Obtaining the Optimal Threshold of the Matched Filter Detector in the Presence of Interference with Frequency Flat Fading Channel

The implemented method for data recovery in some practical code division multiple access (CDMA) systems is the matched filter detector which has zero decision threshold in the symmetric modulations. Because in the multiuser communication systems, the cochannel interference changes the observation noise model to Non-Gaussian one, using zero thresholds is not optimal anymore. In this paper, we obtain the optimal threshold of the matched filter detector in the presence of the block faded interference and fast frequency flat Rayleigh faded desired user signal. We show that the probability of error for this system can be decreased using the obtained optimal threshold. To this end, we derive the analytic probability of error of the communication system with interference which leads to the condition of having an optimal threshold for this system and its value. We have also compared the obtained analytic results with the Monte Carlo simulation curves to validate the derived analytic expressions.