Communicating through a constant modulus interferer using multi-user detection

In this paper, we consider techniques for communicating in the presence of interference. In particular, we consider the simple scenario of a BPSK communication system in the presence of a constant modulus (CM) interferer. Using computer simulations and analytical approximations, we compare the performances of four detectors for recovering the communications signal in an additive white Gaussian noise non-fading environment. We first consider a simple sign detector for equiprobable BPSK symbols, ignoring the presence of the interferer. We then study a novel geometric detector, which takes advantage of the CM property of the interferer. We next examine a successive interference cancellation (SIC)-based detector, which first estimates the interferer, then subtracts it from the received observation, and finally decodes the residual using a sign detector. Lastly, we consider the optimal multi-user (MU) detector, which decodes both the communications signal and interferer concurrently. Comparing the bit error rates (BERs) of the four detectors as a function of signal-to-interference ratio (SIR) or its inverse, the jammer-to-signal ratio (JSR), we find that for low to medium JSRs the geometric detector provides the best performance versus complexity trade-off. For large JSRs, we show that the SIC detector is superior, yielding the same performance as the optimal MU detector at reduced complexity. In fact, for large JSRs, the SIC detector in the presence of the interferer performs as well as a conventional BPSK (sign) detector when no interferer is present.