A Bandwidth Efficient Digital Radio System

Abstract

<p>A feasibility study has been performed on a 4 bits/s/Hz digital radio system. This system utilizes a 4-level quadrature amplitude modulation scheme with Duobinary filtering to achieve such high bandwidth efficiency. The error rate performance of such systems is evaluated. A repeater structure including the transmitter and the receiver of such systems is developed and analyzed. A decision directed carrier recovery loop is presented and analyzed using stochastic techniques. Expressions for the effective phase detector characteristic and the steady state phase error probability density function are derived. A symbol timing recovery structure is also presented and exhaustive simulations have been performed to analyze the performance of the timing recovery structure.</p>