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The increases in power density and energy consumption of 5G telecommunication base stations make operation reliability and energy-efficiency more important. In this paper, a novel type of rack-level hybrid cooling system which combines a thermosyphon loop with a mechanical refrigeration loop was developed and applied in two parallel cabinets installed different operating powers of the communication equipment. Its performance was tested on-site in a real 5G telecommunication base station in transitional season at Wuhan city, China. Thermal safety and energy consumption under the normal and urgent operation modes were evaluated. The results showed that under the normal daily operation mode 1, communication equipment can be cooled effectively, but the power usage effectiveness value reached 1.59. Under the urgent mode 7, communication equipment can maintain safe operation for over 20 min. In view of this, five novel energy-saving operation modes 2–6 were proposed and tested. The cooling effect and energy consumption under different modes were analyzed and compared. Under the thermosyphon mode 6, the cooling system can only meet the cooling demand for one side of the cabinet when the outdoor temperature is around 20 °C. Compared to mode 1, mode 5 was recommended due to the 7–9 °C lower operating temperature and 27.3% decrease of energy consumption. • A novel hybrid cooling system was developed. • The operating thermal performance and energy consumption of the system applied in a real 5G TBS were investigated. • The performance of the cooling system was compared and analyzed. [ABSTRACT FROM AUTHOR]

Precise point positioning (PPP) is receiving increasing interest due to its cost-effectiveness, global coverage and high accuracy. However, its application in the urban environment is still full of challenges due to the satellite tracking sky-view. Thus, we presented a comprehensive positioning model by fusing the multi-GNSS (global navigation satellite system) combination, GNSS/INS (inertial navigation system) tightly coupled integration as well as the ionospheric and tropospheric augmentation in the undifferenced and uncombined PPP. The performance of this model in dual-frequency and single-frequency positioning was assessed with two experiments that denoted as T019 and T023, respectively, and both the experiments were carried out in a real urban environment. Particularly, the experiment T023 was carried out in the Second Ring Road of Wuhan city, which can be regarded as a typical downtown environment. Concerning the regional atmospheric augmentation, observations from 5 reference stations with an inter-station distance of about 40 km were also collected during the experimental time. The comparison between reference stations suggested that the regional tropospheric model had a precision of better than 0.6 cm in terms of zenith tropospheric delay, while the regional ionospheric model had a precision of around 0.5 total electron content unit in terms of Vertical Total Electron Content. It can be concluded that the GPS-only PPP can be improved significantly for urban vehicle navigation with these techniques, i.e., the multi-GNSS, INS tightly coupled integration and the atmospheric augmentation, through the positioning analysis, while INS tightly coupled integration makes the most contributions under the downtown environment, and the improvement of the regional atmospheric augmentation in single-frequency PPP is more significant since that single frequency is more sensitive to the ionospheric delay. In addition, it is proved that the regional atmospheric augmentation accelerates positioning convergence. The 3D positioning root-mean-square (RMS) with the comprehensive positioning model for dual frequency are 0.22 m and 0.77 m for T019 and T023, respectively. Concerning single-frequency PPP, the 3D RMS is 0.45 m and 1.17 m for T019 and T023, respectively. Moreover, taking the lane-level navigation under the downtown environment of T023 into consideration, we further presented the cumulative frequency of the horizontal positioning error less than 1 m, i.e., P d N 2 + d E 2 < 1 m , and the best solution can be found with PPP by fusing all the techniques, in which P d N 2 + d E 2 < 1 m is 99.0% and 93.2% for dual frequency and single frequency, respectively. [ABSTRACT FROM AUTHOR]