TABLE OF CONTENTS The principles for design of both binary and four-phase PSK systems were described in Chapter 4. The spectral efficiency of these systems is less than 2 b/s/Hz. Most operational satellite systems are power limited; that is, the available ratio of energy per bit to noise density E b /N o is insufficient to enable the utilization of modems which have a spectral efficiency of more than 2 b/s/Hz and require a higher E b / N o ratio.
The crowded conditions prevailing in many regions of the radio spectrum, combined with the new emphasis on digital satellite transmission, has created a need for improved spectrum utilization techniques. Time-division multiple-access (TDMA) satellite systems, described in Chapters 8 and 9, are among the most powerful spectral and power-efficient system approaches. The intelligent application of spectral efficient (more than 2 b/s/Hz) modulation techniques combined with TDMA may provide a further improvement in the spectral efficiency of these satellite systems. With the recent developments in more powerful microwave high-power amplifier designs and the discovery of new nonlinearly amplified modulation techniques, it is probable that some future generations of satellite systems will have a sufficiently high E b/N o ratio to enable the use of highly spectral efficient modulation techniques.
The terrestrial line-of-sight microwave systems that were developed in the 1950s, 60s, and 70s used predominantly binary and four-phase PSK modulation techniques. In the late 1970s and early...
