THE COARSE ACQUISITION PERFORMANCE OF A CDMA OVERLAY SYSTEM

The coarse acquisition performance of a code-division multiple-access (CDMA) overlay system operating in a mobile communications environment is considered. Specifically, a CDMA system supporting communication b etween several mobile units and one base station shares the frequency band with an existing narrowband user. At the CDMA base station receiv ers, narrowband interference rejection filters are used to suppress th e narrowband user's energy. It is demonstrated that in a nonfading env ironment the presence of the narrowband user does not severely affect the acquisition performance when the ratio of its bandwidth to the CDM A bandwidth is small. As the ratio becomes larger, the acquisition per formance degrades, but the use of the interference rejection filter st ill significantly decreases the time to acquire. When flat Rician fadi ng is introduced, the acquisition performance of the overlay system de grades, especially when the power in the direct component is small.