David A. Bryan

QAM for terrestrial and cable transmission

We introduce quadrature amplitude modulation (QAM) and discuss QAM architectures used to overcome transmission impairments typically encountered on 6 MHz wide terrestrial and cable TV VHF/UHF channels. The input data to the QAM transmitter is mapped into N bit words called symbols; N determines the QAM level. The signal-to-noise ratio at the receiver determines the QAM level that can be used. Typical terrestrial and cable channels allow N=4 and N=8, leading to user data rates of about 20 and 40 Mbits/s, respectively. Transmission impairments include random noise, reflections, phase noise, and frequency offset. Adaptive equalizers are used by the cable and terrestrial QAM receivers to remove amplitude and phase distortion due to reflections and filter imperfections. The cable adaptive equalizer consists of feed-forward and feedback sections; the terrestrial equalizer uses a feed-forward section only. Both the cable and terrestrial receivers accomplish both start-up and steady-state equalization using only the user data. We also describe carrier recovery and symbol timing recovery for the terrestrial receiver. >

Advanced digital HDTV transmission system for terrestrial video simulcasting

Transmission aspects of the advanced digital high definition television (AD-HDTV) system, for terrestrial simulcast delivery of HDTV are described. In AD-HDTV, two quadrature-amplitude-modulated (QAM) carriers, with different power spectral densities, are employed in a frequency division multiplex (FDM) mode within the standard 6-MHz channel. The resulting spectral shaping allows a larger power to be transmitted, compared to that for a single QAM carrier, for the same level of perceptual interference into cochannel NTSC. The coded video data are split into high-priority (HP) data and standard-priority (SP) data, and the vital information is sent on the appropriate QAM carrier, resulting in a robust audio and video transmission system. The availability is higher in scenarios where the carrier-to-noise ratio (CNR) is above the threshold for HP reception but below the threshold for SP reception; this is important in fringe areas. The NTSC planning factors, suitably modified for HDTV delivery, are used to estimate the coverage area for AD-HDTV. The calculated AD-HDTV coverage area of 54.5 miles is comparable to that for NTSC transmission. >

A digital vestigial-sideband (VSB) channel decoder IC for digital TV (DTV)

This paper describes a second-generation integrated 8-VSB demodulator-decoder which can receive digital TV (DTV) signals that are formatted according to the ATSC standard. This IC presents significant improvements over the first generation for the reception of strongly impaired signals.

Channel coding, modulation, and transmission for north american digital television

Abstract We introduce the transmission system selected for the next generation of North American broadcast television and for high data rate transmission on cable TV systems. We describe key features of the digital vestigial sideband (VSB) modulation and error protection employed in this system, and of the quadrature amplitude modulation (QAM) systems that competed against it for selection. We review the process used to select this system, in addition to the criteria by which the selection was made. We further review the performance of the system under actual field conditions. The 8-VSB terrestrial mode was found to perform better than the existing NTSC broadcasting system. The 16-VSB high data rate cable mode was found to perform essentially error-free at all receiving locations that met Federal Communications Commission (FCC) specifications for carrier-to-noise ratio.

A New NTSC Co-Channel Interference Rejection Filter with Coded 6-VSB Modulation for Improved ATV Coverage

The Advanced Television Systems Committee (ATSC) advanced television (ATV) standard and its service area predictions assume the use of a comb filter at the receiver However, such a filter is not required by the ATV standard. There are also unresolved questions about the efficacy of the comb filter. We describe a new system, including an NTSC co-channel interference rejection filter with coded 6-level digital vestigial sideband (6-VSB) modulation, of comparable complexity, which offers improved ATV service area. Coverage analysis results demonstrate that the system provides much better co-channel performance today, with a comparable carrier-to-noise (C/N) threshold and better threshold performance when NTSC transmission ceases in the future. The new system obviates concerns about the reliability of the comb filter under conditions of noise, interference, and multipath.