Low Complexity Adaptive Channel Estimation and QR Decomposition for an LTE-A Downlink

This paper presents a link adaptive processor to perform low-complexity channel estimation and QR decomposition (QRD) in Long Term Evolution-Advanced (LTE-A) receivers. The processor utilizes frequency domain correlation of the propagation channel to adaptively avoid unnecessary computations in the received signal processing, achieving significant complexity reduction with negligible performance loss. More specifically, a windowed Discrete Fourier transform (DFT) algorithm is used to detect channel conditions and to compute a minimum number of sparse subcarrier channel estimates required for low complexity linear QRD interpolation. Furthermore, the sparsity of subcarrier channel estimates can be adaptively changed to handle different channel conditions. Simulation results demonstrate a reduction of 40%-80% in computational complexity for different channel models specified in the LTE-A standard.