If you're experiencing connection issues then it is usually one of the following problems:
Wi-Fi Channel - Usually if several users are using the same channel in the same wireless frequency, the connection between the router and the user will always be disrupted by some other person's radio waves.
This is a common occurrence in Apartment buildings and areas where there are a lot of wireless hot-spots. To fix this problem take a look at the how to speed up your wi-fi connection post.
Distance between router and computer - If your laptop or computer is too far from your wireless router your connection will obviously suffer. Along with that, if you happen to have a lot of walls (or even worse steel/iron re-enforcements between the walls) your connection will gradually attenuate over time. The best way to fight this is buy a wireless range extender that will regenerate the signals so they can travel further.
Cordless Phones and Microwaves - Yup, your cordless phones and microwaves can actually cause disruptions in your wireless network. This is because they too usually use the same frequency (2.4 GHz which can be either called 802.11 b (old standard) 802.11 g (current standard) or 802.11 n (new standard)) as your router does.
So the best way to solve this is either get rid of your phone or get a router that broadcasts information on another frequency such as 5 GHz. Keep in mind though that your hardware, i.e. your laptop must also be compatible with a 5 GHz (802.11 a) router. Most modern laptops usually have support for this, but if you have an older laptop or a wireless card this might not work. In that case you'll have to replace the cordless phone and get one that runs on the 5 GHz frequency.
Router or wireless card problems - Last but not least, the problem might actually lie in your router or wireless card. The best way to check this is to test it with alternative hardware. For example if you suspect the router has problems take it to a friends house and test it out. The same can be done for the laptop, where you can take it to someone else's house and make sure it works right.
You might also want to do a quick search on the internet to find out if other people are experiencing the same kind of problems with the specific brand/model of router or wireless device you have.
Encrypt and secure your network - This is the step that most people neglect. Many don't even know what encryption is. If you are one of those people then you'd better catch up. You can take a look at my wireless security tips post to ensure you know how to encrypt your network.
Encryption prevents people from stealing your internet or messing around with your network. And of course doing so will certainly hinder the speed of the network. Therefore, you're better of setting an administrator password on your router and using at least WPA encryption.
If all instances mentioned above fail to cure the problem, post a comment and I'll do my best to reply as soon as possible.
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