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6-6 Fade Reduction (dB) 6 5 4 3 2 1 0 Propagation Effects for Vehicular and Personal Mobile Satellite Systems 60° 45° 30° 0 2 4 6 8 10 12 14 16 18 20 Maximum Fade (dB) Figure 6-4: Fade reduction due to switching lanes at 870 MHz versus equi-probability attenuation at the indicated path elevation angles. Fade Reduction (dB) 10 9 8 7 6 5 4 3 2 1 0 60° 45° 30° 2 4 6 8 10 12 14 16 18 20 22 24 26 Maximum Fade (dB) Figure 6-5: Fade reduction due to switching lanes at 1.5 GHz versus equi-probability attenuation (inner lane) at the indicated path elevation angles.
Polarization, Antenna Gain and Diversity Considerations 6-7 Table 6-2: Coefficients of the fade reduction formulation at f = 870 MHz. El. Angle (°) a0 a1 a2 a3 dB Range 30 -5.020 x 10 -3 0.3354 -2.439 x 10 -2 45 -0.8193 0.8430 -5.758 x 10 -2 60 -0.2305 0.2288 6.773 x 10 -2 Table 6-3: Coefficients of the fade reduction formulation at f = 1.5 GHz. 7.764 x 10 -4 1.222 x 10 -3 -3.608 x 10 -3 El. Angle (°) a0 a1 a2 a3 dB Range 30 0.3181 0.26153 -1.573x 10 -2 45 -1.073 0.8816 -4.651 x 10 -2 60 -8.127 x 10 -2 0.2044 5.781 x 10 -2 3.734 x 10 -4 7.942 x 10 -4 -2.235 x 10 -3 It is interesting to note that larger fade reductions occur at the greater elevation angles. This arises because at the larger angles, a change of lanes may radically alter the earthsatellite path from a shadowed to a non-shadowed state. At the lower elevation angles, this change of state becomes less likely. It is noted from Figure 6-5 that the L-Band fade is reduced from 10 dB to approximately 8 dB, 6 dB, and 4.5 dB at 30°, 45°, and 60°, respectively. At UHF (Figure 6-4), the 10 dB fade is reduced to 8 dB, 7 dB, and 5 dB at 30°, 45°, and 60°, respectively. 6.5 Antenna Separation Diversity Gain A space diversity simulation has been carried out employing the database corresponding to 400 km of roadside tree shadowing measurements taken during the Australian campaign [Vogel et al., 1992]. Space diversity operation for LMSS configurations may be envisaged by the scenario of two spaced antennas mounted atop a vehicle where each antenna is fed to a separate receiver system. Because the signal levels at the two antennas are expected to be different at any instant of time, rapid switching between the two receiver outputs followed by subsequent processing should enable the larger signal to be accessed. Such a system should therefore require smaller fade margins for the same “signal access distance” than single terminal systems. The “signal access distance” represents that distance over which the received signal level operates within the designed fade margin. Questions addressed here are: (1) what is the increase in “signal access distance” as a function of antenna spacing along the driving direction, and (2) what is the improvement in terms of reduced fading (enhanced signal) for a given “signal access distance” as a function of antenna spacing? The first question is addressed employing the concept of “diversity improvement factor, DIF” and the second “diversity gain, DG”, both of which are characterized in the following paragraphs. 2-20 2-12 2-11 3-25 3-17 3-15
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A2A-98-U-0-021 (APL) EERL-98-12A (E
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Table of Contents 1 Introduction __
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10 Optical Methods for Assessing Fa
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Table of Contents 1 Introduction __
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1-2 Propagation Effects for Vehicul
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Table of Contents 2 Attenuation Due
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Chapter 2 Attenuation Due to Trees:
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Attenuation Due to Trees: Static Ca
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Table of Contents 3 Attenuation Due
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Figure 3-23: Fade distributions at
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3-4 Relative Signal Level (dB) 5 0
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3-10 Percent of Distance the Fade >
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3-12 Propagation Effects for Vehicu
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3-14 3.4.3 Austin, Texas at K-Band
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3-20 Relative Signal Level (dB) 5 0
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3-24 Percentage of Distance Fade >
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3-26 and where 1 2 Propagation Effe
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3-28 Percentage of the Time Fade >
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Earth-Satellite Propagation Effects
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Chapter 9 Maritime-Mobile Satellite
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Figure 9-7: Fading depth versus pat
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9-6 Roughness Parameter, u (Rad) 28
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9-8 Cθ = ( θo − 7) / 2 dB for
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9-10 Fading Depth (dB) 6 5 4 3 2 1
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9-12 Fading Depth (dB) 6 5 4 3 2 1
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9-18 Mean Fade Occurrence Interval,
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9-20 Mean Fade Duration, T D (sec)
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9-22 Fade Depth (dB) 7.0 6.5 6.0 5.
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Table of Contents 10 Optical Method
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Chapter 10 Optical Methods for Asse
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Optical Methods for Assessing Fade
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Table of Contents 11 Theoretical Mo
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Chapter 11 Theoretical Modeling Con
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Theoretical Modeling Considerations
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Table of Contents 12 Summary of Rec
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Table 12-7: Tabulation of azimuth a
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12-14 Standard Deviation (dB) 4 3 2
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12-18 Fade Depth (dB) 7.0 6.5 6.0 5
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Index 13-1 Index 2 2-state Markov m
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Index 13-3 Jongejans, A. et al., 3-
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