Interference Rejection in DS Spread Spectrum Systems Using Nonlinear Interpolation Lattice Filters

An Mth-order adaptive lattice filter automatically generates all M of the outputs that would be provided by M separate transversal filters. This feature can effectively suppress the narrow-band interference (NBI) of time-varying bandwidth in direct-sequence (DS) spread-spectrum systems for which the order of the interference rejection filter that achieves the optimal performance is unknown and is constantly changing. This work develops a computationally efficient and numerically stable adaptive nonlinear QR-decompositionbased lattice interpolator to effectively suppress NBI. Simulation results indicate that the proposed nonlinear lattice interpolators provide a fast convergence rate and SNR improvements that closely approach the upper bound.