Article

# 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: 2.81). 02/2012; DOI: 10.1109/TSP.2011.2169059 Source: IEEE Xplore

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**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. · 1.67 Impact Factor -
##### Article: Doubly-Selective Channel Estimation Using Superimposed Training and Weighted First-Order Statistics

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**ABSTRACT:**Doubly-selective channel estimation using superimposed training and complex exponential basis expansion model is considered. By taking a weighted averaging operation of the received data, a weighted first-order statistical estimator is proposed, where the time-varying channel estimation is reduced to the simple average-based solution of time-invariant coefficients and the dominant effect of information-induced interference on channel estimation can be suppressed. To further improve the estimation performance with a limited training power, a joint iterative channel estimation and symbol detection scheme is developed where the detected symbol is exploited to enhance estimation performance instead of being viewed as interference. Theoretical analysis and simulation results show that the proposed scheme is superior to data-dependent superimposed training scheme and competitive with the conventional time-multiplexed training in terms of symbol error rate over doubly-selective channels.Wireless Personal Communications 12/2013; · 0.43 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. · 0.43 Impact Factor

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