Low Complexity Turbo Receiver for LTE Uplink with Transmitter IQ Imbalance

Rui LIU  Lv DING  Xi Qi GAO  

IEICE TRANSACTIONS on Communications   Vol.E95-B   No.3   pp.913-923
Publication Date: 2012/03/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E95.B.913
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
LTE,  SC-FDMA,  Tx IQI,  MMSE,  turbo equalization,  EXIT chart,  

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In this paper, we investigate two improved turbo receivers for the Long Term Evolution (LTE) uplink in the presence of transmitter (Tx) in-phase and quadrature-phase imbalance (IQI) with parameters known at eNodeB. For multiuser multiple-input multiple-output (MU-MIMO) single-carrier frequency division multiple access (SC-FDMA) systems, we derive a optimal joint linear minimum mean square error (MMSE) turbo multiuser detector (MUD) based on the mirror symmetry clusters. For the single use SC-FDMA system with Tx IQI, we derive an optimal widely linear MMSE (WLMMSE) turbo equalizer. Both receivers are implemented in the discrete frequency domain and only slightly increase the computational complexity compared to the conventional turbo receivers. Monte Carlo simulations show that the proposed receivers significantly outperform the conventional turbo receivers. The simulation results are then confirmed by the extrinsic information transfer (EXIT) chart analysis.