UNIT 1(Introduction to IoT)

Introduction to IoT:
• Internet of things(IoT) comprises things that have unique identities and are
connected to the internet.
• While many existing devices, such as networked computers or 4G enabled
mobile phones, already have some form of unique identities and are also
connected to the internet, the focus on IoT is in the configuration, control and
networking via the internet of devices or “things” that are traditionally not
associated with the internet.
• The scope of IoT is not limited to just connecting things to the Internet.
IoT also allows these things to communicate and exchange data while executing
meaningful applications towards a common user or machine goal.

Applications of IoT:
1) Home
2) Cities
 3) Environment
4) Energy systems
5) Retail
6) Logistics
7) Agriculture
8) Industry
9) Health & Life Style Homes:
 Smart lighting that adapt the lighting to suit the ambient conditions, smart
appliances that can be remotely monitored and controlled, intrusion
detection systems, smart smoke detectors, etc.
 Cities: Smart parking systems that provide status updates on available
slots, smart lighting that helps in saving energy, smart roads that provide
information on driving conditions and structural health monitoring
systems.
 Environment: Weather monitoring, air and noise pollution, forest fire
detection and river flood detection systems.
 Energy Systems: Smart grids, grid integration of renewable energy
sources and prognostic health management systems.
 Retail Domain: Inventory management, smart payments and smart
vending machines.
 Agriculture: Smart irrigation systems that help in saving water while
enhancing productivity and green house control systems.
 Industrial Applications: Machine diagnosis and prognosis systems that
help in predicting faults and determining the cause of faults and indoor air
quality systems.
 Health and Life style: Health and fitness monitoring systems and
wearable electronics.

Definition and characteristics of IoT:

A Dynamic global network infrastructure with self configuring capabilities
based on standard and interoperable communication protocols where physical
and virtual “things” have identities, physical attributes, and virtual personalities
and use intelligent interfaces, and are seamlessly integrated into information
network , often communicate data associated with users and their environments.
Characteristics:
• Dynamic and self adapting
• Self –configuring
• Interoperable communication protocols
• Unique identity
• Integrated into Information Network
Dynamic & Self Adapting:
 IoT devices and systems may have the capability to dynamically adapt
with the changing contexts and take actions based on their operating
conditions, users context or sensed environment.
 Eg: the surveillance system is adapting itself based on context and
changing conditions.
Self Configuring:
 Allowing a large number of devices to work together to provide certain
functionality.
Inter Operable Communication Protocols:
 Support a number of interoperable communication protocols and can
communicate with other devices and also with infrastructure.
Unique Identity:
 Each IoT device has a unique identity and a unique identifier(IP address).
Integrated into Information Network:
 that allow them to communicate and exchange data with other devices
and systems.

Physical Design of Internet of Things (IOT)

The physical design of an IoT system is referred to as the Things/Devices and
protocols that are used to build an IoT system. all these things/Devices are
called Node Devices and every device has a unique identity that performs
remote sensing, actuating and monitoring work. and the protocols that are used
to establish communication between the Node devices and servers over the
internet.
Things/Devices Things/Devices are used to build a connection, process data,
provide interfaces, provide storage, and provide graphics interfaces in an IoT
system.
All these generate data in a form that can be analyzed by an analytical system
and program to perform operations and used to improve the system.
IoT devices can:
Exchange data with other connected devices and applications (directly or
indirectly), or Collect data from other devices and process the data locally
Send the data to centralized servers or cloud-based application back ends for
processing the data,
Perform some tasks locally and other tasks within the IoT infrastructure, based
on temporal and space constraints.
Things in IoT/Generic block diagram of an IoT Device:
 The things in IoT refers to IoT devices which have unique identities and
perform remote sensing, actuating and monitoring capabilities. IoT devices can
exchange data with other connected devices applications. It collects data from
other devices and process data either locally or remotely. An IoT device may
consist of several interfaces for connections/
 communication to other devices, both wired and wireless.
These includes:
I/O interfaces for sensors.
Interfaces for Internet connectivity.
Memory and storage interfaces.
Audio/video interfaces
  HDMI: High definition multimedia Interface.
 3.5mm: Audio Jack which headphone adapter.
 RCA: Radio corporation of America.
 UART: Universal Asynchronous Receiver Transmitter.
 SPI: Serial Peripheral Interface.
 I2C: Inter integrated circuit
 CAN: Controller Area Network used for Micro-controllers and devices to
communicate.
 SD: Secure digital (memory card)
 MMC: multimedia card
 SDIO: Secure digital Input Output
 GPU: Graphics processing unit.
 DDR: Double data rate

IoT Protocols:
Link Layer:
Protocols determine how data is physically sent over the network’s physical
layer or medium. Local network connect to which host is attached. Hosts on the
same link exchange data packets over the link layer using link layer protocols.
Link layer determines how packets are coded and signaled by the h/w device
over the medium to which the host is attached.
Protocols:
802.3-Ethernet: IEEE802.3 is collection of wired Ethernet standards for the
link layer. Eg: 802.3 uses co-axial cable; 802.3i uses copper twisted pair
connection; 802.3j uses fiber optic connection; 802.3ae uses Ethernet over
fiber.
802.11-WiFi: IEEE802.11 is a collection of wireless LAN (WLAN)
communication standards including extensive description of link layer. Eg:
802.11a operates in 5GHz band, 802.11b and 802.11g operates in 2.4GHz
band, 802.11n operates in 2.4/5GHz band, 802.11ac operates in 5GHz band,
802.11ad operates in 60Ghzband.
802.16 - WiMax: IEEE802.16 is a collection of wireless broadband
standards including exclusive description of link layer. WiMax provide data
rates from 1.5 Mb/s to 1Gb/s
 802.15.4-LR-WPAN: IEEE802.15.4 is a collection of standards for low rate
wireless personal area network (LR-WPAN). Basis for high level
communication protocols such as ZigBee. Provides data rate from 40kb/s
to250kb/s.
 2G/3G/4G-Mobile Communication: Data rates from 9.6kb/s(2G) to up
to100Mb/s(4G).

Network/Internet Layer:
Responsible for sending IP datagrams from source n/w to destination n/w.
Performs the host addressing and packet routing. Datagrams contains source
and destination address.
Protocols:
 IPv4: Internet Protocol version4 is used to identify the devices on a n/w
using a hierarchical addressing scheme. 32 bit address. Allows total of
2**32addresses.
IPv6: Internet Protocol version6 uses 128 bit address scheme and allows
2**128 addresses.
 6LOWPAN:(IPv6overLowpowerWirelessPersonalAreaNetwork) operates
in 2.4 GHz frequency range and data transfer 250 kb/s.

Transport Layer:
Provides end-to-end message transfer capability independent of the underlying
n/w. Set up on connection with ACK as in TCP and without ACK as in UDP.
Provides functions such as error control, segmentation, flow control and
congestion control.
Protocols:
TCP: Transmission Control Protocol used by web browsers (along with
HTTP and HTTPS), email (along with SMTP, FTP). Connection oriented and
stateless protocol. IP Protocol deals with sending packets, TCP ensures reliable
transmission of protocols in order. Avoids n/w congestion and congestion
collapse.
 UDP: User Datagram Protocol is connectionless protocol. Useful in time
sensitive applications, very small data units to exchange. Transaction oriented
and stateless protocol. Does not provide guaranteed delivery

Application Layer:
Defines how the applications interface with lower layer protocols to send data
over the n/w. Enables process-to-process communication using ports.
Protocols:
HTTP: Hyper Text Transfer Protocol that forms foundation of WWW.
Follow request- response model Stateless protocol.
 CoAP: Constrained Application Protocol for machine-to-machine (M2M)
applications with constrained devices, constrained environment and constrained
n/w. Uses client- server architecture. WebSocket: allows full duplex
communication over a single socket connection.
MQTT: Message Queue Telemetry Transport is light weight messaging
protocol based on publish-subscribe model. Uses client server architecture.
Well suited for constrained environment.
XMPP: Extensible Message and Presence Protocol for real time
communication and streaming XML data between network entities. Support
client-server and server-server communication.
DDS: Data Distribution Service is data centric middleware standards for
device-to-device or machine-to-machine communication. Uses publish
subscribe model.
AMQP: Advanced Message Queuing Protocol is open application layer
protocol for business messaging. Supports both point-to-point and publish
subscribe model.

LOGICAL DESIGN of IoT

Refers to an abstract represent of entities and processes without going into the
low level specifies of implementation.
1) IoT Functional Blocks
2) IoT Communication Models
3) IoT Comm. APIs

IoT Functional Blocks: Provide the system the capabilities for identification,
sensing, actuation, communication and management
 Device: An IoT system comprises of devices that provide sensing,
actuation, monitoring and control functions. Communication: handles
the communication for IoT system.
 Services: for device monitoring, device control services, data publishing
services and services for device discovery.
 Management: Provides various functions to govern the IoT system.
 Security: Secures IoT system and priority functions such as
authentication, authorization, message and context integrity and data
security.
 Application: IoT application provide an interface that the users can use
to control and monitor various aspects of IoT system.
IoT Communication Models:
A) Request-Response
B) Publish-Subscribe
C)Push-Pull
D) Exclusive Pair
Request-Response : Request-Response is a communication model in which the
client sends requests to the server and the server responds to the requests. When
the server receives a request, it decides how to respond, fetches the data,
retrieves resource representations, prepares the response, and then sends the
response to the client.

Publish-Subscribe communication model:

 a. Publish-Subscribe is a communication model that involves publishers,
brokers and consumers.
b. Publishers are the source of data. Publishers send the data to the topics which
are managed by the broker. Publishers are not aware of the consumers.
c. Consumers subscribe to the topics which are managed by the broker.
d. When the broker receives data for a topic from the publisher, it sends the data
to all the subscribed consumers

Push-Pull communication model:

Push-Pull is a communication model in which the data producers push the data
to queues and the consumers pull the data from the queues. Producers do not
need to be aware of the consumers.
b. Queues help in decoupling the messaging between the producers and
consumers.
c. Queues also act as a buffer which helps in situations when there is a
mismatch between the rate at which the producers push data and the rate at
which the consumers pull.
Exclusive Pair communication model:
a. Exclusive Pair is a bidirectional, fully duplex communication model that uses
a persistent connection between the client and server.
b. Once the connection is setup it remains open until the client sends a request
to close the connection.
c. Client and server can send messages to each other after connection setup.

IoT Communication APIs:

a) REST based communication APIs(Request Response Based Model)
b) WebSocket based Communication APIs(Exclusive Pair Based Model)

Request-Response model used by REST: RESTful webservice is a collection

of resources which are represented by URIs. RESTful web API has a base
URI(e.g: http://example.com/api/tasks/). The clients and requests to these URIs
using the methods defined by the HTTP protocol(e.g: GET, PUT, POST or
DELETE). A RESTful web service can support various internet media types.

b. Web Socket Based Communication APIs: WebSocket APIs allow bi-

directional, full duplex communication between clients and servers. WebSocket
APIs follow the exclusive pair communication model.

Sensing:
Generally speaking, a sensor is a device that is able to detect changes in an
environment.
By itself, a sensor is useless, but when we use it in an electronic system, it plays
a key role.
A sensor is able to measure a physical phenomenon (like temperature, pressure,
and so on) and transform it into an electric signal.
These three features should be at the base of a good sensor:
• It should be sensitive to the phenomenon that it measures
• It should not be sensitive to other physical phenomena
• It should not modify the measured phenomenon during the measurement
process
• There is a wide range of sensors we can exploit to measure almost all the
physical properties around us.
A few common sensors that are widely adopted in everyday life include
thermometers, pressure sensors, light sensors, accelerometers, gyroscopes,
motion sensors, gas sensors and many more
A sensor can be described using several properties, the most important
being:
Range:
The maximum and minimum values of the phenomenon that the sensor can
measure.
• Sensitivity: The minimum change of the measured parameter that causes a
detectable change in output signal.
• Resolution: The minimum change in the phenomenon that the sensor can
detect.
Sensor Classification:
Sensors can be grouped using several criteria:
Passive or Active:
Passive sensors do not require an external power source to monitor an
environment, while Active sensors require such a source in order to work.
A passive sensor is one which just ‘listens’ to what is happening.
Examples include:
● A light sensor which detects if a light is shining on it.
● An infra-red sensor which detects the temperature of an object.
An active sensor is one which transmits a signal into the environment and
then measures the response that comes back. One example is an ultrasonic
system:
● A pulse of ultrasound is emitted.
● If an object is in the way, the pulse is reflected back.
● The sensor detects it.
● The time taken between emission and detection gives an indication of the
distance of the object.
Analog and Digital:
Analog sensors produce an analog, or continuous, signal while digital sensors
produce a discrete signal.
There are different types of sensors that produce continuous analog output
signal and these sensors are analog sensors. This continuous output signal
produced by the analog sensors is proportional to the measurand
Digital Sensor produce discrete values (0 and 1’s). Discrete values often called
digital or binary signals in digital communication. Electronic sensors or
electrochemical sensors in which data conversion and data transmission take
place digitally are digital sensors.

Some of the types of sensors:

Temperature Sensors
• Temperature sensors measure the amount of heat energy in a source, allowing
them to detect temperature changes and convert these changes to data.
Machinery used in manufacturing often requires environmental and device
temperatures to be at specific levels. Similarly, within agriculture, soil
temperature is a key factor for crop growth.
Humidity Sensors
• These types of sensors measure the amount of water vapor in the atmosphere
of air or other gases. Humidity sensors are commonly found in heating, vents
and air conditioning (HVAC) systems in both industrial and residential
domains. They can be found in many other areas including hospitals, and
meteorology stations to report and predict weather.
Pressure Sensors
• A pressure sensor senses changes in gases and liquids. When the pressure
changes, the sensor detects these changes, and communicates them to connected
systems. Common use cases include leak testing which can be a result of decay.
Pressure sensors are also useful in the manufacturing of water systems as it is
easy to detect fluctuations or drops in pressure.
Proximity Sensors
Proximity sensors are used for non-contact detection of objects near the sensor.
These types of sensors often emit electromagnetic fields or beams of radiation
such as infrared. Proximity sensors have some interesting use cases. In retail, a
proximity sensor can detect the motion between a customer and a product in
which he or she is interested. The user can be notified of any discounts or
special offers of products located near the sensor. Proximity sensors are also
used in the parking lots of malls, stadiums and airports to indicate parking
availability. They can also be used on the assembly lines of chemical, food and
many other types of industries.
Level Sensors
• Level sensors are used to detect the level of substances including liquids,
powders and granular materials. Many industries including oil manufacturing,
water treatment and beverage and food manufacturing factories use level
sensors. Waste management systems provide a common use case as level
sensors can detect the level of waste in a garbage can or dumpster.
Gyroscope
• Gyroscope sensors measure the angular rate or velocity, often defined as a
measurement of speed and rotation around an axis. Use cases include
automotive, such as car navigation and electronic stability control (anti-skid)
systems. Additional use cases include motion sensing for video games, and
camera-shake detection systems.
Gas Sensors
• These types of sensors monitor and detect changes in air quality, including the
presence of toxic, combustible or hazardous gasses. Industries using gas sensors
include mining, oil and gas, chemical
research and manufacturing. A common consumer use case is the familiar
carbon dioxide detectors used in many homes.
Optical Sensors
Optical sensors convert rays of light into electrical signals. There are many
applications and use cases for optical sensors. In the auto industry, vehicles use
optical sensors to recognize signs, obstacles, and other things that a driver
would notice when driving or parking. Optical sensors play a big role in the
development of driverless cars. Optical sensors are very common in smart
phones. For example, ambient light sensors can extend battery life. Optical
sensors are also used in the biomedical field including breath analysis and heart-
rate monitors.

Actuators:
• An IoT device is made up of a Physical object (“thing”) + Controller (“brain”)
+ Sensors + Actuators + Networks (Internet). An actuator is a machine
component or system that moves or controls the mechanism or the system.
Sensors in the device sense the environment, then control signals are generated
for the actuators according to the actions needed to perform. • A servo motor is
an example of an actuator. They are linear or rotatory actuators, can move to a
given specified angular or linear position. We can use servo motors for IoT
applications and make the motor rotate to 90 degrees, 180 degrees, etc., as per
our need. • The following diagram shows what actuators do; the controller
directs the actuator based on the sensor data to do the work.

The control system acts upon an environment through the actuator. It requires a
source of energy and a control signal. When it receives a control signal, it
converts the source of energy to a mechanical operation. On this basis, on which
form of energy it uses, it has different types given below.
Types of Actuators:
Hydraulic Actuators – A hydraulic actuator uses hydraulic power to perform a
mechanical operation. They are actuated by a cylinder or fluid motor. The
mechanical motion is converted to rotary, linear, or oscillatory motion,
according to the need of the IoT device. Example- construction equipment uses
hydraulic actuators because hydraulic actuators can generate a large amount of
force. So, this name suggests, these hydraulic actuators consist of a cylinder or
fluid motor that uses hydraulic power to facilitate mechanical operation.
Pneumatic Actuators
– A pneumatic actuator uses energy formed by vacuum or compressed air at
high pressure to convert into either linear or rotary motion. Example- Used in
robotics, use sensors that work like human fingers by using compressed air.
Pneumatic actuator, pneumatic means air based. A pneumatic actuator basically
converts the energy formed by vacuum or compressed air at high pressure into
either linear or rotatory motion. Pneumatic actuators basically exert a lot of
force and for example, the pneumatic brakes can be very responsive to small
changes in pressure that are applied by the driver. Pneumatic brakes are quite
common in different devices like trucks etc. They use pneumatic brakes. So,
hydraulic brakes are more common in cars, in trucks pneumatic brakes are quite
common. The advantage of pneumatic brakes, is that they are very responsive to
small changes.
Electrical Actuators
– An electric actuator uses electrical energy, is usually actuated by a motor that
converts electrical energy into mechanical torque. An example of an electric
actuator is a solenoid based electric bell. An electric actuator is generally
powered by a motor that converts electrical energy into mechanical torque. So,
this electrical energy is used to actuate the equipment, such as the solenoid
valve which control the flow of water in pipes in response to electrical signals.
Thermal /Magnetic Actuators
– • Actuators are simply devices used to transform energy into motion. A
thermal actuator is a type of non-electric motor made of components such as a
piston and a thermal sensitive material capable of producing linear motion in
response to temperature changes.
Mechanical Actuators
– • A mechanical actuator executes movement by converting rotary motion into
linear motion. It involves pulleys, chains, gears, rails, and other devices to
operate.

Basics of Networking in IoT:

These are basically physical objects are fitted with different sensors and these
sensors basically sense different physical phenomena that are occurring around
them. These sensors fitted things, sensors actuators and different other emirate
devices, these are one component of the IoT, but these become different nodes
in the network, these are the individual nodes in the network. These nodes they
have to communicate with one another and the information that is sensed by one
of these sensors fitted to these nodes, this information from the sensor and the
other sensors, these are taken and are sent to the other sensor nodes, the
destination nodes.
Basically an IoT is a very complex system involving sensors, actuators,
networks, local area, wide area internet and different servers, different
algorithms, machine learning and so on, all executing together to make the
system function as one single entity. So, going back we have in this local
network as you are saying then we have the internet, we have the backend
services and finally, the applications that have been served. So, what we have
we are these different physical objects which are fitted with different sensors.
These things could be telephones, lightning systems, could be cameras, could be
different other scanner, sensors like the temperature sensor and so on and these
things are able to communicate with one another with the help of wireless
technologies like Zigbee, Bluetooth, WiFi and so on.
So, above is a figure which shows that we have different sensors, processors
and Phone. It refitted to each of these devices or the sensor nodes or the sensor
motes or the IoT motes as you may want to call them. So, these motes, they talk
to one another, but these different sensor nodes, they are basically within the
jurisdiction or the domain of the gateway. So, the gateway is basically tasked to
assign different locally unique addresses to these different nodes, to these
different IoT nodes and the gateway basically takes care of the local addressing
within that particular local area network.

Complexity of Networks:
The consideration that has to be taken into account while building the IoT
systems the complexity of the networks. If the number of nodes in the network
increases, then in the solution the system is going to be sustainable or whether it
can be scaled up or not, then we have interference among the different devices.
This is very much vital in any network.
● Interference is a crucial issue and particularly IoT networks involve lot of
large number of typically densely deployed nodes and these nodes as you know
typically wireless power by wifi or bluetooth or zigbee and so on. So,
interference between these different communication between these different
nodes that at the corresponding radios and so on is possible. So, how do you
handle it? Network management, involving computation management,
involving communication management, involving service management and
infrastructure management and so on.
● Addressing Issues is incredibly high number of nodes each of which will
produce content that should be retrievable by any authorized user. This requires
effective addressing policies IPv4 protocol may already reached its limit. IPv6
addressing has been proposed for low-power wireless communication nodes
within the 6LoWPA context IPv6 addresses are expressed by means of 128 bits
which is addresses, enough to identify objects worth to be addressed
IoT Protocols/Communication protocols
IoT Protocols/Communication protocols: A) Link Layer: Protocols determine
how data is physically sent over the network‘s physical layer or medium. Local
network connect to which host is attached. Hosts on the same link exchange
data packets over the link layer using link layer protocols. Link layer determines
how packets are coded and signalled by the h/w device over the medium to
which the host is attached.
Protocols:
802.3-Ethernet: IEEE802.3 is collection of wired Ethernet standards for the
link layer.
Eg: 802.3 uses co-axial cable; 802.3i uses copper twisted pair connection;
802.3j uses fiber optic connection; 802.3ae uses Ethernet over fiber.
802.11-WiFi: IEEE802.11 is a collection of wireless LAN (WLAN)
communication standards including extensive description of link layer.
Eg: 802.11a operates in 5GHz band, 802.11b and 802.11g operates in 2.4GHz
band, 802.11n operates in 2.4/5GHz band, 802.11ac operates in 5GHz band,
802.11ad operates in 60Ghzband.
802.16 - WiMAX: IEEE802.16 is a collection of wireless broadband standards
including exclusive description of link layer.
WiMAX provide data rates from 1.5 Mb/s to 1Gb/s.
802.15.4-LR-WPAN: IEEE802.15.4 is a collection of standards for low-rate
wireless personal area network (LR-WPAN). Basis for high level
communication protocols such as ZigBee. Provides data rate from 40kb/s
to250kb/s. So, this particular standard is helpful in environments which are
noise prone and have lot of interferences and in a presence of noise and
interference, this particular standard can help in improving the reliability of the
network. 2G/3G/4G-Mobile Communication: Data rates from 9.6kb/s(2G) to up
to100Mb/s(4G). B)
Network/Internet Layer:
Responsible for sending IP datagrams from source n/w to destination n/w.
Performs the host addressing and packet routing. Datagrams contains source
and destination address.
Protocols:
IPv4: Internet protocol version 4 (IPV4) is the most deployed Internet protocol
that is used to identify the devices on a network using hierarchical addressing
scheme. 32bit address. Allows total of 2*32addresses.
IPv6: Internet Protocol version6 uses 128bit address scheme and allows
2*128addresses.
● 6LOWPAN:(IPv6over Low power Wireless Personal Area Network) operates
in 2.4 GHz frequency range and data transfer 250 kb/s. it allows for the smallest
devices and each of these devices having limited processing ability to transmit
information wirelessly over the internet protocol. So, we have low power small
devices limited processing capability as is typical of IoT systems and wireless
communication being present. So, it basically helps in establishing connectivity
in this kind of networks.
Transport Layer: Provides end-to-end message transfer capability independent
of the underlying n/w. Set up on connection with ACK as in TCP and without
ACK as in UDP. Provides functions such as error control, segmentation, flow
control and congestion control.
Protocols:
● TCP: Transmission Control Protocol used by web browsers (along with
HTTP and HTTPS), email (along with SMTP, FTP). Connection oriented and
stateless protocol. IP Protocol deals with sending packets, TCP ensures reliable
transmission of protocols in order. Avoids n/w congestion and congestion
collapse.
UDP: User Datagram Protocol is connectionless protocol. Useful in time
sensitive applications, very small data units to exchange. Transaction oriented
and stateless protocol. Does not provide guaranteed delivery.
Application Layer:
Defines how the applications interface with lower layer protocols to send data
over the n/w. Enables process-to-process communication using ports.
Protocols:
 HTTP: Hyper Text Transfer Protocol that forms foundation of WWW.
Follow request response model Stateless protocol. HTTP follows a
request response model where a client sends request to a server using the
HTTP commands. An HTTP can be a browser or an application running
on the client.
 CoAP: Constrained Application Protocol for machine-to-machine(M2M)
applications with constrained devices, constrained environment and
constrained network. Uses client-server architecture. This protocol is
particularly used for web transfer and by web transfer very similar to the
HTTP, but web transfer in the context of constrained networks resource,
constrained networks with nodes which are constrained with respect to
 different resources, such as limited energy or power supply, limited
computational resources, limited communication resource, limited
bandwidth environment and so on.
 WebSocket: Allows full duplex communication over a single socket
connection. They allow bi-directional between clients and servers.
WebSocket follow the exclusive pair communicational model.
WebSocket communication begins with a connection setup request sent.
WebSocket communication presents a suitable protocol for the IoT
environment where bundles of data are transmitted continuously within
multiple devices. A WebSocket makes server and device communication
easy. A server needs a WebSocket library to be installed and we need to
have the WebSocket client and web browser installed on the client or
device that supports WebSocket.
MQTT: Message Queue Telemetry Transport is light weight messaging
protocol based on publish-subscribe model. Uses client server
architecture. Well suited for constrained environment. So, in MQTT there
are three concepts that are involved. The first we are going to go through
is the concept of a message broker the concept of a message broker that
basically serves like a broker which takes control of publishing of the
messages and subscription of the messages. So, publish subscribe is
basically controlled by the message broker. The data are sent to the
clients by the message broker, this data are distributed by the message
broker to the clients who have subscribed to the services.
 XMPP: Extensible Message and Presence Protocol for real time
communication and streaming XML data between network entities.
Support client-server and server-server communication. So, it is a
message oriented middleware that is based on XML, whereas XML is
particularly used for unstructured data. XMPP is useful for real time
exchange of structured data and it is an open standard protocol. XMPP
uses a client server architecture, it uses a decentralized model meaning
that there is no server that is involved in the message transfer and it
provides facilities for discovery of messages which are residing locally or
globally across the network and the availability information of these
services. some of these highlights of the XMPP protocol, it is based on
the concept of decentralization where there is no central server and then,
you know everybody can run the XMPP server theoretically and it is
based on open standard.
 DDS: Data Distribution Service is data centric middleware standards for
device-to-device or machine-to-machine communication. Uses publish
subscribe model. Designed and summarized by Object Management
Group (OMG), Data Distribution Service (DDS) is a competent IoT
protocol for scalable, real-time M2M communication. This protocol
leverages multicasting techniques in the transmission of data and high-
 quality QoS in the small memory footprint devices and to applications. It
employs Data-Centric Public Subscribe (DCPS) layer to directly
communicate the information from publishers to subscribers and deliver
reliable, scalable performance in embedded systems.
 AMQP: Advanced Message Queuing Protocol is open application layer
protocol for business messaging. Supports both point-to-point and publish
subscribe model. So, this standard basically helps define how mists are
going to be passed from businesses, business applications or
organizations. So, in other words, a particular business is comprised of
different systems and different processes, business processes. So, a
business can be conceived as a collection of different systems and
business processes. So, this particular standard helps in communicating
between these systems connecting rather connecting between these
different systems and the business processes of that particular business.

Sensor Network:
Sensor network is a very important technology that is used for building
IoT. Sensors, transducers, actuators these are all very important things for
realization of IoT systems about sensors
In sensor networks we have individual sensors, which are embedded in
something known as sensor devices or sensor nodes. So, these nodes or devices
they have one of their components which is the sensor, and they
have other components as well. So, these components taken together they
comprise that particular node or the device which can help them to
communicate.
one device communicates with another device, that device communicates with
another device, the third device with a fourth, fourth with the first and so on.
We can expand the sensing by having them communicate with one another. So,
what we have are different types of topologies. We can have all sorts of
topologies that we have already heard of in networks being implemented in the
case of sensor networks as well we can use a star topology. We can use a mesh
topology we can have a mesh of we can have a mesh of sensor nodes that are all
put together.
Sensor Networks
Constraints On Sensor Networks:
● Small size maybe less than cubic cm.
● Must consume extremely low power.
● Operate in an unattended manner in highly dense area.
● Should have low production cost and be dispensable.
● Be autonomous.
● Be adaptive to the environment.
Applications:
● Temperature measurement
● Humidity measurement
● Lightening condition
● Soil makeup
● Air pressure
● Noise level
● Vibration