Wifi disabled for Intel Centrino Wireless-N 1000 Intel in 12.04 [duplicate]

I have a HP Pavilion dm4-2070us which has an Intel Corporation Centrino Wireless-N 1000 adapter.

The problem is that my computer doesn't show the wireless networks after I upgraded my system to Ubuntu 11.10. Following is my output for sudo lshw -class network:

*-network DISABLED      
   description: Wireless interface
   product: Centrino Wireless-N 1000
   vendor: Intel Corporation
   physical id: 0
   bus info: pci@0000:01:00.0
   logical name: wlan0
   version: 00
   serial: 8c:a9:82:81:5a:30
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
   configuration: broadcast=yes driver=iwlagn driverversion=3.0.0-12-generic firmware=39.31.5.1 build 35138 latency=0 link=no multicast=yes wireless=IEEE 802.11bgn
   resources: irq:42 memory:c2500000-c2501fff

*-network
   description: Ethernet interface
   product: AR8151 v2.0 Gigabit Ethernet
   vendor: Atheros Communications
   physical id: 0
   bus info: pci@0000:08:00.0
   logical name: eth0
   version: c0
   serial: 2c:41:38:07:f3:e3
   size: 100Mbit/s
   capacity: 1Gbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress vpd bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=atl1c driverversion=1.0.1.0-NAPI duplex=full firmware=N/A ip=192.168.1.7 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
   resources: irq:44 memory:c1400000-c143ffff ioport:2000(size=128)

The output for rfkill list all:

0: hp-wifi: Wireless LAN
    Soft blocked: no
    Hard blocked: no
1: hp-bluetooth: Bluetooth
    Soft blocked: no
    Hard blocked: no
2: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
3: hp-wwan: Wireless WAN
    Soft blocked: no
    Hard blocked: no

I have also searched about the status of the WiFi network being shown as disabled. Somehow everything pointed to the fact that my wireless device is switched off and it can be switched on from Windows only. However, I don't have windows partition and it has just Ubuntu 11.10 so I don't see any point in switching the device on in Windows.

Solution 1:

After trying out different distributions and struggling with my wireless card I finally stumbled upon a link that gives a work around to the problem. Apparently the new kernel fails to detect the Centrino 1000 N wireless card in some laptops(hp dm4) while there are other laptops on which it works completely fine like Lenovo Y560P.

The following link gives the solution!! Even though I am not sure whether this work around will have any greater impacts later or not, but for now its working fine.

http://community.linuxmint.com/tutorial/view/608

"To (temporarily) get the wireless working on newer kernels:

sudo mv /lib/firmware/iwlwifi-1000-5.ucode /lib/firmware/iwlwifi-1000-5.ucode.backup
sudo modprobe -r iwlagn
sudo modprobe iwlagn

This should make the wireless use the old 1000-3.ucode which works at the moment."

Solution 2:

None of the solutions above worked for me I had to pass the mod option below

/etc/modprobe.d/iwl.conf 
options iwlwifi bt_coex_active=0 

I picked this up from intel forum that I can't find the link to right now.

Solution 3:

I tried:

echo 'options iwlagn 11n_disable=1' | sudo tee /etc/modprobe.d/iwlagn.conf >/dev/null

and it's working.