3.

1 Overview of Wireless Sensor Networks

What is a Wireless Sensor Network?

 Definition: Wireless Sensor Networks (WSNs) are self-configured,

infrastructure-less wireless networks designed to monitor physical or
environmental conditions, such as:

o Temperature

o Pressure

o Motion

o Sound

o Vibration

o Pollutants

 Functionality: WSNs collect data through sensor nodes and transmit this
information to a central point known as a sink or base station, where data
is analyzed and observed.

 Base Station Role:

o Acts as an interface between users and the network.

o Can retrieve information by sending queries and collecting results.

 Network Composition:

o Typically consists of thousands of sensor nodes.

o Nodes communicate using radio signals.

 Node Characteristics:

o Equipped with sensors, radio transceivers, computing devices, and

power components.

o Resource-constrained with limited processing speed, storage

capacity, and communication bandwidth.

 Self-Organization: After installation, sensor nodes self-organize to create

a network, often using multi-hop communication.

3.2 Structure of Wireless Sensor Network

The structure of WSNs includes different types of topologies for radio

communication networks:
1. Star Network

 Description: A single base station communicates with multiple remote

nodes.

 Communication: Remote nodes cannot send messages to each other.

 Advantages:

o Simple structure.

o Minimal power consumption for remote nodes.

o Low latency communications.

 Disadvantages:

o Base station must be within range of all nodes.

o Less robust due to dependency on a single base station.

2. Mesh Network

 Description: Nodes can transmit data directly to other nodes within radio
range.

 Multi-Hop Communication: Allows communication to nodes outside

direct range using intermediate nodes.

 Advantages:

o High redundancy and scalability.

o If one node fails, communication can continue via other nodes.

 Network Expansion: Easily extended by adding more nodes.

3. Hybrid Star Network

 Description: Combines features of star and mesh networks.

 Power Management: Low-power nodes do not forward messages to

conserve energy.

 Multi-Hop Capability: Other nodes can forward messages, enhancing

network communication while maintaining low power consumption.

3.3 IEEE 802.11 Standards

 Overview: IEEE 802.11 standards govern Wireless Local Area Networks

(WLANs).
  Service Type: Provides time-bounded and asynchronous services for
various download/upload speeds.

 Global Standard: The most popular specification for wireless LAN,

covering physical and data link layers.

 Protocol Families:

o 802.11: Used for Wi-Fi.

o 802.15: Used for Bluetooth.

o 802.16: Used for Wi-Max.

IoT Communication Protocols

The following communication protocols are crucial for consumer and

industrial Internet of Things (IoT) applications:

1. IEEE 802.15.4

2. Zigbee

3. 6LoWPAN

4. Bluetooth

IEEE 802.15.4

Features:

 Standard for WPAN: Designed for low data-rate wireless personal

area networks (WPANs).

 Low Power Consumption: Ideal for low-data-rate monitoring and

control applications.

 Layer Support: Utilizes the physical (PHY) and medium access

control (MAC) layers, along with logical link control (LLC) and
service-specific convergence sub-layer (SSCS).

 Modulation:

o DSSS: Direct sequence spread spectrum modulation for noise

tolerance.

o BPSK/O-QPSK: Low-speed uses Binary Phase Shift Keying

(BPSK); high-speed uses offset-quadrature phase-shift keying
(O-QPSK).
  Access Method: Carrier sense multiple access with collision
avoidance (CSMA-CA).

 Topologies Supported: Star and mesh.

Network Nodes:

1. Full Function Device (FFD)

o Communicates with all device types.

o Supports full protocol functionality.

2. Reduced Function Device (RFD)

o Communicates only with FFDs.

o Designed for lower power consumption and minimal resource

requirements.

Zigbee

Features:

 Enhancement of IEEE 802.15.4: Most widely deployed protocol

for low-power, low-data-rate applications.

 Layer Structure: Operates on layers 3 and 4 for communication

enhancements, including:

o Security: Authentication and encryption.

o Mesh Networking: Data routing and forwarding capabilities.

Components:

 ZigBee Device Object (ZDO): Manages device functionality and

security.

 Application Support Sub-layer (APS): Bridges the network with

other layers and provides control services.

ZigBee Device Types:

1. ZigBee Coordinator (ZC):

o Root of the ZigBee network tree, managing network initiation

and security.
 2. ZigBee Router (ZR):

o Runs applications and relays information between connected

nodes.

3. ZigBee End Device (ZED):

o Communicates with the parent node but cannot relay

messages; designed for energy efficiency.

Applications:

 Building automation

 Remote control (RF4CE)

 Smart energy monitoring

 Health care and fitness tracking

 Home automation

 LED lighting control

 Telecom services

6LoWPAN

Overview:

 IPv6 for Low-Power Wireless Networks: Designed to enable

small devices with limited processing power to communicate
wirelessly using Internet protocols.

 IETF Standards: Defined by RFC 5933 and RFC 4919.

Features:

 Addressing: Supports both 64-bit globally unique addresses and

16-bit PAN-specific addresses.

 Packet Compression: IPv6 packets are compressed to fit within

the IEEE 802.15.4 packet format.

 Network Range: Up to 200 meters outdoors with a maximum data

rate of 200 kbps.

 Node Capacity: Supports approximately 100 nodes.

Routing:

 Mesh Routing: Within PAN space and between IPv6 and PAN
domains.

 Routing Protocols:

o LOADng: Manages route requests and replies.

o RPL: A distance vector IPv6 routing protocol for lossy and low-
power networks.

Bluetooth

Overview:

 Short-Range Wireless Technology: Designed for data exchange

between devices over short distances, facilitating personal area
networks (PANs).

 Cable Replacement: Intended to replace physical cables

connecting portable devices.

Features:

 ISM Band Operation: Operates in the 2.4 to 2.485 GHz range.

 Data Rates:

o 1 Mbps for version 1.2

o 3 Mbps for version 2.0

 Connection Ranges:

o Class 3: Up to 1 meter

o Class 2: Up to 10 meters (common in mobile devices)

o Class 1: Up to 100 meters (industrial applications)

Connection Establishment:

 Inquiry: Discover nearby devices.

 Paging: Establish connection between two Bluetooth devices.

 Piconets: Configurations of Bluetooth devices acting as masters or

slaves, enabling dynamic role switching.
Applications:

 Audio players

 Home automation

 Smartphones

 Toys

 Hands-free headphones

 Sensor networks

Data Messaging Protocols

MQTT (Message Queue Telemetry Transport)

Overview

 Type: Publish-subscribe-based lightweight messaging protocol.

 Purpose: Designed for connectivity (primarily embedded) between

applications and middleware, as well as networks and
communications.

 Control: A message broker manages the publish-subscribe

messaging pattern.

Key Features

 Topic-Based Communication: Clients subscribe to topics, and the

broker distributes messages to those topics.

 Designed For:

o Remote connections

o Limited bandwidth

o Small code footprint

Components

1. Publishers:

o Lightweight sensors that send data.

2. Subscribers:

o Applications interested in receiving sensor data.

 3. Brokers:

o Connect publishers and subscribers, classifying sensor data

into topics.

 Publish/Subscribe Architecture:

 MQTT employs a publish/subscribe architecture, contrasting with

HTTP's request/response paradigm. This structure is designed for
efficient message distribution.

 Event-Driven Messaging:

 The publish/subscribe mechanism is event-driven, allowing

messages to be pushed to clients as they occur, rather than clients
needing to request them actively.

 Role of the MQTT Broker:

 The MQTT broker acts as the central communication point. It is

responsible for dispatching messages between publishers (senders)
and subscribers (receivers).

 Topic-Based Routing:

 When a client publishes a message, it includes a topic. This topic

serves as routing information, enabling the broker to direct the
message to the appropriate subscribers.

 Clients interested in receiving messages subscribe to specific topics.

The broker ensures that all messages corresponding to those topics
are delivered to the subscribers.

 Decoupled Communication:

 Clients do not need to be aware of each other's identities or

connections; they interact solely through the topics. This decoupling
allows for greater flexibility in communication.

 Scalability:

 The architecture supports highly scalable solutions, enabling

numerous data producers and consumers to operate independently
without direct dependencies on one another

Applications

 Messaging:
 o Used by Facebook Messenger for online chat.

 Cloud Services:

o Employed by Amazon Web Services (AWS) IoT.

 IoT Platforms:

o Microsoft Azure IoT Hub utilizes MQTT for telemetry messages.

o EVRYTHNG IoT platform uses MQTT for machine-to-machine

(M2M) communication.

 IoT Experimentation:

o Adafruit IO provides a free MQTT cloud service for IoT

experimenters.

Constrained Application Protocol (CoAP)

 Overview:

o CoAP stands for Constrained Application Protocol, a web

transfer protocol tailored for constrained nodes and networks.
It is specifically designed for Machine-to-Machine (M2M)
applications, such as smart energy systems and building
automation.

 Architecture:

o CoAP operates on a request-response model, facilitating

asynchronous client-server interactions over a datagram-
oriented transport protocol, typically UDP (User Datagram
Protocol). This choice enhances efficiency, especially for low-
power devices.

 Lightweight RESTful Interface:

o CoAP offers a lightweight RESTful interface, drawing

inspiration from the Representational State Transfer (REST)
standard used in HTTP. This design is crucial for minimizing
overhead and power consumption in IoT applications.

 Power Efficiency:

o The protocol is optimized for low-power sensors, allowing

them to effectively use RESTful services without significant
power drains.
  Messaging Sub-Layers:

o CoAP is structured into two main sub-layers:

 Messaging Layer: Responsible for reliability and

ensuring message duplication.

 Request/Response Layer: Manages the

communication between clients and servers.

 Messaging Modes:

o CoAP supports four messaging modes:

 Confirmable: Ensures reliable transmission; the sender

awaits acknowledgment.

 Non-confirmable: Used for unreliable transmissions; no

acknowledgment is expected.

 Piggyback: Allows the server to send its response

immediately within the acknowledgment message.

 Separate: The server’s response is sent in a separate

message after the acknowledgment, which may take
additional time.

 Request Methods:

o Similar to HTTP, CoAP employs standard methods for

operations:

 GET: Retrieve data.

 PUT: Create or update a resource.

 POST: Create a resource.

 DELETE: Remove a resource.

Overview of Wireless Modems

1. RF (Radio Frequency) Modems

 Description:

o RF Modems enable wireless data transmission using radio

signals. They employ digital signal processing, modulation,
demodulation, forward error correction, and other advanced
functions.
  Functionality:

o RF signals are generated by an antenna in the transmitting

device and received by an antenna in the receiving device.
The received signals are demodulated to decode the payload
data.

 Common Uses:

o RF communication is used in various technologies, including

Bluetooth, Wi-Fi, and LoRaWAN.

 Advantages:

o Low Power Consumption: Efficient for battery-powered

devices.

o Good Operating Range: Can operate over varying

distances.

o High Data Transmission Rate: Supports fast data transfer.

o Penetration: RF signals can penetrate walls and do not

require a line of sight

GSM Overview

 Definition: GSM, or Global System for Mobile Communications, is a

standard for mobile communications widely recognized as 2G or
Second Generation technology. It supports voice, text messaging,
and data services, ensuring interoperability and seamless roaming
across different countries.

 Frequency Bands:

o GSM operates on four frequency bands:

 850 MHz

 900 MHz

 1800 MHz

 1900 MHz

 Access Techniques:

o It employs a combination of Frequency Division Multiple

Access (FDMA) and Time Division Multiple Access
(TDMA) to manage communication channels.
  Standards:

o Various GSM standards exist based on RF carrier frequency

bands, including GSM900, EGSM900, GSM1800, and GSM1900.

Architecture of GSM

The GSM network consists of three main subsystems:

1. Mobile Station (MS):

o The mobile device used for communication, which includes:

 DSP: Digital Signal Processor

 RF Chip: Radio Frequency Chip

 SIM: Subscriber Identity Module, containing subscriber

information and network data.

2. Base Station Subsystem (BSS):

o Manages traffic and signaling between mobile phones and the

network.

o Divides regions into cells (size ranges from 100 meters to 35

kilometers).

o Components:

 BTS (Base Transceiver Station): Facilitates wireless

communication between user equipment and the
network.

 BSC (Base Station Controller): Controls multiple

BTSs, managing radio frequency assignments and
handovers between BTSs.

3. Network and Switching Subsystem (NSS):

o Interfaces between the GSM cellular system and circuit-

switched telephone networks (PSTN).

o Handles call processing, switching, and maintenance.

o Components:

 VLR (Visitor Location Register): Contains location

information of mobile subscribers in the service area.
  HLR (Home Location Register): Stores subscriber
data and permissions for using the GSM network.

 AUC (Authentication Center): Authenticates mobile

subscribers seeking to connect to the network.

 EIR (Equipment Identity Register): Maintains records

of allowed and banned devices within the network.

Key Components of GSM Architecture

1. Mobile Switching Center (MSC)

 Definition: The MSC is a crucial component responsible for

communication switching functions within the GSM network.

 Functions:

o Call Setup: Establishes connections between callers.

o Call Release: Ends calls and releases resources.

o Routing: Directs calls to the appropriate destinations.

o Call Tracing and Forwarding: Manages features such as call

forwarding and tracking for billing and operational purposes.

 Components:

o VLR (Visitor Location Register): Temporarily stores

information about subscribers currently within the MSC's
service area.

o HLR (Home Location Register): Stores permanent

subscriber data and status.

o AUC (Authentication Center): Provides security by

authenticating users.

o EIR (Equipment Identity Register): Maintains a database

of mobile equipment identities to prevent fraud.

o Connection to PSTN: Links the GSM network to the

traditional telephone network.

2. Public Switched Telephone Network (PSTN)

 Definition: PSTN is the traditional circuit-switched telephone

network that connects calls using physical lines.
  Characteristics:

o Initially comprised of analog fixed-line systems but is now

predominantly digital.

o Includes both mobile and fixed telephone networks.

o Provides connectivity for landline phones in homes and

businesses.

3. Operating Subsystem (OSS)

 Definition: OSS refers to the systems that enable network

operators to monitor, control, and maintain the GSM network.

 Purpose: Supports cost-effective maintenance and operational

management of GSM services.

 Components:

o OMC (Operation Maintenance Center): Responsible for

monitoring and maintaining the performance of Mobile
Stations (MS), Base Station Controllers (BSC), and Mobile
Switching Centers (MSC).

Interfaces Connecting the Subsystems

The GSM architecture includes three key interfaces that facilitate

communication between different subsystems:

1. Air Interface (UM Interface):

o Description: Also known as the UM interface, it connects the

Mobile Station (MS) to the Base Transceiver Station (BTS).

o Analogy: Similar to the U interface of ISDN (Integrated

Services Digital Network), which facilitates digital
communication.

2. Abis Interface:

o Description: An internal interface within the Base Station

Subsystem (BSS) that links the BTS to the Base Station
Controller (BSC).

o Function: Facilitates communication and control between the

BTS and BSC, handling signaling and data traffic.
 3. A Interface:

o Description: This interface provides communication between

the Base Station Subsystem (BSS) and the Mobile Switching
Center (MSC).

o Function: Supports call processing, mobility management,

and overall network operation.

GSM System Specifications

1. Access Method

 Techniques Used:

o TDMA (Time Division Multiple Access): Divides the

frequency into time slots to allow multiple users to share the
same frequency channel.

o FDMA (Frequency Division Multiple Access): Allocates

separate frequency bands to different users, allowing
simultaneous communication.

2. Frequency Bands

 Uplink Frequency Band:

o Range: 890 to 915 MHz

o Purpose: Used for communication from the mobile device to

the base station.

 Downlink Frequency Band:

o Range: 935 to 960 MHz

o Purpose: Used for communication from the base station to

the mobile device.

3. System Specifications

 System Bandwidth:

o Total: 200 KHz

o Implication: Bandwidth allocated per channel supports the

transmission of voice and data.

 Number of Frequency Channels (ARFCN):

 o Total Channels: 124

o Function: Each channel corresponds to an Absolute Radio

Frequency Channel Number, allowing multiple simultaneous
calls.

 Users per Channel:

o Capacity: 8

o Explanation: Each channel can accommodate up to 8 users

through TDMA.

 Frame Duration:

o Duration: 4.615 ms

o Context: Time duration for one frame in the TDMA structure.

 Spectral Efficiency:

o Value: 1.35 b/s/Hz

o Significance: Measure of how effectively the bandwidth is

utilized.

 Data Rate per User:

o Rate: 33.6 kbps

o Gross Data Rate: 270.833 kbps for 8 users sharing the

channel.

4. Applications of GSM

GSM technology supports a wide range of applications, including:

 Mobile Telephony: Primary use for voice communication.

 VoIP Integration: Facilitates voice over IP services for internet

calling.

 SMS (Short Message Service): Enables text messaging between

mobile devices.

 Mobile Banking: Supports financial transactions via mobile

devices.

 Smart Home Systems: Connects and manages devices in smart

homes.
  Telemedicine: Allows remote medical consultations and
monitoring.

 Surveillance Systems: Used for security and monitoring

applications.

 Alarm Systems: Provides alerts and notifications for security

breaches.

 Cell Broadcasting: Distributes messages to multiple users in a

specific area.

Wi-Fi - Wireless Fidelity Overview

Wi-Fi is a widely used wireless networking technology that enables devices

to connect to networks or communicate with each other without physical
cables. Below are the key features and operational aspects of Wi-Fi:

Key Features of Wi-Fi:

 Wireless Connectivity: Wi-Fi allows devices such as computers,

smartphones, and tablets to connect wirelessly to a local network or
the internet, facilitating seamless data exchange without the need
for wired connections.

 Wireless Local Area Network (WLAN): Wi-Fi operates as a WLAN,

following the IEEE 802.11 standards for wireless communication,
which define the protocols for wireless networking.

 Physical Data Link Layer (PDLL): Wi-Fi functions at the Physical

and Data Link layers of the OSI model, enabling reliable data
transmission by encoding and transmitting data packets over radio
waves.

 Network Interface Controller (NIC): To connect to a Wi-Fi

network, devices require a network interface controller (NIC), which
is integrated into most modern devices such as laptops,
smartphones, digital cameras, and smart TVs.

 Access Points and Client Connections: Wi-Fi networks consist of

access points (or base stations) that facilitate connections between
clients and the network. Clients can also communicate with each
other within the network limits.

 Frequency Bands: Wi-Fi currently operates on two main frequency

bands:
 o 2.4 GHz: Offers a longer range but is more susceptible to
interference from other devices.

o 5 GHz: Provides higher data rates with a shorter range, ideal

for high-speed applications.

Range and Coverage:

 Indoor and Outdoor Range:

o Indoor Range: An access point typically covers about 20

meters (66 feet) indoors, but this can vary based on
obstacles like walls and furniture.

o Outdoor Range: Modern access points can achieve ranges of

up to 150 meters (492 feet) outdoors, given a clear line of
sight.

Applications of Wi-Fi:

Wi-Fi technology is widely used in various applications, including:

 Home networking

 Public hotspots (e.g., cafes, airports)

 IoT devices (smart home systems)

 Business environments for office connectivity

Conclusion

Wi-Fi is a vital technology that enhances connectivity in various

environments, providing flexibility and convenience for users. Its ability to
support multiple devices and applications makes it an essential
component of modern communication infrastructure.