Abstract
Due to the dramatic increase in wireless data traffic and the associated increase in energy consumption, designing energy-efficient wireless networks with improved spectral efficiency is a pressing concern. The focus of this article is the design of a green, highly energy-efficient cellular heterogeneous network (HetNet) by taking advantage of multiple-input-multiple-output (MIMO) structure and deployment of small cells. We consider the downlink of a two-tier HetNet, in which multiple-antenna small cells are coordinated to serve users. Even though the deployment of MIMO together with small cells improves the communication system's performance in terms of data rate and reliability, circuit energy consumption in such a network is a critical issue. To address this, an energy-efficient antenna selection and radio resource block assignment algorithm is proposed for the small cells, and a single radio-frequency (RF) chain structure is considered for the massive MIMO macro base station. Then, while coordinating transmissions between cells subject to user-centric clustering, an energy-efficient beamforming design and power allocation optimization problem with respect to the quality of service requirement of users, transmit power budget of base stations, and fronthaul capacity is formulated; the problem is solved using the Dinkelbach method. Simulation results demonstrate the performance potential of our proposed algorithm in terms of energy efficiency and spectral efficiency.
Highlights
F IFTH GENERATION (5G) cellular systems are expected to answer increasing capacity demands and quality of service (QoS) requirements of mobile users
Block diagonalization (BD) has been widely used in related literature [65]–[67]; the same null-space projection technique has been used in [22], [27], [68] in the context of single-antenna users, as it is with our work
Since the exhaustive search complexity rapidly grows with the variables involved, we have considered a simpler network; besides the macro base stations (BSs), only 1 small cell (SC) BS equipped with 4 antennas is used, and 6 users (3 per BS) are served on 5 resource block (RB)
Summary
F IFTH GENERATION (5G) cellular systems are expected to answer increasing capacity demands and quality of service (QoS) requirements of mobile users. The authors of [36] have considered the problem of joint user association, carrier allocation, antenna selection, and power control in the uplink of a MIMO HetNet to maximize the data rate of small cell users, by imposing a maximum threshold on the cross-tier interference. We consider energy-efficient user-centric clustering and CoMP precoding is performed at both the macro cell and SCs. Second, radio resources (i.e., RBs and power) should be optimally allocated to maximize EE. The authors of [52] have examined a user association optimization problem to maximize both EE and SE along with a heuristic solution method; they have assumed single-antenna In this CRAN-based network, there is a massive MIMO macro BS with NM antennas whose coverage is overlaid with several densely-deployed SC BSs each equipped with.
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