BER performance of notch filtered direct sequence spread spectrum signal

A certain level of immunity to narrowband interference is inherent in a direct sequence spread spectrum (DSSS) signal. In many applications a system using notch filters rejects any narrowband interference occurring in the spread-spectrum band. Depending upon the number of notches, the notch width, the notch depth, and the location of the notches within the spread-spectrum band, the bit-error rate (BER) performance degradation varies. The spread signal distortion and the resulting intersymbol interference (ISI) at the chip level cannot always be directly accounted for in the data BER through analysis, and it is much easier to employ Monte Carlo simulation techniques to characterize the BER degradation. In some scenarios a notch-filtered spread-spectrum signal may also result in blanking certain portions of the spread-spectrum signal to satisfy regulatory requirements. In such situations it is important to know the level of degradation a priori so that it can be accounted for in the link performance. In this paper, we describe the simulation work carried out to relate the notch-filtering effect of the spread signal on the BER followed by simulation results