MIMO Two-Way Amplify-and-Forward Relaying with Imperfect Receiver CSI
IEEE Transactions on Vehicular Technology vol. 59, no. 9, pp. 4377-4387, Nov. 2010.
In this paper, we investigate the effects of channel estimation error at the receiver of multiple-input multiple-output amplify-and-forward two-way relaying. The estimation is conducted via training using known pilot symbols transmitted from the terminals, a method commonly referred to as pilot symbol-aided modulation. In this context, linear minimum-mean-square estimation of composite as well as individual channels is analyzed. We show that orthogonal pilots, i.e. pilot sequences that are orthogonal over the antenna arrays as well as over the communicating terminals, minimize the composite and individual mean-square errors. Using notions of worst-case noise, we obtain lower-bounds on the sum-rate of information transmission in both directions of the bi-directional relay link and show that the orthogonal pilots maximize this bound. Simulations reveal the sufficiency of minimal training and illustrate the effects of various system parameters.
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