Low-Complexity Variable Forgetting Factor Techniques for RLS Algorithms in Interference Rejection Applications

In this work, we propose a low-complexity variable forgetting factor (VFF) mechanism for recursive least square (RLS) algorithms in interference suppression applications. The proposed VFF mechanism employs an updated component related to the time average of the error correlation to automatically adjust the forgetting factor in order to ensure fast convergence and good tracking of the interference and the channel. Convergence and tracking analyses are carried out and analytical expressions for predicting the mean squared error of the proposed adaptation technique are obtained. Simulation results for a direct-sequence code-division multiple access (DS-CDMA) system are presented in nonstationary environments and show that the proposed VFF mechanism achieves superior performance to previously reported methods at a reduced complexity.