MOBILE STATION DEVICE

PROBLEM TO BE SOLVED: To provide a mobile station device capable of conducting direct communications among mobile stations without generating a drop in frequency-utilization efficiency and an interference in a radio system using an OFDM. SOLUTION: The mobile station device includes a switching circuit for switching a mode for communication among base stations in conducting communication with a base station 1 and a mode for direct communications among mobile stations in conducting direct communication with the other mobile stations 2a to 2d without the base station 1. The communication is conducted by using an OFDM signal using a center carrier as a carrier hole in the mode for communications among the base stations, and the communication is conducted by using only the center carrier for the OFDM signal in the mode for direct communication among the mobile stations. Bits of each symbol are modulated by a second modulation system having an excellent error resistance with fewer BPSKs or the like than a first modulation system, which is carried out in the mode for communication among base stations, and a complex base band signal is generated in the mode for direct communication among mobile stations. COPYRIGHT: (C)2010,JPO&INPIT