The Internet of Things

It is based on the IEEE 802.15.4 communication protocol standard and is used for personal area networks or PANs. The IEEE 802.15.4 standard has low power MAC and physical layers and has already been explained in Section 7.3. Zigbee was developed by the Zigbee alliance, which works for reliable, low energy, and cheap communication solutions. The range of Zigbee device communication is very small (10–100 meters). The details of the network and application layers are also specified by the Zigbee standard. Unlike BLE, the network layer here provides for multihop routing.

There are three types of devices in a Zigbee network: FFD (Fully Functional Device), RFD (Reduced Functional Device), and one Zigbee coordinator. A FFD node can additionally act as a router. Zigbee supports star, tree, and mesh topologies. The routing scheme depends on the topology. Other features of Zigbee are discovery and maintenance of routes, support for nodes joining/leaving the network, short 16-bit addresses, and multihop routing.

The framework for communication and distributed application development is provided by the application layer. The application layer consists of Application Objects (APO), Application Sublayer (APS), and a Zigbee Device Object (ZDO). APOs are spread over the network nodes. These are pieces of software, which control some underlying device hardware (examples: switch and transducer). The device and network management services are provided by the ZDO, which are then used by the APOs. Data transfer services are provided by the Application Sublayer to the APOs and ZDO. It is responsible for secure communication between the Application Objects. These features can be used to create a large distributed application.