Network adapter - Intel Corporation Centrino Advanced-N 6205 [Taylor Peak] - Slow speeds in Ubuntu 14.10

A laptop equipped with an Intel Centrino Advanced-N 6205 wireless network card experienced slow speeds.

Compared to a laptop with a BCM4313 which made 50 Mbit/s this card made barely 24 Mbit/s using iperf -c checks.

I found the solution here:
http://bernaerts.dyndns.org/linux/74-ubuntu/322-ubuntu-trusty-intel-centrino-6235-slow-freeze

It is about bluetooth interference and stuff, see the link from the genius above for more detailed info.

Below I will describe what worked for me, some things are slightly different to fit 6205 and 14.10.

First check that you are affected using: 

lsmod | grep iwlwifi

If you get any results, continue checking with:

modinfo iwlwifi | grep 11n_disable

If you get any results again, then you may be affected.

To solve it, open /etc/modprobe.d/iwlwifi.conf and comment out all things there and add a few lines.
Below is the edited file, compare it to yours.

# /etc/modprobe.d/iwlwifi.conf
# iwlwifi will dyamically load either iwldvm or iwlmvm depending on the
# microcode file installed on the system.  When removing iwlwifi, first
# remove the iwl?vm module and then iwlwifi.

# commented out below
# remove iwlwifi \
# (/sbin/lsmod | grep -o -e ^iwlmvm -e ^iwldvm -e ^iwlwifi | xargs /sbin/rmmod) \
# && /sbin/modprobe -r mac80211

# added below
options iwlwifi bt_coex_active=0 swcrypto=1 11n_disable=8


Now the thing that differs from the instructions in the link above, it appears that the iwldvm is some kind of parent driver of iwlwifi, so you need to reload that module instead:

sudo modprobe -r iwlwifi
sudo modprobe -r iwldvm
sudo modprobe iwldvm
sudo modprobe iwlwifi

After this the speed jumped up to 66 Mbit/s