I found that the problem is related to the location of my laptop! It might not be a Ubuntu related but (e.g. a hardware/environmental problem?), but, there are still hints that I think it is related to ubuntu:
1) the location difference is only relevant in my home, i.e. if I move the laptop out of this specific room it is ok. There is no problem if the laptop sits in another room, or brought to my office).
2) As I emphasised before, there is no problem with other devices in the same room
3) I plugged in a usb wifi adapter, which is recognized as wlan1, can be used without problem, although its signal level seems low (speed is ok). Info about the new usb wifi adapter (Buffalo) are:
a) dmesg:
[ 19.137557] ADDRCONF(NETDEV_UP): wlan1: link is not ready
[ 19.137952] ADDRCONF(NETDEV_UP): wlan1: link is not ready
[ 22.641581] wlan1: authenticate with 14:e6:e4:3b:d2:1e (try 1)
[ 22.643452] wlan1: authenticated
[ 22.709774] wlan1: associate with 14:e6:e4:3b:d2:1e (try 1)
[ 22.713412] wlan1: RX AssocResp from 14:e6:e4:3b:d2:1e (capab=0x431 status=0 aid=2)
[ 22.713419] wlan1: associated
[ 22.713425] wlan1: No basic rates in AssocResp. Using min supported rate instead.
[ 22.745064] ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
[ 32.965311] wlan1: no IPv6 routers present
b) lsusb:
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 09da:054f A4 Tech Co., Ltd
Bus 002 Device 003: ID 0411:01a2 BUFFALO INC. (formerly MelCo., Inc.) WLI-UC-GNM Wireless LAN Adapter
Bus 002 Device 004: ID 10f1:1a27 Importek
I found that the problem is related to the location of my laptop! It might not be a Ubuntu related but (e.g. a hardware/ environmental problem?), but, there are still hints that I think it is related to ubuntu:
1) the location difference is only relevant in my home, i.e. if I move the laptop out of this specific room it is ok. There is no problem if the laptop sits in another room, or brought to my office).
2) As I emphasised before, there is no problem with other devices in the same room
3) I plugged in a usb wifi adapter, which is recognized as wlan1, can be used without problem, although its signal level seems low (speed is ok). Info about the new usb wifi adapter (Buffalo) are:
a) dmesg:
[ 19.137557] ADDRCONF( NETDEV_ UP): wlan1: link is not ready NETDEV_ UP): wlan1: link is not ready NETDEV_ CHANGE) : wlan1: link becomes ready
[ 19.137952] ADDRCONF(
[ 22.641581] wlan1: authenticate with 14:e6:e4:3b:d2:1e (try 1)
[ 22.643452] wlan1: authenticated
[ 22.709774] wlan1: associate with 14:e6:e4:3b:d2:1e (try 1)
[ 22.713412] wlan1: RX AssocResp from 14:e6:e4:3b:d2:1e (capab=0x431 status=0 aid=2)
[ 22.713419] wlan1: associated
[ 22.713425] wlan1: No basic rates in AssocResp. Using min supported rate instead.
[ 22.745064] ADDRCONF(
[ 32.965311] wlan1: no IPv6 routers present
b) lsusb:
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 09da:054f A4 Tech Co., Ltd
Bus 002 Device 003: ID 0411:01a2 BUFFALO INC. (formerly MelCo., Inc.) WLI-UC-GNM Wireless LAN Adapter
Bus 002 Device 004: ID 10f1:1a27 Importek
c) syslog - attached.