Best practices when commissioning ZigBee networks

Issue

Controllers may leave their network and join another if a nearby network has an identical "Extended network ID", "Channel" or "PAN ID"

Product Line

SmartStruxure Lite

Environment

SmartStruxure Lite Multi-Purpose Manager

SE8xxx Room controller
SE8000 Series
SER8300, SE8300, SE8350
Ex. Viconics branding VT8000 Series

Cause

Conflict in zigbee networks (Same "Channel", same "PAN ID" or Same "Extended Network ID")

Resolution

Before deployment, and in order to ensure having a reliable ZigBee network, one has to be aware of the best practices and the limitations of RF signals. Here are some key points to be considered

Network Conflicts: Always change your Extended Network ID from the factory default. The best thing is to use a naming convention that makes sense. One suggestion would be to use “SSLLITxx”, where “xx” is replaced by the floor the network is on. For example, floor 5 would be “SSLLIT05.” If you have multiple networks on the same floor, adding a letter code helps denote them. For example, if there were 2 networks on floor 5, “SSLLI05A” and “SSLLI05B” can be used.

Note: In Firmware 2.20.1, the ZigBee Extended Network ID parameter is set by default to a unique string based on the serial number of the MPM. This will eliminate the possibility of having duplicate Extended ID's in a new deployment. For existing installations, the Extended Network ID will remain unchanged if upgrading from a previous version.

 

Alternating Channels: Alternating channels between network will minimize interference ensure stability. For example, for a 5-story building, alternate between channels 20, 25, 20, 25, 20.

Tx Power Upgrade: The default value for "Tx Power" is 5dBm which was designed in order to meet various regulations in certain countries (Europe). However, the "Tx Power" can be increased to 18dBm in other regions of the world (North America) to boost the transmission power of the MPM.

 

Interference: There are different types of interference when a wireless signal travels through a given space:

  • Physical objects: The number of walls the wireless signal can pass through is determined by the density of the materials used in a building’s construction. Concrete and steel walls are difficult for a signal to pass through. These structures will weaken or at times completely prevent wireless signals.

Also, the presence of individuals or water will diminish the signal due to the water’s ability to absorb the signal.

  • 2.4Ghz Frequency Interference:   
    • Cordless Phone – operates on the same frequency as the ZigBee and can cause a significant decrease in performance.
    • Microwave Oven - operates by emitting a very high power signal in the 2.4GHz band. Often emits a very "dirty" signal across the entire 2.4GHz band.
    • Wireless Routers – Wireless Wi-Fi Networks that share the same channel will have a negative effect on ZigBee network performance.
  • Distance: To ensure reliable communications, a suitable distance between two devices has to be calculated before installation. The distance depends on three factors; transmitter power, sensitivity of the receiver and the propagation path loss. The latter is dependent on the number of walls/physical objects obstructing the signal.  
  • Locations: The physical location where a router or coordinator is placed also has an impact on the signal. Place the devices in higher ground to reduce the impact of physical objects.


Route Redundancy: It is critical that the signal has multiple routes to hop from one device to the other, from one edge of the network to the opposite edge. (See example in images below)