Multipath diversity and channel estimation using time-varying chirps in CDMA systems with unknown CSI

In this paper, we propose the use of wideband chirp signals in modulation schemes that combine multiuser detection with multipath diversity in frequency selective fading channels with known channel state information (CSI). We achieve this by appropriately designing the chirp parameters. For channels with unknown CSI, we also show that good channel estimation can be obtained, even in fast varying channels, with reduced interference by transmitting pilot chirp signals simultaneously with the users information.