topic You can lower it, if you like in Wireless

WISM/Wireless/Radios RSSI level Best practice

Steve Coady — Mon, 05 Jul 2021 07:37:18 GMT

Hello

I am troubleshooting reports of poor connectivity with some Access point. I discovered most of the AP's have a Global power level of (5).

I think increasing this to 3 would provide enough without providing too much.

I also see where the RF parameters have the RSSI set at -80. It is my understanding that best DB levels are between -50 to -73 with -73

being pretty bad.

Please review and advise.

As a follow up: Under optimal

Steve Coady — Fri, 04 Apr 2014 16:21:51 GMT

As a follow up:

Under optimal circumstances, I think AP's have a stated broadcast area of 300 ft. Please correct me if I am wrong

Is that with a power level of 1?

There are (8) power levels. Hypothetically, would a power of 8 be = (300ft / 😎 = 37.5 ft area?

I have a question: Why mess

Leo Laohoo — Fri, 04 Apr 2014 22:17:20 GMT

I have a question: Why mess up the "self-healing" properties of a controller-based wireless network by manually configuring the transmission power?

What happens if you enable TPC to dynamic and let the controller sort the power and channel by itself?

Leo We are using the TPC.

Steve Coady — Mon, 07 Apr 2014 21:19:33 GMT

Leo

We are using the TPC.

What about the RSI threshhold of -80. That seems to high if

a bad signal is experienced at -70.

You can lower it, if you like

patoberli — Tue, 08 Apr 2014 12:29:36 GMT

You can lower it, if you like. -80 is still around 50% - 60% of the maximum possible speed (so if you only have 802.11a that is around 24 - 36 MBit/s), which is normally also ok. In my specific case I prefer to have at least -70 everywhere, so that parameter needs to be tuned slightly (to be on the safe side, I also prefer small cells, I will put it in the next maintenance window to -75).

Patoberli Thank you for the

Steve Coady — Tue, 08 Apr 2014 13:10:28 GMT

Patoberli

Thank you for the response.

I'm not sure I follow what you are saying "-80 is still around 50% - 60% of the maximum possible speed"?

I assume you mean small cells by deploying more AP's with lower power settings?

I'm not sure I follow what

patoberli — Tue, 08 Apr 2014 13:24:07 GMT

I'm not sure I follow what you are saying "-80 is still around 50% - 60% of the maximum possible speed"?

802.11a offers a maximum 54 Mbit/s of theoretical speed. With -70 you get 100% of the maximum possible theoretical speed (54 Mbit/s). With -80 you should still get 50 - 60% of those 54 Mbit/s (shown as 24 Mbit/s or 36 Mbit/s), or even more, depending on the noise (SNR).

assume you mean small cells by deploying more AP's with lower power settings?

Exactly. I have a lot of users on small space (school rooms), so it better to have in every room an AP with low power setting, compared to have every second or third one an AP with a high power setting.

I leave that up to RRM, TPC und DCA to compute and manage.

Patoberli So you get 100% if

Steve Coady — Tue, 08 Apr 2014 13:30:01 GMT

Patoberli

So you get 100% if signal is within -50 to -70 range?

My space is hospital (OR's etc...)

So far we more or less

patoberli — Tue, 08 Apr 2014 13:53:17 GMT

So far we more or less ignored a second very important metric, which is 'noise'. Simply put, noise is other radio waves in the wireless bands. For example the 2.4 GHz band is very crowded with other signals, like microwaves, wireless cameras, Bluetooth and other wireless equipment. The 5 GHz is much better in this regard, but you have less reach through walls and other materials.

Now all those 'foreign' signals are noise. The more noise you have on the same channel, the less you hear the AP (from a laptop point of view). Because of this you have the so called SNR, Signal to Noise Ratio. This SNR actually defines how well the client hears the AP and the other way around. This delta needs to be around 15 dBa for a 100% signal for data, or 20 - 25 dBa for voice.

In any case, if you don't have a hell lot of noise, you get 100% speed if the signal is -70 or better (-50 for example).

Please note that 802.11n has a much better reception and reach at a lower signal than the older 802.11g and 802.11a. I heard the same is also true for 802.11ac.

Patoberli Thanks again for

Steve Coady — Wed, 09 Apr 2014 15:34:22 GMT

Patoberli

Thanks again for the excellent guidance.