Chapter 8Earth -Satellite Propagation

Effects Inside Buildings

8- i

Table of Contents

8 Earth-Satellite Propagation Effects Inside Buildings_______________________ 8-1

8.1 Background ________________________________ _________________________ 8-1

8.2 Satellite Radio Reception Inside Buildings from 700 MHz to 1800 MHz ________ 8-28.2.1 Experimental Features ________________________________ ____________________ 8-28.2.2 Multipath Interference During Frequency and P osition Sweep _____________________ 8-38.2.3 Time Delay Distributions ________________________________ _________________ 8-48.2.4 Cumulative Distributions of Signal Levels ________________________________ ____ 8-58.2.5 Frequency Dependence of Probability ________________________________ ________ 8-88.2.6 Space Diversity Considerations ________________________________ _____________ 8-98.2.7 Bandwidth Distortion Considerations ________________________________ _______ 8-10

8.3 Slant-Path Bu ilding Penetration Measurements at L- and S -Band ___________ 8-128.3.1 Experimental Description ________________________________ ________________ 8-128.3.2 Stability of Measurement ________________________________ _________________ 8-138.3.3 Space Variability ________________________________ _______________________ 8-148.3.4 Frequency Variability ________________________________ ___________________ 8-18

8.4 Slant-Path Building Attenuation Measurements from 0.5 to 3 GHz __________ 8 -218.4.1 Experimental Description ________________________________ ________________ 8-228.4.2 Average Signal Levels over Frequency Band and Positions ______________________ 8-228.4.3 Distance and Frequency Dependence ________________________________ _______ 8-248.4.4 Spatial Autocorrelation Characteristics ________________________________ ______ 8-258.4.5 Relative Signal Loss Versus Frequency ________________________________ ______ 8-27

8.5 Building Attenuation at UHF, L- and S -Band Via Earth-Satellite Measurements 8-298.5.1 Experimental Results ________________________________ ____________________ 8-30

8.6 Attenuation of 900 MHz Radio Waves by Metal Building __________________ 8-31

8.7 Summary and Concluding Remarks ________________________________ ____ 8-318.7.1 Required Fade Margins ________________________________ __________________ 8-318.7.2 Fa ding Dependence on Frequency ________________________________ __________ 8-32

8.7.2.1 Small and Large Bandwidths Effects ________________________________ _____ 8-328.7.2.2 Cumulative Distribution Dependence on Frequency _________________________ 8-338.7.2.3 Distortion Due to Bandwidth ________________________________ ___________ 8-338.7.2.4 Frequency Correlation ________________________________ ________________ 8-33

8.7.3 Fading Effects Due to Antenna P osition ________________________________ _____ 8-338.7.3.1 Antenna Spacing between Maximum and Minimum Signal Levels ______________ 8-338.7.3.2 Signal Variability Due to Antenna Positioning ______________________________ 8-348.7.3.3 Spatial Decorrelation Distances ________________________________ _________ 8-34

8.7.4 Effects Caused by the Human Body ________________________________ ________ 8-34

8.8 References ________________________________ _______________________ 8-34

8- ii

Table of Figures

Figure 8 -1: Maximum and minimum relative signal levels (thin lines) in a composite vertical scanof 80 cm and frequency sweep over the indicated frequency interval for Site 2. Thick curvecorresponds to fixed receiver antenna versus frequency example [Vogel and Torrence, 1993]. .......8-4

Figure 8 -2: Approximate cumulative distributions of time delay at three locations. ................................8-5

Figure 8 -3: Cumulative probabilities of relative signal level as a function of frequency for Site 2.The database reflects measurements taken at 16 positions for 80 cm vertical scans at severallocations and seven bandwidths ....................................................................................................8-6

Figure 8 -4: Example cumulative distributions of relative signal loss for Site 2 based on modeldescribed by (8 -1) through (8 -3). ..................................................................................................8-9

Figure 8 -5: Relative signal level versus vertical measurement distance at six frequencies spacedapproximately 5 MHz apart. (Site 2). ..........................................................................................8-10

Figure 8 -6: Standard deviation versus bandwidth for Site 4 for the average and best cases. ............8-11

Figure 8 -7: Example of 50 s time seri es of relative signal level measured at the Commons for bothco-polarized and cross-polarized levels and fixed antenna positions. ............................................8-14

Figure 8 -8: Received power levels at 1618 MHz and 2492 MHz inside the Commons. The co-polarized and cross-polarized levels are the upper and lower figures, respectively. The uppertraces represent L -Band (left scale) and lower traces S -Band (right scale). ...................................8-15

Figure 8 -9: Summary of statistics at L- and S -Band giving median, 95%, and 5% levels of therelative power losses inside the six buildings for the case in which the antennas were movedhorizontally over multiple 80 cm intervals. .................................................................................8-16

Figure 8 -10: Cumulative probability distribution of signal level difference of the instantaneousS -Band minus the L -Band powers. The in dicated straight line implies a Gaussian distributionwith a mean and standard deviation of 1.9 dB and 7.2 dB, respectively. .......................................8-18

Figure 8 -11: Relative power loss variation with frequency at L -Band (upper figure) and S -Band(lower figure) for various mean power levels over the 160 MHz bandwidth. ................................8-19

Figure 8 -12: Summary statistics giving the median, 95% and 5% levels of the mean fade slope(upper figure) and the standard deviation of the fade slope (lower figure) at the various sitelocations. ....................................................................................................................................8-21

Figure 8 -13: Relative signal level statistics at each of the building locations. .......................................8-23

Figure 8 -14: Relative signal level versus position at four frequencies in the Commons. ........................8-24

Figure 8 -15: Relative signal level versus position at four frequencies in the House. ..............................8-25

Figure 8 -16: Spatial autocorrelation versus frequency at a lag of 50 cm for EERL. ...............................8-26

Figure 8 -17: The spatial autocorrelation at 1625 MHz versus distance lag in Commons, EERL, andFarmhouse. The abscissa distance is the indicated number times 0.05 m. ....................................8-26

Figure 8 -18: Dependence of relative signal level with frequency in the Farmhouse. The trend slopeis shown to be -0.006 dB per MHz. .............................................................................................8-27

Figure 8 -19: Summary of trend slope statistics in the six building. .......................................................8-28

Figure 8 -20: The frequency autocorrelation at a fixed location in each building for frequency lagsfrom 0 to 20%. The lag of 10, for example, implies 10 0.002 f (MHz). .......................................8-29

8- iii

Table of Tables

Table 8-1: Pertinent measurement system parameters of Vogel and Torrence [1993]. .............................8-2

Table 8-2: Site descriptions of indoor propagation measurements of Vogel and Torrence [1993]. ...........8-3

Table 8-3: Mean and standard deviation of best fit Gaussian distributions for frequency and spatialaveraging. ....................................................................................................................................8-7

Table 8-4: Relative median power levels over frequency interval 750 MHz to 1750 MHz. .....................8-7

Table 8-5: Best fit coefficients for the model cumulative distributions (8 -1). ..........................................8-8

Table 8-6: Parameter values for standard deviation versus bandwidth as given by (8 -4) and (8 -5).........8-12

Table 8-7: Building characteristics and measurement parameters. ........................................................8-13

Table 8-8: Summary of medians of the relative signal loss inside the six buildings at L- (1618 MHz)and S -Band (2492 MHz). ............................................................................................................8-16

Table 8-9: Summary of statistics associated with spatial variations of L- (1618 MHz) and S -Band(2492 MHz) co-polarized relative power levels during spatial scans inside buildings. ..................8-17

Table 8-10: Summary of statistics associated with spatial variations of L- (1618 MHz) and S -Band(2492 MHz) cross -polarized relative power levels during spatial scans insid e buildings. ..............8-17

Table 8-11: Statistics associated with power differences between co-polarized S -Band and L -Bandfor spatial scans at each of the site locations. ...............................................................................8-18

Table 8-12: Tabulation of standard deviation parameters in (8 -7) for different site loca tions at L-and S -Band. ................................................................................................................................8-20

Table 8-13: Building names and pertinent characteristics. ....................................................................8-22

Table 8-14: Listing of the mean and standard deviations when relative signal loss is averaged overposition and frequency (0.5 to 3.0 GHz). .....................................................................................8-23

Table 8-15: Median decorrelation distances at each building location. .................................................8-27

Table 8-16: Summary of median decorrelation bandwidths when all positions within each buildingare considered. ...........................................................................................................................8-29

Table 8-17: Average attenuation contributions at UHF, L, and S -Band [Wells, 1977]. ..........................8 -31

Table 8-18: Summary of relative power losses in terms of overall average of worst case fading (allsite average with exception of Site 6 for the first row). ................................................................8-32

Table 8-19: Summary of relative power losses in terms of worst site location. .....................................8-32

Chapter 8Earth -Satellite Propagation Effects Inside

Buildings

8.1 BackgroundNumerous investigations have been reported for the case in which both transmitter andreceiver were located within the same building [e.g., Fujimori and Arai , 1997; ITUR,1995; Polydorou et al. , 1995; Tang and Sobol , 1995, Wang et al. , 1995, Seidel andRappaport , 1992, Bultitude et al. , 1989; Rappaport , 1989]. Other experiments have beenconducted where the transmitter was placed outdoors to simulate antennas mounted closeto the ground radiating into nearby buildings [e.g., Cox et al. , 1986, 1985, 1984; Hoffmanand Cox , 1982]. Few investigators have examined the propagation effects insidebuildings for the case in which transmissions originate from a satellite or a sourcemounted on a platform simulating a satellite. Wells [1977] used transmissions from thegeostationary satellite ATS-6 at 860 MHz, 1.5 GHz and 2.6 GHz to determine theaverage attenuation into wood-frame houses with and without brick veneer at variouselevation angles and frequencies. More recently, Vogel and Torrence [1993, 1995a,1995b, 1995c] described the results of signal loss measurements made interior to a seriesof buildings. The transmitting antenna was mounted on an outside tower that simulated asatellite platform. The various frequencies considered ranged from 500 to 3000 MHz andmeasurements of the relative signal losses were made to characterize the spatial,temporal, and frequency variability . Although propagation effects similarities exist forall of the above scenarios, this chapter is primarily concerned with the latter scenario;namely that corresponding to a transmitter on a satellite platform or on a tower simulatinga satellite platform with reception measurements made within the building. For thisscenario, only results are considered in which outdoor obstacles do not obstruct the line-of-sight path. The indoor results are also presented in the form of signal levels (in dB)relative to those measured immediately outside the structure where an unobstructed line-of-sight existed.

Propagation Effects for Vehicular and Personal Mobile Satellite Systems8-2

8.2 Satellite Radio Reception Inside Buildings from 700 MHz to 1800 MHzThis section deals with the results of Vogel and Torrence [1993] who arrived atpropagation results for measurements inside six buildings comprised of brick, corrugatedsheet-metal, wood frame, mobile-home, and reinforced concrete-wall constructions.Their investigation emphasized geostationary satellite transmissions associated withdirect broadcasting systems since their receiving antenna had a relatively narrowbeamwidth (90) and was pointed along the line-of-sight to the transmitter. Such anantenna experiences less multipath fading than one that has an azimuthally omni-directional gain characteristic.

8.2.1 Experimental Features

Swept CW signals from 700 MHz to 1800 MHz were radiated from an antenna locatedon an 18 m tower attached to a van outside these buildings. The part of the receiversystem inside the buildings was comprised of the above described antenna on a linearpositioner located approximately 1.5 m above t he ground and pointed towards thetransmitting antenna. Measurements were made for the case in which the receiverantenna was sequentially moved in 5 cm steps (for a total of 80 cm) along any of thethree orthogonal directions. The receiver had a resolution bandwidth between 10 KHzand 1 MHz, a carrier to noise ratio of 45 dB, and an overall measurement accuracy ofbetter than 0.5 dB. A summary of the experimental parameters is given in Table 8-1 , anda succinct description of each of the site locations (labeled Site 1 through Site 6) is givenin Table 8-2 .

Table 8 -1 : Pertinent measurement system parameters of Vogel and Torrence [1993].

Characteristics Value

Frequency

Coverage, Df 700 MHz to 1800 MHz in 1 s

Span 0 Hz to 1100 MHz

Resolution 10 KHz to 1 MHz

Amplitude

Transmitted Power 10 mw

Range 45 dB

Resolution 0.2 dB

C/N Ratio 64 to 45 dB over DfError < 0.5 dB

Transmitter and Receiver Antennas

Type Cavity Backed Spiral

Polarization Right-hand Circular

Beamwidth 90 (3 dB)

Gain -2.5 to 4.5 dB over DfElevation Angle (Receiving) 12 to 48

Earth-Satellite Propagation Effects Inside Buildings 8-3

Table 8 -2 : Site descriptions of indoor propagation measurements of Vogel and Torrence[1993].

Site # Description ElevationAngle

1 A corner office (6 X 7 m) with two large windows in a single-story building.Walls are of concrete-block masonry with the interior covered withplasterboard. The ceiling is comprised of acoustic tiles suspended at a height of3 m from metal hangers. A double-glazed opt ically reflective window is locatedin the wall toward the transmitter. Roof is flat and consists of concrete panelssupported by steel beams. Room is furnished with wooden office furniture.Also referred to as the EERL Building

27.5

2 A small room in another building (3 X 4 m) with two windows and constructionsimilar to Site 1. Room furnished with metal filing cabinets.

18

3 A 5 X 5 m corner foyer in another building where a large reflective glass doorencompasses half of one outside wall. The external walls are of concrete wallconstruction, and internal walls have metal frames covered with plasterboard.Also referred to as the Commons.

16

4 A 3 X 6 m shack with corrugated sheet-metal walls and roof on the outside andplywood on the inside. It has one window on each of the two narrow sides anda metal-covered door centered between two windows on one of the wide sides.

25

5 An 1870 vintage restored and furnished two-story house with wood siding. Thewalls are filled with rock wool and covered with plasterboard on the interior andwood siding on the exterior. The gabled roof is covered with wood shingles.Measurements were made in two rooms on the ground floor and one room onthe second level. Also referred to as the Farmhouse.

25

6 A 12 X 2.4 m empty mobile trailer home with sheet-metal exterior andaluminum frame windows with metal screens.

45

8.2.2 Multipath Interference During Frequency and Position Sweep

An example of maximum and minimum multipath interference (of relative signal level)experienced inside Site 2 is given in Figure 8 -1 for a composite frequency sweep andvertical position scan near a window. The set of curves labeled maximum and minimumwere derived by executing a frequency sweep between 700 MHz to 1800 MHz for eachantenna position and culling out the maximum and minimum signal levels (upper andlower traces) at each frequency. The center thick curve is an example of the signalvariability when the antenna position was fixed at an arbitrary position over thefrequency interval. The large variability of the signal due to receiver antenna positionand frequency changes demonstrates that multipath effects may be significant over theindicated position and frequency intervals. For example, the minimum trace shows signallevels which vary between -5 dB to smaller than -30 dB, the maximum trace shows signallevels which vary between +2 dB and -9 dB , and the fixed antenna position trace shows avariability between 0 to -30 dB.

Propagation Effects for Vehicular and Personal Mobile Satellite Systems8-4

700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800FREQUENCY (MHz)

-35

-30

-25

-20

-15

-10

-5

0

5

SIG

NA

L LE

VEL

(dB

) Maximum

Minimum

Single Position

Figure 8 -1 : Maximum and minimum relative signal levels (thin lines) in a compositevertical scan of 80 cm and frequency sweep over the indicated frequency interval forSite 2. Thick curve corresponds to fixed receiver antenna versus frequency example[Vogel and Torrence , 1993].

8.2.3 Time Delay Distributions

Through the execution of a Fast Fourier Transform of the signal level over the frequencyinterval examined, estimates of maximum multipath time delays were derived.Cumulative distributions of these time delays are given in Figure 8 -2 for three differentsite locations. It is clear from this figure that 90% of the power have delays smaller than20 ns, 30 ns, and 80 ns for Sites 2, 4, and 3, respectively, and more than 99% of th epower have associated delays smaller than 100 ns for Sites 2 and 4. These results wereconsistent with power loss measurements employing a series of bandwidths between 1and 90 MHz over the frequency interval from 700 to 1800 MHz in that negligiblebandwidth dependence was found in the loss statistics results.

Earth-Satellite Propagation Effects Inside Buildings 8-5

0 10 20 30 40 50 60 70 80 90 100DELAY (ns)

1.02.0

5.0

10.0

20.0

30.040.050.060.070.0

80.0

90.0

95.0

98.099.099.5

99.9

% P

OW

ER

WIT

H D

ELA

Y