A blind scheme for narrowband interference suppression in CDMA using random walk tracking algorithm

Previous methods for narrowband interference suppression in spread spectrum systems require training sequences. In practical overlay systems, transmission of the training sequences is impossible, because narrowband system and spread spectrum system are two separate entities, and presently the narrowband systems are in use and standardized and any changes may not be allowed. Hence, the narrowband systems cannot transmit training sequences for the spread spectrum system. We present a blind method for narrowband interference suppression in direct sequence code division multiple access (CDMA) systems. The proposed scheme is a nonlinear predictor consisting of a nonlinear device and two random walk tracking algorithms. The main feature of this approach is that it does not require training sequences for tracking and suppressing narrowband interference. Simulation results show that in multiuser case, the performance of the proposed approach is better than Kalman filter.