Basics of ZigBee Technology
Zigbee is an Ad-hoc network technology which is used for LR-WPAN (Low-Rate Wireless Personal Area Networks) based on IEEE 802.15.4 standard. It defines PHY and Mac Layers for ZigBee using 2.45 GHz, 868 MHz and 915 MHz frequency Band. This technology is low in cost, consumes less power and it is less complex as compare to other technology (Ramya, Shanmugaraj & Prabakaran, 2011). The data rate of this technology touches 250Kbps for 2.45GHz, 40 Kbps for 915MHz and 20 Kbps for 868 MHz frequency band.
There are three areas of architectural responsibility in ZigBee engineering effort. It uses peer-to-peer communication with the use of radio waves in Direct Sequence Spread Spectrum. The ZigBee Alliance describes the logical network, application software, security which is implemented in a firmware stack. This technology uses Mesh topology in its architecture. The Stack of ZigBee includes the Microcontroller and RF chip (Li, Zhu, Tang & Sui, 2010).
ZigBee/IEEE 802.15.4 – General Characteristics
- Dual PHY (2.4GHz & 868/915 MHz)
- Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915 MHz), and 20 kbps (@868 MHz)
- Low power consumption
- Optimized for low duty-cycle applications (<0.1%)
- CSMA-CA channel access yields high throughput and low latency for low duty cycle devices such as sensors and controls.
- It supports addressing space of up to: 18,450,000,000,000,000,000 devices (64-bit IEEE address)- 65,535 networks
- The range of ZigBee technology is 50m typical (5-500m based on environment)
- Fully Hand-shake protocol for transfer reliability
- Time slots for applications which require low latency
It supports three types of network topologies which are mentioned below:
- Star Topology
- Mesh Topology
- Cluster Tree Topology
- Star Topology
In this topology, communication is done between the devices with the use of single central controller called as PAN coordinator. The PAN coordinator may be mains-powered while all the devices are most likely to be battery-powered. Applications which are benefited from this topology include personal computer (PC) peripherals, home automation, games etc. In this, each star network uses a PAN identifier which is not used currently by any other network within the radio sphere of influence.
- Mesh Network
Mesh network topology is the key component of the ZigBee protocol. In this, node is interconnected with other nodes so that at least two pathways connect to every node and connection between all the nodes is dynamically updated. In some of the network, mesh topology is partially implemented in which only some of the nodes relate to one another (Alexandre Gouvea da Silva & Leonardo dos Santos, 2017). Mesh Network is decentralized in nature and each node is self-routing which has the capability to connect with the other nodes as required.
- Cluster-Tree Topology
It is the special case of Peer-to-Peer network in which most of the devices are FFDs and RFD which may connect to a cluster-tree network as leave node at the end of the branch node. FFD can act as a coordinator and provide synchronization service other coordinator and devices. The PAN coordinator makes the first cluster with the establishment of cluster head (CLH) with a cluster identifier (CID) of Zero with use of unused PAN identifier and broadcasting beacon frame to neighbor devices.
It is a low-cost wireless technology which has data type support, reliable data transfer, ease of installation, short range operation and less power consumption. This protocol operates on the unlicensed band and in unrestricted geographical use global implementation.
IEEE 802.15.4 Protocol Features
- Master/Slave Topology
- Dynamic Slave Device Addressing
- Power Management Feature
- Automatic Network Configuration
- Virtual Peer-to-Peer links
- Up to 254 (+master) network nodes
- CSMA-CA channel access technique
- TDMA slots can be allocated
- 15ms frame structure
- 28Kbps and 250Kbps data throughput
- Low Impact Internet Capability
- Service Discovery
Applications of ZigBee Protocol
The network of ZigBee handles multiple traffic types with its own unique characteristics which include periodic data, repetitive low latency data and intermittent data.
Device Type and Operating Modes
- ZigBee Coordinator (ZC)
The most capable devices, the coordinator forms the root of the network tree and might bridge to the other networks. It stores information about the network which includes the acting as the Trust Centre & Repository for security keys.
- ZigBee Router (ZR)
While running an application function, a router can act as an intermediate router passing on data from other devices.
- ZigBee End Devices (ZED)
It includes functionality to talk to the parent node either with the use of coordinator or a router. It cannot relay data from other devices (Yadav, Brar & Kaur, 2014). This relationship allows the node to be asleep for a significant amount of time which provides long battery life.
Alexandre Gouvea da Silva, C., & Leonardo dos Santos, E. (2017). A Study of the Mesh Topology in a ZigBee Network for Home Automation Applications. IEEE Latin America Transactions, 15(5), 935-942. Retrieved from https://ieeexplore.ieee.org/document/7910209
Li, J., Zhu, X., Tang, N., & Sui, J. (2010). Study on ZigBee network architecture and routing algorithm. 2010 2Nd International Conference On Signal Processing Systems. Retrieved from https://ieeexplore.ieee.org/document/5555486
Ramya, C., Shanmugaraj, M., & Prabakaran, R. (2011). Study on ZigBee technology. 2011 3Rd International Conference On Electronics Computer Technology. Retrieved from https://ieeexplore.ieee.org/document/5942102
Yadav, M., Brar, P., & Kaur, P. (2014). Comparitive analysis of different modes of operation for Zigbee mac with variation in network size and traffic. 2014 International Conference On Electronics, Communication And Computational Engineering (ICECCE). Retrieved from https://ieeexplore.ieee.org/document/7086649