Coexistence of Zigbee and Wi-Fi networks

Signify Interact for Intelligent Buildings uses the 2.4 GHz band, which is also used by Wi-Fi, Bluetooth and other wireless protocols.

This section describes why systems do not interfere with one another when specific rules are followed.

The rules are described in IEEE 802 set of protocols. In this specific case, the 802.11 describes Wi-Fi and 802.15.4 describes low-power personal networks such as Zigbee, the protocol used by Signify Interact for Intelligent Buildings.

Both networks need to implement the following rules in order to co-exist.

Packets

None of the protocols transmit data continuously, instead, each protocol transmit packets when sufficient bandwidth is available. Since Zigbee packets are very short, the chances of collision with Wi‑Fi packets are low.

Channels

Before commissioning the wireless gateways, prepare a plan to prevent interference between the Zigbee network and the corporate Wi‑Fi network. This includes scanning the existing Wi‑Fi access points and coordinating with the customer’s IT department to identify the channels in use and determine whether the channel selection is static or dynamic.

Wi-Fi channels overlap with one another. It is a common practice to select non-overlapping channels to achieve good coverage with several Wi-Fi access points. Interference between overlapping channels results in lower transmission speeds or complete communication failure. Channels 1, 6, and 11 are most commonly used in customer’s Wi-Fi network installations.

The wireless gateway uses Zigbee to communicate on channels 11, 15, 20, and 25. The channels must be selected during the commissioning process.

  • Recommend to use only channels 15, 20, and 25, as channel 11 might be used by the corporate Wi-Fi access points.

  • Channel 11 is supported and can be used only if the corporate Wi-Fi network is not heavily using it such as heavy file transfer activities.
If the existing Wi-Fi network uses all channels then the Zigbee network will be interrupted.
Maintain a minimum distance of 3 metres (10 feet) between the gateway and any high-traffic 2.4 GHz Wi-Fi access point.

In the following example, the corporate Wi-Fi access points use channels 1, 6, and 11 set at a bandwidth of 20 MHz. The Zigbee channels used in Signify Interact for Intelligent Buildings are 15, 20, and 25 which fit in between the gaps of the channels used by the corporate Wi-Fi access points. In addition, Zigbee has low transmitting power (1 mW) compared to Wi-Fi (80 mW), and therefore Zigbee does not interfere with Wi-Fi in most cases.

wg zigbee channels
It is customer’s responsibility to ensure that the frequencies used by ZigBee network are not interfered by any Wi-Fi or Bluetooth network.

The frequencies used by ZigBee network are:

  • Channel 11 → 2405 MHz

  • Channel 15 → 2425 MHz

  • Channel 20 → 2450 MHz

  • Channel 25 → 2475 MHz

For more information, see www.IEEE.org and www.zigbee.org.