Fundamentals Of Interference In Wireless Networks

By Anritsu Company

As wireless systems proliferate worldwide, the number one enemy of wireless systems designers and service providers is signal interference. Interference hampers coverage and capacity, and limits the effectiveness of both new and existing systems. It is an unavoidable fact that wireless communications systems must coexist in extremely complicated signal environments. These environments are comprised of multiple operating wireless networks ranging from mobile communication services to specialized mobile radio and paging/broadcast systems. At the same time, wireless local area networks (WLANs) and digital video broadcasting are introducing new technologies and signal sources that further threaten to disrupt wireless communications service.

Compounding the problem are regulatory and environmental restrictions which have effectively limited the number of suitable new base station transceiver sites that can be put in place. Hence, many wireless service providers are now faced with co-location issues further contributing to the potential for signal interference as more antennae are placed on individual cell towers.

This article presents the subject of interference and its degrading effects on the performance of wireless networks. It provides a brief theory of operation of communications receivers and antennae, as well as instructions on how to locate and identify an interfering signal. It also reviews the operating principles of the Anritsu Spectrum Master MS2711D and some of its functional routines which make it an ideal interference troubleshooting tool.

With the information contained in this Application Note and a complementary note, "Practical Tips on Measuring Interference" (referred to here as "Measurements Note," Anritsu Publication number 11410-00537), you will understand the basic facts about what causes interference, how it sneaks into a typical affected system receiver, and how you can locate and identify typical sources of those interfering signals. A Glossary of Terms useful for interference measurements is included in the Measurements Note.