Advanced Television Systems Committee (ATSC) released the ATSC 3.0 standard for next-generation broadcast services. ATSC 3.0 achieves more enhanced channel capacity compared to ATSC 1.0. With the advent of highly efficient video codecs, ATSC 3.0 can combine various services in a single RF channel. Beyond this, ATSC 3.0 also supports Multiple Input Multiple Output (MIMO) technology, which doubles the system capacity of a RF channel. This paper briefly introduces physical layer multiplexing in the ATSC 3.0 standard and their applications with MIMO.