 and without loss of video continue to display all these formats in the native format of the television receiver. ATSC signals are designed to work on the same bandwidth as NTSC (6MHz) or PAL (8MHz) channels. The video signals are compressed using MPEG-2, and the data stream is then modulated. The modulation technique varies, depending on the transmission method. Because any terrestrial TV system must overcome numerous channel impairments such as ghosts, noise bursts, signal fades, and interference in order to reach the home viewer, the selection of the right RF modulation format is critical. In the case of terrestrial broadcasters, the technique used is 8-VSB (Vesti- gial Sideband), with a maximum transfer rate of 19.39Mbps. This is sufficient to carry several video channels and metadata. Because cable TV operators usually have a higher signal-to-noise ratio (SNR), they can use 16-VSB or 256-QAM to achieve a throughput of 38.78Mbps using the same size channel. (Modulation techniques are discussed in Chapter 5, "Data Communication Basics.") Table 10.2 shows the details of the various ATSC DTV standards. Multimedia Networking Requirements Table 10.2 ATSC DTV Standard Lines Pixels Aspect Frame Scanning of Resolution per Line Ratio Sequence HDTV-NTSC 1,080 1,920 30,24 Progressive 1,080 1,920 Interlaced 1,080 1,440 30, 24 Progressive 1,080 1,440 Interlaced 1,280 60, 30, 24 Progressive 1,280 Interlaced 60, 30, 24 Progressive Interlaced HDTV-PAL 1,080 1,920 Progressive 1,080 1,920 Interlaced 1,080 1,440 Progressive 1,080 1,440 Interlaced 1,280 50, 25 Progressive 1,280 Interlaced 50, 25 Progressive Interlaced EDTV-NTSC 16:9, 4:3 Progressive EDTV-PAL 16:9, 4:3 Progressive continued Chapter 10 Next-Generation Networks Table 10.2 ATSC DTV Standard (continued) Lines Pixels Aspect Frame Scanning of Resolution per Line Ratio Sequence SDTV-NTSC 60, 30, 24 Progressive Interlaced 60, 30, 24 Progressive Interlaced SDTV-PAL, SECAM 50, 25 Progressive Interlaced 50, 25 Progressive Interlaced ATSC requires about half of the power for