不久前，我在 Windows 笔记本电脑上安装了 Ubuntu 16.04，我发现 wifi 连接比以前更差了：现在 5ghz wifi 网络不会显示在网络管理器界面上，即使检测到 2.4ghz 网络并且工作正常。这台笔记本电脑是华硕 A555L 型号
的输出iwlist wlp3s0 channel为：
wlp3s0 32 channels in total; available frequencies :
Channel 01 : 2.412 GHz
Channel 02 : 2.417 GHz
Channel 03 : 2.422 GHz
Channel 04 : 2.427 GHz
Channel 05 : 2.432 GHz
Channel 06 : 2.437 GHz
Channel 07 : 2.442 GHz
Channel 08 : 2.447 GHz
Channel 09 : 2.452 GHz
Channel 10 : 2.457 GHz
Channel 11 : 2.462 GHz
Channel 12 : 2.467 GHz
Channel 13 : 2.472 GHz
Channel 14 : 2.484 GHz
Channel 36 : 5.18 GHz
Channel 38 : 5.19 GHz
Channel 40 : 5.2 GHz
Channel 42 : 5.21 GHz
Channel 44 : 5.22 GHz
Channel 46 : 5.23 GHz
Channel 48 : 5.24 GHz
Channel 52 : 5.26 GHz
Channel 56 : 5.28 GHz
Channel 60 : 5.3 GHz
Channel 64 : 5.32 GHz
Channel 100 : 5.5 GHz
Channel 104 : 5.52 GHz
Channel 108 : 5.54 GHz
Channel 112 : 5.56 GHz
Channel 116 : 5.58 GHz
Channel 120 : 5.6 GHz
Channel 124 : 5.62 GHz
Current Frequency:2.462 GHz (Channel 11)
所以理论上我应该能够检测并使用 5ghz wifi 网络。
运行后dmesg发现一些错误看起来与这个问题有关：
ERROR @wl_cfg80211_scan : WLC_SCAN error (-22)
ERROR @wl_dev_intvar_get : error (-1)
ERROR @wl_cfg80211_get_tx_power : error (-1)
我尝试重新安装bcmwl-kernel-source驱动程序和我在谷歌上搜索到的其他东西，但没有任何效果。
iw list输出为：
Wiphy phy0
max # scan SSIDs: 1
max scan IEs length: 0 bytes
Retry short limit: 7
Retry long limit: 4
Coverage class: 0 (up to 0m)
Supported Ciphers:
* WEP40 (00-0f-ac:1)
* WEP104 (00-0f-ac:5)
* TKIP (00-0f-ac:2)
* CCMP (00-0f-ac:4)
* CMAC (00-0f-ac:6)
Available Antennas: TX 0 RX 0
Supported interface modes:
* IBSS
* managed
Band 1:
Bitrates (non-HT):
* 1.0 Mbps
* 2.0 Mbps (short preamble supported)
* 5.5 Mbps (short preamble supported)
* 11.0 Mbps (short preamble supported)
* 6.0 Mbps
* 9.0 Mbps
* 12.0 Mbps
* 18.0 Mbps
* 24.0 Mbps
* 36.0 Mbps
* 48.0 Mbps
* 54.0 Mbps
Frequencies:
* 2412 MHz [1] (20.0 dBm)
* 2417 MHz [2] (20.0 dBm)
* 2422 MHz [3] (20.0 dBm)
* 2427 MHz [4] (20.0 dBm)
* 2432 MHz [5] (20.0 dBm)
* 2437 MHz [6] (20.0 dBm)
* 2442 MHz [7] (20.0 dBm)
* 2447 MHz [8] (20.0 dBm)
* 2452 MHz [9] (20.0 dBm)
* 2457 MHz [10] (20.0 dBm)
* 2462 MHz [11] (20.0 dBm)
* 2467 MHz [12] (20.0 dBm) (no IR)
* 2472 MHz [13] (20.0 dBm) (no IR)
* 2484 MHz [14] (20.0 dBm) (no IR)
Band 2:
Bitrates (non-HT):
* 6.0 Mbps
* 9.0 Mbps
* 12.0 Mbps
* 18.0 Mbps
* 24.0 Mbps
* 36.0 Mbps
* 48.0 Mbps
* 54.0 Mbps
Frequencies:
* 5170 MHz [34] (disabled)
* 5180 MHz [36] (20.0 dBm) (no IR)
* 5190 MHz [38] (20.0 dBm) (no IR)
* 5200 MHz [40] (20.0 dBm) (no IR)
* 5210 MHz [42] (20.0 dBm) (no IR)
* 5220 MHz [44] (20.0 dBm) (no IR)
* 5230 MHz [46] (20.0 dBm) (no IR)
* 5240 MHz [48] (20.0 dBm) (no IR)
* 5260 MHz [52] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5280 MHz [56] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5300 MHz [60] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5320 MHz [64] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5500 MHz [100] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5520 MHz [104] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5540 MHz [108] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5560 MHz [112] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5580 MHz [116] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5600 MHz [120] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5620 MHz [124] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5640 MHz [128] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5660 MHz [132] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5680 MHz [136] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5700 MHz [140] (20.0 dBm) (no IR, radar detection)
DFS state: usable (for 275 sec)
DFS CAC time: 60000 ms
* 5745 MHz [149] (20.0 dBm) (no IR)
* 5765 MHz [153] (20.0 dBm) (no IR)
* 5785 MHz [157] (20.0 dBm) (no IR)
* 5805 MHz [161] (20.0 dBm) (no IR)
* 5825 MHz [165] (20.0 dBm) (no IR)
* 5920 MHz [184] (disabled)
* 5940 MHz [188] (disabled)
* 5960 MHz [192] (disabled)
* 5980 MHz [196] (disabled)
* 6000 MHz [200] (disabled)
* 6020 MHz [204] (disabled)
* 6040 MHz [208] (disabled)
* 6060 MHz [212] (disabled)
* 6080 MHz [216] (disabled)
Supported commands:
* set_interface
* new_key
* join_ibss
* set_pmksa
* del_pmksa
* flush_pmksa
* connect
* disconnect
software interface modes (can always be added):
interface combinations are not supported
Device supports scan flush.