A packer that uses an element that swells to the set position is disclosed having a device that boosts the set force of the swollen element against the borehole. The methods and apparatus relate to precoder operations during an initial stage using default precoder tap weights, and a second stage wherein precoder weights obtained from a precoder control indicator channel information are used, provided the signal quality of the precoder control indicator channel is sufficiently reliable. If the projectionsdepressions are not provided, light at a radiation angle which satisfies conditions for total reflection at the interface between a semiconductor device and an air cannot be extracted to the outside of the semiconductor device so that the light emission efficiency of the device is low.