What region are you located?What ISP Service do you have? Cable or DSL?
What ISP Modem Mfr. and model # do you have?
Check ISP MTU requirements, Cable is usually 1500, DSL is around 1492 down to 1472. Call the ISP and ask. Link>
Checking MTU ValuesFor DSL/PPPoE connections on the router, ensure that "Always ON" option is enabled.
Setup DHCP reserved IP addresses for all devices ON the main host router. This ensures each devices gets its own IP address when turned on and connected, eliminates IP address conflicts and helps in troubleshooting.
Ensure devices are set to auto obtain an IP address.
What wireless modes are you using on the main host router?
Try single mode G or N or mixed G and N?
Channel Width set for Auto 20/40Mhz or try
20Mhz only.
Try setting a manual channel to a open or unused channel. 1, 6 or 11. 11 for single mode N if the channel is clear.
What security mode are you using?
Preferred security is WPA-Personal. WPA2/AES Only. Some WiFi adapters don't support AES, so you might want to try TPIK only or Auto.
What wireless devices do you have connected?
Any cordless house phones?
Any other WiFi routers in the area? Link> Use InSSIDer to find out. How many?Try turning off Short GI, WLAN Partition,and Extra Wireless Protection if you have it on the main host router.
Enable
WMM Enable on the main host router
Turn off all anti virus and firewall programs on PC while testing. 3rd party firewalls are not generally needed when using routers as they are effective on blocking malicious inbound traffic.
Turn off all devices accept for one wired PC while testing.