Application of expectation-maximizing algorithm to the detection of direct-sequence signal in pulsed noise jamming

The detection of a direct-sequence spread-spectrum signal received in a pulsed noise jamming environment is considered. The expectation-maximization (EM) algorithm is used to estimate the unknown jammer parameters and hence obtain a decision on the binary signal based on the estimated likelihood functions. The probability of error performance of the algorithm is simulated for a repeat code and a (7,4) block code. Simulation results show that, at low signal to thermal noise ratio and high jammer power, the EM detector performs significantly better than the hard limiter and somewhat better than the soft limiter. Also, at low signal-to-noise ratio (SNR), there is little degradation as compared to the maximum-likelihood detector with true jammer parameters. At high SNR, the soft limiter outperforms the EM detector