A method for initiating a random access includes generating a first downlink control information including random access parameters and selecting a control channel from a first downlink control channel in common search space of a first subframe and a second downlink control channel in a data region of the first subframe. The undercutting system includes an insertion apparatus and a cutting assembly. Thus, with a simple configuration, the brightness of each color can be made uniform without the use of pulse width modulation or the like.