WiFi not working on ubuntu 12.04 dell 3521

I have installed Ubuntu 12.04 alongside Windows 8 on my Dell Inspiron 3521 15R. Wifi is working perfectly fine on windows 8 but its not working on Ubuntu 12.04, rather its not even getting detected.

I have tried installing backports by

 sudo apt-get linux-backports-modules-cw-3.6-precise-generic

This didn't work. I have tried installing almost everything, but still not working.

Result of : lspci

00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Ivy Bridge PCI Express Root Port (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Ivy Bridge Graphics Controller (rev 09)
00:14.0 USB controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04)
00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4)
00:1c.1 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 2 (rev c4)
00:1d.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation Panther Point 6 port SATA Controller [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04)
01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Device 6601
07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 05)
08:00.0 Network controller: Atheros Communications Inc. Device 0036 (rev 01)

Result of: lsusb

Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 0cf3:0036 Atheros Communications, Inc. 
Bus 001 Device 004: ID 0bda:0129 Realtek Semiconductor Corp. 
Bus 001 Device 005: ID 0c45:64ad Microdia 

Result of : rfkill list

0: hci0: Bluetooth
Soft blocked: no
Hard blocked: no

Please try:

sudo apt-get install  linux-backports-modules-cw-3.8-precise-generic

I believe cw-3.8 includes the modalias for your device.

If your device is still not shown, please post:

modinfo ath9k | grep 0036
dmesg | grep ath

Please get a working ethernet connection, open a terminal and do:

sudo apt-get install linux-headers-generic build-essential

Download this file to your desktop: https://www.kernel.org/pub/linux/kernel/projects/backports/2013/11/13/backports-20131113.tar.bz2 Right-click it and select 'Extract Here.' Back to the terminal:

cd Desktop/backports-20131113/
make defconfig-ath9k
make
sudo make install

Reboot and let us know if it is working. You will have compiled the driver for your currently running kernel only. When Update Manager installs a newer kernel version, also known as linux-image, after you reboot, re-compile:

cd Desktop/backports-20131113/
make clean
make defconfig-ath9k
make
sudo make install
sudo modprobe ath9k

Please retain the files and these instructions for that time.