我有一台富士通 Lifebook AH531（我认为无线是英特尔® Centrino® Wireless-N 1030，802.11 b/g/n）
我最近安装了 Ubuntu 14.04 LTS 以前我在同一台机器上使用过 Ubuntu 12.04 LTS 和 Windows 7，WiFi 信号正常。
安装 14.04 LTS 后，WiFi 信号非常弱。相比之下，我的手机和 MacBook 显示满信号。
这是 iwconfig 显示的内容（“x”是我添加的）：
vmnet8 no wireless extensions.
eth0 no wireless extensions.
lo no wireless extensions.
wlan0 IEEE 802.11bgn ESSID:"xxxxxxx"
Mode:Managed Frequency:2.437 GHz Access Point: xx:xx:xx:xx:xx:xx
Bit Rate=65 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=38/70 Signal level=-72 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:2 Invalid misc:33 Missed beacon:0
vmnet1 no wireless extensions.
关于造成这种情况的原因和解决方法，您有什么想法吗？
UPDATE1：这些是 dmesg | grep iwl 的结果：
[ 12.981861] iwlwifi 0000:01:00.0: can't disable ASPM; OS doesn't have ASPM control
[ 12.982170] iwlwifi 0000:01:00.0: irq 43 for MSI/MSI-X
[ 13.395624] iwlwifi 0000:01:00.0: loaded firmware version 18.168.6.1 op_mode iwldvm
[ 13.414785] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEBUG disabled
[ 13.414787] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEBUGFS enabled
[ 13.414788] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEVICE_TRACING enabled
[ 13.414790] iwlwifi 0000:01:00.0: Detected Intel(R) Centrino(R) Wireless-N 1030 BGN, REV=0xB0
[ 13.414893] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 13.435161] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
[ 16.755014] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 16.761688] iwlwifi 0000:01:00.0: Radio type=0x2-0x2-0x1
[ 16.829339] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 16.836056] iwlwifi 0000:01:00.0: Radio type=0x2-0x2-0x1
[ 1795.831710] iwlwifi 0000:01:00.0: no hotplug settings from platform
[ 1797.361326] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 1797.368062] iwlwifi 0000:01:00.0: Radio type=0x2-0x2-0x1
[ 2408.998423] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[ 2408.998438] iwlwifi 0000:01:00.0: Current SW read_ptr 227 write_ptr 101
[ 2408.998496] iwl data: 00000000: 00 00 00 00 00 00 00 00 f8 ff 07 00 00 00 00 00 ................
[ 2408.998540] iwlwifi 0000:01:00.0: FH TRBs(0) = 0x80003019
[ 2408.998584] iwlwifi 0000:01:00.0: FH TRBs(1) = 0x801020f2
[ 2408.998627] iwlwifi 0000:01:00.0: FH TRBs(2) = 0x00000000
[ 2408.998668] iwlwifi 0000:01:00.0: FH TRBs(3) = 0x80300027
[ 2408.998711] iwlwifi 0000:01:00.0: FH TRBs(4) = 0x00000000
[ 2408.998751] iwlwifi 0000:01:00.0: FH TRBs(5) = 0x00000000
[ 2408.998789] iwlwifi 0000:01:00.0: FH TRBs(6) = 0x00000000
[ 2408.998836] iwlwifi 0000:01:00.0: FH TRBs(7) = 0x0070903b
[ 2408.998926] iwlwifi 0000:01:00.0: Q 0 is active and mapped to fifo 3 ra_tid 0x0000 [40,40]
[ 2408.999016] iwlwifi 0000:01:00.0: Q 1 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[ 2408.999116] iwlwifi 0000:01:00.0: Q 2 is active and mapped to fifo 1 ra_tid 0x0000 [227,101]
[ 2408.999205] iwlwifi 0000:01:00.0: Q 3 is active and mapped to fifo 0 ra_tid 0x0000 [26,26]
[ 2408.999293] iwlwifi 0000:01:00.0: Q 4 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2408.999417] iwlwifi 0000:01:00.0: Q 5 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[ 2408.999505] iwlwifi 0000:01:00.0: Q 6 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[ 2408.999635] iwlwifi 0000:01:00.0: Q 7 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[ 2408.999732] iwlwifi 0000:01:00.0: Q 8 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[ 2408.999822] iwlwifi 0000:01:00.0: Q 9 is active and mapped to fifo 7 ra_tid 0x0000 [60,60]
[ 2408.999920] iwlwifi 0000:01:00.0: Q 10 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[ 2409.000007] iwlwifi 0000:01:00.0: Q 11 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000092] iwlwifi 0000:01:00.0: Q 12 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000177] iwlwifi 0000:01:00.0: Q 13 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000269] iwlwifi 0000:01:00.0: Q 14 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000358] iwlwifi 0000:01:00.0: Q 15 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000442] iwlwifi 0000:01:00.0: Q 16 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000521] iwlwifi 0000:01:00.0: Q 17 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000607] iwlwifi 0000:01:00.0: Q 18 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2409.000686] iwlwifi 0000:01:00.0: Q 19 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.855478] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[ 2477.855490] iwlwifi 0000:01:00.0: Current SW read_ptr 70 write_ptr 194
[ 2477.855544] iwl data: 00000000: c0 ff 3f 00 00 00 00 00 00 00 00 00 00 00 00 00 ..?.............
[ 2477.855586] iwlwifi 0000:01:00.0: FH TRBs(0) = 0x8000301b
[ 2477.855624] iwlwifi 0000:01:00.0: FH TRBs(1) = 0x80102055
[ 2477.855661] iwlwifi 0000:01:00.0: FH TRBs(2) = 0x00000000
[ 2477.855697] iwlwifi 0000:01:00.0: FH TRBs(3) = 0x8030002e
[ 2477.855734] iwlwifi 0000:01:00.0: FH TRBs(4) = 0x00000000
[ 2477.855770] iwlwifi 0000:01:00.0: FH TRBs(5) = 0x00000000
[ 2477.855807] iwlwifi 0000:01:00.0: FH TRBs(6) = 0x00000000
[ 2477.855844] iwlwifi 0000:01:00.0: FH TRBs(7) = 0x007090c7
[ 2477.855924] iwlwifi 0000:01:00.0: Q 0 is active and mapped to fifo 3 ra_tid 0x0000 [47,47]
[ 2477.856075] iwlwifi 0000:01:00.0: Q 1 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[ 2477.856159] iwlwifi 0000:01:00.0: Q 2 is active and mapped to fifo 1 ra_tid 0x0000 [70,194]
[ 2477.856237] iwlwifi 0000:01:00.0: Q 3 is active and mapped to fifo 0 ra_tid 0x0000 [28,28]
[ 2477.856324] iwlwifi 0000:01:00.0: Q 4 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.856403] iwlwifi 0000:01:00.0: Q 5 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[ 2477.856488] iwlwifi 0000:01:00.0: Q 6 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[ 2477.856567] iwlwifi 0000:01:00.0: Q 7 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[ 2477.856645] iwlwifi 0000:01:00.0: Q 8 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[ 2477.856725] iwlwifi 0000:01:00.0: Q 9 is active and mapped to fifo 7 ra_tid 0x0000 [200,200]
[ 2477.856805] iwlwifi 0000:01:00.0: Q 10 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[ 2477.856885] iwlwifi 0000:01:00.0: Q 11 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.856965] iwlwifi 0000:01:00.0: Q 12 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857044] iwlwifi 0000:01:00.0: Q 13 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857122] iwlwifi 0000:01:00.0: Q 14 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857202] iwlwifi 0000:01:00.0: Q 15 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857282] iwlwifi 0000:01:00.0: Q 16 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857363] iwlwifi 0000:01:00.0: Q 17 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857443] iwlwifi 0000:01:00.0: Q 18 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[ 2477.857521] iwlwifi 0000:01:00.0: Q 19 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.427882] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[38618.427898] iwlwifi 0000:01:00.0: Current SW read_ptr 20 write_ptr 43
[38618.427952] iwl data: 00000000: 00 00 f0 ff 00 00 00 00 0f 00 00 00 00 00 00 00 ................
[38618.428008] iwlwifi 0000:01:00.0: FH TRBs(0) = 0x80003090
[38618.428064] iwlwifi 0000:01:00.0: FH TRBs(1) = 0x80102023
[38618.428120] iwlwifi 0000:01:00.0: FH TRBs(2) = 0x00000000
[38618.428171] iwlwifi 0000:01:00.0: FH TRBs(3) = 0x8030004c
[38618.428210] iwlwifi 0000:01:00.0: FH TRBs(4) = 0x00000000
[38618.428257] iwlwifi 0000:01:00.0: FH TRBs(5) = 0x00000000
[38618.428322] iwlwifi 0000:01:00.0: FH TRBs(6) = 0x00000000
[38618.428385] iwlwifi 0000:01:00.0: FH TRBs(7) = 0x00709010
[38618.428530] iwlwifi 0000:01:00.0: Q 0 is active and mapped to fifo 3 ra_tid 0x0000 [77,77]
[38618.428677] iwlwifi 0000:01:00.0: Q 1 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[38618.428801] iwlwifi 0000:01:00.0: Q 2 is active and mapped to fifo 1 ra_tid 0x0000 [20,43]
[38618.428929] iwlwifi 0000:01:00.0: Q 3 is active and mapped to fifo 0 ra_tid 0x0000 [145,145]
[38618.429071] iwlwifi 0000:01:00.0: Q 4 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.429173] iwlwifi 0000:01:00.0: Q 5 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[38618.429275] iwlwifi 0000:01:00.0: Q 6 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[38618.429378] iwlwifi 0000:01:00.0: Q 7 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[38618.429463] iwlwifi 0000:01:00.0: Q 8 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[38618.429553] iwlwifi 0000:01:00.0: Q 9 is active and mapped to fifo 7 ra_tid 0x0000 [17,17]
[38618.429655] iwlwifi 0000:01:00.0: Q 10 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[38618.429741] iwlwifi 0000:01:00.0: Q 11 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.429843] iwlwifi 0000:01:00.0: Q 12 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.429939] iwlwifi 0000:01:00.0: Q 13 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430110] iwlwifi 0000:01:00.0: Q 14 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430315] iwlwifi 0000:01:00.0: Q 15 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430448] iwlwifi 0000:01:00.0: Q 16 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430544] iwlwifi 0000:01:00.0: Q 17 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430649] iwlwifi 0000:01:00.0: Q 18 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[38618.430762] iwlwifi 0000:01:00.0: Q 19 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
更新2：我已尝试@chili555 建议的修复方法，结果如下。
dmesg | grep iwl
[ 12.554087] iwlwifi 0000:01:00.0: can't disable ASPM; OS doesn't have ASPM control
[ 12.554303] iwlwifi 0000:01:00.0: irq 42 for MSI/MSI-X
[ 12.928234] iwlwifi 0000:01:00.0: loaded firmware version 18.168.6.1 op_mode iwldvm
[ 12.947135] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEBUG disabled
[ 12.947136] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEBUGFS enabled
[ 12.947137] iwlwifi 0000:01:00.0: CONFIG_IWLWIFI_DEVICE_TRACING enabled
[ 12.947138] iwlwifi 0000:01:00.0: Detected Intel(R) Centrino(R) Wireless-N 1030 BGN, REV=0xB0
[ 12.947242] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 12.967026] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
[ 16.787447] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 16.794188] iwlwifi 0000:01:00.0: Radio type=0x2-0x2-0x1
[ 16.862264] iwlwifi 0000:01:00.0: L1 Enabled; Disabling L0S
[ 16.868991] iwlwifi 0000:01:00.0: Radio type=0x2-0x2-0x1
所有 fifio 错误都不再显示
iwconfig
vmnet8 no wireless extensions.
eth0 no wireless extensions.
lo no wireless extensions.
wlan0 IEEE 802.11bgn ESSID:"xxxxx"
Mode:Managed Frequency:2.437 GHz Access Point: xxxxxxxxxx
Bit Rate=65 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=43/70 Signal level=-67 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:4 Missed beacon:0
vmnet1 no wireless extensions.
链路质量和信号电平都有小幅改善。
但与我拥有的其他设备相比，信号质量仍然较低。
答案1
我注意到您的 dmesg 的一部分是：
无法刷新所有 tx fifo 队列
这是错误报告的主题：https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1361809正如您在评论 #6 中看到的，有一个修补过的内核可用，并且后续报道说它已修复。我知道 ubuntuforums.org 上还有另一个类似的案例，也修复了这个问题。
我建议你去这里：http://people.canonical.com/~sforshee/lp1361809/linux-3.13.0-37.64+lp1361809v201410060628/下载适合您的架构的 linux-image 和 linux-image-extra 的 .deb 文件；32 位或 64 位。从终端查找：
arch
对于 32 位系统，返回 i686；对于 64 位系统，返回 x86_64。因此，例如，如果您的系统是 64 位系统，请下载 linux-image amd64.deb 文件和 linux-image-extras amd64.deb 文件。使用以下命令安装：
cd ~/Downloads <--or wherever you downloaded the files
sudo dpkg -i linux*.deb
重新启动并让我们听到您的结果。
如果性能没有提升，我们来尝试一个驱动参数：
sudo -i
echo "options iwlwifi 11n_disable=8" >> /etc/modprobe.d/iwlwifi.conf
exit
然后重启并测试。
如果此方法无效，请执行以下操作：
gksudo gedit /etc/modprobe.d/iwlwifi.conf
如果您没有文本编辑器 gedit，请使用 nano 或 Kate 或 Leafpad。将最后一行更改为：
options iwlwifi 11n_disable=1
仔细校对，保存并关闭文本编辑器。重新启动并测试。