A Performance Study of Affine Projection Adaptive Equalizers in the Presence of Strong Narrowband Interference

In the presence of narrowband interference, non-Wiener effects have been observed for the normalized least-mean-square (NLMS) equalizers. These effects can lead to performance improvements over the fixed Wiener filter with the same model structure, but the convergence rate of the NLMS equalizer slows down seriously. In this paper, the steady-state and convergence performances of the affine projection (AP) equalizer are studied in the presence of multipath and narrowband interferences. Examples show that non-Wiener effects can also occur with the AP equalizer, especially when the order of the AP equalizer is small. And more importantly, the convergence rate of the AP equalizer with high order is robust to the interference and multipath characteristics. Tradeoff between steady-state and convergence performances, the first order AP equalizer works very well even for severe multipath and narrowband interference, where the NLMS equalizer fails.