Exercises: Elements and communication protocols

Explain in your own words what the Internet of Things is and describe two examples of connected objects you know, stating what data they send or receive.

Every IoT system combines four elements: sensors, actuators, connectivity and application. Explain what each brings to the system and give a specific example of each element within a smart home.

The figure shows the architecture of an IoT system that monitors plant moisture: the sensor sends data via Wi-Fi to the network and the user views it on a mobile app, but one of the elements is covered by a question mark, as shown in the figure.

Indicate which element is missing from the chain and what functions it performs (storing and processing data, being accessible from anywhere...). Then, describe the complete journey of a piece of data from the plant to the cell phone screen.

Explain what a sensor is and describe three common sensors in IoT devices (temperature, humidity, light, motion, distance...), stating what each one measures.

Explain what an actuator is and describe three actuators in a smart home (smart plug relay, motorised lock, irrigation valve), stating what action each one performs.

Explain in your own words what an IP address is and why every device connected to a network needs a unique address (it works like the device's postal address within the network).

What is Bluetooth pairing? Describe a situation in which you have used it and what security is provided by requiring two devices to pair before communicating.

In a smart garden app, the data item "moisture 38%" and the message "water this afternoon" are not the same thing. Explain the difference between data and information, and which part of the system converts the former into the latter.

Compare Wi-Fi and Bluetooth as protocols for an IoT device (range, power consumption, speed, network requirement) and reason which you would choose for: (a) a fitness tracker that synchronizes with a cell phone and (b) a security camera that sends real-time video.

Analyse a smart thermostat: identify what data it captures, where it is processed (on the device itself or in the cloud), what decisions it makes automatically, and what the user sees and can command from the application.

A farmer wants to install twenty soil moisture sensors spread across a field where there is no Wi-Fi coverage. Propose a reasonable connectivity solution (low-power long-range network, intermediate gateway...) and justify your choice compared to simply using Wi-Fi or Bluetooth.

Choose and justify the connectivity (Wi-Fi, Bluetooth, or cellular data) for: (a) a sports watch that synchronizes with a cell phone, (b) a video doorbell that streams live video, and (c) a bicycle tracker that may be far from home. Consider the range, battery consumption, and data cost in each case.

A battery-powered sensor cannot transmit continuously without draining the batteries. Explain two energy-saving strategies in IoT (putting the device to sleep between measurements, sending summaries at intervals instead of every reading) and what is sacrificed with each (immediacy, level of detail).

Some sensors do not connect directly to the Internet, but to a gateway that speaks on their behalf. Explain what an IoT gateway is, when it is needed (sensors using low-power protocols without their own IP address, installations with many sensors), and what management advantage it provides.

Analyse a smart speaker with a voice assistant: what processing occurs on the device itself (detecting the wake word) and what occurs in the cloud (understanding the request and responding), and what features become unavailable when the Internet connection drops.

An IP camera comes with the factory password "admin/admin". Analyse the specific risk of not changing it (lists of default passwords circulate on the Internet and devices can be found with specialised search engines) and describe two basic security measures for any domestic IoT device.

In an automated school greenhouse, it is detected that plants suffer from fungal diseases because the system waters indiscriminately whenever soil moisture drops below 30 %, even at night or under high ambient humidity; furthermore, an occasional Wi-Fi drop caused a flood because the valve remained open. Redesign the IoT system: 1) Select and justify which additional sensors you must incorporate besides the soil moisture sensor. 2) Design a logical control algorithm with compound conditions (soil moisture, ambient humidity, temperature, and time window) to optimize irrigation and prevent plant diseases. 3) Reasonably justify whether the decision to open or close the solenoid valve should be executed on the local microcontroller (Edge Computing) or on a cloud server to ensure facility safety during network outages.

During a security audit of a smart home with IP cameras, smart speakers, and connected plugs, three incidents are detected: a camera streams continuous video traffic externally using unencrypted factory credentials; a speaker sends recordings triggered by false activations to the cloud; and a compromised smart plug allows an attacker inside the Wi-Fi network to intercept local traffic. Analyze the attack vector that exploits each vulnerability and design a technical mitigation strategy that includes network segmentation (separate VLANs or subnets), authentication and encryption policies, and physical or logical configuration adjustments to neutralize all three risks.

A company proposes installing a 100 % cloud-dependent fire alarm and environmental control system in a high school: smoke and CO2 sensors send readings via Wi-Fi to a remote server, which processes the data and sends commands back to actuators to sound sirens and open dampers. Technically refute this proposal by evaluating the risks of latency, network availability, and single points of failure during an emergency. Next, design a hybrid architecture (Edge Computing and Cloud Computing) detailing which specific functions must strictly be executed locally in real time and which should be delegated to the cloud, justifying the division of tasks.

In a classroom of 30 students, the goal is to automate CO2 monitoring and mechanical ventilation. If a fixed threshold of 800 ppm is set, the system continuously turns the exhaust fan on and off whenever the concentration fluctuates between 795 and 805 ppm, causing annoying noise and premature motor wear. 1) Design a control logic with hysteresis (establish two justified thresholds: one for activation and one for deactivation) to solve this problem. 2) Justify the choice of sensor type (NDIR optical technology versus low-cost MOX electrochemical sensors) considering gas selectivity and measurement stability. 3) Evaluate which connectivity technology (Wi-Fi versus Zigbee or Bluetooth LE) is most suitable if the sensor must be placed in the center of the classroom powered by a battery that must last the entire school year.

A battery-powered GPS tracker on a pet collar needs to last for weeks. Analyze which design decisions extend battery life (interval between location updates, low-power network versus cellular data, activating only when movement is detected) and what compromise you accept in tracking accuracy.

The contract for a new IoT voice assistant states that the device periodically records and uploads audio snippets to the server to "train acoustic recognition algorithms and improve user experience". As the person in charge of privacy and technological design: 1) Analyze the technical difference between local processing of the wake word on the device's chip and streaming audio directly to the cloud, evaluating the risks of leaking private conversations or minors' data. 2) Design three rigorous technical requirements (at the hardware, encryption, and data retention policy levels) that you would impose on the manufacturer to prevent passive monitoring without consent before authorizing its purchase.

A user has light bulbs that only work via manufacturer A's cloud app, Zigbee plugs dependent on a proprietary gateway B, and Wi-Fi presence sensors from manufacturer C that do not support external integrations. 1) Explain at a technical level why it is impossible to execute a direct, local rule such as "if sensor C detects motion, turn on light bulb A only if plug B is active". 2) Analyze the issues of latency, security, and obsolescence caused by relying on multi-cloud platforms versus using unified universal standards (such as Matter over Thread networks or open local gateways). 3) Define what three technical criteria of interoperability and protocol compatibility the user should demand before purchasing any new device to guarantee its complete integration.

In a 5 km² agricultural holding, 50 battery-powered humidity and temperature sensor nodes are installed. Each node transmits a 100-byte packet every 10 minutes. The use of conventional Wi-Fi is compared against an LPWAN network (such as LoRaWAN in the 868 MHz band). 1) Calculate the total data volume generated by the entire network in one day (in kB) and in a 30-day month (in MB). 2) Knowing that European regulations in the 868 MHz band impose a maximum duty cycle of 1% (the node cannot transmit for more than 1% of the time), demonstrate numerically whether a node that takes 450 ms to modulate and transmit its packet complies with the law when transmitting every 10 minutes. 3) Technically justify why an LPWAN network is superior to a Wi-Fi network for this specific deployment, assessing topology, range, vegetation penetration, and energy autonomy.