A cross-layer optimization method for controlling a bit rate of a video coder/decoder (codec) in video data transmission for wireless devices such as a wireless broadband (WiBro) system terminal that adapts to changing transmission/reception characteristics and usage. The method typically includes checking, by a sender, radio channel state information of a sender side and a receiver side; determining, by the sender, a transmission bit rate of a video codec by using the radio channel state information of the sender side; and adjusting, by the sender, the transmission bit rate of the video codec by using the radio channel state information of the receiver side when a communication network used by a receiver typically based on the type of a communication network being used by the sender.