evision a critical aspect of convergence on all fronts, including devices, applications, fixed networks, wireless infrastructure, and service providers. The Move to DTV and HDTV One main application of DTV is to carry more channels in the same amount of bandwidth, either 6MHz or 8MHz, depending on the standard in use. The other key application is to carry high-definition program- ming, known as HDTV. Because DTV makes use of a digital signal, many common analog broadcasting artifacts can be eliminated, including static in the audio, snow on the screen, and the presence of ghost images (called multipath distortion). ever, digital signals can also suffer from artifacts. For example, when the data rate is too low, MPEG compression results in artifacts such as blocking, or blocky images. In addition, while analog TV may produce an impaired picture under some circumstances, it is still viewable, whereas DTV may not work at all in the same sit- uation. Basically, depending on the level and sophistication of error correction defined by the standard and chosen by the provider, DTV may work either per- fectly or not at all. The move to DTV systems is generally associated with a switch in picture for- mat, going from the aspect ratio of 4:3 to one of 16:9, although both HDTV and SDTV are available in both formats. However, the aspect ratio is only part of HDTV. The History of Aspect Ratio The 4:3 aspect ratio was originally developed by W. K. L. Dickson in 1889 while he was working at Thomas Edison's laboratories. Dickson was experimenting with a motion- picture camera called a Kinescope, and he made his film 1 inch wide with frames 0.75 inch high. This film size, and its aspect ratio, became the standard for the film and motion-picture industry because there was no apparent reason to change. In 1941, when the NTSC proposed standards for television broadcasting, they adopted the same ratio as the film industry. Multimedia Networking Requirements In the 1950s, Hollywood wanted to give the public a reason to buy a ticket to 