A Bandwidth-Efficient Signaling Scheme

Abstract-In most transmission channels, bandwidth is a t a premium, and an important attribute of any good digital signaling scheme is i t s ability to make efficient use of the bandwidth. Conventional Nyquist-type pulse amplitude modu-lation signaling schemes, which are designed to eliminate inter-symbol interference, achieve high data rates only a t the ex-pense of a large number of signal levels. In many applications, correlative coding or partial response signaling, which intro-duces intersymbol interference in a controlled way, is able to achieve high data rates with fewer levels and hence with better error rate performance. In addition to higher data rates, cor-relative schemes achieve convenient spectral shapes and have error-detecting capabilities without introducing redundancy into the data stream. This paper explains how correlative schemes work and why they are advantageous.--- x