A wireless communication system performs high-speed and low-speed transmission of information signals for short-distance communication and long-distance communication by using a short spread code and a long spread code, respectively. A wireless transmission unit includes an interface, a buffer, a spreading processor, an ultra wide band (UWB) wireless transmitter, a controller, a data memory, and an antenna. The controller detects the entry of information signal into the buffer, and then determines the transmission rate depending on the state of wireless linkage and indicates the determined transmission rate to the spreading processor.