I did a clean install of Xubuntu 13.04 and i am experiencing now a very slow wifi connection compared to 12.04. My laptop sees also less wifi-networks than before.
The problem exist with the build-in wifi adapter. I used also another usb wifi adapter and it was as slow as the build in (though the reception was better as the antenna is huge). Then I activated the usb-tethering of my smartphone, plugged it to the laptop and checked the connection, it was as fast as it used to be. So it seems to be wifi related, but not related with networking in general.
wlan0 Link encap:Ethernet HWaddr 00:08:ca:e6:76:d8 inet addr:192.168.178.51 Bcast:192.168.178.255 Mask:255.255.255.0 inet6 addr: fe80::208:caff:fee6:76d8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2653 errors:0 dropped:0 overruns:0 frame:0 TX packets:3198 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1526256 (1.5 MB) TX bytes:382403 (382.4 KB)
wlan0 IEEE 802.11bgn ESSID:"xxxxxxx" Mode:Managed Frequency:2.472 GHz Access Point: 00:1C:4A:47:CB:29 Bit Rate=27 Mb/s Tx-Power=15 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=23/70 Signal level=-87 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:12 Invalid misc:43 Missed beacon:0
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.178.1 0.0.0.0 UG 0 0 0 wlan0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan0 192.168.178.0 0.0.0.0 255.255.255.0 U 9 0 0 wlan0
I have experimented with the following commands (http://www.unixmen.com/resolve-slow-connexion-when-using-wifi-in-ubuntu-1104-natty-narwhal/) but they seem not to work anymore as i received either errors or no effect.