On combating multipath effects using spread-spectrum systems

This paper discusses briefly the origins of multipath propagation, their effects on radio communication systems, and schemes for suppressing these effects. Major attention is given to spread spectrum schemes to demonstrate their capacity to combat multipath effects, to examine conditions under which the schemes would be effective, and to assess the merits of the schemes. Multipath propagation can occur under various atmospheric and geographical conditions as illustrated by simple examples. The adverse effects of multipath propagation on communication systems can be described in terms of selective fading and intersymbol interference. Simple measures can be found if the multipath propagation is predictable, but sophisticated techniques are required to combat unpredictable multipath interference. It has been shown that spread spectrum systems are superior to other approaches in terms of effectiveness in combating multipath interference and other valuable features. However, the ability of spread spectrum systems to suppress interference depends on the process gain of the system and the system performance depends on the degree of synchronization which can be established by the system.