lshw -class network. Look at the logical name for your wireless card. Let that be denoted
<wlan>. CD into a relevant directory, store your current wireless config:
iwconfig <wlan> > current_wireless_config to restore settings later if need be.
Post the output to
iwlist <wlan> channel here. You may wish to follow the advice in this answer: https://askubuntu.com/a/55748 or you may download linSSID from the app center and find a good open channel and frequency and set it as follows.
Turn your wifi off, then run:
sudo iwconfig <wlan> mode Managed
sudo iwconfig <wlan> freq <desired-freq>
sudo iwconfig <wlan> channel <desired-channel>
Make sure this is in agreement with your output from
iwlist <wlan> scan or
iwlist <wlan> channel and the frequency matches the corresponding channel. Reboot computer.
WARNING: According to
man iwconfig under "freq/channel":
When using Managed mode, most often the Access Point dictates the
channel and the driver may refuse the setting of the frequency.
As per your discussion on askubuntu, Managed mode may be the best option you have. So try just that without changing the frequency or channel parameters and see how it goes.
Other parameters of your wireless interface may also be the culprit for your connectivity issues. To be sure, post the output to
iwconfig <wlan> in your question.