Showing papers on "Spectral efficiency published in 1972"
01 Oct 1972
TL;DR: The spectral occupancy of transmitted digital data can be reduced by employing symbols from an M-ary alphabet and the bandwidth efficiency of the principal APK sets and PSK is presented as a function of alphabet size to illustrate the bandwidth-power tradeoff.
Abstract: The spectral occupancy of transmitted digital data can be reduced by employing symbols from an M-ary alphabet. A modulation technique combining both amplitude and phase keying (APK) requires less peak and average power than M-ary PSK to achieve the same symbol error probability. Efficient signal set designs have been found by an empirical search of a large number of candidate sets with a comparison based on symbol error probability. New 8-ary and 16-ary designs are presented which outperform previously suggested designs on both a peak and average SNR basis. The bandwidth efficiency of the principal APK sets and PSK is presented as a function of alphabet size (4-ary to 128-ary) to illustrate the bandwidth-power tradeoff.
16 citations
01 Oct 1972
TL;DR: This work has shown that the bandwidth efficiency attainable in practice for the transmission of digital data is determined by the burst data rate for a pulse transmitter, and the additional degree of freedom of amplitude modulation could be applied in a quasi-linear channel.
Abstract: Introduction For TDMA operation, the bandwidth efficiency attainable in practice for the transmission of digital data is determined by the burst data rate for a pulse transmitter which has sole access to the finite-bandwidth channel. For a hard-limiting channel, the possible signaling alphabets are based on multiphase shift keying, restricted for implementation convenience to biphase, quadriphase, and eight-phase. The additional degree of freedom of amplitude modulation could be applied in a quasi-linear channel, but this would impose an operationally undesirable requirement for power control on all transmitters.