Cambium PTP 450 series, Руководство пользователя

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PTP 450 User Guide Link planning
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ptp-450 (July 2014)
Link planning
This section describes factors to be taken into account when planning links, such as range, obstacles, path loss and
throughput.
Range and obstacles
Calculate the range of the link and identify any obstacles that may affect radio performance.
Perform a survey to identify all the obstructions (such as trees or buildings) in the path and to assess the risk of
interference. This information is necessary in order to achieve an accurate link feasibility assessment.
The PTP 450 Series is designed to operate in Near-Line-of-Sight (nLOS), Non-Line-of-Sight (NLOS) and Line-of-
Sight (LOS) environments. An NLOS environment is one in which there is no optical line-of-sight, that is, there are
obstructions between the antennas. See Figure 1 .
OFDM technology can often use multi-pathing to an advantage to overcome nLOS, especially in cases where the
Fresnel zone is only partially blocked by buildings, “urban canyons”, or foliage. OFDM tends to help especially
when obstacles are near the middle of the link, and less so when the obstacles are very near the BHS or BHM.
However, attenuation through walls and trees is substantial for any use of the 3.5 GHz, 3.6 GHz, 5.4 GHz, and 5.8
GHz frequency bands. Even with OFDM, these products should not be expected to penetrate walls or extensive
trees and foliage.