Abstract
This letter focuses on the spectrum efficiency (SE) and energy efficiency (EE) of $K$ -tier heterogeneous networks (HetNets), in which massive multiple-input multiple-output (MIMO) is employed in the macro cells. We consider the impact of massive MIMO on flexible cell association. We develop an analytical approach to examine SE and EE of HetNets. We confirm that using flexible cell association can improve the EE of HetNets by offloading data traffic to small cell. This is due to an increase of EE in the macro cell. Moreover, we show that serving moderate number of users in the macro cells with massive MIMO can boost both SE and EE.
Highlights
A LTHOUGH there is no preliminary 5G standard yet, heterogeneous networks (HetNets) and massive multipleinput multiple-output (MIMO) are two key enablers for 5G [1], [2]
Different from the aforementioned literature, we focus on the spectrum efficiency (SE) and EE in K-tier massive MIMO aided HetNets, where the massive MIMO macro cell BS adopts linear zero-forcing beamforming (ZFBF) to serve multiple users over the same time and frequency band
We assume that the first tier represents the class of macro cell base stations (MBSs), where each MBS is equipped with a large antenna array
Summary
A LTHOUGH there is no preliminary 5G standard yet, heterogeneous networks (HetNets) and massive multipleinput multiple-output (MIMO) are two key enablers for 5G [1], [2]. The deployment of small cells improves the coverage and spectrum efficiency (SE), since the mobile devices are closer to the base stations. In [6], inter-tier interference coordination was considered for throughput improvement in HetNets with massive MIMO. Different from the aforementioned literature, we focus on the SE and EE in K-tier massive MIMO aided HetNets, where the massive MIMO macro cell BS adopts linear zero-forcing beamforming (ZFBF) to serve multiple users over the same time and frequency band. We study the impact of massive MIMO on the user association, and consider flexible cell association that allows tier selection for cell load balancing, and potential SE and EE improvement.
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