The present invention proposes methods for facilitating and improving the performance of MU-MIMO transmission in wireless communication systems. In one embodiment, the system may perform several caching functions of data passing between a database and a user on a CAD system. Connections or other requests with similar or common network sub-paths are also determined. The drying machine having the above described configuration can efficiently eliminate creases of clothes. In another embodiment of the invention, a mobile communication device is used to confirm a transaction. The simple method of the present invention is capable of evenly and efficiently coating an inner surface of a polyvinyl chloride medical tube with a sufficient amount of an antithrombogenic material without causing appearance deterioration or uneven coating due to elution of the plasticizer.