Transform domain LMS convergence in tone interference

Direct-sequence spread spectrum (DSSS) signaling techniques are often used in conjunction with digital signal processors to combat undesired interference in both military and civilian communications systems. Although spread spectrum signals are inherently robust with respect to non-white interference, the extent to which such interference affects communications reliability depends on the system's processing gain and may be augmented using adaptive filtering techniques. In this paper, the received waveform is filtered in the transform domain using various Least-Mean-Squared (LMS) filtering implementations. The convergence performance of both conventional and normalized pre- and post-correlation transform domain LMS (TDLMS) algorithms is studied as it relates to jammer frequency and misadjustment noise. Analytical and simulation results obtained in the presence of tone interference sources are presented.