Detection of the Weak Signal in the Presence of Strong Interference Using Locally Optimal Rule and Estimation of the Parameters with the Method of Moments

In this paper we introduce a multiple access scheme in which frequency reuse is achieved using the difference in the signal amplitudes. For this amplitude division multiple access (ADMA) system, a locally optimal multiuser detector (LOMUD) is proposed to detect a weak binary phase shift keying (BPSK) signal in the presence of a similar modulated cochannel interference and additive white Gaussian noise (AWGN). For the proposed detector, there is no need for signal level estimation, which is a computational burden when the desired signal is weak. An analytic expression for the bit error probability of the LOMUD detector is also derived. Furthermore, it is shown that the performance of the proposed detector approaches the lower bound when the signal to interference ratio (SIR) is low enough. We also present some estimators for estimation of the required parameters in the receiver and investigated their efficiencies.