Highly recommend that you read and follow this guide → https://github.com/zigpy/zigpy/wiki/Generic-best-practice-tips-on-improving-Zigbee-network-range-and-general-stability
Update: Check out this more extentive community guide instead → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Other than updating Zigbee Coordinator firmware + connecting the Zigbee Coordinator USB adapter via a long USB extension cable to USB 2.0 port/hub (and not a USB 3.0 port/hub), the most importantly is that you should add mains-powered “Zigbee Router” devices closer to the Zigbee Coordinator to extend the range and coverage before trying to add battery-powered devices further away from the Zigbee Coordinator, as that is a common mistake that can lead to a bad experience.
Zigbee uses mesh networking topology, which means that most mains-powered devices are a “Zigbee Router” that can act as signal repeater and range extended by transmitting data over long distances by passing data messages through the Zigbee network mesh of intermediate devices to reach more distant Zigbee devices. Thus to have a healthy Zigbee network you need many Zigbee Router devices relativly close to each other in order to achieve good coverage and range.
Simply start by adding mains-powered Zigbee devices (i.e. “Zigbee Router” devices) and/or decrease the distance between Zigbee Router devices in Zigbee network mesh to get better range and coverage:
- Zigbee uses mesh networking and depends on having many “Zigbee Router” devices to extend range and coverage:
- Recommendation is to add additional mains-powered Zigbee devices known to be good Zigbee Router devices.
- Add more Zigbee Router devices and reduce their distances to extend network mesh coverage and range.
- Note that not all mains-powered devices have firmware that make it act as a Zigbee Router device.
- Some brands/models of Zigbee Router devices are know to only work well with same brand of devices.
- Buy a few known good dedicated Zigbee Router product (like example the “IKEA Tradfri Signal Repeater”).
- Search community forums for more “Zigbee signal repeater” or “Zigbee range extender” Zigbee Router tips.
- Buy a few additional new Zigbee USB adapters to use after re-flashing them with Zigbee Router firmware.
- Reflash/reuse modern Zigbee USB adapters to act as Zigbee Router by updating to other Zigbee firmware.