Abstract
Drastic improvements in transmission rate and system capacity are required towards 5th generation mobile communications (5G). One promising approach, utilizing the millimeter wave band for its rich spectrum resources, suffers area coverage shortfalls due to its large propagation loss. Fortunately, massive multiple-input multiple-output (MIMO) can offset this shortfall as well as offer high order spatial multiplexing gain. Multiuser MIMO is also effective in further enhancing system capacity by multiplexing spatially de-correlated users. However, the transmission performance of multiuser MIMO is strongly degraded by channel time variation, which causes inter-user interference since null steering must be performed at the transmitter. This paper first addresses the effectiveness of multiuser massive MIMO transmission that exploits the first eigenmode for each user. In Line-of-Sight (LoS) dominant channel environments, the first eigenmode is chiefly formed by the LoS component, which is highly correlated with user movement. Therefore, the first eigenmode provided by a large antenna array can improve the robustness against the channel time variation. In addition, we propose a simplified beamforming scheme based on high efficient channel state information (CSI) estimation that extracts the LoS component. We also show that this approximate beamforming can achieve throughput performance comparable to that of the rigorous first eigenmode transmission. Our proposed multiuser massive MIMO scheme can open the door for practical millimeter wave communication with enhanced system capacity.
Highlights
The rapid diffusion of smartphones has triggered extensive diversification in mobile services. is data traffic exploding, and terminals are crowding public sites such as stations, airports and event venues
We focus on multiuser massive multiple-input multiple-output (MIMO) with only 1st eigenmode transmission to each user equipments (UEs) to achieve stable and high transmission capacity, even in high mobility situations
This paper verified the effectiveness of 1st eigenmode transmission in multiuser massive MIMO
Summary
The rapid diffusion of smartphones has triggered extensive diversification in mobile services. is data traffic exploding, and terminals are crowding public sites such as stations, airports and event venues. The rapid diffusion of smartphones has triggered extensive diversification in mobile services. Existing frequency resources are depleted, especially in the microwave band, since many kinds of wireless communication systems such as wireless fidelity (Wi-Fi), worldwide interoperability for microwave access (WiMAX) or long-term evolution (LTE). Overcoming this shortfall is a critical issue in wireless communication. Drastic improvements of transmission rate and system capacity are required towards 5th generation mobile communications (5G) [1]. Promising solutions are to exploit millimeter wave bands for their rich spectrum resources and shrinking the cell size for improved area spectral efficiency [2,3]. The main problem with using the millimeter wave band is its link budget shortfall
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