DocumentCode :
1305375
Title :
An Accurate Model for EESM and its Application to Analysis of CQI Feedback Schemes and Scheduling in LTE
Author :
Donthi, Sushruth N. ; Mehta, Neelesh B.
Author_Institution :
Broadcom Corp., Bangalore, India
Volume :
10
Issue :
10
fYear :
2011
fDate :
10/1/2011 12:00:00 AM
Firstpage :
3436
Lastpage :
3448
Abstract :
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.
Keywords :
Long Term Evolution; OFDM modulation; Rayleigh channels; log normal distribution; CQI feedback schemes; LTE; Long Term Evolution; OFDM based wireless systems; Rayleigh distributed channel; base station; channel quality indicator; codeword error rate; downlink rate adaptation; effective exponential SNR mapping; feedback averaging; feedback scheduling; flat-fading gain; link adaptation; lognormal random variable; multiple antenna mode; multiple subchannels; next generation orthogonal frequency division multiplexing; probability distribution; subchannel gains; Adaptation models; Analytical models; Bandwidth; Downlink; Frequency domain analysis; OFDM; Signal to noise ratio; Effective exponential SNR mapping (EESM); adaptive modulation and coding; channel quality feedback; frequency-domain scheduling; lognormal random variable; long term evolution (LTE); multiple antenna diversity; orthogonal frequency division multiplexing (OFDM);
fLanguage :
English
Journal_Title :
Wireless Communications, IEEE Transactions on
Publisher :
ieee
ISSN :
1536-1276
Type :
jour
DOI :
10.1109/TWC.2011.081011.102247
Filename :
5995298
Link To Document :
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