2012-09-11

CRDA

• 最近裝了 Ubuntu 12.04 LTS 經常會看到如下的訊息，說明無線網路在不同的國碼(Country Code)之間變動。先前做過 WSU 計劃的經驗知道國碼會決定無線的頻道採用哪些頻率，所以必須設法讓模組載入時，預設固定在某個國碼。先前知道可以用指令 iw (隸屬於套件 ​iw)來控制，不過想說如果可以在 /etc/modprobe.d 中設定，就不用老是靠指令去改。

  Sep 11 08:31:33 jazzbook kernel: [  206.775604] cfg80211: Regulatory domain changed to country: EC
  Sep 11 08:31:33 jazzbook kernel: [  206.775605] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
  Sep 11 08:31:33 jazzbook kernel: [  206.775607] cfg80211:     (2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm)
  Sep 11 08:31:33 jazzbook kernel: [  206.775609] cfg80211:     (5170000 KHz - 5250000 KHz @ 20000 KHz), (300 mBi, 1700 mBm)
  Sep 11 08:31:33 jazzbook kernel: [  206.775610] cfg80211:     (5250000 KHz - 5330000 KHz @ 20000 KHz), (300 mBi, 2300 mBm)
  Sep 11 08:31:33 jazzbook kernel: [  206.775612] cfg80211:     (5735000 KHz - 5835000 KHz @ 20000 KHz), (300 mBi, 3000 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  211.943255] ADDRCONF(NETDEV_UP): wlan0: link is not ready
  
  ..............
  
  Sep 11 08:31:39 jazzbook kernel: [  212.845224] cfg80211: Regulatory domain changed to country: US
  Sep 11 08:31:39 jazzbook kernel: [  212.845229] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
  Sep 11 08:31:39 jazzbook kernel: [  212.845235] cfg80211:     (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2700 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  212.845242] cfg80211:     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 1700 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  212.845248] cfg80211:     (5250000 KHz - 5330000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  212.845255] cfg80211:     (5490000 KHz - 5600000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  212.845261] cfg80211:     (5650000 KHz - 5710000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
  Sep 11 08:31:39 jazzbook kernel: [  212.845268] cfg80211:     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 3000 mBm)
  

• [參考] ​Wlan administration and usage
• [作法] 修改 /etc/modprobe.d/regdom.conf

  ~$ cat /etc/modprobe.d/regdom.conf 
  options cfg80211 ieee80211_regdom=US