Frequency domain interference suppression in a DSSS system

In this paper the performance of a narrow-band interference rejection scheme using the frequency domain signal processing is studied in a DSSS system. The signal of interest is modulated directly by a PN code sequence and the narrow-band interference itself is BPSK-type with high power level relative to DSSS signal that can be located either intentionally or unintentionally within the DS-bandwidth. Using frequency domain interference suppression algorithm will reduce the influence of the narrow-band interference. The interference suppression takes place in the frequency domain after which the signal is transformed back to time domain where the rest of signal processing is performed. The transform from the time domain to the frequency domain and vice versa are made by FFT and IFFT respectively. The criterion used for the evaluation of the performance of the interference rejection algorithm is the BER as a function of E_b/n₀ and SJR, which is obtained by computer simulations.