Roughly, what wifi signal strength would be low but still acceptable?

What would be roughly the lower end of an acceptable wifi signal strength?

My brother isn't satisfied with his router's signal range, and asked me to help improve it. I was thinking maybe have the router on one side of the house and a repeater on the other side, and for them to be connected with a power line adapter if the wiring permits, or Ethernet cable if not. That way the router and repeater will have distance to reduce some of the interference created by overlapping signals, and the signal range would be as wide as I can get it. But for all I know, there might still be spots that are too weak, and require another repeater. Or maybe I just need to put an app on their phones to connect better to a weak signal. I don't know yet.

But before I buy anything or decide for sure what I'm going to do, I want to get an idea of where the weak spots and dead spots are, including the driveway (he wants to connect while in his driveway sometimes). So I put an app on my phone that measures the wifi signal in dBm. I want to try to make it so him and his family can usually get an acceptable connection in any of the places in their home that they are likely to be while using the internet. But some devices are able to connect to a wifi signal that is too weak for another device. So I need to have an idea of what the bottom end of acceptable would be. By acceptable, I mean a signal strength that is enough to let all properly working devices maintain a connection most of the time that is good enough to browse web pages and watch youtube.

Your opinions would be appreciated.

Hello

The signal level required would all depend on what requirements you have and what noise floor that exists in your area

Eg: do you require high speed connection to make data transfer on the internal network as fast as possible?
Or are you just using the wifi to browse the web and perhaps stream a movie from Netflix?

All these things are related

These two charts will tell you how much signal level you need to achieve a certain speed

Start with this one and find the transfer speed you require (eg single stream AC, 400mbit which equates to 40MHz VHT MCS 9. This would be your typical phone or cheap computer)
http://www.wlanpros.com/wp-content/uploads/2015/06/Screenshot-2014-09-28-10.11.56-1024x837.png

Then look up what Signal to Noise ratio you need to achieve it here:
http://www.wlanpros.com/wp-content/uploads/2015/06/Revolution-Wi-FI-MCS-to-SNR-Single-Page.pdf

So, for VHT MCS 9 you would need atleast 34dB signal to noise ratio.

If noise level is at -84dBm that would mean that you would need -50dBm signal strength to get the full speed for that


If on the other hand you dont need such fast transfers, you would need a lower signal strength

Eg: 20MHz 802.11n 130mbit which would need VHT MCS 7
Then you would need a 25dB signal to noise ratio

If noise level is still at -84dBm you would need -59dBm signal strength to achieve that goal
 

So, basically:
1. Check what equipment you have. AC, N, B/G standard?
2. Determine useage. What transfer speed do you need?
3. Measure channel availability in your area. Are there many neighbors? Are there any free channels?

5GHz band will give a lot more room for you since there are more non overlapping channels there.
Dont be a spectrum hog. If you dont need 80MHz channel width because you transfer large files internally there is no need to use that much. 40MHz should normally cover you very well.
Also, remember that if your wifi device connects at say 400mbit, your real world speeds will be around half of that

PS: absolutely NO NONE whatsoever 40MHz channel useage in 2,4GHz band. You will not only affect your neighbors network, but they will in turn affect yours. When one of you transmits the others got to be silent

4. Find noise floor and then plan accordingly. Place access points in house and use an app on your phone to measure signal strength. If not satisfactory, move accesspoints and re-measure


Hth!

tfn