TABLE OF CONTENTS The reliability of communications systems is an important factor in design considerations. In this context, the system gain is a very useful concept since it aggregates into a single, convenient measure many of the significant factors which affect reliability.
In this chapter we first present a brief survey of reliability objectives, after which system gain requirements necessary to meet these objectives are defined and displayed graphically. The factors which contribute to overall system gain are examined.
There follows a discussion of the mechanism of multi-path fading, its impact on unprotected, single-channel system, and the options available to designers to compensate for this phenomenon.
Co-channel interference, resulting from the two-frequency plans favored by regulatory authorities for frequency spectrum conservation, is a major cause of degradation in system gain. The term co-channel interference refers to interference from a source having a frequency close to that of the desired carrier. Its effects on system design are examined, and the compromises inherent in various digital modulation schemes are outlined.
Finally, there is a preliminary discussion of frequency-selective fading and its practical effects on system implementation. This section includes a survey of published quantitative values for amplitude and delay distortions caused by frequencyselective fading.
Operators of communications systems naturally expect reliability. Public utilities such as telephone, electric, oil, and gas companies, because of the nature of their business, require highly reliable systems. Their reliability objectives are usually specified in terms of the maximum...
