Optimum interference excision in spread spectrum communications using open-loop adaptive filters

A generalized approach for interference suppression in PN spread-spectrum c ommunications using open-loop adaptive excision filtering is introduced. Th e excision filter coefficients under this technique depend on the jammer po wer and its instantaneous frequency (IF) information, and both values can b e gained in the time-frequency domain. The dependency of the excision filte r characteristics on the interference power, which was absent in past contr ibutions in this area, is of significant importance as it allows optimum tr adeoff between interference removal and the amount of self-noise generated from the induced correlation across the PN chip sequence, due to filtering, This tradeoff is bounded by the two extreme cases of no self-noise, which implies preprocessing disabled, and full interference excision, which the c ase previously considered. In this paper, we derive the FIR excision filter s that maximize the receiver signal-to-noise ratio for narrowband interfere nce and discuss the generalization to nonstationary jamming environment.