Abstract
In next-generation radio communication systems, the use of higher frequency bands and the massive multiple-input-multiple-output (MIMO) systems has turned into hot research topics because they have the potential to increase network capacity significantly by exploiting the available narrowband and broadband spectrums. Therefore, the narrowband channel measurements are executed at the following five potential frequency bands, including 2.6 GHz, 3.5 GHz, 5.6 GHz, 10 GHz, and 28 GHz in the Shanghai subway tunnel environment in order to fulfill the latest standards of fifth generation (5G). Moreover, in the broadband channel measurements, the center frequency is 3.5 GHz and 5.6 GHz and the bandwidth is considered as 160 MHz, respectively. At the transmitter (Tx) side, a uniform rectangular antenna array composed of 32 elements is fixed on the platform near the tunnel walls. The receiver (Rx) is equipped with a uniform cylindrical antenna array consisting of 64 elements, which is set on a trolley along the track. Based on the acquired massive MIMO channel impulse responses, delay spread, angle spread, eigenvalue and channel capacity are analyzed. The results reveal that the multipath delay in the tunnel scenario is quite short, the delay spread and angle spread drop rapidly as the distance between Tx and Rx increases and the channel matrix gradually becomes serious. This research provides a reference for the deployment of future 5G systems in the subway tunnel.
Highlights
In recent years, in order to ensure the safety and efficiency of train operations, it is necessary to transmit data such as ultra-high-definition video stream monitoring, train operation control, and on-board sensing at a high rate and high reliability between train and ground, which has created an urgent need for the application and deployment of 5G in subway communications. e characteristics of the wireless propagation channel determine the final performance of the wireless communication system. erefore, it is very important to detect the actual performance of wireless propagation channels in a real tunnel environment
Based on the collected data, we modeled the path loss parameters and analyzed the power delay profile (PDP), root-mean-square delay spread (RMSDS), root-mean-square angle spread (RMS-AS), eigenvalue, and channel capacity
In order to explore the deployment prospects of massive MIMO in subway tunnel scenarios, we focus on the influence of the Tx-Rx distance and the number of transmitting antenna elements on the channel capacity
Summary
In order to ensure the safety and efficiency of train operations, it is necessary to transmit data such as ultra-high-definition video stream monitoring, train operation control, and on-board sensing at a high rate and high reliability between train and ground, which has created an urgent need for the application and deployment of 5G in subway communications. e characteristics of the wireless propagation channel determine the final performance of the wireless communication system. erefore, it is very important to detect the actual performance of wireless propagation channels in a real tunnel environment. On the basis of channel measurements in a subway tunnel, the influence of polarization diversity, International Journal of Antennas and Propagation space diversity, and cross section of the tunnel on the capacity of MIMO channel capacity is considered in [3,4,5,6], which provides suggestions for the design of the MIMO system in tunnel scenario. It is pointed out that the increment of the cross-sectional area improves the MIMO channel performance through measurements conducted in a two-section tunnel-like environment in [7]. To the best of the authors’ knowledge, the current MIMO antenna system used for channel measurements in real tunnel scenarios does not exceed 4×4 and the research on the long-distance train-to-ground communication system in actual subway tunnel scenarios is lacking.
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