## 3 Materials and Methods  
The laboratory experiment was performed by simulating various conditions to evaluate the signal-reaching performance of UFH RFID in a multilayer medium and propose an optimal utilization methodology. We planned a laboratory experiment to analyze the attenuation of signals while simulating the materials for road pavement and communication cable installation. The objectives of the experiment were (1) to determine the maximum reach depth of the signal, (2) to define the fundamental cross-section and compare signal attenuation according to various materials, and (3) to analyze signal attenuation due to moisture. Finally, we investigated the effect of the change in the thickness of the surface layer on signal attenuation. A tag contained an antenna of dimensions 8 cm \(\times\) 2 cm. The reader was a commercially available product (WYUAN PDA6000) manufactured following the ISO-18000-6C standard [23]. The experiment was conducted by building a mold as shown in Figure 1. It was designed with dimensions of 25 cm \(\times\) 25 cm \(\times\) 80 cm and shielded on five sides except for the top with aluminum to prevent electromagnetic waves from being transmitted to the side. Before the experiment, we confirmed that the signal could not be transmitted during aluminum shielding. In the experiment, we performed rammer compaction 25 times for every 10 cm of filler and repeated the measurement 5 times for each experimental condition. To check the maximum depth of reach of the signal, we fixed the surface thickness of the cold mix asphalt at 10 cm and changed the thickness of the subgrade soil (yellow soil) from 20 cm to 70 cm by 10 cm. Simultaneously, we installed the tag into six levels from 30 cm to 80 cm. As an experimental cross-section for analyzing signal attenuation according to the type of material, the surface layer maintained a thickness of 10 cm; however, the thickness of the material was set to 15 cm, 30 cm, 45 cm, and 60 cm (four levels). Assuming that the underground utility does not reach the auxiliary base layer and road surface as the depth of the underground utility is limited when applying the trench method, three types of fillers were selected: subgrade soil, sand, and graded gravel materials. Assuming that the excavation width is 25 cm and there is no effect due to reflection or scattering of electromagnetic waves that may occur at the cutting interface, we considered only electromagnetic waves that reach straight. The decision variable for evaluating the moisture effect was limited to the moisture ratio. We controlled the surface layer thickness to 10 cm and the subgrade soil filler thickness to 25 cm. Only the moisture ratio conditions varied from dry (<8%) to optimum (8-20%) or saturated (>20%). Finally, to verify the applicability in the case of the increase or decrease in packaging thickness due to construction error and maintenance, we experimented by varying the thickness of the surface layer and the subgrade soil filler. We set the surface layer depth to 5 cm, 10 cm, 15 cm, and 20 cm and the filler depth to 20 cm, 25 cm, 30 cm, and 35 cm. The cold mix asphalt that is a commercial product was applied for the surface layer. Its volume density was relatively low at 1.15 to 1.25 g/cm\({}^{3}\) compared to other materials. The density of the subgrade soil used as a filler was 1.6 g/cm\({}^{3}\). We expected the soil close to the clay to have a significant impact on electromagnetic wave attenuation. The sand density was 1.54 g/cm\({}^{3}\) and belonged to coarse sand based on the fitness modulus (3.22%) and particle size distribution. The graded gravel material was granite with a maximum aggregate size of 31.5 mm, which can be classified as a permeable base material that does not contain fine aggregate (Figure 2). The design strength and air volume of mortar were 23 MPa and 4.9%, respectively, and the ratio of cement, sand, and water was 1:3:0.5 (weight ratio). We used the same sand and typical Type I cement. Figure 1: A scheme of experimental setup.