Zigbee: A Smart Solution for Smart Street Lighting

• Energy efficiency: Zigbee can reduce the energy consumption of street lights by up to 80%, by allowing them to dim, brighten, or switch off automatically based on the ambient light and motion sensors. Zigbee can also enable demand response and load balancing, by adjusting the power output of street lights according to the grid conditions and peak hours.

• Reliability: Zigbee can improve the reliability of street lighting systems, by detecting and reporting faults, failures, and anomalies in real time, and by enabling remote diagnostics and troubleshooting. Zigbee can also enhance the resilience of street lighting networks, by allowing them to reconfigure and recover from disruptions and damages.

• Security: Zigbee can ensure the security of street lighting systems, by encrypting the data and commands exchanged between devices, and by authenticating the identity and authority of the network participants. Zigbee can also prevent unauthorized access and tampering, by implementing access control and security policies.

• Scalability: Zigbee can support the scalability of street lighting systems, by allowing the addition, removal, and modification of devices and networks without affecting the existing infrastructure and functionality. Zigbee can also facilitate the integration and interoperability of street lighting systems with other smart city applications and services, such as smart meters, smart parking, smart waste management, and smart emergency response.

The thesis statement of this article is: Zigbee is a wireless technology standard that offers a smart solution for smart street lighting, by enabling energy efficiency, reliability, security, and scalability.

Zigbee Network Architecture

• Coordinator: The coordinator is the device that initiates and manages the zigbee network. It is responsible for assigning network addresses, maintaining network information, and coordinating network activities. There can be only one coordinator in a zigbee network, and it must be powered on at all times.

• Router: The router is the device that relays messages between nodes in the zigbee network. It acts as an intermediate device that forwards data packets from the source to the destination. It can also join and leave the network dynamically, and form links with other routers and end devices. There can be multiple routers in a zigbee network, and they must be powered on when the network is active.

• End device: The end device is the device that controls the street light in the zigbee network. It can send and receive data packets to and from the coordinator or the router, and perform the desired functions, such as switching on/off, dimming, or brightening. It can also report its status and performance to the network. There can be many end devices in a zigbee network, and they can be powered on or off depending on the need.

Zigbee network architecture supports three types of network topologies: star, tree, and mesh.

• Star: In a star network, the coordinator is the central node that connects to all the end devices directly. The end devices communicate only with the coordinator, and not with each other. The star network is simple and easy to set up, but it has limited range and capacity, and it depends on the availability and performance of the coordinator.

• Tree: In a tree network, the coordinator is the root node that connects to one or more routers, which in turn connect to other routers or end devices. The end devices communicate with the coordinator or the router, but not with each other. The tree network is more flexible and scalable than the star network, but it has higher latency and complexity, and it is prone to bottlenecks and single points of failure.

• Mesh: In a mesh network, the coordinator, the routers, and the end devices can all communicate with each other directly or indirectly, forming multiple paths and routes. The end devices can also act as routers, relaying messages for other nodes. The mesh network is the most robust and reliable among the three network types, as it can self-organize and self-heal, and it can adapt to changes and failures. However, it also has the highest overhead and power consumption, and it requires more coordination and synchronization.

The advantages and disadvantages of each network type for smart street lighting applications are summarized in the table below:

Zigbee Communication Protocol

• Addressing: The network layer assigns a unique 64-bit extended address and a 16-bit short address to each device in the network. The extended address is fixed and globally unique, while the short address is variable and locally unique. The network layer uses the short address for routing and addressing, and the extended address for joining and leaving the network.

• Routing: The network layer supports various routing protocols and algorithms for finding and establishing the optimal paths and routes between nodes in the network. The routing protocols and algorithms can be based on different criteria, such as hop count, link quality, energy consumption, and traffic load.

• Security: The network layer implements various security mechanisms and services for protecting the data and commands exchanged between nodes in the network, such as encryption, decryption, authentication, and key management. The network layer uses the Advanced Encryption Standard (AES) with 128-bit keys for encrypting and decrypting the data and commands, and the Message Integrity Code (MIC) for verifying the authenticity and integrity of the data and commands.

The application layer provides the role and components for defining and executing the application logic and functionality, such as:

Zigbee Device Objects (ZDOs): The ZDOs are the entities that manage the device roles, capabilities, and behaviors in the network. The ZDOs perform tasks such as device discovery, service discovery, binding, and configuration. The ZDOs also define the device types, such as coordinator, router, and end device, and the device profiles, such as home automation, building automation, and industrial automation.
Manufacturer-defined application objects: The manufacturer-defined application objects are the entities that implement the specific application functions and features for the devices in the network. The manufacturer-defined application objects can be customized and extended according to the needs and requirements of the application domain and the device manufacturer. The manufacturer-defined application objects use the Application Support Sublayer (APS) to communicate with the network layer and the ZDOs, and the Application Framework (AF) to communicate with other application objects.

Zigbee communication protocol provides examples of how it implements data transmission, data encryption, and data acknowledgment in smart street lighting scenarios, such as:

• Data transmission: When an end device wants to send data to the coordinator or the router, it first checks the channel availability and the network status. If the channel is clear and the network is active, it sends a data request to the coordinator or the router, and waits for a data confirmation. If the data confirmation is positive, it sends the data packet to the coordinator or the router, and waits for a data acknowledgment. If the data acknowledgment is positive, it completes the data transmission. If the data confirmation or the data acknowledgment is negative, it retries the data transmission until it succeeds or reaches the maximum number of retries.

• Data encryption: When a node wants to encrypt the data or the commands before sending them to another node, it first generates a random nonce, which is a 13-byte value that consists of the source address, the frame counter, and the security control field. It then uses the nonce and the network key to encrypt the data or the commands using the AES algorithm. It then appends the nonce and the MIC to the encrypted data or commands, and sends them to the destination node. The destination node uses the nonce and the network key to decrypt the data or the commands using the AES algorithm, and verifies the MIC to ensure the security of the data or the commands.

• Data acknowledgment: When a node receives a data packet from another node, it first checks the validity and the integrity of the data packet, such as the frame type, the frame control, the frame check sequence, and the destination address. If the data packet is valid and the data packet is valid, it sends a data acknowledgment to the source node, indicating the success of the data reception. If the data packet is invalid or corrupted, it discards the data packet, and does not send a data acknowledgment to the source node, indicating the failure of the data reception. The source node waits for a data acknowledgment from the destination node for a certain period of time. If the data acknowledgment is received, it completes the data reception. If the data acknowledgment is not received, it retries the data reception until it succeeds or reaches the maximum number of retries.

Zigbee Applications and Challenges

• Adaptive lighting: Zigbee can enable adaptive lighting, which is the ability to adjust the brightness and color of street lights according to the environmental conditions and the user preferences. For example, zigbee can dim the street lights when there is sufficient natural light, or when there is no traffic or pedestrian activity. Zigbee can also change the color temperature of street lights to create different moods and effects, such as warm, cool, or neutral.

• Charging station: Zigbee can enable charging station, which is the ability to provide electric power to electric vehicles and other devices using street lights. For example, zigbee can connect street lights to smart meters and smart grids, and allow users to pay and charge their vehicles or devices using their smartphones or RFID cards. Zigbee can also monitor and manage the power consumption and availability of the charging station, and optimize the power distribution and pricing.

• Environmental monitoring: Zigbee can enable environmental monitoring, which is the ability to measure and report the environmental parameters and indicators using street lights. For example, zigbee can equip street lights with sensors and cameras, and collect and transmit data on air quality, noise level, temperature, humidity, rainfall, and traffic flow. Zigbee can also analyze and visualize the data, and provide feedback and alerts to the users and the authorities.

• Traffic management: Zigbee can enable traffic management, which is the ability to control and optimize the traffic flow and safety using street lights. For example, zigbee can synchronize street lights with traffic signals and signs, and adjust the timing and intensity of the street lights according to the traffic density and speed. Zigbee can also detect and prevent traffic accidents and violations, and notify the emergency services and the law enforcement.

• London, UK: Zigbee was used to implement a smart street lighting project in London, covering more than 14,000 street lights. The project resulted in a 60% reduction in energy consumption, a 50% reduction in maintenance costs, and a 30% reduction in carbon emissions.

• Copenhagen, Denmark: Zigbee was used to implement a smart street lighting project in Copenhagen, covering more than 20,000 street lights. The project resulted in a 57% reduction in energy consumption, a 40% reduction in maintenance costs, and a 28% reduction in carbon emissions.

• Los Angeles, USA: Zigbee was used to implement a smart street lighting project in Los Angeles, covering more than 200,000 street lights. The project resulted in a 63% reduction in energy consumption, a 70% reduction in maintenance costs, and a 47% reduction in carbon emissions.

• Interference: Zigbee can use techniques such as frequency hopping, channel agility, and adaptive power control to avoid and reduce the interference from other wireless technologies. Zigbee can also use alternative frequency bands, such as 868 MHz or 915 MHz, which are less crowded and more reliable than the 2.4 GHz band.

• Compatibility: Zigbee can use standards and protocols such as Zigbee 3.0 and Zigbee IP to ensure the compatibility and interoperability among different zigbee devices and networks. Zigbee can also use certification and testing programs such as Zigbee Certified and Zigbee Compliant Platform to verify and validate the functionality and quality of zigbee devices and networks.

• Standardization: Zigbee can use alliances and partnerships such as Zigbee Alliance and Connected Lighting Alliance to promote and advocate the use and adoption of zigbee for smart street lighting. Zigbee can also use collaboration and cooperation with other wireless technology standards and organizations to create and support a common and harmonized framework and platform for smart street lighting.

Conclusion