Abstract
Abstract 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 compound signals from multiple transmitters more separable on its constellation at the receiver by coordinating both the transmit power level and carrier phase offsets of the transmitters. In this article, we propose a feedback-based transmit power and carrier phase adjustment scheme that estimates the symbol energy and the carrier phase offset for each transmitter’s received signal, computes the optimal received power level and carrier phase shift to maximize the minimum Euclidean distance between the constellation points, and finally feeds the optimal transmit power level and phase shift information back to the transmitters. We then evaluate the performance of the proposed transmit power and carrier phase adjustment scheme and subsequently show that the proposed scheme significantly reduces the error probability in a multiuser communication system having MPR capability.
Highlights
In conventional wireless networks, each receiver is only capable of decoding signals from one transmitter at a time; referred to as single-user detection (SUD)
We subsequently evaluate the performance of the proposed transmit power level and carrier phase adjustment scheme and compare it to that of the no adjustment case for QPSK and 8PSK with 2–4 transmitters
3.2 Transmit power level and carrier phase offset for multiple transmitters We propose an optimization-based approach for deriving the optimal transmit power levels and carrier phase offsets for multiple transmitters
Summary
Each receiver is only capable of decoding signals from one transmitter at a time; referred to as single-user detection (SUD). We consider the coordination of the transmitters’ carrier phase offsets and their transmit power levels In this system, a receiver with MPR capability performs multiuser detection and estimates the symbol energy and the carrier phase offset for each transmitter’s signal from the compound signals. To determine the optimal transmit power level and carrier phase shift, we formulate an optimization problem in order to maximize the minimum Euclidean distance between the constellation coordinates of the compound signals. The network capacity in the multiuser communication system is not maximized, since the error probability of multiple signals is increased according to the short minimum Euclidean distance To overcome this problem, the Euclidean distances between constellation points at the receiver side should be kept as large as possible by adjusting the carrier phase offsets at the transmitter side. This condition implies that the transmit power levels for simultaneously transmitting users should be properly coordinated to ensure performance improvements in MPR communication systems
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