8VSB

8VSB (8-level Vestigial SideBand) is the modulation method used by the ATSC system for digital television. 8VSB is a kind of amplitude modulation for binary data. The data stream is broken up in groups of 2 bits. To each group of 2 bits is an additional bit added for error correction. The 3 bits are used to give a signal one of 8 different levels (-7, -5, -3, -1, 1, +3, +5 or +7). This data signal is used to modulate the amplitude of the radio-frequent carrier. After the modulation the signal is filtered in such a way that only the carrier and 6 MHz of the upper band are left.