Zigbee Interview Questions and Answers

This document provides a set of Zigbee interview questions and answers, designed to help you prepare for a job interview in the Zigbee wireless domain. These questions are also useful for Zigbee viva sessions.

Top 10 Zigbee Interview Questions

Question -1: Explain the basics of Zigbee technology.

Answer -1: Zigbee is a low-power, low-data rate wireless communication technology primarily used for applications like home automation, industrial control, and sensor networks. It operates in unlicensed radio frequency bands, including 2.4 GHz, 868 MHz (Europe), and 915 MHz (US). Zigbee offers a balance between range, data rate, and power consumption, making it suitable for battery-powered devices and mesh networking topologies.

Question -2: Mention how many frequency channels are supported in Zigbee in different PHY versions.

Answer -2: The number of frequency channels supported by Zigbee varies depending on the physical layer (PHY) version:

• 2.4 GHz Zigbee: Supports 16 channels.
• 868 MHz Zigbee: Supports 1 channel.
• 915 MHz Zigbee: Supports 10 channels.

Question -3: Explain the different components which form a Zigbee network or system.

Answer -3: A Zigbee network consists of three main component types:

• Coordinator: The central node of the network. It establishes the network, manages security, and allows devices to join. There is only one coordinator in each Zigbee network.
• Router: Routers extend the network’s range and provide connectivity for end devices. They can route data between devices and the coordinator.
• End Device: These are the devices that perform specific tasks within the network, such as sensors or actuators. End devices typically communicate with a router or the coordinator.

Question -4: What is Zigbee RF4CE version?

Answer -4:

Zigbee RF4CE is a lightweight, low-power wireless communication protocol designed for remote control applications, primarily in consumer electronics such as TVs, set top boxes, and home entertainment systems. It is an alternative to traditional infrared (IR) remotes, offering greater range, bi-directional communication, and improved reliability.

Question -5: What is Zigbee 6LoWPAN version?

Answer -5:

Zigbee 6LoWPAN is a version of Zigbee that integrates IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN), enabling direct IP-based communication for IoT devices. It allows Zigbee-based networks to connect seamlessly with the internet, improving interoperability with other IP-enabled devices. This version is designed for low-power, low-data-rate applications, making it ideal for smart homes, industrial automation, and sensor networks.

Question -6: Explain Zigbee network architecture and how it is established.

Answer -6: Zigbee supports different network topologies, including star, tree, and mesh. The network architecture is determined by the application requirements and the distribution of devices. A Zigbee network is established when the coordinator node initiates the network. Devices can then join the network by associating with the coordinator or a router.

Question -7: Explain the block diagram of Zigbee physical layer modules.

Answer -7: The Zigbee physical layer (PHY) has two main versions: 2.4 GHz and 868/915 MHz. The block diagram typically includes components for modulation/demodulation, frequency synthesis, power amplification, and channel selection. (Provide specific details about the block diagram components for each PHY version here if possible, like the type of modulation used).

Question -8: Explain the Zigbee frame structure and explain different fields.

Answer -8: Zigbee uses a specific frame structure for data transmission at both the PHY and MAC layers.

• PHY Layer Frame Format: (Describe the PHY layer frame format, including preamble, start-of-frame delimiter, and PHY header. If possible include a basic illustration).

• MAC Layer Frame Format: (Describe the MAC layer frame format, including frame control field, sequence number, addressing fields, and payload. If possible include a basic illustration).

Question -9: Explain the Zigbee routing protocol.

Answer -9: Zigbee primarily uses the AODV (Ad-hoc On-demand Distance Vector Protocol) for routing. AODV is a reactive routing protocol, which means that routes are established only when needed. When a node needs to send data to another node for which it does not have a route, it initiates a route discovery process.

Question -10: Can you compare Zigbee with WiFi?

Answer -10: Zigbee and WiFi are both wireless communication technologies, but they cater to different needs. Zigbee is designed for low-power, low-data rate applications like automation and sensor networks, while WiFi is optimized for higher bandwidth applications like internet access. WiFi typically supports more devices than Zigbee, but Zigbee excels in power efficiency and mesh networking. WiFi is often used to share an internet connection among a limited number of devices or as an offloading solution for cellular internet connections.

This set of Zigbee interview questions and answers is suitable for both freshers and experienced professionals seeking job opportunities in the Zigbee domain. Good luck!