898 Bluetooth Assessment and Exercises
Comprehensive Quizzes and Practice Problems
bluetooth quiz, ble assessment, gatt quiz, bluetooth exercises
898.1 Learning Objectives
By completing this assessment, you will:
- Validate your understanding of Bluetooth fundamentals
- Apply knowledge to real-world IoT scenarios
- Identify areas needing further study
- Practice problem-solving for Bluetooth design decisions
898.2 Quick Review Quiz
Test your understanding of core Bluetooth concepts:
Q1: What is the main advantage of BLE over Classic Bluetooth?
BLE’s 50-99% lower power consumption enables months to years of battery life instead of days to weeks. Fast pairing (6ms vs 6s), aggressive sleep modes, and optimized protocols make BLE ideal for battery-powered IoT sensors.
Q2: What is the maximum number of active slaves per piconet?
7 active slaves per master due to 3-bit Active Member Address (AMA). Additional slaves can be “parked” (up to 255) but cannot actively communicate until unparked.
Q3: What frequency band does Bluetooth operate in?
2.4 GHz ISM band shared with Wi-Fi, Zigbee, and microwave ovens. Bluetooth uses FHSS at 1600 hops/second for interference mitigation.
Q4: Can slaves communicate directly with each other in a piconet?
No, not directly. In a piconet, all communication routes through the master using TDM. For direct peer communication, use BLE Mesh.
Q5: Which Bluetooth profile is used for wireless keyboards?
HID Profile for keyboards, mice, game controllers. Based on USB HID spec with low latency. BLE keyboards use HID-over-GATT (HOGP).
898.3 Scenario-Based Questions
Apply Bluetooth knowledge to real-world IoT scenarios:
Scenario 1: You’re designing a fitness tracker that must last 6 months on a coin cell battery while continuously monitoring heart rate and syncing with a smartphone. Which Bluetooth technology should you use?
BLE is designed for battery-powered sensors with intermittent data transmission. Classic BT idle current is 30-60mA (continuous), while BLE idle is 1-15µA with periodic advertising. For fitness tracker: BLE average <200µA enables 6+ months vs 7 days with Classic BT.
Scenario 2: Your smart home hub (Bluetooth master) controls 12 devices: 8 smart bulbs, 3 door sensors, and 1 thermostat. Suddenly, only 7 devices respond. The others show “disconnected” even though they’re powered and within range. What’s the most likely cause?
Piconet limit of 7 active slaves is a fundamental protocol limitation. 12 devices require either multiple piconets, BLE (20+ connections on modern chipsets), or Bluetooth Mesh (32,000+ nodes).
Scenario 3: You’re building a medical IoT device (continuous glucose monitor) that transmits patient data via BLE to a smartphone app. Which security configuration is MINIMUM acceptable for regulatory compliance (HIPAA)?
LE Secure Connections (BLE 4.2+) with strong authentication is mandatory for medical devices. Just Works is vulnerable to MITM, legacy pairing uses weak encryption. HIPAA requires encryption in transit (AES-128+), device authentication, and audit logging.
Scenario 4: Your BLE temperature sensor advertises every 1 second with 31 bytes of data. After deployment, you notice smartphone battery drains faster than expected when the app is running. What’s the optimization?
GATT connection is more efficient than continuous advertising scanning. Phone scanning draws 15-50mA vs 1-5mA idle in connected mode. Connect briefly, receive data via GATT Notify, then sleep between transmissions.
Scenario 5: You’re implementing a BLE smart lock. The phone sends “unlock” command via GATT Write. The lock sometimes misses commands when phone is 5m away but works perfectly at 1m. Advertising and connection succeed at 5m. What’s wrong?
Write Without Response lacks delivery guarantee - packets can be lost at weaker signal strengths. Use Write With Response for critical commands (locks, payments). At 5m with obstacles, packet error rate can be 5-10%.
Scenario 6: Your building automation system uses Bluetooth Mesh with 50 smart lights. When you send “all lights OFF” command, only 35 lights turn off. The 15 failed lights are spread throughout the building, not clustered. What’s the likely cause?
TTL too low causes messages to expire before reaching all nodes. Each relay decrements TTL; when TTL=0, message stops propagating. Lights 5+ hops away never receive command. Solution: Increase TTL to match network diameter (typically 2x measured hop count).
898.4 Technical Deep-Dive Questions
Q7: What is a BLE GATT characteristic?
A GATT characteristic contains: Value (actual data bytes), Properties (READ, WRITE, NOTIFY, INDICATE), and Descriptors (metadata). Hierarchy: Profile → Service → Characteristic → Value/Properties/Descriptors.
Q8: What is an iBeacon?
iBeacon is Apple’s BLE beacon protocol with: Proximity UUID (16 bytes) for application ID, Major (2 bytes) for coarse location, Minor (2 bytes) for fine location, TX Power (1 byte) for distance estimation.
Q9: What is Bluetooth’s frequency hopping rate?
1600 hops per second across 79 channels (Classic) or 40 channels (BLE). FHSS provides interference mitigation, Wi-Fi coexistence, improved security, and reliability.
Q10: What is the purpose of Bluetooth pairing?
Pairing establishes secure authentication and generates encryption keys. Process: discovery, authentication (PIN/passkey), key generation (LTK), bonding (store keys). Protects against eavesdropping and MITM attacks.
898.5 Comparison Questions
| Feature | Classic Bluetooth | BLE |
|---|---|---|
| Best for continuous audio streaming | ||
| 50-99% lower power consumption | ||
| Pairing time: 6ms | ||
| Uses 79 channels @ 1 MHz | ||
| Ideal for battery-powered sensors |
- Audio streaming: Classic (A2DP profile)
- Lower power: BLE (50-99% less)
- 6ms pairing: BLE (Classic takes ~6 seconds)
- 79 channels: Classic (BLE uses 40 @ 2 MHz)
- Battery sensors: BLE (months-years battery life)
898.6 Matching Questions
Q12: Match each Bluetooth profile/service to its typical IoT application.
HID for input devices, A2DP for audio, SPP for serial data, Heart Rate Service (0x180D) for fitness devices.
898.7 Calculation Problem
Q13: A BLE temperature sensor advertises every 1000ms (1 second) using non-connectable advertising with 20-byte payload. Advertising consumes 15mA for 2ms per advertisement. Sleep mode consumes 2µA. The device uses a CR2032 battery (220mAh capacity). Calculate the estimated battery life in days.
days
Calculation: 1. Duty cycle: 2ms active / 1000ms = 0.2% 2. Average current: (15mA × 0.002s + 0.002mA × 0.998s) / 1s = 0.032mA 3. Battery life: 220mAh / 0.032mA = 6,875 hours = 286-365 days
Accounting for self-discharge (~15%/year) and temperature variations yields approximately 1 year of battery life.
898.8 Ranking Question
Q14: Rank these Bluetooth technologies by maximum range (longest to shortest).
Ranking (longest to shortest): 1. BLE 5.0 Long Range (Coded PHY): ~1000m with S=8 coding 2. Classic Class 1 (+20dBm): ~100m for industrial use 3. BLE 5.0 Standard (1M PHY): ~30-50m typical 4. Classic Class 2 (+4dBm): ~10m for consumer devices
898.9 Practice Exercises
Objective: Build a BLE scanner that discovers and analyzes nearby devices.
Tasks: 1. Implement BLE scanning with 5-second duration 2. Extract device name, MAC address, RSSI, manufacturer data 3. Filter devices by service UUID (e.g., Heart Rate 0x180D) 4. Calculate estimated distance using RSSI
Expected Skills: - BLE Central role configuration - Advertisement packet parsing - RSSI-to-distance conversion
Objective: Connect to a BLE device and interact with GATT characteristics.
Tasks: 1. Scan and connect to a specific device 2. Enumerate all services and characteristics 3. Enable notifications on Heart Rate Measurement (0x2A37) 4. Log real-time heart rate data with timestamps
Expected Skills: - GATT service discovery - CCCD configuration - Notification callback handling
Objective: Analyze and implement BLE security measures.
Tasks: 1. Compare pairing methods (Just Works, Passkey, Numeric Comparison) 2. Implement LE Secure Connections pairing 3. Enable BLE privacy (random MAC rotation) 4. Create security checklist for medical device
Expected Skills: - Security level selection - Pairing implementation - Privacy configuration
Scenario: Smart home with 15 sensors and 1 central hub.
Tasks: 1. Design network to overcome 7-device piconet limit 2. Calculate connection intervals for each sensor type 3. Estimate power budget for 2-year battery life 4. Optimize advertising vs GATT connection strategy
Expected Skills: - Topology selection (BLE vs Mesh vs scatternet) - Power budget calculation - Connection parameter optimization
898.10 Summary
This assessment covered:
- Quick Review: Core Bluetooth/BLE concepts
- Scenarios: Real-world IoT application problems
- Deep-Dive: Technical details (GATT, iBeacon, security)
- Comparisons: Classic vs BLE feature mapping
- Calculations: Battery life estimation
- Exercises: Hands-on implementation practice
898.11 What’s Next
Return to the Bluetooth Overview for a summary of all chapters, or continue to IEEE 802.15.4 to explore the foundation protocol for Zigbee and Thread mesh networks.