Superimposed Training-Based Channel Estimation and Data Detection for OFDM Amplify-and-Forward Cooperative Systems Under High Mobility

Dept. of Electr. & Electron. Eng., Univ. of Hong Kong, Hong Kong, China
IEEE Transactions on Signal Processing (Impact Factor: 3.2). 02/2012; DOI: 10.1109/TSP.2011.2169059
Source: IEEE Xplore

ABSTRACT In this paper, joint channel estimation and data detection in orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) cooperative systems under high mobility is investigated. Unlike previous works on cooperative systems in which a number of subcarriers are solely occupied by pilots, partial data-dependent superimposed training (PDDST) is considered here, thus preserving the spectral efficiency. First, a closed-form channel estimator is developed based on the least squares (LS) method with Tikhonov regularization and a corresponding data detection algorithm is proposed using the linear minimum mean square error (LMMSE) criterion. In the derived channel estimator, the unknown data is treated as part of the noise and the resulting data detection may not meet the required performance. To address this issue, an iterative method based on the variational inference approach is derived to improve performance. Simulation results show that the data detection performance of the proposed iterative algorithm initialized by the LMMSE data detector is close to the ideal case with perfect channel state information.

  • [Show abstract] [Hide abstract]
    ABSTRACT: In amplify-and-forward (AF) type relaying assisted orthogonal frequency division multiplexing (OFDM) systems, channel estimation (CE) is a challenging task due to the increased frequency selectivity caused by the cascaded source-to-relay-to-destination $(Srightarrow Rrightarrow D)$ multipath channel. Typically, such cascaded channels result in severe time dispersion. Consequently, it requires additional pilot overhead for CE as well as longer cyclic prefix (CP) for eliminating the inter-symbol interference (ISI), which will inevitably reduce the achievable diversity provided by cooperative transmissions. In this letter, a three-step CE scheme is proposed without the need of increasing pilot overhead. Furthermore, by reconstructing the CP at the relay node, the CP length does not necessarily need to be extended for the cascaded channel. Simulation results demonstrate the effectiveness of our proposed scheme even in severely time-dispersive multipath fading channels.
    IEEE Signal Processing Letters 10/2012; 19(10):651-654. · 1.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper a new combined time and channel estimation method for OFDM based multi-relay networks is proposed. Based on the channel statistics knowledge at the receiver, a maximum a posteriori estimate (MAP) of the channel impulse response is derived. Based on the channel estimate, we discern for the timing error. Computer simulations are presented to corroborate our analytical results.
    Wireless Personal Communications 03/2014; 75(1):593-600. · 0.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work presents a novel technique to enhance the robustness of space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) systems. The proposed system shapes the channel matrix of a frequency-selective fading channel into a piece-wise flat fading over each block of two adjacent subcarriers. Analytical and simulation results show that the proposed scheme substantially outperforms the conventional SFBC in frequency-selective fading channels which assumes that the channel parameters are equal over the duration of the codeword. Moreover, we demonstrate that the proposed system offers a superior performance in fast time-varying channels where the interference that results from the channel variations acts only as an additive noise. In addition to its superior performance, the proposed system has low computational complexity, because it is based on short block length Walsh Hadamard Transform (WHT).
    IEEE Transactions on Vehicular Technology 01/2014; · 2.64 Impact Factor

Full-text (2 Sources)

Available from
Nov 25, 2014