Optimal Detector for Discrete Transmit Signals in Gaussian Interference Channels

Abstract

Abstract-This paper addresses the design of optimal and nearoptimal detectors for a practical interference channel scenario where the transmitters employ discrete modulation schemes. The conventional detectors, which either ignore the interference or successively detect then cancel the interference, typically assume that the desired signal and/or the interference are Gaussian. This paper proposes detectors that explicitly take into account the modulation formats of both the desired signal and the interference. The optimal maximum-likelihood (ML) detector that minimizes the probability of detection error for a given set of modulation schemes is derived first. A joint minimumdistance detector (MD) is then presented as a low-complexity approximation of the optimal ML detector. It is demonstrated by analysis and by simulation that the proposed detectors can significantly outperform their conventional counterparts. In particular, while the interference-ignorant and the successive interference cancellation detectors are both prone to error floors, the proposed optimal ML and joint MD detectors are not.

Interference mitigation via joint detection in a fading environment

“…As was shown in previous work by the authors [10], for a given channel realization, the symbol error rate (SER) curve for an interference-ignorant detector reaches an error floor as the signal-to-noise ratio (SNR) increases for a given level of signal-to-interference ratio (SIR). However, with the exception of a finite number of SIR values, no such error floor appears if a maximum-likelihood (ML) detector is employed that incorporates knowledge of the interfering channel and the statistics of the interference.…”

“…The interference-ignorant detector has the advantage that it does not need any information on the channel gains and modulation formats of interfering users, whereas all the other detectors require such information. As is shown in [10] in the fixed channel, the joint MD detector has almost the same performance as the optimal ML detector except at very low SNR and requires much lower complexity than the optimal ML detector. Moreover, the joint MD detector significantly outperforms the SIC detector.…”

“…In this section, 4 detectors, which were considered in [10], are briefly reviewed: an interference-ignorant detector, a successive interference cancellation (SIC) detector, the optimal ML detector, and the joint minimum-distance (MD) detector. The interference-ignorant detector for x 1 simply divides the received signal y by the direct channel gain h 1 and then maps it to the closest point of the signal constellation of transmitter 1.…”

“…The following lower-complexity joint MD detector can be derived as an approximation of the optimal ML detector [10]:…”

A SDR Prototype for Backscatter Sensor Networks

“…Equation (21) to Equation (24) indicate that demodulation and extraction of the sensor data are realized by using the constraint of Equation (20).…”