Abstract
This paper considers multiple-input multiple-output (MIMO) relay communication in multi-cellular (interference) systems in which MIMO source-destination pairs communicate simultaneously. It is assumed that due to severe attenuation and/or shadowing effects, communication links can be established only with the aid of a relay node. The aim is to minimize the maximal mean-square-error (MSE) among all the receiving nodes under constrained source and relay transmit powers. Both one- and two-way amplify-and-forward (AF) relaying mechanisms are considered. Since the exactly optimal solution for this practically appealing problem is intractable, we first propose optimizing the source, relay, and receiver matrices in an alternating fashion. Then we contrive a simplified semidefinite programming (SDP) solution based on the error covariance matrix decomposition technique, avoiding the high complexity of the iterative process. Numerical results reveal the effectiveness of the proposed schemes.
Highlights
Due to scarcity of frequency spectrum in practical wireless networks, multiple communicating pairs are motivated to share a common time-frequency channel to ensure efficient use of the available spectrum
To avoid the complexity of the iterative process, we extend the error covariance matrix decomposition technique applied to pointto-point multiple-input multiple-output (MIMO) relay systems in [18] to interference MIMO relay systems in this paper
We compare the performance of the proposed min-max MSE-based one-way algorithms with that of the sum-MSE minimization algorithm in [8] as well as the naive AF (NAF) approach in terms of the MSE normalized by the number of data streams (NMSE) with K = 3, Ns = 3, Nr = 9, and Nd = 3
Summary
Due to scarcity of frequency spectrum in practical wireless networks, multiple communicating pairs are motivated to share a common time-frequency channel to ensure efficient use of the available spectrum. Our aim is to minimize the maximal MSE among all the source-destination pairs yet satisfying the transmit power constraints at the source as well as the relay nodes To fulfill this aim, the following joint optimization problem is formulated: the matrix derivative formulas, the gradient ∇WHk (tr (Ek)) can be written as. For given source and receiver matrices {Bk} and {Wk}, the relay precoding matrix F optimization problem can be formulated as where (9b) and (9c), respectively, constrains the transmit power at the relay node and the kth transmitter to Pr > 0, Ps,k > 0. Tk tr INb,k + T H GHk Gk T −1 s.t. tr T T H ≤ Pr. Even given the structure, an analytical optimal solution to the joint optimization problem is still difficult to obtain due to the cross-link interference from the relay node to the destination nodes.
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