IoT Module-4 Notes

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
SUBJECT: IOT & WIRELESS SENSOR NETWORKS (17EC752/15EC752)

MODULE: 4
1. Challenges for wireless sensor networks:

The characteristics with new mechanisms is the major challenges of the vision of the wireless
sensor networks.
Characteristics Requirements:
 Type of Service: The service type rendered by a conventional communication network is
evident – it moves bits from one place to another. For a WSN, moving bits is only a means
to an end, but not the actual purpose.
 Quality of Service: Closely related to the type of a network’s service is the quality of that
service. Traditional quality of service requirements.
 Fault Tolerance: Since nodes may run out of energy or might be damaged, or since the
wireless communication between two nodes can be permanently interrupted, it is important
that the WSN as a whole is able to tolerate such faults.
 Lifetime: In many scenarios, nodes will have to rely on a limited supply of energy (using
batteries). Replacing these energy sources in the field is usually not practicable, and
simultaneously, a WSN must operate at least for a given mission time or as long as possible.
 Scalability: Since a WSN might include a large number of nodes, the employed
architectures and protocols must be able scale to these numbers.
 Wide range of densities: In a WSN, the number of nodes per unit area – the density of
the network – can vary considerably. Different applications will have very different node
densities.
 Programmability: Not only will it be necessary for the nodes to process information, but
also they will have to react flexibly on changes in their tasks. These nodes should be
programmable, and their programming must be changeable during operation when new
tasks become important.
 Maintainability: Maintainability As both the environment of a WSN and the WSN itself
change (depleted batteries, failing nodes, new tasks), the system has to adapt.
Required Mechanisms:
To realize these requirements, innovative mechanisms for a communication network have to be
found, as well as new architectures, and protocol concepts. Some of the mechanisms that will form
typical parts of WSNs are:
 Multihop wireless communication: While wireless communication will be a core
technique, a direct communication between a sender and a receiver is faced with
limitations.
 Energy efficient operation: To support long lifetimes, energy-efficient operation is a key

technique. Options to look into include energy-efficient data transport between two nodes.
 Auto Configuration: A WSN will have to configure most of its operational parameters
autonomously, independent of external configuration – the sheer number of nodes and

simplified deployment will require that capability in most applications.
 Collaboration and In network processing: In some applications, a single sensor is not

able to decide whether an event has happened but several sensors have to collaborate to
detect an event and only the joint data of many sensors provides enough information.
2. Enabling technologies for wireless sensor networks:
 Building such wireless sensor networks has only become possible with some fundamental
advances in enabling technologies.
 First and foremost among these technologies is the miniaturization of hardware. Smaller
feature sizes in chips have driven down the power consumption of the basic components
of a sensor node to a level that the constructions of WSNs can be contemplated.
 This is particularly relevant to microcontrollers and memory chips as such, but also, the
radio modems, responsible for wireless communication, have become much more energy
efficient.
 Reduced chip size and improved energy efficiency is accompanied by reduced cost, which
is necessary to make redundant deployment of nodes affordable.
3. Single node architecture:
Hardware Components: (Sensor Node Hardware Overview):
A basic sensor node comprises five main components:
 Controller: A controller to process all the relevant data, capable of executing
arbitrary code.
 Memory: Some memory to store programs and intermediate data; usually, different
types of memory are used for programs and data.
 Sensors and actuators: The actual interface to the physical world: devices that can
observe or control physical parameters of the environment.
 Communication: Turning nodes into a network requires a device for sending and
receiving information over a wireless channel.
 Power supply: As usually no tethered power supply is available, some form of

batteries are necessary to provide energy. Sometimes, some form of recharging by
obtaining energy from the environment is available as well.
Fig. Sensor node hardware components.

 Each of these components has to operate balancing the trade-off between as small
an energy consumption as possible on the one hand and the need to fulfill their tasks
on the other hand.
 For example, both the communication device and the controller should be turned
off as long as possible.

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

SUBJECT: IOT & WIRELESS SENSOR NETWORKS (17EC752/15EC752)

1. Challenges for wireless sensor networks:

 Energy efficient operation: To support long lifetimes, energy-efficient operation is a key

autonomously, independent of external configuration – the sheer number of nodes and

 Collaboration and In network processing: In some applications, a single sensor is not

2. Enabling technologies for wireless sensor networks:

 Power supply: As usually no tethered power supply is available, some form of

Fig. Sensor node hardware components.

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