Novel adaptive methods for narrowband interference cancellation in CDMA multi-user detection

When overlaying spread spectrum (SS) transmission over a narrowband system, the performance is significantly degraded by the narrowband signal. The paper presents an adaptive predictor approach for narrowband interference suppression in SS code-division multiple-access (CDMA) systems. Two adaptive methods are derived; one uses a linear predictor and the other a nonlinear predictor. They both use a predictor to estimate the interference which is then subtracted from the received signal to improve performance. The proposed adaptive methods are blind in the sense that they do not require training data. The proposed methods not only provide faster convergence speed than the case without using a predictor, but also give better BER performance. At a BER of 10^-4 and SINR = -20 dB, the proposed methods yield 1.4 dB and 2.4 dB improvement in SNR (E_b/N₀) respectively.