WiFi Coverage vs Capacity: Why More Access Points Can Be Worse
Wireless problems are usually coverage and capacity problems dressed up as equipment problems. This covers what actually decides whether a wireless network works.
Coverage and capacity are different problems
Confusing them is why adding access points sometimes makes things worse.
A coverage problem is a place with no usable signal. The fix is an access point closer to it.
A capacity problem is a place with good signal where everything is slow because too many devices share it. Adding a nearby access point on an overlapping channel makes this worse, not better, because the two then interfere.
The diagnostic question: is the signal weak, or is the signal strong and the throughput poor? Those lead to opposite fixes.
Why more access points is not automatically better
Wireless is a shared medium. Two access points on the same or overlapping channels in earshot of each other must take turns, and each sees the other’s traffic as interference.
Three consequences.
Channel planning matters more than access point count. Neighbouring access points need non-overlapping channels, and the number of genuinely non-overlapping channels is limited, particularly in the lower band.
Transmit power should usually be lower than default. An access point shouting across the building interferes with every other one. Lower power with more access points gives better capacity than fewer at full power.
The higher band is the workhorse. It has far more non-overlapping channels and less range, which is an advantage — less range means less interference between cells.
The uplink nobody sizes
Every access point connects back by cable, and that cable carries everything its clients do.
Two things people get wrong.
Gigabit uplinks on modern access points are a bottleneck. Current wireless standards can exceed gigabit in aggregate, and an access point capable of more than its uplink is limited by the cable, not the radio.
The cabling may not support the upgrade. Multi-gigabit uplinks need the cabling to carry them, and that is decided years before the access point is bought. Our cabling guide covers what each category carries.
Power: PoE budget and standards
Access points are powered over Ethernet, and modern ones draw more than older standards deliver.
Two checks. The PoE standard the access point requires against what the switch delivers per port. And the switch’s total PoE budget against every device you will connect, not just the access points. Our switch guide covers why the total budget matters more than the per-port figure.
An access point that boots, works, and occasionally restarts is frequently an underpowered one rather than a faulty one.
Placement
Four rules that cost nothing.
Ceiling-mounted, in the open. Access points radiate downward and outward. Above a ceiling tile is acceptable; inside a metal enclosure or behind ductwork is not.
Away from metal and water. Both block signal effectively. Racking, shelving, lift shafts and large aquariums all cast shadows.
Not in the corner of the building. An access point in a corner radiates half its coverage outside.
Consider what is above and below. Signal passes between floors, and access points stacked directly above each other interfere.
Warehouses and industrial spaces
Different rules, because the environment is different.
Racking blocks signal and moves. Coverage measured in an empty warehouse is not coverage in a full one, and coverage changes as stock moves. Our warehouse WiFi guide covers surveying properly.
Roaming matters more than raw coverage. Devices on forklifts and in hands move constantly between cells, and a device that drops during roaming loses its session. Our mobile computers guide covers device-side behaviour.
Survey, do not estimate. Concrete, steel racking and stock make prediction unreliable in a way office environments are not.
Frequently asked questions
Will adding more access points fix my slow WiFi?
Only if it is a coverage problem. If the signal is strong and throughput is poor, it is a capacity problem, and adding a nearby access point on an overlapping channel makes it worse through interference.
Should I turn transmit power up?
Usually down. An access point shouting across the building interferes with every other one. Lower power with more access points gives better capacity than fewer at full power.
Is a gigabit uplink enough for an access point?
Increasingly not. Current wireless standards can exceed gigabit in aggregate, so the access point is limited by the cable rather than the radio. Multi-gigabit uplinks need cabling that supports them.
Why does my access point keep restarting?
Frequently insufficient power rather than a fault. Check the PoE standard the access point requires against what the switch delivers per port, and the switch’s total PoE budget against everything connected.
Where should access points be mounted?
Ceiling-mounted in the open, away from metal and water, not in a building corner where half the coverage radiates outside, and not stacked directly above each other between floors.
Do I need a wireless survey for a warehouse?
Yes. Concrete, steel racking and stock make prediction unreliable, and coverage measured in an empty warehouse is not coverage in a full one. Coverage also changes as stock moves.
Tell us the space, the device count and what the devices do, and we will help you work out whether you need coverage or capacity.
