Sensing and Actuation & IoT Connectivity & IoT Networking

Transducer

• Converts a signal from one physical form to another.
• Physical forms include thermal, electric, mechanical, magnetic, chemical, and optical.
• Acts as an energy converter.
• Examples:
  • Microphone: Sound to electrical signal.
  • Speaker: Electrical signal to sound.
  • Antenna: Electromagnetic energy to electricity (and vice versa).
  • Strain gauge: Strain to electrical.

Definition of Sensor

• Detects the presence of a physical quantity.
• Output is a signal converted to human-readable form.

Sensor

• Senses physical changes in a system in response to stimuli.
• Input: Physical parameter or stimuli (e.g., temperature, light, gas, pressure, sound).
• Output: Response to stimuli.

Sensor Characteristics

• Static characteristics: Output change in response to input change after steady state.
• Dynamic characteristics: System's transient response to an input.

Static Characteristics

• Accuracy: Correctness of output compared to a superior system.
• Range: Highest and lowest value the sensor can sense.
• Resolution: Smallest change in input that a sensor can sense.
• Errors: Difference between standard and sensor value.
• Sensitivity: Ratio of incremental change in response to incremental change in input parameter.
• Linearity: Deviation of sensor value curve from a straight line.
• Drift: Difference in measurements over long periods.
• Repeatability: Deviation between measurements under same conditions.

Dynamic Characteristics

• How well a sensor responds to changes in its input.
• Zero order system: Output responds to input with no delay.
  • Example: Potentiometer for linear/rotary displacements.
• First order system: Output gradually approaches final value.
• Second order system: Oscillates before steady state.

Sensor Classification

• Passive and active.
• Analog and digital.
• Scalar and vector.

Passive Sensor

• Cannot independently sense the input.
• Example: Accelerometer, soil moisture, water-level, and temperature sensors.

Active Sensor

• Independently sense the input.
• Example: Radar, sounder, and laser altimeter sensors.

Analog Sensor

• Output is a continuous function of its input.
• Example: Temperature sensor, LDR, analog pressure sensor, and Analog Hall effect/Magnetic Sensor

Digital Sensor

• Responses in binary nature.
• Designs to overcome the disadvantages of analog sensors
• Example: Passive infrared (PIR) sensor and digital temperature sensor (DS1620).

Scalar Sensor

• Detects input parameter based on magnitude.
• Not affected by direction.
• Example: Temperature, gas, strain, color and smoke sensors.

Vector Sensor

• Response depends on magnitude, direction, and orientation of input.
• Example: Accelerometer, gyroscope, magnetic field, and motion detector sensors.

Actuator

• Deals with control action (mechanical action).
• Mechanical or electro-mechanical devices.

Actuator Details

• Requires a control signal input and an energy source.
• Available in micro and macro scales.
• Examples: Electric motor, solenoid, hard drive stepper motor, comb drive, hydraulic cylinder, piezoelectric actuator and pneumatic actuator.

Classification of Actuators

• Electric Linear
• Electric Rotary
• Fluid Power Linear
• Fluid Power Rotary
• Linear Chain Actuators
• Manual Linear
• Manual Rotary

Electric Linear Actuator

• Powered by electrical signal.
• Converts electrical energy into linear displacement.
• Used in automation applications.

Electric Rotary Actuator

• Powered by electrical signal.
• Converts electrical energy into rotational motion.
• Applications include quarter-turn valves, windows, and robotics.

Fluid Power Linear Actuator

• Powered by hydraulic fluid, gas, or differential air pressure.
• Produces linear displacement.
• Used in automation applications (e.g., clamping, welding).

Fluid Power Rotary Actuator

• Powered by fluid, gas, or differential air pressure.
• Converts pressure into rotational motion.
• Applications include opening/closing dampers, doors, and clamping.

Linear Chain Actuator

• Provides linear motion using specialized chains.
• Used in motion control applications.

Manual Linear Actuator

• Provides linear displacement through manual rotation of screws/gears.
• Used for manipulating tools and workpieces.

Manual Rotary Actuator

• Provides rotary output through manual rotation of screws, levers or gears.
• Used for operating valves.

Communication Protocols for IoT

• IEEE 802.15.4
• Zigbee
• 6LoWPAN
• Wireless HART
• Z-Wave
• ISA 100
• Bluetooth
• NFC
• RFID

IEEE 802.15.4

• Framework for lower layers (MAC and PHY) of WPAN.
• PHY: Defines frequency band, transmission power, and modulation scheme.
• MAC: Defines medium access and flow control.
• Used for low power, low cost, and low speed communication (< ~75m).

Features of IEEE 802.15.4

• Uses DSSS (direct sequence spread spectrum) coding scheme.
• Utilizes phase shift keying modulation.
• BPSK - 868/915 MHz, data rates 20/40 kbps.
• OQPSK - 2.4 GHz, data rate 250 kbps.
• Tolerant to noise and interference, improving link reliability.
• Line of sight (LOS) transmission preferred.
• Range: 10 to 75m.
• Uses CSMA-CA (carrier sense multiple access with collision avoidance).
• Infrequent short packets for low power consumption.
• Supports star and peer-to-peer topologies.

Variants of IEEE 802.15.4

• 802.15.4 - 2003: Basic version, fixed modulation schemes and data rates for different frequency bands.
• 802.15.4 - 2006: Higher data rate on lower frequency bands, uses OQPSK for all bands.
• 802.15.4 a: Increased range capability, defines new physical layers (UWB and CSS).
• 802.15.4 c: 780 MHz band in China, uses O-QPSK or MPSK, 250 kb/s.
• 802.15.4 d: 950 MHz band in Japan, uses GFSK (100 kb/s) or BPSK (20 kb/s).
• 802.15.4e: MAC developments toward ISA SP100.11a application.
• 802.15.4f: New PHYs for 433 MHz, 2.4 GHz, and UWB.
• 802.15.4g: New PHYs for smart utility networks (902 - 928 MHz).

Zigbee

• Framework for medium-range communication in IoT.
• Defines PHY and MAC layers for interoperability at low data rates.
• Operates at:
  • 868 MHz (1 channel, 20 kbps)
  • 902-928MHz (10 channels, 40 kbps)
  • 2.4 GHz (16 channels, 250 kbps).

Features of Zigbee

• Lower frequency bands use BPSK.
• 2.4 GHz band uses OQPSK.
• 128 bytes packet size, 104 bytes max payload.
• Line of sight (LOS) transmission.
• Range: up to 70m.
• Low power consumption (around 1mW).
• Adaptable duty cycle, low data rates, low coverage radio.
• Networking topologies: star, peer-to-peer, cluster-tree (hybrid), mesh.

Zigbee Nodes

• Coordinators: Initialize, maintain, and control the network (one per network).
• Routers: Connected to coordinator or other routers, multi-hop routing.
• End devices: Do not contribute in routing.
• Star topology: One coordinator, zero or more end devices.
• Mesh/tree topologies: One coordinator, several routers/end devices.
• Cluster-tree network: Coordinators linked to parent coordinator.

Zigbee Variants

• ZigBee.
• ZigBee Pro: Scalability, security, and improved performance.

6LoWPAN

• IPv6 over Low-Power Wireless Personal Area Networks.
• Optimizes IPv6 packet transmission in low power and lossy networks (LLN).
• Operates at:
  • 2400–2483.5 MHz (worldwide)
  • 902–929 MHz (North America)
• Uses 802.15.4 in unslotted CSMA/CA mode.

Features of 6LoWPAN

• Converts data format for IEEE 802.15.4 lower layer system.
• IPv6 MTU is 1280 bytes, IEEE 802.15.4 packet size is 127 bytes.
• Adaptation layer provides:
  • Packet fragmentation & reassembly
  • Header compression
  • Routing of data link layer.
• Fragmentation header allows 2048 bytes packet.
• Header compression reduces transmission overhead.
• Stateless auto configuration allows automatic IPv6 address creation.
• Data link layer routing:
  • mesh-under: Uses link layer address.
  • route-over: Uses network layer IP address.
• Link layer security (AES-128) from IEEE 802.15.4.

Wireless HART

• Based on HART (Highway Addressable Remote Transducer).
• First international industrial wireless standard (IEC 62591), based on IEEE 802.15.4.
• Functions in the 2.4GHz ISM band, up to 250 kb/s.
• Supports 11 to 26 channels, 5MHz gap between adjacent channels.
• Same channel cannot be used consecutively.

Features of Wireless HART

• Exploits IEEE 802.15.4 DSSS coding scheme.
• Channel hopping with every packet.
• Modulation technique is offset quadrature phase shift keying (OQPSK).
• Transmission Power around 10dBm (adjustable).
• Maximum payload is 127 bytes.
• Employs TDMA (time division multiple access), 10ms time slot for each transmission.
• Collision-free and deterministic communications.
• 100 consecutive time slots per second grouped into a super frame.
• Slot sizes and super frame length are fixed.
• Supports multiple super frames.
• Communication occurs in allotted timeslot and frequency channel.
• Supports both star and mesh topologies.

Z-Wave

• Low power radio communication technology for home automation and security systems.
• Simpler and cheaper alternative to Zigbee for small to medium range connectivity.
• Operates on the unlicensed ISM band.
• Mesh Network Topology, supporting up to 232 nodes in a network.

Features of Z-Wave

• Controller and Slave.
• The Controller is a central entity which sets up the Z-wave network and manages other slave devices in the network.
• Network ID (4 Bytes) and Node ID(1 Byte).
• Nodes can communicate only within their home network
• Offers a data rate of up to 100kbps and communication range of 30 meters.
• Source routed network mesh topology using 1 primary controller.
• Radio dead-spots can be bypassed using a process called Healing.

Application of Z-Wave

• Home/Office Automation
• Smart Energy Management
• Smart Security and Surveillance
• Voice control enabled applications
• Appliances automation and control

ISA 100.11a

• Standard for wireless network technology.
• International Society of Automation (ISA).
• Implementation of automation in the industrial environment.
• Protocol stack is in compliance with IoT.
• Based on the IEEE 802.15.4 protocol.

Features of ISA 100.11a

• Supports multiple devices working on different protocols to interact in a single network, simultaneously.
• Enables interoperability and communication between different devices
• Uses the IPv6 based technology and adds increased address space and security.
• 128 bits AES encryption security.
• Supports 2 network topologies for operation: 1)Star and 2)Mesh.
• Uses TDMA/CSMA schemes for resource sharing, collision avoidance.

Application of ISA 100.11a

• Automation in large scale complex industries.
• Wireless monitoring of the industrial network and devices.
• Process monitoring and control automation in the industrial environment with large and complex setups.

Bluetooth

• Short range wireless communication technology.
• Replacing cables with wireless medium to communicate between portable devices
• Based on Ad-hoc technology, also known as Ad-hoc Piconets.
• Network can be established between 2 to 8 Bluetooth devices.

Features of Bluetooth

• Low power consumption.
• Uses the unlicensed ISM band at 2.4 to 2.485 GHZ.
• Supports 1Mbps and 3Mbps data rate for version 1.2 and 2.0, respectively.
• The operating range: 1 meter for Class 3 radios, 10 meters for Class 2 radios, and 100 meters for Class 1 radios

Application of Bluetooth

• Connectivity with desktop and laptop peripherals
• Wireless connectivity between mobile phones and other portable devices
• Multimedia transfer between devices
• Automobiles use Bluetooth for connecting with multimedia and navigation devices.

RFID

• Stands for “radio-frequency identification” .
• System consists of RFID tag, RFID reader and RFID software.
• Tag stores digitally encoded data, which is read by a RFID reader.
• Tag data can be read outside the line-of-sight, as compared to traditional barcodes and QR codes.

Features of RFID

• Tag consists of an integrated circuit and an antenna, covered with a protective material.
• Tags can be classified as passive or active.
• Active tags use their own power supply for operation and data transfer.
• Passive tags have to be powered by a reader inductively in order to transmit data.

Application of RFID

• Store product tracking
• Asset and baggage tracking
• Supply chain management
• Livestock tracking and management
• Automobile tracking
• Authentication and access control

NFC

• Near field communication, or NFC, has been derived from radio-frequency identification (RFID).
• Works within close proximity without any physical contact between the devices like RFID.
• Active and passive devices.

Features of NFC

• Operates at 13.56 MHz frequency.
• The communication range of NFC devices is less then 10 centimeters.
• Data rate supported are 106, 212 or 424 Kbps (kilobits per second).
• Two communication modes are supported between two devices: Active-Active or Active-Passive mode.

Application of NFC

• Banking and payments using NFC enabled smartphones, transaction cards.
• Tracking goods
• Data Communication between smart phones
• Security and authentication using NFC enabled ID cards
• Low-power home automation systems

Introduction to IoT Networks

• IoT devices have low processing power, small size, energy constraints.
• IoT networks have low throughput, high packet loss, tiny payload size, frequent topology change.
• Classical Internet is not meant for constrained IoT devices.
• Challenges include heterogeneous devices, heterogeneous traffic, and heterogeneous access.

Enabling Classical Internet for IoT Devices

• Proprietary non-IP based solution.
• Internet Engineering Task Force (IETF) IP based solution including:
  • IPv6 over Low power Wireless Personal Area Networks (6LoWPAN)
  • Routing Over Low power and Lossy networks (ROLL)
  • Constrained RESTful Environments (CoRE)

Proprietary non-IP based solution drawbacks

• Limited flexibility to end users: vendor specific APIs
• Interoperability: vendor specific sensors and gateways
• Limited last-mile connectivity

IETF IP based solution

• IPv6 over Low power Wireless Personal Area Networks (6LoWPAN)
  • By header compression and encapsulation it allows IPv6 packets to transmit and receive over IEEE 802.15.4 based networks.
• Routing Over Low power and Lossy networks (ROLL)
  • New routing protocol optimized for saving storage and energy.
• Constrained RESTful Environments (CoRE)
  • Extend the Integration of the IoT devices from network to service level.

CoRE

• Provides a platform for applications meant for constrained IoT devices.
• This framework views sensor and actuator resources as web resources.
• The framework is limited to applications which:
  • Monitor basic sensors
  • Supervise actuators
• CoAP includes a mechanism for service discovery.

CoRE: Service Discovery

• IoT devices (act as mini web servers) register their resources to Resource Directory (RD) using Registration Interface (RI).
• RD, a logical network node, stores the information about a specific set of IoT devices.
• RI supports Representational State Transfer (REST) based protocol such as HTTP (and CoAP- optimized for IoT).
• IoT client uses Lookup interface for discovery of IoT devices.

IoT Network QoS

• Quality-of-service (QoS) of IoT network is the ability to guarantee intended service to IoT applications through controlling the heterogeneous traffic generated by IoT devices.
• QoS policies for IoT Network includes:
  • Resource utilization
  • Data timeliness
  • Data availability
  • Data delivery

Resource Utilization

• Requires control on the storage and bandwidth for data reception and transmission.
• QoS policies for resource utilization:
  • Resource limit policy
    • Controls the amount of message buffering
    • Useful for memory constrained IoT devices
  • Time filter policy
    • Controls the data sampling rate (interarrival time) to avoid buffer overflow
    • Controls network bandwidth, memory, and processing power

Data Timeliness

• Measure of the freshness of particular information at the receiver end
• Important in case of healthcare, industrial and military applications
• Data timeliness policies for IoT network include
  • Deadline policy
    • Provides maximum interarrival time of data
    • Drops the stale data; notify the missed deadline to the application end
  • Latency budget policy
    • Latency budget is the maximum time difference between the data transmission and reception from source end to the receiver end.
    • Provides priority to applications having higher urgency

Data Availability

• Measure of the amount of valid data provided by the sender/producer to receiver/consumer
• QoS policies for data availability in IoT network include
  • Durability policy
    • Controls the degree of data persistence transmitted by the sender
    • Data persistence ensures the availability of the data to the receiver even after sender is unavailable
  • Lifespan policy
    • Controls the duration for which transmitted data is valid
  • History policy
    • Controls the number of previous data instances available for the receiver.

Data Delivery

• Measure of successful reception of reliable data from sender to receiver
• QoS policies for data delivery include
  • Reliability policy
    • Controls the reliability level associated with the data distribution
  • Transport priority
    • Allows transmission of data according to its priority level

Requirements of IoT Network

• Coverage
• High throughput
• Low latency
• Ultra reliability
• High power efficiency

MQTT

• Message Queue Telemetry Transport
• Introduced by IBM and standardized by Organization for the Advancement of Structured Information Standards (OASIS) in 2013
• Works on Publish/Subscribe framework on top of TCP/IP architecture
• Advantages
  • Reliable, Lightweight, and cost-effective protocol

MQTT QoS

• QoS of MQTT protocol is maintained for two transactions
  • First transaction: Publishing client -> MQTT Server
  • Second transaction: MQTT Server -> Subscribing Client
• Client on each transaction sets the QoS level
  • For the first transaction, publishing client sets the QoS level
  • For second transaction, client subscriber sets the QoS level

MQTT QoS Levels

• Supports 3-level of QoS
  • QoS 0:
    • Also known as “at most once” delivery
    • Best effort and unacknowledged data service
    • Publisher transmits the message one time to server and server transmits it once to subscriber
    • No retry is performed
  • QoS 1:
    • Also known as “at least once” delivery
    • Message delivery between the publisher, server and then between server and subscribers occurs at least once.
    • Retry is performed until acknowledgement of message is recieved
  • QoS 2:
    • Also known as “exactly once” delivery
    • This QoS level is used when neither packet loss or duplication of message is allowed
    • Retry is performed until the message is delivered exactly once

CoAP

• Constrained Application Protocol
• CoAP was designed by IETF Constrained RESTful Environment (CoRE) working group to enable application with lightweight RESTful (HTTP) interface
• Works on Request/Response framework based on the UDP architecture, including Datagram Transport Layer Security (DTLS) secure transport protocol

CoAP Messages

• CoAP defines four types of messages
  • CON: Conformable
  • NON: Non-conformable
  • RST: Reset
  • ACK: Acknowledgement
• For conformable type message, the recipient must explicitly either acknowledge or reject the message.
• In case of non-conformable type message, the recipient sends reset message if it can’t process the message
• Utilizes GET, PUT, OBSERVE, PUSH, and DELETE messages requests to retrieve, create, initiate, update, and delete subscription respectively.
• Supports caching capabilities to improve the response time and reduce bandwidth consumption.
• Uses IP multicast to support data requests sent to a group of devices.
• Specialized for machine-to-machine (M2M) communication.

XMPP

• Extensible Messaging and Presence Protocol
• Supports Publish/Subscribe messaging framework on top of TCP protocol
• The communication protocol is based on Extensive Markup Language (XML).
• Uses Datagram Transport Layer Security (DTLS) secure transport protocol
• XMPP model is decentralized, no central server is required.

Advantages of XMPP

• Interoperability: Supports interoperability between heterogeneous networks
• Extensibility: Supports privacy lists, multi-user chat, and publish/subscribe chat status notifications
• Flexibility: Supports customized markup language defined by different organizations according to their needs

AMQP

• Advance Message Queuing Protocol
• Optimized for financial applications
• Binary message-oriented protocol on top of TCP
• Supports Publish/Subscribe framework for both:
  • Point-to-point (P2P)
  • Multipoint communication
• Uses token-based mechanism for flow control
• Ensures no buffer overflow at the receiving end

Message delivery guarantee services:

• At least once: Guarantees message delivery but may do so multiple times
• At most once: Each message is delivered once or never
• Exactly once: No message drop and delivered once one

IEEE 1888

• Energy-efficient network control protocol
• Defines a generalized data exchange protocol between network components over the IPv4/v6-based network.
• Universal Resource Identifiers (URIs) based data identification
• Applications: Environmental monitoring, energy saving, and central management systems.

DDS RTPS

• Distributed Data Service Real Time Publish and Subscribe
• Supports Publish/Subscribe framework and on top of UDP transport layer protocol.
• Data-centric and binary protocol
• Data is termed as “topics”.
• The users/listeners may subscribe to their particular topic of interest
• A single topic may have multiple speakers of different priorities

Supports enlisted QoS for data distribution

• Data persistence
• Delivery deadline
• Reliability
• Data freshness
• Applications: Military, Industrial, and healthcare monitoring