FIGURE 3 Distance dependencies of the path loss (linear scale) Based on these data, cumulative probabilities of the path loss are derived in Fig. 4. The difference between these two probabilities is approximately 18 dB. This indicates that the radiowave exits from the house with an attenuation of approximately 18 dB and propagates with the same attenuation coefficient in distance as that for free space. FIGURE 4 Cumulative probabilities of measured path loss data 5 Building entry loss – slant path measurements 5.1 UHF satellite signal measurements (860 MHz – 2.6 GHz) Representative UHF satellite signal attenuation observed within rooms located near an exterior wall in timber-framed private homes is summarized in Table 1. For interior rooms, 0.6 dB must be added to the tabulated values. For timberframed buildings the attenuation shows little variation with weather or path elevation angle but, as the Table illustrates, there is a systematic variation with frequency, polarization, construction materials, insulation and position within the structure. Some aluminium-backed insulating and construction materials contribute up to 20 dB of loss. TABLE 1 UHF signal attenuation (dB) through timber-framed buildings* Building condition Frequency (MHz) and polarization (Horizontal: H, Vertical: V) Exterior Insulation (non-metallic type) 860 H 860 V 1 550 V 2 569 V Wood siding Ceiling only 4.7 2.9 5.0 5.8 Ceiling and wall 6.3 4.5 6.6 7.4 Brick veneer Ceiling only 5.9 4.1 6.2 7.0 Bricks Ceiling and wall 7.5 5.7 7.8 8.6 * The Table is for rooms located near to the exterior wall; for interior rooms, 0.6 dB should be added. 5.2 Slant-path measurements from towers or high rise buildings Measurements of building entry loss using 18 to 20 m towers to simulate a satellite transmitter were performed in the bands 700 MHz to 1.8 GHz and 500 MHz to 3 GHz to determine the mean loss and spatial variability in a variety of buildings. There are insufficient data to give precise prediction methods, but the data in Tables 2 to 3 are indicative.
TABLE 2 Signal distributions at the average position and best position within buildings (over the frequency 700 to 1 800 MHz) Building number Construction Elevation angle Average position Best position Mean loss (dB) Standard deviation (dB) Mean loss (dB) Standard deviation (dB) 1 Corner office, large windows, singlestory building. Concrete block, plasterboard, double-glazing. Concrete roof on steel beams 27.5 (LoS through window, azimuth between wall and LoS is 50) 7.9 5.5 4.2 4.2 2 Small room with windows being 5/8 of exterior wall 18 (LoS through window, azimuth angle between wall and LoS is 50) 9.1 4.4 5.4 3.7 3 Corner foyer, large reflective glass door in half of one exterior wall. External walls concrete, internal walls plasterboard on metal frame 16 (LoS through window, 45 azimuth angle between one wall and LoS, both exterior walls illuminated by transmitter) 15.4 8.4 9.7 6.7 4 metal shack with plywood interior. One small unscreened window on each of two sides, metal-covered door 25 (azimuth angle between wall and LoS is 60) 9.7 6.3 5.2 4.9 5 wood-side house, rockwool insulation (walls and attic); gypsum board, no metallic heatshield. No metallic screens on windows. Woodshingled roof 25 (azimuth angle between wall and LoS is 45) 9.0 4.5 5.4 3.7 6 Empty sheet-metal mobile trailer home, metal frame windows with metal screens 25 (azimuth angle between wall and LoS is 45) 24.9 3.8 19.8 3.4
15 Cumulative distribution functions of the excess path loss in all buildings 16 Mean excess path loss plotted against floor number for the different carrier frequencies in buildings 11, 27, 32, 37 and 81 For further details refer to J. Medbo et al., “Multi-Frequency Path Loss in an Outdoor to Indoor Macrocellular Scenario”, EuCAP 2009, Berlin, Germany. 8.3 Average excess loss results Building entry loss can be evaluated using two methods: Method 1: Loss difference indoors and outdoors at ground level: Lout – Lin Method 2: Excess loss at floor levels where building is LoS: LFS – Lin 17 Methods for evaluation of building entry loss (left = method 1, right = method 2) Penetration loss data for LoS conditions is not available in many cases since the buildings do not reach LoS height. For such buildings (e.g. building 81), LLoS may be taken as the difference LDiff between measured loss outdoors and indoors at ground level. This was done for buildings 27, 37 and 81 (see Table 15). For buildings 27 and 37 it is possible to compare the two methods. It turns out that LDiff underestimates LLoS in these two cases. The underestimation may be explained by the fact that the outdoor loss measurements were restricted to areas around the buildings which were not facing the transmitter (see Fig. 15) and thus giving higher loss. Since LLoS is not known for building 81 the best one can do is assume LLoS = LDiff. The resulting floor number where LoS occurs, nFlb, is around 9 which is consistent with visual inspection done at the transmitter location. The present results indicate that the two methods to determine the building entry loss give similar results. The outdoor measurement method is however uncertain due to large variations in shadowing suggesting the use of LLoS whenever possible. TABLE 15 Estimates of LLoS Building Frequency (MHz) Loss – Ground (dB) Loss – Outdoors (dB) Loss difference (dB) 81 460 48 27 21 880 48 28 20 1 860 51 26 25 5 100 – 25 – 37 460 38 16 22 880 38 21 17