Channel Estimation and Optimal Training Design for Amplify and Forward MIMO Relay Channel under Spatial Fading Correlation

Abstract

In this paper, we study the channel estimation problem for time division multiplex amplify-and-forward (AF) relay channels. Both the source and the destination and also the in-between relay node comprise multiple antennas, and there are spatial fading correlations in each hop. We first derive a linear minimum mean square error (LMMSE) channel estimator from a simple scenario where there are no correlations among the relay antennas to a more general scenario where the multiple relay antennas are also spatially correlated. And then we design the optimal training sequences by minimizing the mean square error (MSE). Also the impacts of spatial correlations, relay power gain and the number of relay antennas on the MSE are studied to some extent. It is proved that the channel estimation and optimal training sequences have nothing to do with the spatial correlation at the destination and the derived estimator and designed sequences can be directly extended to multi-hop relay channels. Simulations are conducted to corroborate the proposed studies.

Simultaneous estimation of multi-relay MIMO channels

“…Remark 3: The covariance matrix of the observation vector at all the receive antennas of the destination, Σ y defined in (7), is a function of the unknown channels from relays to destination,…”

“…Nevertheless, the proposed algorithm in [6] is based on the assumption that the overall CSI corresponding to source-relay-destination links is known at the destination. In [7], channel estimators and training sequence design guidelines are proposed for correlated single-relay MIMO cooperative networks. However, the approach in [7] is only capable of estimating a small portion of the cooperative network's CSI.…”

“…In [7], channel estimators and training sequence design guidelines are proposed for correlated single-relay MIMO cooperative networks. However, the approach in [7] is only capable of estimating a small portion of the cooperative network's CSI. As a result, the effect of the estimator in [7] on the performance of MIMO cooperative networks is not investigated.…”

“…However, the approach in [7] is only capable of estimating a small portion of the cooperative network's CSI. As a result, the effect of the estimator in [7] on the performance of MIMO cooperative networks is not investigated. Finally, in [8] and [9] the authors devise new channel estimators for full-duplex multirelay MIMO cooperative networks, i.e., where all nodes within the network can transmit and receive at the same time.…”

Channels and Parameters Acquisition in Cooperative OFDM Systems

“…Concerning the twoway relay proposed an estimator based on new training strategy to jointly estimate the channels and frequency offset. For MIMO relay channels (Pang et al 2010) derived the linear mean square error estimator and optimal training sequences to minimize the MSE. However to the best of our knowledge channel estimation for EF protocol that use Alamouti coding from the base station (BS) to relay node (RN), equalizes, amplifies the signals and then forward it to the UT has not been considered from the channel estimation point of view in the literature.…”