Verint Nextiva S1700e Series Betriebsanweisung PDF herunterladen (Seite 30)

2: System and RF Planning

14 Verint Video 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 Video

Solutions 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 signal 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:

Distance

(mi./km)

2.45 GHz

(feet/m)

5.3 GHz

(feet/m)

5.8 GHz

(feet/m)

Earth curvature effect

(feet/m)

1 / 1.6 14 / 4.2 9.5 / 2.9 8.9 / 2.7 0

4 / 6.5 27 / 8.4 18.7 / 5.7 18 / 5.5 2 / 0.6

7 / 11.3 37 / 11 25 / 7.6 23.6 / 7.2 6 / 1.8

15 / 24 53 / 16 36.4 / 11.1 35 / 10.6 29 / 8.8

Visual line of sight First Fresnel zone (F1)

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 110 111

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Verint Nextiva S1700e Series Betriebsanweisung Seite 30