Speed Up Slow WiFi Connection In Linux Ubuntu18.x

 There are some tricks which speed up slow WiFi connection in Linux Ubuntu18.04

Solution 1. Trick is to force disable the 802.11n protocol. Even after so many years, most of the world runs 802.11a,b and g. While 802.11n provides better data rate, not all the routers support it, especially the older ones. It has been observed that disabling the 802.11 n helps speed up the wireless connection in Ubuntu and other OS.
Open the terminal and use the following command:
sudo rmmod iwlwif
sudo modprobe iwlwifi 11n_disable=1
you should make the changes permanent by using these commands:
sudo su
echo "options iwlwifi 11n_disable=1" >> /etc/modprobe.d/iwlwifi.conf
Restart your computer and live your life at full speed.

Solution 2. Fix the bug in Debian Avahi-daemon:
To fix this bug, you have to edit the nsswitch configuration file. Open a terminal and use the following command:
sudo gedit /etc/nsswitch.conf
This will open the configuration file in gedit so that you could edit it easily in GUI. In here, look for the following line:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
If you find this file, replace it with the following line:
hosts: files dns
Save it, close it, restart your computer. It should fix the slow wireless connection problem for you. If it doesn’t check the other solution.

Solution 3. Disable IPv6 Support:
IPv6 is still in deployment mode and a significant number of ISPs don’t even support it
To disable IPv6 support, use the following commands one by one:
sudo su
echo "#disable ipv6" >> /etc/sysctl.conf
echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.conf
echo "net.ipv6.conf.lo.disable_ipv6 = 1" >> /etc/sysctl.conf
Restart your computer and it should do the magic. If not try the next one.

Solution 4: More Power to Wireless Adapter:
At the time of Ubuntu 11.04, Linux Kernel had a power management system. This troubled some users with their wireless connection speed as it sent less power to the wireless adaptor and thus affecting its performance. As a result, wireless connection would be some times fast and some times dead slow. While this is probably fixed in later Kernels, systems running older Linux Kernel may still face it.
sudo iwconfig
It will give you the name of your wireless device. Normally it should be wlan0. Now use the following command:
sudo iwconfig wlan0 power off
This will switch off the special power management system for the wireless adaptor and thus it will get more power and will work more.

Solution 5: For Slow WiFi in Atheros Wireless Network Adapters:
First, you need to find your wireless network adapter. You can do so by using lshw -C network command in terminal. If your adapter manufacturer is Atheros, this solution should work for you.

Open a terminal (Ctrl+Alt+T in Ubuntu) and use the following commands one by one:
sudo su
echo "options ath9k nohwcrypt=1" >> /etc/modprobe.d/ath9k.conf
This will add the additional line to the configuration file. Restart your computer and you should be good to go. If it does not fix or if you don’t have Atheros WiFi adaptor, try other above solutions.

Solution 6:ENJOY!!!