Verint Nextiva S1100w, User Manual

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2: System and RF Planning
18 Verint Video Intelligence Solutions
RF Planning
Successful operation of a wireless link depends on proper RF path planning and antenna
installation. You have to install the devices in such a way that there is a clear RF line of
sight between the two antennas.
Location Evaluation
The path between the two antennas must be free of obstacles that could disturb
propagation. For very short link distances—less than 500 feet (152 meters)—you may be
able to establish a working link despite partial path obstruction. However, radio waves will
be in part absorbed and in part diffracted by the obstacles, therefore affecting link
reliability. Because the reliability of such an installation is highly unpredictable, Verint does
not recommend it. A path free of any obstacle is called an RF line-of-sight path.
To establish an RF line-of-sight path, you must take into account the beam width of the
radio signal transmitted between the two antennas. This beam width is an elliptical area
immediately surrounding the visual line of sight. It varies in thickness depending on the
length of the line of sight; the longer the length, the thicker the beam width becomes.
The region outlined by the signal beam width is known as the first Fresnel zone. The
Fresnel zone is always thicker at the mid-point between the two antennas. Therefore what
appears to be a perfect line-of-sight path between the base and a remote station may not
be adequate for a radio signal; this is the difference between “visual” and “RF” line of sight.
In practice, it has been determined that a radio path can be considered an RF line-of-sight
path if it has a clear opening through 60% of the first Fresnel zone (or 0.6 F1). Here are
values for 0.6 F1 for various signal path distances and frequency bands:
For distances under seven miles, the earth curvature effect is negligible. However, for
greater distances, you need to consider it in your calculations; for instance, for a 15-mile
link in the 2.4 GHz band, the two antennas must be located 82 feet higher than the highest
obstacle in the RF line of sight between them (that is, 53 feet for the Fresnel zone plus
29 feet for the earth curvature effect). For help, consult the Verint Video Intelligence
Solutions Support group.
Distance
(mi./km) 2.45 GHz
(feet/m) 4.9 GHz
(feet/m) 5.3 GHz
(feet/m) 5.8 GHz
(feet/m) Earth curvature effect
(feet/m)
1 / 1.6 14 / 4.2 9.8 / 3.0 9.5 / 2.9 8.9 / 2.7 0
4 / 6.5 27 / 8.4 19.5 / 5.9 18.7 / 5.7 18 / 5.5 2 / 0.6
7 / 11.3 37 / 11 25.8 / 7.9 25 / 7.6 23.6 / 7.2 6 / 1.8
15 / 24 53 / 16 37.8 / 11.5 36.4 / 11.1 35 / 10.6 29 / 8.8
Visual line of sight First Fresnel zone (F1)