There are a lot of factors/variables that determines WiFi signal strength. Let's list some!
- Access Point broadcast strength/frequency
- Client NIC broadcast strength/frequency
- Building density/layout
- Interference on the wavelength (cordless phones, microwaves, other WiFi networks, etc)
- Which standard of WiFi you're using (a/b/g/n/ac)
- Distance from client to AP
- etc
Now you can configure some routers/APs to put more power into their broadcast signal, but this comes at the risk of overheating. You cannot increase the strength of most NICs (WiFi cards/etc) however, so that will be one of your bottlenecks. You can always move closer to the router/AP, but then you might as well use ethernet cables (assuming you're using a PC/laptop). You can always improve speed/connectivity by using a higher WiFi standard, but that means buying new stuff. WiFi signals can penetrate walls to a certain extent (iirc, lower frequencies have higher penetration, but it also depends what's in your walls like lead or steel that can interfere) but more often than not it will just bounce of walls to get from A to B, so keeping your doors open may be an idea. Also if you set your WiFi to a higher frequency (5Ghz instead of 2.4Ghz) then there won't be as much interference from cordless interfaces.
The other way to boost the signal is either to use a WiFi repeater half way between you and the router/AP, or just run a cable to a nearby location (e.g. in your room) and buy another router/AP to share WiFi in your room.
If you want to improve internet speed as @luklands pointed out, that is also determined by several things. Let's list some!
- Speed from your ISP to your local phone/cable line (base speed)
- Speed your router/modem is able to handle (effective speed)
- Speed of your network between your router/AP to your device (actual speed)
- Speed your device is able to handle (buffer/render speed)
Now the more tech-minded may notice I'm skipping things, but the point is finding the bottleneck that's keeping your speed down.
