The characteristic of broadband mobile channel is analyzed, then we construct a model of bidimensions wideband mobile channel based on delay and Doppler frequency domain. On the basis of describing OFDM theory, the design on initial physical layer of broadband cellular mobile communication systems is proposed. Simulation for base band system is ground on channel model proposed above. The results of experiment and simulation are relatively inosculated, which manifest the well prospect of the communication system proposed for future application.