What is wireless signal strength?
In the list of available wireless networks, you will see a symbol that shows the wireless signal strength for each network. The more bars, the stronger the signal. A strong signal (five bars) usually means that the wireless network is close or there is no interference. For best performance, connect to the wireless network with the strongest signal. However, if an unsecured network has a stronger signal than a security-enabled one, it is safer for your data if you connect to the security-enabled network (but you must be an authorized user of that network). To improve the signal strength, you can move your computer closer to the wireless router or access point, or move the router or access point so it is not close to sources of interference such as brick walls or walls that contain metal support beams.
Note: This information provided by Microsoft.