An orthogonal frequency division multiplexed signal transmitting apparatus executes a time-division multiplexing process that inserts a reference signal at a predetermined interval based on reference signal position information into an information signal to be transmitted. A transportation schedule that includes planned records for first trips and associations between the first trips and corresponding first trip IDs may be accessed. An electrically insulating layer is deposited on walls of the aperture to reduce an extent of the aperture and form a smaller aperture, while depositing substantially no insulating layer on a region of the nanotube that is at the aperture.