Joint fronthaul link selection and transmit precoding for energy efficiency maximization of multiuser MIMO-aided distributed antenna systems

Abstract

We jointly select the fronthaul links and optimize the transmit precoding matrices for maximizing the energy efficiency of a multiuser multiple-input multiple-output aided distributed antenna system . The fronthaul link’s power consumption is taken into consideration, which is assumed to be proportional to the number of active fronthaul links quantified by using indicator functions. Both the rate requirements and the power constraints of the remote access units are considered. Under realistic power constraints some of the users cannot be admitted. Hence, we formulate a two-stage optimization problem. In Stage I, a novel user selection method is proposed for determining the maximum number of admitted users. In Stage II, we deal with the energy efficiency optimization problem. First, the indicator function is approximated by a smooth concave logarithmic function. Then, a triple-layer iterative algorithm is proposed for solving the approximated energy efficiency optimization problem, which is proved to converge to the Karush-Kuhn-Tucker conditions of the smoothened energy efficiency optimization problem. To further reduce the complexity, a single-layer iterative algorithm is conceived, which guarantees convergence. Our simulation results show that the proposed user selection algorithm approaches the performance of the exhaustive search method. Finally, the proposed algorithms is capable of achieving an order of magni- tude higher energy efficiency than its conventional counterpart operating without considering link selection.

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ORCID for Lajos Hanzo: orcid.org/0000-0002-2636-5214

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