Link adaptation in LTE-A uplink with Turbo SIC receivers and imperfect channel estimation.
ABSTRACT In this paper, we propose an efficient link adaptation scheme for the 3GPP Long Term Evolution Advanced (LTEA) uplink with turbo successive interference cancelation (Turbo-SIC) receiver and imperfect channel estimation. Link adaptation for non-linear MIMO receivers such as Turbo SIC is not straightforward because the soft-outputs of such receiver cannot be simply modeled using a scalar Gaussian channel and the post-processing signal-to-interference-plus-noise ratio (SINR) does not have an explicit closed-form expression. In addition, the lack of perfect channel state information due to estimation errors imposes further uncertainty and challenges in the link adaptation design. To circumvent these difficulties, we propose a prediction method that can effectively characterize the Turbo SIC performance and derive an approximate post-detection SINR for each layer by considering the channel estimation error statistic. We particularly consider the link adaptation for precoded multi-rank MIMO transmission with both inter-codeword(CW) and intra-codeword(CW) interference cancelation. Realistic and extensive simulations reveal that the proposed link adaptation scheme accurately predicts the turbo SIC performance and results in highest spectrum efficiency and robustness compared to other competing schemes.
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Conference Paper: Turbo Receivers for Single User MIMO LTE-A Uplink[Show abstract] [Hide abstract]
ABSTRACT: The paper deals with turbo detection techniques for Single User Multiple-Input-Multiple-Output (SU MIMO) antenna schemes. The context is on the uplink of the upcoming Long Term Evolution - Advanced (LTE-A) systems. Iterative approaches based on Parallel Interference Cancellation (PIC) and Successive Interference Cancellation (SIC) are investigated, and a low-complexity solution allowing to combine interstream interference cancellation and noise enhancement reduction is proposed. Performance is evaluated for Orthogonal Frequency Division Multiplexing (OFDM) and Single Carrier Frequency Division Multiplexing (SC-FDM) as candidate uplink modulation schemes for LTE-A. Simulation results show that, in a 2times2 antenna configuration, the turbo processing allows a consistent improvement of the link performance, being SC-FDM the one having higher relative gain with respect to linear detection. The turbo receiver's impact is however much reduced for both modulation schemes in a 2times4 configuration, due to the higher diversity gain provided by the additional receive antennas.Vehicular Technology Conference, 2009. VTC Spring 2009. IEEE 69th; 05/2009
Conference Paper: Design of high performance MIMO receivers for LTE/LTE-A uplink[Show abstract] [Hide abstract]
ABSTRACT: In this paper we design high performance multiple-input-multiple-output (MIMO) receivers for the DFT-Spread-OFDM based long term evolution (LTE) cellular uplink. In the LTE uplink multiple single-antenna users can be scheduled on the same time-frequency resource block via space division multiple access. The designed receivers are also applicable to the LTE-Advanced cellular uplink wherein simultaneous transmission of multiple streams by a single user will be possible. Two types of advanced non-linear receivers are considered and optimized, namely, a receiver based on a two-symbol max-log soft-output demodulator (two-symbol MLD) and a turbo minimum mean squared error successive interference cancelation (turbo MMSE-SIC) receiver. Based on extensive simulations, it is shown that both the two-symbol MLD and the turbo MMSE-SIC receivers exhibit superior performance compared to the conventional linear MMSE (LMMSE) receiver. In general, the turbo MMSE-SIC receiver is robust to timing offsets and offers the best performance but also introduces larger latency and higher computational complexity. Upon employing a proposed new pairing method, the two-symbol MLD based receiver is also found to yield a good performance that is robust to timing offsets and which entails a moderate complexity and latency.Signals, Systems and Computers (ASILOMAR), 2010 Conference Record of the Forty Fourth Asilomar Conference on; 12/2010
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ABSTRACT: We consider the design of a block equalizer for an intersymbol interference channel, given that the channel impulse response is not perfectly known at the receiver. In contrast to other schemes, our receiver is designed for imperfect channel state information and incorporates the statistics of the channel estimation error. In particular, we suggest an error model for data transmission that takes the influence from the data symbols on the estimation noise into account. We derive the optimum detection rule for the considered error model according to the maximum likelihood criterion and verify that the covariance matrix of the estimation noise depends on the actual transmitted data symbols. Motivated by this result, we propose a realizable receiver structure adopting the turbo principle that exploits the data-dependency of the covariance matrix of the estimation noise. The proposed scheme outperforms conventional receivers that neglect the exact statistics of the estimation noise. The core of our receiver is a soft-input soft-output block equalizer based on constrained minimum variance filter design. We assess the performance of the proposed turbo equalization scheme for block Rayleigh fading channels, applying both one-shot training-based channel estimation and iterative data-aided channel estimationIEEE Transactions on Wireless Communications 02/2007; · 2.42 Impact Factor