Linux Wifi¶
Setup linux wifi using iwd and systemd networkd
i had to switch my desktop from a wired gigbit connection to a wifi connection. Wifi uses a fritzbox 7530 ax, and a tp-link ax 3000.
Setup¶
iwd will do the wifi encryption and establish the link (layer 2). It’s written by intel and a more modern replacement of wpa_supplicant.
Install iwd (pacman -S iwd), enable and start service (systemctl enable --now iwd).
Run an interactive configuration iwctl
# list devices/adapters
[iwd]# device list
Devices
--------------------------------------------------------------------------------
Name Address Powered Adapter Mode
--------------------------------------------------------------------------------
wlan0 1c:c1:0c:30:xx:xx on phy0 station
# update list of access points and show them
[iwd]# station wlan0 scan
[iwd]# station wlan0 get-networks
Available networks
--------------------------------------------------------------------------------
Network name Security Signal
--------------------------------------------------------------------------------
> ssid1 psk ****
Granola psk ****
devolo-999 psk ****
# connect to ssid1
[iwd]# station wlan0 connect ssid1
Type the network passphrase for ssid1 psk.
Passphrase: *************
# done.
# connection info of for the access point/station we are connected to
[iwd]# station wlan0 show
From now on, we will autoconnect to ssid1. Password is saved in /var/lib/iwd as a clear text.
networkd will configure the ip (layer 3).
Create a config file /etc/systemd/network/25-wireless.network
[Match]
Name=wlan0
[Network]
DHCP=yes
and reload networkd systemctl reload systemd-networkd
Theory¶
query the device about the connection info iw dev wlan0 station dump
Station dc:15:c8:1c:xx:xx (on wlan0)
inactive time: 0 ms
rx bytes: 378033674
rx packets: 3437343
tx bytes: 18475174117
tx packets: 435543
tx retries: 4598
tx failed: 0
beacon loss: 0
beacon rx: 47481
rx drop misc: 159
signal: -51 [-51, -58] dBm
signal avg: -51 dBm
beacon signal avg: -50 dBm
tx bitrate: 960.7 MBit/s 80MHz HE-MCS 9 HE-NSS 2 HE-GI 0 HE-DCM 0
tx duration: 0 us
rx bitrate: 960.7 MBit/s 80MHz HE-MCS 9 HE-NSS 2 HE-GI 0 HE-DCM 0
rx duration: 0 us
authorized: yes
authenticated: yes
associated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no
DTIM period: 1
beacon interval:100
short slot time:yes
connected time: 4901 seconds
associated at [boottime]: 732.337s
associated at: 1655628087914 ms
current time: 1655632988960 ms
The tx/rx bitrates and the signal are the interesting values.
For sending and receiving we use a 80Mhz wide frequency, that is we use a wifi channel with a base frequency (for example 5ghz channel 48 which is at 5240 Mhz) and spread our signal +/- 40 Mhz, which means we overlap with the neighbouring channels. Limited by the fritzbox
Our data is encoded in a specific way (MCS = Modulation and Coding Scheme) resulting in 480 Mbit (see wikipedia wifi 6).
We are using two stream (NSS = Number of spatial streams). Limited by the two antennas on the wifi client.
As a result we get 2 * 480 = 960 Mbit.
So why is tp-link writing something about 2400 Mbit? Best scanario 160Mhz wide, MCS encoding 11, two channels is 2 * 1201 = 2400
Performance¶
I tested ping flooding and iperf with a local server on the same subnet.
Connection |
ping (min/avg/max/dev) |
iperf |
|---|---|---|
wired |
0.061/0.073/6.811/0.022 |
941 Mbits/sec |
wireless |
0.773/1.046/42.266/0.248 |
830 Mbits/sec |
Comparing to a wired connection, Bandwidth is fine with a loss of about 12 percent. Ping is a lot slower with a factor of 15. But one millisecond is only one millisecond. As long as i don’t start competitive online gaming…
Monitoring¶
To figure out the placement of the external antenna i want to monitor the damping and the bandwith.
Beware that powersaving will automaticly fiddle around with the bandwith and encoding. Keeping
a iperf running prevents it. Running interactive iwctl
[iwd]# station wlan0 show
Station: wlan0
--------------------------------------------------------------
Settable Property Value
--------------------------------------------------------------
Scanning no
State connected
Connected network ssid1
IPv4 address 192.168.1.42
ConnectedBss dc:15:c8:1c:xx:xx
Frequency 5240
Security WPA2-Personal
RSSI -54 dBm
AverageRSSI -55 dBm
RxMode 802.11ax
RxMCS 10
TxMode 802.11ax
TxMCS 10
TxBitrate 1080600 Kbit/s
RxBitrate 1080600 Kbit/s
iwd is live updating these values. A bit more fance cli with ascii art is wavemon