reader with an antenna sends the radio signal and reads the reply; a back-end system (middleware and database) processes the ID.

RFID working. The reader emits a radio field; a passive tag is powered by it, and replies with its ID by backscatter; the reader passes the ID to the back-end.

NFC definition. NFC is a short-range wireless technology on 13.56 MHz, built on HF RFID, that works within about 4 cm at 106 to 424 kbps.

Key points.

1. RFID frequency bands are LF (125 to 134 kHz, about 10 cm), HF (13.56 MHz, about 1 m), UHF (860 to 960 MHz, several metres) and microwave (2.45 GHz).
2. Passive tags have no battery and are cheap, while active tags have a battery and give longer range.
3. RFID applications include supply chain and inventory tracking, toll collection, access control, livestock tagging and library management.
4. NFC modes of operation are reader/writer (read a tag), peer-to-peer (exchange data between two phones) and card emulation (the phone acts as a payment or access card).
5. NFC differs from RFID in that it is two-way, is limited to about 4 cm, and needs no pairing, so it is more secure for payment.
6. Bluetooth is a 2.4 GHz short-range technology of about 10 m that forms a piconet of one master and up to seven active slaves; Bluetooth Low Energy (BLE) is its low-power form for IoT wearables and beacons.
7. A wireless sensor network (WSN) is a group of spatially distributed, battery-powered sensor nodes that sense conditions and pass data to a sink or base station over a multi-hop wireless network. Its applications are environment and habitat monitoring, agriculture, healthcare, military surveillance and smart cities.
8. Relation between WSN and IoT: a WSN is the sensing and data-collecting network that forms a subset of IoT; when its sink node is connected through an Internet gateway to the cloud, the sensed data become part of IoT.

Example. In smart farming, soil-moisture nodes form a WSN that sends readings hop by hop to a sink; the gateway forwards them over the Internet to a cloud app, which starts irrigation and alerts the farmer's phone.

Answer frame. For NFC and RFID: open with both definitions; draw a tag-reader block figure with the back-end; give components and frequencies, then NFC principle, range and three modes; close with the comparison table and the identification versus payment use. For WSN and IoT: open by defining both; draw sensor nodes, sink, gateway and cloud; give the subset relation and the smart-farming example; close with one sentence that WSN gathers the data and IoT delivers it to the Internet.

Pitfall: Do not call NFC and RFID the same; NFC is a short-range, two-way HF form of RFID.

Asked: [7 marks] (May 2023) Explain Near Field Communication (NFC) and RFID. Asked: [7 marks] (May 2023) What is relation between WSN and IoT? Explain with example.

Last-minute revision

• The six IoT functional blocks are device, communication, services, management, security and application.
• The communication block links devices to the network using the link, network, transport and application layer protocols.
• IEEE 802.15.4 defines only the PHY and MAC layers of LR-WPAN; ZigBee and 6LoWPAN sit on top of it.
• 802.15.4 rates are 250 kbps (2.4 GHz), 40 kbps (915 MHz) and 20 kbps (868 MHz), with a 127-byte packet.
• ZigBee node types are Coordinator, Router and End device.
• RFID bands are LF 125 kHz, HF 13.56 MHz, UHF 860 to 960 MHz and microwave 2.45 GHz.
• NFC works at 13.56 MHz within about 4 cm, with reader/writer, peer-to-peer and card emulation modes.
• Bluetooth uses 2.4 GHz, a piconet with one master and seven active slaves.
• A WSN is a subset of IoT that becomes IoT when its sink reaches the cloud through a gateway.

Memory hooks

• DCSMSA: Device, Communication, Services, Management, Security, Application.
• ZigBee = CRE: Coordinator, Router, End device.
• RFID frequencies climb with range and speed: LF, HF, UHF, microwave.
• NFC = "Near, Fast, Contactless": three modes RPC (Reader, Peer, Card).
• WSN collects, IoT connects.

Coverage checklist

• Basics of IoT Networking, IoT Components, Functional components of IoT: communication block function, other blocks, block diagram (May 2023).
• IoT service oriented architecture, IoT challenges: no past questions; definition, layers and challenges.
• 6LowPAN, IEEE 802.15.4, ZigBee and its types: IEEE 802.15.4 and its relation to IoT (May 2023).
• RFID Features, RFID working principle and applications, NFC (Near Field communication), Bluetooth, Wireless Sensor Networks and its Applications: NFC and RFID; WSN and IoT relation (May 2023).