Abstract
Orthogonal frequency division multiplexing- (OFDM-) based amplify-and-forward (AF) cooperative communication is an effective way for single-antenna systems to exploit the spatial diversity gains in frequency-selective fading channels, but the receiver usually requires the knowledge of the channel state information to recover the transmitted signals. In this paper, a training-sequences-aided linear minimum mean square error (LMMSE) channel estimation method is proposed for OFDM-based cooperative diversity systems with multiple AF relays over frequency-selective fading channels. The mean square error (MSE) bound on the proposed method is derived and the optimal training scheme with respect to this bound is also given. By exploiting the optimal training scheme, an optimal low-rank LMMSE channel estimator is introduced to reduce the computational complexity of the proposed method via singular value decomposition. Furthermore, the Chu sequence is employed as the training sequence to implement the optimal training scheme with easy realization at the source terminal and reduced computational complexity at the relay terminals. The performance of the proposed low-complexity channel estimation method and the superiority of the derived optimal training scheme are verified through simulation results.
Highlights
Multiple-input multiple-output (MIMO) wireless communication systems have attracted considerable interest in the last few years for their advantages in improving the link reliability, as well as increasing the channel capacity [1, 2]
The performance of the proposed linear minimum mean square error (LMMSE) channel estimation method and the superiority of the derived optimal training scheme in the multiple AF-relays-assisted cooperative communication scenario are evaluated by computer simulations
We consider an OFDM cooperation system where each relay terminal utilizes the coding method as in [20] to perform distributed space-time coding (DSTC) in data transmission section. This type of DSTC is chosen because it obtains the optimal diversity-multiplexing gain (D-MG) performance of the considered orthogonal AF protocol, but other types of DSTC are applicable since we are only interested in the performance of the proposed channel estimation method
Summary
Multiple-input multiple-output (MIMO) wireless communication systems have attracted considerable interest in the last few years for their advantages in improving the link reliability, as well as increasing the channel capacity [1, 2]. It is not practical to equip multiple antennas at some terminals in wireless networks due to the cost and size limits. To overcome these limitations, the concept of cooperative diversity has been recently proposed for singleantenna systems to exploit the spatial diversity gains in wireless channels [3,4,5,6]. Utilizing the broadcasting nature of radio waves, the source terminal can cooperate with the relay terminals in information transport In this manner, the spatial diversity gains can be obtained even when a local antenna array is not available. In the DF scheme, the relay terminals first decode their received signals and forward them to the destination terminal. We focus our attention on the AF relay scheme in this paper
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