Enhanced blind adaptive narrowband interference suppression in DSSS

This paper addresses blind adaptive suppression of a digital narrowband interferer in direct sequence spread spectrum (DSSS) communications. We apply an adaptive suppression method for wideband interference proposed by Honig, Madhow and Verdu (see IEEE Trans. on Info. Theory, vol.41, no.7, p.944-60, 1995) to a narrowband interferer. We identify the eigenspaces of the system dynamics to: (1) significantly decrease the convergence times via a new constraint on step size, (2) introduce a simple parameterization of the mean output energy and signal-to-interference ratio, and (3) identify modes of operation where the algorithm ceases to effectively cancel interference. We propose a new adaptive receiver that avoids the convergence anomalies, while capitalizing on the new step size for faster convergence