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A hybrid joint ML technique for CFO, timing offset, and channel estimations in an OFDMA uplink
Author(s) -
Thafasal Ijyas V.P.,
Sameer S.M.
Publication year - 2014
Publication title -
international journal of communication systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.344
H-Index - 49
eISSN - 1099-1131
pISSN - 1074-5351
DOI - 10.1002/dac.2396
Subject(s) - telecommunications link , computer science , carrier frequency offset , subcarrier , orthogonal frequency division multiple access , estimator , channel (broadcasting) , frequency division multiple access , orthogonal frequency division multiplexing , base station , algorithm , offset (computer science) , user equipment , joint (building) , real time computing , computer network , frequency offset , mathematics , statistics , engineering , architectural engineering , programming language
SUMMARY In this paper, we propose a novel hybrid joint maximum‐likelihood estimator for carrier frequency offset (CFO), timing offset, and channel response of all users in the uplink of an orthogonal frequency division multiple access (OFDMA) system. The proposed estimation method significantly reduces complexity of this multiparameter, multidimensional optimization problem, using the concept of separation of the different user signals by means of newly defined projection operators. This projection technique is combined with the alternating projection method available in the literature to arrive at a new hybrid algorithm that offers significant performance advantages in terms of computational complexity and estimator performance. The joint estimation of the CFOs, timing offsets, and channel coefficients for all active users together at the base station of the OFDMA uplink is a rarely addressed task. The proposed method also offers the flexibility of application to any subcarrier assignment scheme used in OFDMA systems. Extensive simulation studies corroborate the advantages of the new hybrid method for all three estimation requirements in the multiuser OFDMA uplink. Copyright © 2012 John Wiley & Sons, Ltd.