A novel power allocation scheme for two-user GMAC with finite input constellations

Harshan, J. ; Sundar Rajan, B. (2013) A novel power allocation scheme for two-user GMAC with finite input constellations IEEE Transactions on Wireless Communications, 12 (2). pp. 818-827. ISSN 1536-1276

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Official URL: http://ieeexplore.ieee.org/document/6409503/

Related URL: http://dx.doi.org/10.1109/TWC.2012.122212.120324


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:Article
Source:Copyright of this article belongs to Institute of Electrical and Electronics Engineers.
Keywords:Finite Constellations; Constellation Constrained Capacity Regions; Multiple Access Channels; Power Allocation
ID Code:107724
Deposited On:08 Dec 2017 10:12
Last Modified:08 Dec 2017 10:12

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