Thermal Impact of 5G Antenna Systems in Sandwich Walls

Abstract

The 5th generation (5G) cellular networks offer high speeds, low latency, and greater capacity, but they face greater penetration loss through buildings than 4G due to their higher frequency bands. To reduce this loss in energy-efficient buildings, a passive antenna system was developed and integrated into sandwich walls. However, the thermal effects of this system, which includes highly thermally conductive metals, require further study. In this research, three-dimensional heat transfer simulations were performed using COMSOL Multiphysics to determine the thermal transmittances (U-values) of 5G antenna walls. The results revealed that, using stainless steel as the connector material (current design), the U-value rose from 0.1496 (for the wall without antenna) to 0.156 W/m2K, leading to an additional heating loss per year of only 0.545 KWh/m2 in Helsinki. In contrast, with the previous design that used copper as the connector material, the U-value increased dramatically to 0.3 W/m2K, exceeding the National Building Code of Finland’s limit of 0.17 W/m2K and causing 12.8 KWh/m2 additional heat loss (23.5 times more than the current design). The current design significantly reduces thermal bridging effects. Additionally, three analytical methods were used to calculate antenna wall U-values: parallel paths, isothermal planes, and ISO 6946 combined. The isothermal planes method was found to be more accurate and reliable. The study also found that a wall unit cell with a single developed 5G antenna and a wall consisting of nine such cells arranged in a 3 × 3 grid pattern had the same U-values. Furthermore, areas affected by thermal bridging were typically smaller than the dimensions of a wall unit cell (150 mm × 150 mm).

Analytical Characterization of a Transmission Loss of an Antenna-Embedded Wall

“…The signal transmissive wall consists of multiple components like a wall, antenna elements, and coaxial cables. In this manuscript, we continue working on the same bare load-bearing wall as used in our previous works [7]- [10] as illustrated in Fig. 1(a).…”

“…It is calculated from the radiation pattern over the solid angle Ω of 2π, which represents the ratio of radiated power to the half sphere and input power. This allows us to define the antenna system loss Lant = 10 α dB 10 • ϵtot.…”

“…In previous works of the authors [7]- [10] we introduced an antenna embedded wall called a signal-transmissive wall where passive antenna elements were embedded back-to-back to a load bearing concrete sandwich wall. Numerical full-wave simulation models of the signal-transmissive wall were verified against experiments up to 8 GHz radio frequency.…”

A Novel AI-Based Thermal Conductivity Predictor in the Insulation Performance Analysis of Signal-Transmissive Wall

“…For instance, the temperature at the sampling point located at a height of 12.5 cm (the intersection between the first concrete and rock wool layer) decreased from 23 • C at 0 min to 6.2 • C after 500 min and remained at 5.3 • C after 1000 min. The thermal performances of the two samples appeared to be the same with consideration of the ambient temperature differences, which have been verified using the COMSOL in [19]. However, some thermal property parameters of the handmade samples in the laboratory significantly deviated from their theoretical values.…”

“…The two center connectors were connected to the spiral arms, while the remaining elements of the dual coaxial cable touched the PCBs. The PCB was embedded in the Styrofoam board to the same level as the concrete [19]. These two samples had the same general sizes and main materials.…”