Handbook of Propagation Effects for Vehicular and ... - Courses

8-34
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
8.7.3.2 Signal Variability Due to Antenna Positioning
Table 8-9 lists the standard deviations of the relative signal loss due to spatial variations
of 80 cm at L- and S-Bands (1618 MHz and 2492 MHz). The standard deviations vary
between 5.7 and 8.1 dB at L-Band with an overall average of 6.5 dB. At S-Band the
standard deviations vary between 5.1 dB and 7.3 dB with an overall average of 6.5 dB.
Figure 8-8 shows an example of the instantaneous spatial variability as a function of
location within a specific site (Commons). It is noted that within a 1 m interval,
fluctuations of the signal level of 20 dB are possible.
8.7.3.3 Spatial Decorrelation Distances
Autocorrelation calculations by Vogel and Torrence [1995c] were carried out for lags
between 0 to 3.2 m in the frequency interval between 0.5 to 3.0 GHz. The median
decorrelation distance varied between 0.5 m to 1.1 m with an overall average of 0.71 m,
(Table 8-15).
8.7.4 Effects Caused by the Human Body
Vogel and Torrence [1993] found in the frequency interval of 700 MHz to 1800 MHz,
that typically, people moving near the receiving antenna but outside the antenna Fresnel
region, produced variations of less than 0.5 dB. On the other hand, a person blocking the
transmission produced fades of 6 to 10 dB at an average location in the site rooms. The
ITU-R [1995] reports that at 1.7 GHz, a person moving into the line-of-sight path causes
6 to 8 dB attenuation in the received power level. When a hand-held terminal is used, the
proximity of the antenna to the user’s head and body affect the received signal level. For
example, at 900 MHz, measurements with a dipole antenna showed the received signal
strength to decrease in the vicinity of 4 to 7 dB when the terminal was held at the waist,
and 1 to 2 dB when the terminal was held against the head.
8.8 References
Bultitude, R. J. C., S. A. Mahmoud, W. A. Sullivan [1989], “A Comparison of Indoor
Radio Propagation Characteristics of 910 MHz and 1.75 GHz,” IEEE Journal of
Selected Areas in Communications, Vol. 7, No. 1, January, pp. 20-30.
Cox, D. C., R. R. Murray, H. W. Arnold, A. W. Norris, and M. F. Wazowics [1986],
“Cross-Polarization Coupling Measured for 800 MHz Radio Transmission In and
Around Houses and Large Buildings,” IEEE Transactions on Antennas and
Propagation, Vol. AP-34, No. 1. January, pp. 83-87.
Cox, D. C., R. R. Murray, and A. W. Norris [1984], “800 MHz Attenuation Measured in
and around Suburban Houses,” Bell Labs Tech. J., Vol. 63, pp. 921-954.
Cox, D. C., R. R. Murray, and A. W. Norris [1985], “Antenna Height Dependence of
800 MHz Attenuation Measured in Houses,” IEEE Transactions on Vehicular
Technology, Vol. VT-34, No. 2, May, pp. 108-115.