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

5-14
5.10 Summary and Recommendations
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
The recommended fade duration distribution is given by (5-1) and plotted in Figure 5-3
for L-Band frequencies and a 5 dB threshold fade [ITU-R, 1994]. This relation may be
used for moderate elevation angles ranging from 30° to 60° and roadside tree conditions
corresponding from moderate to severe tree shadowing having percentage of optical
shadowing levels (POS) of 55% to 75%. The corresponding median and 10% distance
durations are 0.22 m and 1.04 m, respectively.
The recommended non-fade duration distribution is given by (5-6) and plotted in
Figure 5-7 for “moderate” and “extreme” shadowing conditions. These are applicable for
the same conditions described above for the fade duration distributions. The parameters
of (5-6) are tabulated in Table 5-4. Non-fade duration distances are 3.5 m and 0.22 m for
the 10% and 50% levels, respectively, associated with the “moderate” tree shadowing
case, and 1.2 m and 0.18 m for the “extreme” shadowing case. The “extreme” and
“moderate” non-fade duration distributions were similar to the “non-fade” duration
distributions measured in central Maryland at 30° and 60°, respectively.
Equation (5-8) and Figure 5-8 for the “moderate” and “extreme” road shadowing
conditions, respectively, give the phase fluctuation distribution. Over the range 5% to
95%, the phases are within ± 15° relative to the median. Hence, the influence of phase
fluctuations on demodulation techniques at the elevation angle considered (e.g., 51°) is
minimal and LMSS channel characteristics can be estimated without considering phase.
At lower elevation angles (e.g., smaller than 20°), this may not be the case.
5.11 References
Butt, G., M., A. N. Parks, and B. G. Evans [1995], “Narrowband and Wideband
Characterisation of Satellite Mobile/PCN Channel,” International Mobile Satellite
Conference, IMSC ’95, Ottawa, Ontario, Canada, pp. 128-133.
Goldhirsh, J. and W. J. Vogel [1989], “Mobile Satellite System Fade Statistics for
Shadowing and Multipath from Roadside Trees at UHF and L-Band,” IEEE
Transactions on Antennas and Propagation, Vol. 37, No. 4, April, pp. 489-498.
Hase, Y., W. J. Vogel, and J. Goldhirsh [1991], “Fade-Durations Derived from Land-
Mobile-Satellite Measurements in Australia,” IEEE Transactions on
Communications, Vol. 39, No. 5, May, pp. 664-668.
ITU-R [1994], “Propagation Data Required for the Design of Earth-Space Land Mobile
Telecommunication Systems,” Recommendation ITU-R PN.681-1, pp. 358-365.
Sforza, M. and S. Buonomo [1993], “Characterisation of the LMS Propagation Channel
at L- and S-bands: Narrowband Experimental Data and Channel Modelling,”
Proceedings of the Seventeenth NASA Propagation Experimenters Meeting (NAPEX
XVII) and the Advanced Communications Technology Satellite (ACTS) Propagation
Studies Miniworkshop, Pasadena, California, June 14-15, 1993 (JPL Publication 93-
21, August 1, 1993, F. Davarian; Editor).