The best approach to improving WiFi signal strength in a specific dead zone depends on the cause of the dead zone, but WiFi repeaters and extenders are useful in many cases. High-gain antennas on routers and computers can also help improve reception, as can modifying certain wireless network settings.
WiFi extenders and repeaters are devices that accept and retransmit signals from a wireless network access point and connected devices. Since WiFi signals lose strength as distance from the access point increases, it is possible for a dead zone to result in areas too far from the access point. When an extender or repeater retransmits the signal, it is stronger than the signal from the access station itself, often eliminating the dead zone entirely.
The primary drawback of using extenders and repeaters are that these devices add additional latency to the network, since the WiFi signal must be received and retransmitted. While this does not usually affect web browsing, latency-sensitive applications, including online gaming, often suffer when using repeaters and extenders. Using upgraded antennas on a network's access point or connected devices can boost signal strength directly, but not all devices and access points can accommodate an upgraded antenna.
If a wireless dead zone occurs in an area with many competing wireless networks, changing the wireless network channel on which the network operates can help eliminate interference from other networks and reduce or eliminate the dead zone as well.