VDV Wireless Technology 4 — Questions and Answers
Question 1: Which wireless protocol operates in the 900 MHz band and is commonly used for long-range IoT sensor networks?
- Zigbee
- Z-Wave
- LoRaWAN (Correct answer)
- Bluetooth LE
Correct answer: LoRaWAN
LoRaWAN uses 915 MHz (in the US) and is designed for low-power, long-range IoT applications spanning many miles.
Question 2: In 802.11 networks, what is the purpose of the RTS/CTS mechanism?
- To encrypt data transmissions
- To reserve the wireless medium before transmitting large frames, reducing collisions (Correct answer)
- To authenticate clients before association
- To control transmit power levels automatically
Correct answer: To reserve the wireless medium before transmitting large frames, reducing collisions
RTS/CTS (Request to Send/Clear to Send) is a collision avoidance mechanism that reserves the channel before large frame transmissions.
Question 3: What is the typical frequency range of Bluetooth Classic technology?
- 900 MHz – 928 MHz
- 2.400 GHz – 2.4835 GHz (Correct answer)
- 5.150 GHz – 5.850 GHz
- 60 GHz – 64 GHz
Correct answer: 2.400 GHz – 2.4835 GHz
Bluetooth Classic and Bluetooth Low Energy (BLE) both operate in the 2.4 GHz ISM band from 2.400 to 2.4835 GHz.
Question 4: A VDV technician needs to connect a building's access points back to a central switch without running cables through the ceiling. Which technology is most appropriate?
- Wireless mesh networking (Correct answer)
- MoCA (Multimedia over Coax)
- Power over Ethernet (PoE)
- Fiber channel switching
Correct answer: Wireless mesh networking
Wireless mesh networking allows APs to backhaul traffic wirelessly to each other and ultimately to a wired uplink point.
Question 5: What is the maximum transmission power typically allowed for 2.4 GHz Wi-Fi in the United States per FCC Part 15 rules?
- 100 mW (20 dBm) (Correct answer)
- 1 W (30 dBm)
- 4 W (36 dBm)
- 10 mW (10 dBm)
Correct answer: 100 mW (20 dBm)
FCC Part 15 limits 2.4 GHz WLAN transmitter output to 1 W (30 dBm), but with antenna gain the EIRP is limited to 4 W; typical device limits are 100 mW (20 dBm).
Question 6: Which wireless technology uses frequency hopping spread spectrum (FHSS) to avoid interference?
- 802.11a
- Bluetooth Classic (Correct answer)
- 802.11n
- Zigbee
Correct answer: Bluetooth Classic
Bluetooth Classic uses FHSS, rapidly hopping between 79 channels in the 2.4 GHz band 1,600 times per second.
Question 7: When performing a passive wireless site survey, the technician walks through the facility without doing what?
- Carrying a laptop or tablet
- Associating with the wireless network or generating traffic (Correct answer)
- Measuring signal strength readings
- Noting interference sources
Correct answer: Associating with the wireless network or generating traffic
A passive survey measures existing RF conditions by listening only, without connecting to or generating traffic on the network.
VDV Wireless Technology 4
Which wireless protocol operates in the 900 MHz band and is commonly used for long-range IoT sensor networks?