Practice problems and interactive quizzes to test your Zigbee understanding
977.1 Learning Objectives
By completing these exercises, you will:
Reinforce your understanding of Zigbee concepts through practical scenarios
Apply protocol knowledge to real-world design problems
Identify common deployment mistakes and their solutions
Test your readiness for Zigbee implementation projects
977.2 Knowledge Checks
Test your understanding with these interactive questions covering key Zigbee concepts.
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{const container =document.getElementById('kc-zb-ex-1');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"Your smart home has 25 Zigbee devices: 8 smart bulbs (ceiling-mounted), 12 door sensors (battery), 3 motion sensors (battery), 1 thermostat (wired), and 1 coordinator hub. How many mesh routers does this network have?",options: [ {text:"1 - only the coordinator routes messages",correct:false,feedback:"The coordinator routes messages, but so do all mains-powered devices. Smart bulbs and the thermostat can also act as routers since they're always powered."}, {text:"9 - the coordinator plus all 8 smart bulbs",correct:false,feedback:"Close! The coordinator routes, and so do the 8 bulbs, but don't forget the wired thermostat - it's mains-powered and can also route."}, {text:"10 - coordinator, 8 bulbs, and 1 thermostat",correct:true,feedback:"Correct! Any mains-powered Zigbee device can act as a router: the coordinator (1), smart bulbs (8), and wired thermostat (1) = 10 routers. The 15 battery-powered sensors are End Devices that cannot route - they sleep to conserve power."}, {text:"25 - all devices participate in routing",correct:false,feedback:"Battery-powered devices (door sensors, motion sensors) cannot route messages. They're End Devices that sleep 99% of the time. Only mains-powered devices can be routers."} ],difficulty:"easy",topic:"zigbee-device-roles" })); }}
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{const container =document.getElementById('kc-zb-ex-2');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"An office building has Wi-Fi access points on channels 1, 6, and 11 for maximum coverage. The facilities team is deploying a new Zigbee sensor network. Which Zigbee channel should they select for best performance?",options: [ {text:"Channel 11 (2.405 GHz) - it's the lowest frequency available",correct:false,feedback:"Channel 11 overlaps with Wi-Fi channel 1 (2.401-2.423 GHz). This would cause severe interference with the existing Wi-Fi network."}, {text:"Channel 17 (2.430 GHz) - it's in the middle of the spectrum",correct:false,feedback:"Channel 17 falls directly within Wi-Fi channel 6's range (2.426-2.448 GHz). This is one of the worst choices for coexistence."}, {text:"Channel 25 or 26 (2.475-2.480 GHz) - above all standard Wi-Fi channels",correct:true,feedback:"Correct! Channels 25 and 26 are above Wi-Fi channel 11's upper frequency (2.473 GHz). With Wi-Fi on 1, 6, and 11, these are the only Zigbee channels that don't overlap with any Wi-Fi traffic."}, {text:"Channel 20 (2.450 GHz) - it's between Wi-Fi channels",correct:false,feedback:"Channel 20 is at the boundary between Wi-Fi channels 6 and 11. It still experiences interference from both, especially since Wi-Fi channels are 22 MHz wide."} ],difficulty:"medium",topic:"zigbee-wifi-coexistence" })); }}
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{const container =document.getElementById('kc-zb-ex-3');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"A Zigbee network uses AODV (Ad-hoc On-Demand Distance Vector) routing. When an end device needs to send a message to the coordinator for the first time, what happens?",options: [ {text:"The device sends directly to the coordinator using its pre-programmed route",correct:false,feedback:"AODV is an on-demand protocol. Routes are not pre-programmed - they're discovered when needed."}, {text:"The device broadcasts a Route Request (RREQ), and the coordinator responds with a Route Reply (RREP) through intermediate routers",correct:true,feedback:"Correct! AODV discovers routes on-demand: (1) Source broadcasts RREQ, (2) RREQ floods through routers toward destination, (3) Destination sends RREP back along the path, (4) Each router stores the route. Subsequent messages use the cached route."}, {text:"The coordinator proactively broadcasts routes to all devices periodically",correct:false,feedback:"That would be a proactive routing protocol (like OLSR). AODV is reactive/on-demand - it only discovers routes when traffic needs to flow."}, {text:"The device queries its parent router, which has the complete network routing table",correct:false,feedback:"Zigbee routers store partial routing tables, not complete network topology. Route discovery still requires RREQ/RREP for unknown destinations."} ],difficulty:"hard",topic:"zigbee-aodv-routing" })); }}
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{const container =document.getElementById('kc-zb-ex-4');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"A company's Zigbee coordinator hub failed after a power surge. They have 120 devices on the network. What critical information must they restore to avoid re-pairing all devices?",options: [ {text:"The coordinator's MAC address must match the failed unit",correct:false,feedback:"MAC addresses are hardware-specific and can't be changed. Devices use the network key and PAN ID to authenticate, not the coordinator's MAC address."}, {text:"The network key, PAN ID, and device address table from the backup",correct:true,feedback:"Correct! The coordinator stores: (1) 128-bit network key used to encrypt all traffic, (2) PAN ID identifying the network, (3) device address table mapping IEEE addresses to network addresses. Restoring these from backup allows devices to automatically rejoin."}, {text:"Only the firmware version - devices will auto-discover the new coordinator",correct:false,feedback:"Devices cannot auto-discover a new coordinator with a different network key. They're cryptographically bound to the original network credentials."}, {text:"The channel number is the only critical setting needed",correct:false,feedback:"While the channel must match, the network key is the critical security credential. Without it, devices cannot decrypt messages from the new coordinator."} ],difficulty:"medium",topic:"zigbee-coordinator-backup" })); }}
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{const container =document.getElementById('kc-zb-ex-5');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"An IoT product team is deciding between Zigbee and Thread for a new smart home sensor line. Which factor most strongly favors Thread for NEW product development?",options: [ {text:"Thread has better battery life than Zigbee",correct:false,feedback:"Both Thread and Zigbee use IEEE 802.15.4 with similar power profiles. Battery life is comparable."}, {text:"Thread provides native IPv6 addressing, enabling direct cloud connectivity without protocol translation",correct:true,feedback:"Correct! Thread devices have full IPv6 addresses, allowing direct IP communication with cloud services. Zigbee uses 16-bit proprietary addresses requiring gateway translation. Thread + Matter provides native IP and unified ecosystem support."}, {text:"Thread supports more devices per network than Zigbee",correct:false,feedback:"Zigbee actually supports more devices (65,000 vs Thread's ~250). Device count favors Zigbee."}, {text:"Thread has lower hardware costs than Zigbee",correct:false,feedback:"Both use similar IEEE 802.15.4 radio hardware with comparable costs ($2-5 per module)."} ],difficulty:"medium",topic:"zigbee-vs-thread" })); }}
977.3 Practice Exercises
977.3.1 Exercise 1: Smart Home Network Design
Objective: Design a Zigbee network topology for a residential deployment.
Scenario: Plan a 25-device Zigbee network for a 2-story house (200 mΒ²): - 10 smart light bulbs (mains-powered, ceiling fixtures) - 8 door/window sensors (battery-powered, 5-year life expected) - 5 motion detectors (battery-powered) - 1 smart thermostat (wired to HVAC 24V power) - 1 Zigbee coordinator (SmartThings hub, plugged in)
Tasks:
Classify each device as Coordinator, Router, or End Device based on power source
Draw the network topology showing mesh backbone and parent-child relationships
Calculate mesh coverage with 15-meter router range
EndDevice 0x0003 sends temperature reading to Coordinator 0x0000.
Tasks:
Trace RREQ broadcast from EndDevice
Show RREP return path
Calculate route: source β destination
Simulate Router1 failure and re-routing
NoteSolution
RREQ Broadcast:
1. 0x0003 broadcasts RREQ "Looking for 0x0000"
2. 0x0001 (Router1) receives, forwards
3. 0x0000 receives directly from 0x0001
RREP Return:
1. 0x0000 sends RREP to 0x0001 "I'm 0 hops away"
2. 0x0001 forwards RREP to 0x0003 "Route via me, 1 hop"
Established Route:
0x0003 β 0x0001 β 0x0000 (2 hops)
Router1 Failure Scenario:
1. 0x0003 sends data to 0x0001
2. No ACK received (3 retries, 300ms)
3. Mark route invalid, broadcast new RREQ
4. If Router2 (0x0002) or Router3 (0x0004) in range:
0x0003 β 0x0002 β 0x0000
5. If not in range: Device orphaned, rejoin needed
977.3.4 Exercise 4: Battery Life Calculation
Objective: Calculate expected battery life for a Zigbee sensor.
Scenario: Temperature sensor specifications: - Battery: CR2450 (620 mAh) - Reporting interval: 5 minutes - Active current: 20 mA for 10ms transmission - Sleep current: 5 Β΅A - Parent poll interval: 30 seconds, 15ms at 18mA
Dominant Consumer: Parent polling (88% of consumption)
Optimization: Increase poll interval from 30s to 60s: - Polls: 1,440/day - Poll energy: 0.108 mAh/day - New total: 0.136 mAh/day - New battery life: 12.5 years
977.3.5 Exercise 5: Security Deployment
Objective: Plan a secure Zigbee deployment.
Scenario: Commercial office with 50 sensors. Requirements: - High security (sensitive data) - No default keys - Auditable device management
Tasks:
Choose commissioning method and justify
Describe secure joining procedure
Plan key backup strategy
Design monitoring/alerting approach
NoteSolution
Commissioning Method: Install Codes (High Security) - Each device has unique pre-shared secret - No default keys used over-the-air - Per-device authentication
Secure Joining Procedure:
1. Verify Permit Join is CLOSED
2. Enter device Install Code into Coordinator
3. Open Permit Join for 60 seconds
4. Activate device pairing mode
5. Verify correct device joined (check MAC)
6. Close Permit Join
7. Log join event with timestamp and admin
Key Backup Strategy:
Backup items:
- Network Key (encrypted, HSM if available)
- PAN ID and Extended PAN ID
- Device table export
- Install Code documentation
Storage:
- Encrypted backup file
- Offsite secure storage
- Access limited to 2+ admins
- Test restoration quarterly
Use these exercises to prepare for real-world Zigbee deployments. The concepts apply whether youβre deploying a small smart home or a large commercial installation.
977.5 Whatβs Next
In the next chapter, Zigbee Common Mistakes, we examine frequent deployment errors and how to avoid them, learning from real-world troubleshooting experience.