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An adaptive modulation scheme for two-user fading MAC with quantized fade state feedback

Kundu, Sudipta and Rajan, Sundar B (2012) An adaptive modulation scheme for two-user fading MAC with quantized fade state feedback. In: 2012 IEEE 23rd International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), 9-12 Sept. 2012, Sydney, NSW.

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Official URL: http://dx.doi.org/10.1109/PIMRC.2012.6362839


For transmission over the two-user Gaussian Multiple Access Channel with fading and finite constellation at the inputs, we propose a scheme which uses only quantized knowledge of fade state at users with the feedback overhead being nominal. One of the users rotates its constellation without varying the transmit power to adapt to the existing channel conditions, in order to meet certain pre-determined minimum Euclidean distance requirement in the equivalent constellation at the destination. The optimal modulation scheme has been described for the case when both the users use symmetric M-PSK constellations at the input, where M = 2λ, λ being a positive integer. The strategy has been illustrated by considering examples where both the users use QPSK signal set at the input. It is shown that the proposed scheme has considerable better error performance compared to the conventional non-adaptive scheme, at the cost of a feedback overhead of just [log2 (M2/8 - M/4 + 2)] + 1 bits, for the M-PSK case.

Item Type: Conference Paper
Publisher: IEEE
Additional Information: Copyright of this article belongs to IEEE.
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 13 Dec 2013 15:19
Last Modified: 13 Dec 2013 15:19
URI: http://eprints.iisc.ac.in/id/eprint/47922

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