Intermittent Connection

Hi All,

Please help me, I'm having trouble fixing our intermittent connection via WIFI/AP, but in LAN no intermittent.

my network setup is:  Internet mode----Firewall device/AP controller----Switch----2xAP,

Troubleshoot Made: VIA LAN Connection

                              = Ping gateway and google = result ok

                              = Ping gateway, google and browse sites and video streaming the ping result is still ok

                              VIA WIFI/AP Connection

                              = Ping gateway and google = result ok

                              = Ping gateway, google and browse sites and video streaming the ping result is 

                                 intermittent every time the latency ping get high.

plaese help me how can i trace the cause of intermittent.