| Why 2.4 GHz WLAN is no fun in the city | Created: 13.08.2016 14:55 |
|
I've long since given up on using 2.4 GHz wireless at home, because
just 3 meters from the access point there was packet loss and it
really wasn't fun to use. That wasn't surprising, because I live in
a big city, and since everybody has a WiFi network at home those
days, I can receive about 20 foreign WiFi networks just sitting in
my living room. And of course, because 2.4 GHz effectively only has
3 different usable channels (1, 6, 11), they very much interfere and
disturb each other. Recently, I had a spare old WiFi router with OpenWRT on it lying around, and got the idea from IRC to use this for measuring just how full the 2.4 GHz band is. On an OpenWRT router, the command iw dev devicename survey dump will display something like: Survey data from wlan0
frequency: 2412 MHz
noise: -95 dBm
channel active time: 22017 ms
channel busy time: 9749 ms
channel receive time: 9457 ms
channel transmit time: 0 ms
It will show that for all channels. The active time is the amount
of time the device was tuned to that channel, and the busy time
is the amount of time the device thought the channel to be in use
by others (since it doesn't send anything itself). I wrote a
simple script to change channels every 22 seconds so
that stats for all relevant channels were available. From the
collected data, I drew graphs. Here is the result: Now as you can see, on any average day just the noise from foreign WiFis blocks all available 2.4 GHz channels for a huge percentage of time. There is hardly any airtime left for sending data. You can also see why I switched to using only 5 GHz WiFi some time ago: Channel 040 is the 5 GHz channel I use, and noone in the neighbourhood besides me uses it. There is only one other 5 GHz WLAN on channel 36 that I can occassionally receive in my appartment, all the other channels are unused. |
|
|
no comments yet write a new comment:
|
|