What does Zigbee mean? Half of the smart devices at home don't use WiFi, and all 28 sensors are connected to a single gateway

Last month,

helped a neighbor adjust the router and counted online devices in his own backend—about twenty in total. But my home clearly has only fifty smart devices—where did the rest go? I stared at the Mi Home app for a long time before realizing: the human body sensor, door and window sensor, wireless switch—these little gadgets don't connect to my home WiFi at all. They operate on a network invisible to routers, called Zigbee.

to clarify: Zigbee is another network hidden within 2.4G

At first, I thought all the wireless devices at home were managed by the router, but I realized I was completely wrong. Zigbee is another complete communication protocol that operates in the 2.4GHz band like WiFi, but it doesn't recognize your router—it only recognizes one thing—the gateway.

You can think of it this way: the router runs the WiFi network, the gateway runs the Zigbee network, and both networks are packed into the 2.4G room, but they don't communicate with each other. The multi-mode gateway in my home is the 'platform founder' for Zigbee networks, called a coordinator in jargon. When the sensor leaves the factory, it only recognizes the gateway, and pairing is done with the gateway. From birth to death, you never know what the router looks like.

so the router never sees them in the background. To count these devices, you have to browse through the Mi Home app. That's also why my 28 small sensors don't occupy a single router bay—in the router's eyes, there's only one extra device called a 'gateway' at home. When I wrote about the load count, I calculated this account: when 62 devices were downsized the actual number of routers actually pressed down was far less than expected, and all gateway devices were kept outside by the gateway.

Zigbee specs are rather shabby: based on the IEEE 802.15.4 standard, with a speed of 250kbps. WiFi 6 can easily reach over 2,000 Mbps, while Zigbee is less than a fraction of that. But what the sensors transmit is far too small—a temperature data of dozens of bytes is more than enough for them to ride a bicycle on the highway.

Why do sensors love using it: saving power

pitfalls I made were the WiFi version sensors. For convenience, I bought a WiFi version of the human motion sensor light controller, charged every three months, and after the third charge, I got tired of it. I switched it to the bedside as a night light—out of sight, out of mind.

Zigbee version has a completely different style. Again, with the same sensor, Zigbee's strategy is "sleeping": lying face down most of the time consumes almost no power, waking up hundreds of times a day, each time in fractions of a second, throwing out the data to sleep. A CR2450 button battery is officially listed for one and a half to two years. It's been fourteen months since my door was magnetically installed, and the battery is still over forty percent.

the root of the gap lies in the "heartbeat." WiFi devices need to stay connected to routers to be found at any time, and this "standby salary" runs out of battery as they eat up. Zigbee sub-devices don't need to be online all the time; they only speak when there's a need, and if the battery runs out, they can report a few seconds later. For devices like door magnets, water leak, and smoke alarms, even a second late doesn't matter; For batteries, that's the difference between a year and a half versus three months.

my two door locks have proven the same principle: WiFi direct locks require battery replacement every four months, while Bluetooth versions over a year. The low-power protocol ultimately reflects in the frequency of battery replacement.

the whole house grows into a network: the outlet is the relay station

Zigbee also has another trick I think is the most clever: devices can relay each other, i.e., self-networking.

rules are simple: the equipment connected to the grid is a "full-time node," working both for themselves and for neighbors to relay messages. Smart sockets, smart lights, curtain motors—these are always plugged in, so naturally they're relay stations. Battery-powered sensors are 'part-time nodes'—they only send their own data and don't run errands for others.

the farthest motion sensor from my home is in the corner of the balcony, separated by two walls, the signal to the gateway has already deteriorated. But it is relayed through a smart socket next to it—sensors feed data to the socket, which then passes it to the gateway. I don't deserve anything, the internet itself has grown like this.

this is why veteran users say Zigbee becomes more stable the more you use it: every additional socket gives the network an extra foothold. Conversely, if you cut power off a socket for too long, the sensors relaying power from it may all lose contact. Don't rush to replace the battery—try plugging the socket back in first.

also has a hidden benefit: the linkage logic is stored locally at the gateway. My curtains are Zigbee versions. the timed opening is stored in the gateway, the external network still executes promptly at 7:00. That time, the firmware flash disconnected for half a night, but the curtains stayed open the next day. If this logic were hanging in the cloud, I'd have to get up in the dark.

three net pendulums together: WiFi, Bluetooth Mesh, Zigbee

the ones who truly confused me were these three brothers. Especially Bluetooth Mesh and Zigbee, which are basically cousins—both have low power consumption, require gateways, and can be networked. I laid out the household accounts and looked at a table:

The fourth row in

table is the easiest to overlook. WiFi devices occupy the router's space; no matter how many gateway devices there are, the router only cares about the gateway. After I had over thirty devices at home, this became a big deal. I only realized after counting all the devices at home back then that I realized why people always recommend choosing the gateway version for bulbs, sockets, and sensors.

So why has Xiaomi's new devices in recent years used Zigbee less and Bluetooth Mesh more and more? I looked around and found the answer is very straightforward: Bluetooth chips are cheap, and phones and speakers already have Bluetooth. Xiaomi speakers can directly serve as Bluetooth gateways. my speaker Pro is a free-found Bluetooth Mesh gateway, and some newer routers also have this feature. Saving on a gateway lowers the entry barrier.

Zigbee the host here is Green Rice Aqara. Starting from security sensors, it's all Zigbee, and the inventory of devices accumulated over several years is astonishing. So when you buy Aqara's door and window sensors or water leak sensors, it's still Zigbee. No need to worry about both ends—one multi-mode gateway is included: my Xiaomi Multi-Mode Gateway Gen 2 supports Bluetooth, Bluetooth Mesh, and Zigbee protocols, and even has a network port. All two generations of devices at home are managed by it.

and WiFi under the same roof: channels must be staggered

trouble came too—WiFi and Zigbee both lived in the 2.4GHz room, and the "driveway" inside was fixed. 2.4G has more than a dozen channels. The commonly used WiFi channels 1, 6, and 11 each occupy a segment, while Zigbee is further divided into 16 channels (numbered 11 to 26), each 5MHz wide and overlapping with WiFi lanes.

I've seen the consequences of

car accidents once: the neighbor installed a new router, and the human body sensors in my front door suddenly dulled all at once, so the lights took two or three seconds to turn on. After a long search, finally stuck the old channel interference method the router 2.4G to channel 1, the IoT private network section to channel 11, and the Zigbee channel to the Lumi gateway app, which happened to fall right in the middle gap. The next day, all sensors were restored.

is simple: WiFi occupies 1, 6, and 11, while Zigbee picks the area between 15, 20, and 25. Most gateways come with the default channel in the neutral mode, so the most common home use method is to pin down your own WiFi 2.4G channel and not enable auto. Once the channel jumps, it automatically jumps. If you hit Zigbee one day, you'll have to replay that two or three seconds of light on the lights. The mass disconnection of WiFi devices like vacuum cleaners and cameras is also the root cause. I recorded the inspection order in the of the Mi Home device offline section, which requires separate checks for the gateway and WiFi versions.

disconnect, check the gateway first; before buying equipment, check the protocol

to put it a bit into words. No matter how good Zigbee is, its lifeline is obvious: gateway. When it loses power, all 28 sub-devices lose contact at once—even more straightforward than a router crash—at least the router needs to be restarted, but if the gateway is broken, even the door magnet outside the door won't work. So there's a clear order for troubleshooting smart devices: first check if the WiFi device is still working, then check the gateway version. Most likely, it's about the gateway. I've written the full order in the article on Mijia Offline Device Troubleshooting .

the threshold for buying devices has also dropped: those who want to recognize the Mijia ecosystem and save trouble can buy the Bluetooth Mesh version with their eyes on new devices, and speakers or routers with gateway functions can be directly taken away. which routers have Bluetooth gateways, I checked the backend and found a list ; If you have an Aqara sensor at home, the Zigbee network can't be disconnected. Place the gateway in the center of the room and don't put it in a weak current box; For those with many devices, having a multi-mode gateway as a backup is the most worry-free.

To wrap up the

order: go into the Mijia app and count the gateway version devices to see how many are connected; Then pin the router's 2.4G channel to 1 or 11; if you have a Green Rice gateway, log in to the app to check if the Zigbee channel is down; then find a socket in the middle of the room for the gateway to avoid conflicting with the metal weak current box. After four steps, this invisible network is even more worry-free than WiFi.