Overview
How ZigBee works
The ZigBee wireless personal network technology protocol provides a framework for reliable, cost- effective, low-power, wireless networked, monitoring and control products based on an open global standard. (More information on the ZigBee standard is available at http://www.zigbee.org.) Many ZigBee-enabled devices use ZigBee exclusively as a communication and control interface, but not all: some have the option of switching between ZigBee, standard IR, or a combination of the two.
The NXR-ZGW, acting as a gateway, allows ZigBee-enabled devices to communicate both to and from an ICSP master. A device connects to the NXR-ZGW and is then represented to the master as an ICSP device. The master then communicates to the device through ICSP messages via a translation step at the NXR-ZGW level.
The NetLinx master regularly sends "heartbeat" queries to the NXR-ZGW device; in return, the NXR- ZGW provides the master with a response for all devices on the ZigBee network that have an ICSP address and use ZigBee as their primary interface to the master. The response provided by the NXR- ZGW is based on the last known status of the ZigBee-enabled device. If the NXR-ZGW determines it is no longer in communication with a device, it will indicate to the master that the device is non-responsive or has left the network.
Network structure
A ZigBee network is a Personal Area Network (PAN) consisting of one gateway, the option of one or more repeaters, and one or more end devices.
A gateway initiates a ZigBee network and all devices linking to the PAN gateway do so through either direct links or through repeaters. The gateway’s job is to establish the network’s parameters, e.g., channel and PAN ID. Within each PAN, a gateway or repeater can have up to 8 end devices, depending on the design of your system. Additional repeaters may be added to extend the range of your PAN, but care should be taken to understand the associated increases in bandwidth consumption and message latency. The topology information is contained in the Browser-based Configuration Manager pages (please refer to the NXR-ZGWBrowser-based Configuration Manager Pages section on page 15 for more information).
A repeater like the NXR-ZRP is used to expand the coverage of NXR-ZGW gateways. Every device in the PAN has a parent (a device connecting it to the master), and repeaters can have children (devices using them as a conduit to the master). Adding repeater devices to a network can reduce the number of hops an end device needs to make to reach the gateway. Adding repeaters also extends the coverage area for the entire network. Any device attached to a repeater NXR-ZRP appears attached to the gateway NXR-ZGW in the Browser-Based Configuration Manager pages.
An end device will always connect to a repeater or gateway based on the least depth of the connection, and then the best quality. For instance, given a choice between connecting to a repeater with two hops to a gateway or directly to a gateway, an end device will always connect first to the gateway, even if the repeater has a slightly better connection. End devices cannot have children. The use of the NXR-ZGW and NXR-ZRP allow ZigBee-type devices to roam seamlessly from repeater to repeater within the same
PAN ID.
Because of power saver options and other features, mobile end devices tend to sleep frequently and thus enter and leave the network regularly. Upon awakening, the end device may be in a new physical location or the network may have changed channels. The end device will seamlessly search for a new parent and scan channels upon awakening.
For more information on ZigBee network communication with other AMX products, refer to the "Getting the Most From Your Mio Modero R-4" chapter in the Mio Modero R-4 remote user manual, available at www.amx.com.
