Best wireless transmission power: low, maximum or default

Installing and Using OpenWrt
1

Dear friends,

I would like to learn more about WIFI transmission power.

From my understanding a maximum power might "leak" the WIFI signal outside a house and as a result the AP might be listening to other APs in the neibourhood and share the same bandwidth. When several APs share the same channel, they talk to each other to avoid interferences. As a result, speed drops, sometimes dramatically.

A lot of people think :"I have a powerfull AP so I set up transmission to a maximum level to get maximum range and speed". But they are wrong if you pick up other APs signal. Correct me if this is not the case.

So we should always be carefull to find the right balance and avoid maximum power whenever possible, so the AP is not seen by other APs on the same channel. Sometimes you cannot avoid to share a frequency, because the signal of other APs is too strong.

So if someone could explain more about transmission power and interference, this would be nice. For example, what is the impact of clients with strong emission power? Do they also listen to other APs with trong signal. So we also need to lower the transmission power of clients ... but I am not very sure and don't know how to do it (and whether it is worth doing so).

I am also wondering what is default transmission power. Is this same as "maximum"?

Kind regards,

1 Like
2

First off, the txpower setting does not alter the receiver hardware's performance at all.

Wi-Fi uses carrier sensed multiple access, which means that if an AP or a STA detects another wifi signal on the channel(*), it will defer transmission until that signal ends.

So on the one hand you'd want to transmit a strong signal to be more sure to be detected and not clobbered, but on the other hand everyone ought to transmit weaker signal to not interfere with the neighbors in the first place.

Numerous PhDs have been written on the subject.

  • Note that this works a lot better if you are tuned to exactly the same channel as the neighbors, rather than trying to split between channels.
3 Likes
3

So:

  • APs should be on the same channel as neighbors.
  • We shoudl find the right balance between strong and week signal to avoid the AP reaching other APs on the same channel.

And why is not the AP auto tuning itself?

Thank-you.

1 Like
4

I didn't read that anyone specifically told you that. There are only three non-overlapping 2.4 GHz channels in most nations, they are: 1, 6 and 11. So picking a channel between those would be a "split between channels" as @mk24 noted.

I would pick the channel with the least combinations of BSSIDs, clients and power levels from other BSSIDs the channel.

What does this mean?

5

Hi all,

Can Tx power be changed in the web UI?

I actually want to reduce power because I sit immediately next to my devices and don't need the WiFi to go to further rooms

Can someone please show a screenshot of where to see Tx power adjusted in web UI ?

6

Go to Network--->Wireless and click Edit on an AP. About in the middle of the page is the Maximum Transmit Power.

Note that if you have multiple interfaces on the same radio (e.g. an AP on the LAN and an AP for guests), their power cannot be controlled independently. They will all operate at the same power. The two radios in a dual-band router can be set to different powers.

1 Like
7

Thank you!