The first Advanced Television System Committee (ATSC) standard was developed in the mid-1990s parallel to the first digital video broadcasting standards. It describes the physical transportation layer, including the multiplex input format and the content format of the multiplex input signal, and has quite strict limiting rules for the source coding. This chapter describes some of the main aspects of the ATSC 3.0 standard that are expected to be close to the final version of the standard. The guard interval corresponds to the maximum length of an echo path that can be handled by the orthogonal frequency-division multiplexed (OFDM) system. The peak-to-average power reduction block in the OFDM section is for limiting the crest factor. In contrast to the frequency division multiplexing and the time division multiplexing approaches, the entire bandwidth is used the entire time. Layer Division Multiplexing describes the constellation superposition of multiple data streams at different power levels.