Narrow-band interference rejection in DS CDMA communications using an adaptive IIR notch filter

Suppression of narrow-band interference (NBI) in direct-sequence code-division multiple-access (DS CDMA) system using a lattice-based adaptive infinite impulse response (IIR) notch filter is studied. A simplified normalized coefficient update algorithm that requires no gradient signal generating filters is proposed. Convergence behaviour of the algorithm is shown not to vary much with the number of active users for a tone NBI model. Closed form expression for the SNR improvement at the pseudonoise (PN) correlator input is derived. Computer simulations are shown to verify the analyses and compare the performance of the proposed NBI suppression scheme with that of a linear prediction filter.