By Dr. Kamilo Feher, DIGCOM, Inc.
New emerging modulation-demodulation (modem) and coding techniques suitable for spectrally and power efficient digital TV and HDTV distribution systems over coaxial cable and subcarrier multiplexed (SCM) fiber optics systems are described. Efficient and robust modulators/demodulators (modems) combined with low redundancy forward error correction (FEC) - integrated circuits attain a spectral efficiency in the 2 b/s/Hz to 7 b/s/Hz range and a bit error rate (BER) in the lQ-7 to lQ-10 range. Recently developed VLSIASIC chips, having a universal QPSK-QAMQPRS modem architecture combined with FECchips, operating up to 100 Mb/s, with a 3% to 10% redundancy will enable the transmission of 30 Mb/s rate (or even higher bit rate) digitized TV signals in one conventional analog TV band.
Requirements for FDM shared analog and digitized TV distribution systems are highlighted. The performance of a new class of QPRS filtered modems invented by the author is compared to conventional QPRS and QAM-8-PSK cable systems. The performance advantages of our new class of "above Nyquist rate" modems and of an operational SQPRS (staggered) QPRS system developed by Digital Radio Laboratories are highlighted.