Vehicle compartment wireless communications apparatus

A vehicle compartment wireless communications apparatus for executing ultra wide band communications in a vehicle compartment having a flat internal ceiling wall made of a metal material,

• the apparatus comprising:
• at least two horizontally polarized wave antennas including a first horizontally polarized wave antenna and a second horizontally polarized wave antenna;
• at least one vertically polarized wave antenna;
• a propagation characteristic determination device to determine whether each of a plurality of subcarriers included in one channel of an ultra wide band has an adequate propagation characteristic;
• and
• a transmission unit to assign a subcarrier with transmission data so as to transmit a transmission signal containing the transmission data from one of the antennas,
• the propagation characteristic determination device being further configured to determine whether each of the plurality of subcarriers has an adequate propagation characteristic in the first horizontally polarized wave antenna,
• the transmission unit being further configured to
• assign a subcarrier, which is determined to have an adequate propagation characteristic in the first horizontally polarized wave antenna among the plurality of subcarriers, with transmission data so as to transmit a transmission signal containing the transmission data from the first horizontally polarized wave antenna, and
• assign a subcarrier, which is determined not to have an adequate propagation characteristic in the first horizontally polarized wave antenna among the plurality of subcarriers, with transmission data so as to transmit a transmission signal containing the transmission data from one of the second horizontally polarized wave antenna and the vertically polarized wave antenna,
• the transmission unit thereby executing diversity by (i) the first horizontally polarized wave antenna and (ii) one of the second horizontally polarized wave antenna and the vertically polarized wave antenna.