Time-varying multichirp rate modulation for multiple access systems

We propose a modulation scheme that is based on wideband time-varying chirp signals for use in frequency-hopped code division multiple-access systems. The scheme is designed such that each user is assigned unique modulating chirp signals that efficiently occupy the hop bandwidth for identification at the receiver. We explain how the chirp modulation reduces multiple-access interference, and we demonstrate with simulations our improved performance for various fading channels. The bandwidth efficiency of the chirp signaling is further exploited by assigning multiple chirp rates to each user.