Abstract
Propagation measurements of wireless channels performed in the tunnel environments at 6 GHz are presented in this paper. Propagation characteristics are simulated and analyzed based on the method of shooting and bouncing ray tracing/image (SBR/IM). A good agreement is achieved between the measured results and simulated results, so the correctness of SBR/IM method has been validated. The measured results and simulated results are analyzed in terms of path loss models, received power, root mean square (RMS) delay spread, Ricean K-factor, and angle of arrival (AOA). The omnidirectional path loss models are characterized based on close-in (CI) free-space reference distance model and the alpha-beta-gamma (ABG) model. Path loss exponents (PLEs) are 1.50–1.74 in line-of-sight (LOS) scenarios and 2.18–2.20 in non-line-of-sight (NLOS) scenarios. Results show that CI model with the reference distance of 1 m provides more accuracy and stability in tunnel scenarios. The RMS delay spread values vary between 2.77 ns and 18.76 ns. Specially, the Poisson distribution best fits the measured data of RMS delay spreads for LOS scenarios and the Gaussian distribution best fits the measured data of RMS delay spreads for NLOS scenarios. Moreover, the normal distribution provides good fits to the Ricean K-factor. The analysis of the abovementioned results from channel measurements and simulations may be utilized for the design of wireless communications of future 5G radio systems at 6 GHz.
Highlights
The generation (5G) of wireless communications will use systems operating from 500 MHz to 300 GHz [1, 2]
The values of Path loss exponents (PLEs) are identical for measured CI-opt models in both LOS-2 and LOS-3 paths. These results indicate that the values of PLE are less than the free-space PLE (n = 2), implying that the multipath components (MPCs) from both side walls and floor add up constructively in the tunnel environments, as a guided wave phenomenon
They could be attributed to scattering by small objects within the tunnel scenarios and are not expected to influence the performance of wireless communication system
Summary
The generation (5G) of wireless communications will use systems operating from 500 MHz to 300 GHz [1, 2]. Many extensive EHF wireless channel measurement campaigns have been investigated for different scenarios in multiple outdoor and indoor environments, yielding empirically based path loss models and delay dispersion properties. A large number of channel-measured results can provide reliable channel model, the expense of highprecision measurement equipment is very high and the number of observation points is limited in measurement campaigns, which are both great challenges for channel sounding As an another approach, the shooting and bouncing ray-tracing/image (SBR/IM) method [33] is an effective method, which can extend the sparse empirical datasets and can be utilized to investigate the propagation characteristics of EHF bands.
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