A Novel Power Allocation Scheme for Two-User GMAC with Finite Input Constellations

Harshan, J and Rajan, Sundar B (2013) A Novel Power Allocation Scheme for Two-User GMAC with Finite Input Constellations. In: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, 12 (2). pp. 818-827.

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Abstract

Constellation Constrained (CC) capacity regions of two-user Gaussian Multiple Access Channels (GMAC) have been recently reported, wherein an appropriate angle of rotation between the constellations of the two users is shown to enlarge the CC capacity region. We refer to such a scheme as the Constellation Rotation (CR) scheme. In this paper, we propose a novel scheme called the Constellation Power Allocation (CPA) scheme, wherein the instantaneous transmit power of the two users are varied by maintaining their average power constraints. We show that the CPA scheme offers CC sum capacities equal (at low SNR values) or close (at high SNR values) to those offered by the CR scheme with reduced decoding complexity for QAM constellations. We study the robustness of the CPA scheme for random phase offsets in the channel and unequal average power constraints for the two users. With random phase offsets in the channel, we show that the CC sum capacity offered by the CPA scheme is more than the CR scheme at high SNR values. With unequal average power constraints, we show that the CPA scheme provides maximum gain when the power levels are close, and the advantage diminishes with the increase in the power difference.

Item Type:	Journal Article
Publication:	IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS
Publisher:	IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Additional Information:	Copyright for this article belongs to the IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, USA.
Keywords:	Constellation constrained capacity regions; multiple access channels; power allocation; finite constellations
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	15 Apr 2013 11:42
Last Modified:	15 Apr 2013 11:42
URI:	http://eprints.iisc.ac.in/id/eprint/46401

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