Replace your cordless phone. Cordless phones are among the worst sources of interference for wireless networks. They tend to transmit at a higher power output than Wi-Fi gear, making them louder and therefore harder to talk over, and they tend to transmit frequently, especially when the handset and base station are separated. Some 2.4GHz cordless phones let you select a channel, in which case you can try separating the phone's frequency from the frequency of your wireless network. For example, set your phone to channel 1 and your wireless router to channel 11. If your phone doesn't let you select a channel, try putting some distance between your phone and your router. Generally, it's not a good idea to place a cordless phone next to a Wi-Fi router. If this doesn't help, consider replacing your 2.4GHz phone with a 5GHz phone. This way, your phone and network won't be sharing the same airspace and won't interfere with each other.
