Abstract
We introduce the superimposed training strategy into the multiple-input multiple-output (MIMO) amplify-and-forward (AF) one-way relay network (OWRN) to perform the individual channel estimation at the destination. Through the superposition of a group of additional training vectors at the relay subject to power allocation, the separated estimates of the source-relay and relay-destination channels can be obtained directly at the destination, and the accordance with the two-hop AF strategy can be guaranteed at the same time. The closed-form Bayesian Cramér-Rao lower bound (CRLB) is derived for the estimation of two sets of flat-fading MIMO channel under random channel parameters and further exploited to design the optimal training vectors. A specific suboptimal channel estimation algorithm is applied in the MIMO AF OWRN using the optimal training sequences, and the normalized mean square error performance for the estimation is provided to verify the Bayesian CRLB results.
Highlights
In recent years, the use of relays has gained significant interest for the advantage of enhancing link reliability and increasing channel capacity in a wireless network
For Multiple-input multiple-output (MIMO) relay channels where every terminal in the wireless network can be deployed with multiple antennas, studies are mainly concentrated on spatial multiplexing (SM) systems
For many practical estimation problems, popular estimators such as the maximum likelihood (ML) estimator or the maximum a posteriori (MAP) estimator are infeasible, so one has to resort to suboptimal estimators, which are typically evaluated by determining mean square error (MSE) through simulations and by comparing this error to theoretical performance bounds
Summary
The use of relays has gained significant interest for the advantage of enhancing link reliability and increasing channel capacity in a wireless network. In relay beamforming schemes [13, 14], especially in noncoherent MIMO relay networks, where the optimization process is performed at the destination [7], the individual CSIs are utilized to design the optimal amplifying matrix at the relay and the power allocation between the source and relay so as to maximize the instantaneous capacity of the two-hop MIMO AF relay system. In a practical scenario, it is important to design a MIMO relay scheme that provides both in accordance with the two-hop data transmission and the estimates of individual channels at the destination.
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