WLC42-6: Non-Linear Precoding for OFDM Systems in Spatially-Correlated Frequency-Selective Fading MIMO Channels

Abstract

This paper presents non-linear precoding design in closed-loop multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) over spatiallycorrelated, frequency-selective fading channels. Our analysis takes into consideration receiver channel mismatch due to imperfect channel estimates, and transmitter channel mismatch due to estimation errors, channel variations over feedback delay and feedback noise. We present a general spatially-correlated, frequency-selective fading MIMO channel model and derive the conditional means of the channel response. Exploiting the channel statistics, which are only available at the receiver, we design new non-linear zero-forcing (ZF) Tomlinson-Harashima precoding (THP) for uncoded MIMO OFDM. The channel statistics do not need to be sent back to the transmitter, which avoids the possible maximum-Doppler-shift transmitter mismatch. Our proposed precoders are robust against time variations, channel estimation errors and antenna correlations, and offer a significant system performance gain over conventional THP.

Tomlinson-Harashima Precoding for Multiuser MIMO Downlink with Imperfect Channel State Information

“…The THP design with perfect CSI and the conventional THP design with imperfect CSI are also included for comparison. For the conventional THP design, the BS considers Ĥ as equivalent channel of H , and then the THP filters are given by (6)- (9), where the H in them is substituted by Ĥ and the matrix Ĥ is reshaped from the vector ĥ . Fig.…”

“…Bizaki [8] optimized THP filters together with the channel estimation to find spatial power loading in broadcast channels. For spatially correlated single user MIMO fading channels, a new ZF THP optimization was presented to against channel estimation errors and antenna correlation [9].…”

“…Hence, it is more realistic to assume that the transmitter only has imperfect CSI. Bayes' theorem using conditional estimation has been applied to incorporate imperfect CSI into THP design [6][7][8][9]. In spatially uncorrelated channels, Hunger [6] firstly proposed a robust THP design based on zero-forcing (ZF) criterion in broadcast channels assuming erroneous CSI.…”

Irregular Sampling of GPS Signal for Real-Time Implementation of Pipelined PFFT

“…To reduce multipliers used in FFT arithmetic, we propose an efficient irregular sampling method for no-multipliers assembly line PFFT architecture [4] based on parallel distributed arithmetic. The architecture takes lookup table as the basic computing unit, and real-time decimal point and prime number point DFT models as basic block.…”

Precoding for Multiuser Orthogonal Space-Time Block-Coded OFDM: Mean or Covariance Feedback?

“…The conditional means H u|Tu [k, i] and H u|Ru [k, i] can be described as equivalent channels exploiting the channel statistics and uncertainty structure to mitigate the impact of imperfect CSI at the BS and the receivers [12]. The covariances C u|Tu and C u|Ru indicate the CSI at the transmitter (CSIT) and CSI at the receiver (CSIR) uncertainty given by the equivalent channels, respectively.…”