[Solved]My SSID is invisible in wifi list

Question

This problem occured some weeks ago.(I don't remember exact date)
Oneday, suddenly I couldn't have connected my home wifi which had no problem at all before.
The problem occured while I'm using my laptop without any update or reboot.
And, I found that the problem is that I cannot get the SSID of my home wifi when scanning.(It was visible before of course.)
From that time, I still cannot use my home wifi.
With netctl/networkmanger/iwlist scan, they show same problem.
There's no connection issue with visible SSID and wired one.
Also, when I enable my Android hotspot, my laptop detects the AP well.
What should I do? Here's my environment:
Model: Macbook Pro 13inch 2011 early
DE: latest stable release of KDE4
LAN Chipset: Broadcom, from lspci:
  Ethernet controller: Broadcom Corporation NetXtreme BCM57765 Gigabit Ethernet PCIe (rev 10)
  Network controller: Broadcom Corporation BCM4331 802.11a/b/g/n (rev 02)
Firmware: broadcom-wl-6.30.223.141 (from AUR)
Please let me know any other informations which you need in order to find answer.
Last edited by xylosper (2013-11-30 05:58:50)

Answer 1

Any chance you have somehow directed your hardware on the Arch box to use only channel 1?
Also, as to other networks on the same channel -- 802.11 b/g/n use direct sequencing digital spread spectrum communications.  Every network on the channel has a different chipping sequence.  The only interference comes in the form of a reduced signal/noise ratio; but I digress
I know you said you had used multiple network managers, so that would tend to mitigate the issue.  Perhaps you had more than one running at a time?   Maybe one put the hardware into an odd state, and when you changed to the other managers the hardware was already in la-la land.
Try this.  Disable all of your network managers.   Power down (not reboot).  Start cold and boot the system.   Look at the output of sudo iw wlan0 scan    (Replace wlan0 with the name of your link)