Q22Internet of Things

A Wireless Sensor Network (WSN) is an aggressive physical architecture consisting of hundreds or thousands of spatially distributed, autonomous, microscopic devices (Nodes/Motes). They cooperatively use sensors to monitor physical conditions (temperature, vibration) and mathematically pass their data through the network to a central location. WSN is the physical muscle; IoT is the cloud brain that processes it.

Every single WSN node is a highly constrained mathematical system consisting of four absolute subsystems:

• Sensing Subsystem: The physical sensor (e.g., a thermocouple) attached to an Analog-to-Digital Converter (ADC). It mathematically digitizes the physical world.
• Processing Subsystem: A microscopic microcontroller (MCU) with severely limited RAM. It executes the routing algorithms and formats the JSON payloads.
• Communication Subsystem: The ultra-low-power radio transceiver (usually Zigbee / 802.15.4). It can only transmit data a few dozen meters.
• Power Subsystem: A tiny battery. Because replacing 10,000 batteries in a forest is physically impossible, the entire node architecture is violently optimized to sleep 99.9% of the time.

Because Node A cannot physically reach the Gateway 500 meters away, it must bounce its packet through Node B, then Node C (Mesh Networking). The node must mathematically calculate the best path using Routing Protocols. WSN routing is catastrophically difficult because nodes constantly run out of battery and die, causing the physical topology to change every hour.

A. Proactive (Table-Driven) Routing (e.g., DSDV)

• Mechanism: Every single node mathematically calculates and maintains a massive Routing Table detailing the exact path to every other node in the entire forest. They constantly broadcast updates to keep the tables accurate.
• Merit: If a packet needs to be sent, the route is known instantly (zero latency).
• Demerit: The constant mathematical broadcasting of tables violently drains the batteries of all nodes, rendering this useless for massive WSNs.

B. Reactive (On-Demand) Routing (e.g., AODV)

• Mechanism: The nodes are completely dumb. They maintain NO tables. When Node A wants to send data to the Gateway, it violently broadcasts a Route Request (RREQ) to all its neighbors. The neighbors forward it until it hits the Gateway. The Gateway sends a Route Reply (RREP) back down the exact same path.
• Merit: It saves massive amounts of battery power because routes are ONLY calculated when absolutely mathematically necessary.
• Demerit: High initial latency. The first packet takes a long time to transmit while the network mathematically hunts for a path.

C. Hierarchical (Clustering) Routing (e.g., LEACH)

The absolute standard for IoT. The network is mathematically divided into Clusters. A "Cluster Head" is violently elected. The microscopic nodes only talk to their local Cluster Head. The Cluster Head aggregates the data and uses high power to blast it to the Gateway. To prevent the Cluster Head's battery from dying, the algorithm mathematically randomly rotates the "Head" role among all nodes every hour.