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An Accurate Model for EESM and its Application to Analysis of CQI Feedback Schemes and Scheduling in LTE

Donthi, Sushruth N and Neelesh, Mehta B (2011) An Accurate Model for EESM and its Application to Analysis of CQI Feedback Schemes and Scheduling in LTE. In: IEEE Transactions on Wireless Communications, 10 (10). pp. 3436-3448.

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The Effective Exponential SNR Mapping (EESM) is an indispensable tool for analyzing and simulating next generation orthogonal frequency division multiplexing (OFDM) based wireless systems. It converts the different gains of multiple subchannels, over which a codeword is transmitted, into a single effective flat-fading gain with the same codeword error rate. It facilitates link adaptation by helping each user to compute an accurate channel quality indicator (CQI), which is fed back to the base station to enable downlink rate adaptation and scheduling. However, the highly non-linear nature of EESM makes a performance analysis of adaptation and scheduling difficult; even the probability distribution of EESM is not known in closed-form. This paper shows that EESM can be accurately modeled as a lognormal random variable when the subchannel gains are Rayleigh distributed. The model is also valid when the subchannel gains are correlated in frequency or space. With some simplifying assumptions, the paper then develops a novel analysis of the performance of LTE's two CQI feedback schemes that use EESM to generate CQI. The comprehensive model and analysis quantify the joint effect of several critical components such as scheduler, multiple antenna mode, CQI feedback scheme, and EESM-based feedback averaging on the overall system throughput.

Item Type: Journal Article
Publication: IEEE Transactions on Wireless Communications
Publisher: IEEE
Additional Information: Copyright 2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: Effective exponential SNR mapping (EESM);long term evolution (LTE);orthogonal frequency division multiplexing (OFDM);channel quality feedback;multiple antenna diversity; frequency-domain scheduling;adaptive modulation and coding; lognormal random variable.
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 29 Dec 2011 05:15
Last Modified: 29 Dec 2011 05:15
URI: http://eprints.iisc.ac.in/id/eprint/42789

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