ATSC-M/H (Advanced Television Systems Committee - Mobile/Handheld) is a standard in the USA for mobile digital TV, that allows TV broadcasts to be received by mobile devices.
Just as the DVB-H and 1seg are mobile TV extensions to the DVB-T and ISDB-T terrestrial digital TV standards respectively, ATSC-M/H is an extension to the available digital TV broadcasting standard ATSC A/53. ATSC is optimized for a fixed reception in the typical North American environment and uses 8VSB modulation. The ATSC transmission scheme is not robust enough against doppler shift and multipath radio interference in mobile environments, and is designed for highly directional fixed antennas. To overcome these issues, additional channel coding mechanisms are introduced in ATSC-M/H to protect the signal.
Read more about ATSC-M/H: Structure of Mobile DTV Standard, Principle, Technology, Other Mobile Standards