What Is Backhaul in Mesh Wi-Fi

People buy a mesh system for one reason: Wi-Fi at the far end of the house is weak. After installing it, the signal icon in the back room is indeed full. But the speed test is often disappointing, sometimes a third of what you get near the router.

The cause is almost never the signal you can see. It's the link you can't: the backhaul.

Two links at every node

Every mesh node other than the main one handles two connections at once:

• The link to devices, the Wi-Fi your phone and laptop use. This is what the signal icon shows.
• The link to the previous node, carrying internet from the main router to this node. This is the backhaul.

Internet in a room can't be faster than the backhaul of the node serving it. Full signal from a node with weak backhaul is like a large tap connected to a thin pipe.

Three kinds of backhaul

Shared wireless. Nodes talk to each other on the same band your devices use. This is the most common form on dual-band mesh. The problem is that one channel does two jobs: receiving from the previous node and serving devices. A Wi-Fi radio can't talk and listen at the same time on the same channel, so airtime is split.

Wireless with a dedicated band. On tri-band mesh, one band is set aside only for traffic between nodes. Devices use the other two. Backhaul no longer competes with the phones in the same room, and the result is far more stable, especially with three or more nodes.

Wired (ethernet backhaul). Nodes are connected to the router with a LAN cable. Backhaul uses no airtime at all, isn't affected by walls, and every radio on the node is free for devices. This is the best form, and most modern mesh systems support it even though the box rarely mentions it.

Why speed drops at every hop

With shared wireless backhaul, each hop roughly halves the available speed. The second node receives from the first and passes it on using the same radio, so its airtime is split in two. With three nodes in a line, the last one may get only a quarter of the speed near the router.

Add wall attenuation and distance, and the real number is often lower still. That's why adding a node doesn't always add speed; sometimes it just adds a hop that slows the end of the chain. The same symptom happens with ordinary repeaters, compared in mesh Wi-Fi vs repeaters.

Node placement decides the backhaul

The most common mistake is putting a node in the room where signal is weakest. It feels logical, but the node then receives an equally weak backhaul and just rebroadcasts a weak signal with a fuller icon.

A better rule:

• Place nodes halfway, between the router and the area you want to cover, where the router's signal is still good. Usually one or two walls from the previous node, not at the far end of the house.
• Avoid heavy obstacles between nodes: thick concrete walls, concrete stairs, tiled bathrooms, aquariums, and metal cabinets.
• In multi-storey houses, put the upstairs node roughly above the router, not in a far corner. Concrete floors are a big obstacle; more on this in weak Wi-Fi upstairs.
• Aim for a star, not a chain. All nodes connecting directly to the main router beats a third node that depends on the second.

The principles of placing a router apply to nodes too, explained in placing your router.

Use a cable if you can

One LAN cable to the farthest node often gives a bigger improvement than buying another node. A few things to know:

• Cat5e is enough for gigabit, and Cat6 gives more headroom. How to choose is in choosing a LAN cable.
• Going through a switch is fine, as long as it's an ordinary one and not one that separates networks.
• If running a cable isn't possible, powerline or old cable-TV coax can be a middle ground. Results vary; the options are covered in powerline and alternatives.
• Check the settings. Some systems detect the cable automatically, others need it switched on in the app.

How to check backhaul in the app

Nearly every mesh app shows the state of each node. The names differ by brand, but you're looking for the same things:

• The node's connection type: wired or wireless. If you've connected a cable but it says wireless, the cable isn't being detected.
• Connection quality to the parent node, often shown as "good", "fair", or "weak", or as a link speed. A node labelled weak should move one step closer to its parent.
• Its parent node. Make sure a node meant to connect to the main router actually does, rather than to another, farther node.

The most honest test is still simple: run a speed test standing near each node and compare it with the result near the router. A large gap at one node is almost always a backhaul problem. Tools for reading signal in more detail are in Wi-Fi signal analyser apps, and the difference between link speed and the speed you actually get is explained in bandwidth, latency, and throughput.

When choosing a mesh system

• Two nodes, a house that isn't too large: dual-band is usually enough.
• Three or more nodes, no cables: choose tri-band so the backhaul has its own band.
• Cables are possible: make sure every node has a LAN port and supports ethernet backhaul. With cables, even cheaper models can perform very well.

Devices moving from one node to another as you walk around the house is a separate matter from backhaul, covered in roaming between access points.

Frequently asked questions