Visual Learning: - Videos Hub - WSN deployment case studies, energy optimization techniques - Architecture walkthroughs: Cluster formation, routing protocol animations, real-world WSN systems
Recommended Learning Path: 1. Read this review chapter for comprehensive understanding 2. Test knowledge with WSN quizzes (energy calculations, topology decisions) 3. Experiment with simulators (network topology, duty cycling trade-offs) 4. Watch deployment case studies for real-world context
386.3 Knowledge Check
Test your understanding of WSN architectural concepts with these auto-gradable questions.
NoteAuto-Gradable Quick Check
Question: In battery-powered WSNs, which radio behavior often dominates energy use if you don’t duty-cycle?
💡 Explanation: B. Idle listening can draw nearly as much as transmitting, so sleep scheduling often yields the largest lifetime gains.
Question: Which architectural change best mitigates the WSN “hotspot problem” in many-to-one deployments?
💡 Explanation: C. Hotspots happen because inner nodes relay everyone’s traffic; distributing sinks reduces that relay burden.
Question: In a duty-cycled MAC with periodic wake-ups, what bounds worst-case event-to-delivery latency?
💡 Explanation: B. Worst-case latency is waiting until the next wake window; energy is mainly determined by duty-cycle percentage.
Question: In contention-based WSNs, what is often the primary practical benefit of aggregation/clustering?
💡 Explanation: C. Reducing the number of competing transmitters can dramatically improve delivery by cutting collisions/backoff waste.
386.4 Additional Practice Questions
NoteEnergy Management Questions
Question: A sensor node with 2000 mAh battery and 50 mAh/day consumption will last approximately how long?
💡 Explanation: A. 2000 mAh / 50 mAh/day = 40 days. This is a simple battery life calculation that every WSN designer should be able to perform quickly.
Question: Which MAC protocol requires time synchronization between nodes?
💡 Explanation: D. S-MAC (Sensor-MAC) uses synchronized sleep schedules where nodes agree on common wake/sleep periods, requiring time synchronization. B-MAC and X-MAC are asynchronous protocols that use preambles instead.
Question: In LEACH clustering, why do cluster heads rotate periodically?
💡 Explanation: B. Cluster heads consume significantly more energy (receiving from members, aggregating, transmitting to sink). Rotation ensures this burden is shared, preventing premature death of fixed cluster heads.
NoteTopology and Routing Questions
Question: What is the primary advantage of star topology over mesh topology for battery-powered sensors?
💡 Explanation: C. In star topology, sensors communicate directly with the gateway and never relay traffic for other nodes. This eliminates the relay energy burden that drains batteries in mesh networks.
Question: TTL (Time-To-Live) in packet headers primarily prevents which routing problem?
💡 Explanation: A. TTL limits how many hops a packet can traverse. Without it, packets caught in routing loops (due to stale routing information) would circulate indefinitely, wasting energy.
Question: Which data aggregation approach is most useful for irrigation control decisions?
💡 Explanation: D. MIN reveals “where is it too dry?” (needs watering) and MAX reveals “where is it too wet?” (drainage issue). SUM is mathematically valid but operationally useless—you can’t water “the sum.”
386.5 Summary
This chapter provided knowledge check questions covering:
Energy Dominance: Idle listening as the primary energy drain in non-duty-cycled systems
Hotspot Problem: Architectural solutions using multiple sinks to distribute relay burden
Duty Cycling: Wake interval determines latency, duty cycle percentage determines energy
Aggregation Benefits: Collision avoidance through reduced contention
Topology Trade-offs: Star vs. mesh energy implications
Protocol Selection: Synchronized vs. asynchronous MAC approaches
386.6 What’s Next
Continue to detailed scenario analysis with worked examples of WSN design decisions.