If you have bought a Wi-Fi router in the last several years, you have probably seen beamforming listed as a feature. The advertising usually shows the same thing: a router spraying Wi-Fi everywhere, then magically narrowing that RF energy into a beam pointed directly at a laptop or phone.
I have a problem with that explanation.
I think consumer Wi-Fi beamforming, as it is presented to consumers, is basically fake. There is real signal processing happening underneath it, but what manufacturers call “beamforming” is not what most people are being led to picture.
Without beamforming, the router broadcasts equally in every direction. With beamforming, it figures out where your device is and concentrates the Wi-Fi signal directly toward it.
That sounds like an electronically steered directional antenna.
That is not a good description of what a normal home Wi-Fi router is doing.
Typical 802.11 beamforming uses multiple RF chains along with information about the wireless channel. The transmitter changes the phase and amplitude relationships between those signals so that they arrive more favorably at a particular receiver.
That is precoding and spatial signal processing.
It does not necessarily mean there is a nice narrow RF lobe shooting across your living room toward your phone.
Indoor RF propagation is a mess. Signals bounce off walls, furniture, floors, ceilings, appliances and people. Multiple copies of the same transmission arrive at the receiver at different times and phases. Wi-Fi actually takes advantage of some of that multipath behavior.
So when an AP improves the signal at a particular receiver, that does not automatically mean it created the neat directional “beam” shown on the router box.
Wi-Fi is bidirectional.
The access point sends data to the client, and the client has to send data back.
An access point may have multiple antennas, multiple RF chains and transmit-beamforming capability. But the client on the other end may be a phone, laptop, television, thermostat, camera or other small device with much simpler radio hardware.
A client can participate in an AP's beamforming process without necessarily having equivalent transmit-beamforming capability of its own.
So you can have:
AP → client: beamformed/precoded transmission.
Client → AP: ordinary transmission.
That is not the two-way focused RF connection that the advertising tends to imply.
The AP may still improve reception of the client's return signal using multiple receive antennas, diversity or combining techniques, but that is a different process. It does not suddenly mean the client is “beamforming” back toward the router.
A router with six antennas looks impressive.
But six pieces of plastic sticking out of a box do not automatically make it a precision phased array.
Actual beamforming performance depends on things such as antenna spacing, antenna geometry, independent RF chains, calibration, phase control and accurate channel information.
Simply adding more antennas does not magically create a narrow steerable RF beam.
Changing relative amplitude and phase across multiple transmit paths can absolutely change the combined electromagnetic field. That has been known in antenna engineering for a very long time.
802.11 channel sounding and precoding are also real.
What I call fake is the consumer explanation of what is happening.
If manufacturers called the feature something like:
Call it:
That is the gimmick.
A beam is directional. You point it somewhere.
When consumers see drawings of RF energy narrowing from the router directly onto a laptop, they reasonably assume the router is determining the physical direction of that laptop and electronically steering a concentrated RF pattern toward it.
That is not necessarily what is happening.
The system is trying to manipulate the wireless channel so that the intended receiver gets a better result.
Those are not the same statement.
I am saying consumer Wi-Fi “beamforming” is a marketing label that makes ordinary channel-aware signal processing sound like something much more dramatic than it really is.
And when the access point can perform transmit beamforming while the client cannot do the same thing in the opposite direction, the idea that the two devices have established some kind of focused directional Wi-Fi link becomes even harder to defend.
The signal processing is real.
The little laser-beam-looking Wi-Fi connection they sell you is not.
I have a problem with that explanation.
I think consumer Wi-Fi beamforming, as it is presented to consumers, is basically fake. There is real signal processing happening underneath it, but what manufacturers call “beamforming” is not what most people are being led to picture.
The picture they sell you
The normal explanation goes something like this:Without beamforming, the router broadcasts equally in every direction. With beamforming, it figures out where your device is and concentrates the Wi-Fi signal directly toward it.
That sounds like an electronically steered directional antenna.
That is not a good description of what a normal home Wi-Fi router is doing.
Typical 802.11 beamforming uses multiple RF chains along with information about the wireless channel. The transmitter changes the phase and amplitude relationships between those signals so that they arrive more favorably at a particular receiver.
That is precoding and spatial signal processing.
It does not necessarily mean there is a nice narrow RF lobe shooting across your living room toward your phone.
Indoor RF propagation is a mess. Signals bounce off walls, furniture, floors, ceilings, appliances and people. Multiple copies of the same transmission arrive at the receiver at different times and phases. Wi-Fi actually takes advantage of some of that multipath behavior.
So when an AP improves the signal at a particular receiver, that does not automatically mean it created the neat directional “beam” shown on the router box.
And then there is the client problem
This is the part that makes the marketing claim even harder for me to accept.Wi-Fi is bidirectional.
The access point sends data to the client, and the client has to send data back.
An access point may have multiple antennas, multiple RF chains and transmit-beamforming capability. But the client on the other end may be a phone, laptop, television, thermostat, camera or other small device with much simpler radio hardware.
A client can participate in an AP's beamforming process without necessarily having equivalent transmit-beamforming capability of its own.
So you can have:
AP → client: beamformed/precoded transmission.
Client → AP: ordinary transmission.
That is not the two-way focused RF connection that the advertising tends to imply.
The AP may still improve reception of the client's return signal using multiple receive antennas, diversity or combining techniques, but that is a different process. It does not suddenly mean the client is “beamforming” back toward the router.
More antennas do not automatically mean more beamforming
Another thing that bothers me is the obsession with antenna count.A router with six antennas looks impressive.
But six pieces of plastic sticking out of a box do not automatically make it a precision phased array.
Actual beamforming performance depends on things such as antenna spacing, antenna geometry, independent RF chains, calibration, phase control and accurate channel information.
Simply adding more antennas does not magically create a narrow steerable RF beam.
So is the technology completely fake?
The underlying math is not fake.Changing relative amplitude and phase across multiple transmit paths can absolutely change the combined electromagnetic field. That has been known in antenna engineering for a very long time.
802.11 channel sounding and precoding are also real.
What I call fake is the consumer explanation of what is happening.
If manufacturers called the feature something like:
almost nobody would care.Channel-aware MIMO precoding
Call it:
and suddenly it sounds like your $150 router has a miniature electronically scanned radar array inside it.BEAMFORMING — focuses Wi-Fi directly at your devices!
That is the gimmick.
My problem with the word “beam”
The word creates a very specific mental image.A beam is directional. You point it somewhere.
When consumers see drawings of RF energy narrowing from the router directly onto a laptop, they reasonably assume the router is determining the physical direction of that laptop and electronically steering a concentrated RF pattern toward it.
That is not necessarily what is happening.
The system is trying to manipulate the wireless channel so that the intended receiver gets a better result.
Those are not the same statement.
Bottom line
I am not claiming that phase relationships, MIMO, channel sounding or precoding are imaginary.I am saying consumer Wi-Fi “beamforming” is a marketing label that makes ordinary channel-aware signal processing sound like something much more dramatic than it really is.
And when the access point can perform transmit beamforming while the client cannot do the same thing in the opposite direction, the idea that the two devices have established some kind of focused directional Wi-Fi link becomes even harder to defend.
The signal processing is real.
The little laser-beam-looking Wi-Fi connection they sell you is not.