Carrier Phase Adjustment for Multiple Access Communication Systems with Multi-Packet Reception Capability

Driven by advances in signal processing and multiuser detection (MUD) technologies, it has become possible for a wireless node to simultaneously receive multiple signals from other transmitters. In order to take full advantage of MUD in multi-packet reception (MPR) capable wireless networks, it is highly desirable to make the compounded signal from multiple transmitters more separable on its constellation at the receiver by coordinating the carrier phase offsets of the transmitters. In this paper, we propose a feedback-based carrier phase adjustment scheme that estimates the carrier phase offset for each user´s received signal, computes the optimal phase shift to maximize the minimum Euclidean distance between the constellation points, and finally feeds the phase shift information back to the transmitters. We then evaluate the performance of the proposed carrier phase adjustment scheme and compare it to that of the no carrier phase adjustment case for QPSK and 8PSK with 2-4 users, and subsequently show that the proposed scheme significantly reduces the error probability in a multiuser communication system having MPR capability.