Meu laptop é o Thinkpas T400 com link interno intel wifi 5100 AGN. Minha conexão sem fio se perde depois de um tempo desde cada reinicialização. Isso acontece tanto no meu 14.04 de 64 bits atual quanto no 12.04 de 32 bits anterior. (Em 14.04, às vezes meu adaptador ethernet também não funciona.)
Eu encontrei algumas dicussões pesquisando "intel wifi 5100 AGN Ubuntu", e eles estavam tentando diferentes abordagens sem resolver o problema.
Eu postei minha saída do dmesg aqui para meu adaptador sem fio wlan0 e seu driver iwlwifi e espero por alguma ajuda.
$ dmesg | grep wlan0
[ 22.680318] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 29.424514] wlan0: authenticate with 00:25:9c:1b:57:21
[ 29.427265] wlan0: send auth to 00:25:9c:1b:57:21 (try 1/3)
[ 29.429960] wlan0: authenticated
[ 29.430048] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 29.430051] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[ 29.432078] wlan0: associate with 00:25:9c:1b:57:21 (try 1/3)
[ 29.434535] wlan0: RX AssocResp from 00:25:9c:1b:57:21 (capab=0x411 status=0 aid=5)
[ 29.437742] wlan0: associated
[ 29.437771] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 30.444281] wlan0: deauthenticating from 00:25:9c:1b:57:21 by local choice (Reason: 2=PREV_AUTH_NOT_VALID)
[ 30.446133] wlan0: authenticate with 00:25:9c:1b:57:21
[ 30.446981] wlan0: send auth to 00:25:9c:1b:57:21 (try 1/3)
[ 30.449875] wlan0: authenticated
[ 30.450038] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 30.450041] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[ 30.452151] wlan0: associate with 00:25:9c:1b:57:21 (try 1/3)
[ 30.454658] wlan0: RX AssocResp from 00:25:9c:1b:57:21 (capab=0x411 status=0 aid=5)
[ 30.457904] wlan0: associated
[ 5120.374230] wlan0: deauthenticated from 00:25:9c:1b:57:21 (Reason: 7=CLASS3_FRAME_FROM_NONASSOC_STA)
[ 5123.676199] wlan0: authenticate with 00:25:9c:1b:57:21
[ 5123.677937] wlan0: send auth to 00:25:9c:1b:57:21 (try 1/3)
[ 5123.680496] wlan0: authenticated
[ 5123.680754] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 5123.680763] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[ 5123.684315] wlan0: associate with 00:25:9c:1b:57:21 (try 1/3)
[ 5123.688858] wlan0: RX AssocResp from 00:25:9c:1b:57:21 (capab=0x411 status=0 aid=5)
[ 5123.691922] wlan0: associated
[16757.341736] wlan0: deauthenticated from 00:25:9c:1b:57:21 (Reason: 7=CLASS3_FRAME_FROM_NONASSOC_STA)
[16757.380215] wlan0: authenticate with 00:25:9c:1b:57:21
[16757.386911] wlan0: send auth to 00:25:9c:1b:57:21 (try 1/3)
[16757.391132] wlan0: authenticated
[16757.391424] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[16757.391433] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[16757.392110] wlan0: associate with 00:25:9c:1b:57:21 (try 1/3)
[16757.395611] wlan0: RX AssocResp from 00:25:9c:1b:57:21 (capab=0x411 status=0 aid=2)
[16757.397671] wlan0: associated
[21321.548607] wlan0: deauthenticated from 00:25:9c:1b:57:21 (Reason: 7=CLASS3_FRAME_FROM_NONASSOC_STA)
$ dmesg | grep iwl
[ 13.916985] iwlwifi 0000:03:00.0: can't disable ASPM; OS doesn't have ASPM control
[ 13.917156] iwlwifi 0000:03:00.0: irq 50 for MSI/MSI-X
[ 13.959583] iwlwifi 0000:03:00.0: loaded firmware version 8.83.5.1 build 33692 op_mode iwldvm
[ 14.475382] iwlwifi 0000:03:00.0: CONFIG_IWLWIFI_DEBUG disabled
[ 14.475386] iwlwifi 0000:03:00.0: CONFIG_IWLWIFI_DEBUGFS enabled
[ 14.475387] iwlwifi 0000:03:00.0: CONFIG_IWLWIFI_DEVICE_TRACING enabled
[ 14.475389] iwlwifi 0000:03:00.0: Detected Intel(R) WiFi Link 5100 AGN, REV=0x54
[ 14.475454] iwlwifi 0000:03:00.0: L1 Disabled - LTR Disabled
[ 14.500372] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
[ 22.554089] iwlwifi 0000:03:00.0: L1 Disabled - LTR Disabled
[ 22.554494] iwlwifi 0000:03:00.0: Radio type=0x1-0x2-0x0
[ 22.651233] iwlwifi 0000:03:00.0: L1 Disabled - LTR Disabled
[ 22.651625] iwlwifi 0000:03:00.0: Radio type=0x1-0x2-0x0
[ 29.430048] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 29.430051] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[ 30.450038] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 30.450041] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[ 5123.680754] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[ 5123.680763] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
[16757.391424] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
[16757.391433] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:24:7e:e0:62:50
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Interrupt:20 Memory:fc600000-fc620000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:37304 errors:0 dropped:0 overruns:0 frame:0
TX packets:37304 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3623278 (3.6 MB) TX bytes:3623278 (3.6 MB)
wlan0 Link encap:Ethernet HWaddr 00:26:c6:3e:30:34
inet addr:192.168.1.100 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::226:c6ff:fe3e:3034/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:102840 errors:0 dropped:0 overruns:0 frame:0
TX packets:96036 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:78001233 (78.0 MB) TX bytes:16544959 (16.5 MB)
$ lshw -C network
WARNING: you should run this program as super-user.
*-network
description: Ethernet interface
product: 82567LM Gigabit Network Connection
vendor: Intel Corporation
physical id: 19
bus info: pci@0000:00:19.0
logical name: eth0
version: 03
serial: 00:24:7e:e0:62:50
capacity: 1Gbit/s
width: 32 bits
clock: 33MHz
capabilities: bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=2.3.2-k firmware=1.8-3 latency=0 link=no multicast=yes port=twisted pair
resources: irq:45 memory:fc600000-fc61ffff memory:fc625000-fc625fff ioport:1840(size=32)
*-network
description: Wireless interface
product: PRO/Wireless 5100 AGN [Shiloh] Network Connection
vendor: Intel Corporation
physical id: 0
bus info: pci@0000:03:00.0
logical name: wlan0
version: 00
serial: 00:26:c6:3e:30:34
width: 64 bits
clock: 33MHz
capabilities: bus_master cap_list ethernet physical wireless
configuration: broadcast=yes driver=iwlwifi driverversion=3.16.0-31-generic firmware=8.83.5.1 build 33692 ip=192.168.1.100 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn
resources: irq:50 memory:f4200000-f4201fff