Cambium Networks PTP 550E Series, Руководство пользователя

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Chapter 3: System planning Link planning
Page 3-29
Link planning
This section describes factors to be taken into account when planning links, such as range, obstacles path loss,
and throughput. LINKPlanner is recommended.
LINKPlanner
The Cambium LINKPlanner software and user guide may be downloaded from the support website (see
Contacting Cambium Networks on page 1 ).
LINKPlanner imports path profiles and predicts data rates and reliability over the path. It allows the system
designer to try different antenna heights and RF power settings. It outputs an installation report that defines
the parameters to be used for configuration, alignment, and operation. Use the installation report to compare
predicted and actual link performance.
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 550/550E Series is designed to operate in 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.
The PTP 550/550E Series will operate at ranges from 100 m (330 ft) to 200 km (122 miles). The operation of
the system will depend on obstacles in the path between the units. Operation at 40 km (25 miles) or above will
require a near line-of-sight path. Operation at 100 m (330 ft) could be achieved with one unit totally obscured
from the other unit, but with the penalty of transmitting at higher power in a non-optimal direction, thereby
increasing interference in the band.
Path loss
Path loss is the amount of attenuation the radio signal undergoes between the two ends of the link. The path
loss is the sum of the attenuation of the path if there were no obstacles in the way (Free Space Path Loss), the
attenuation caused by obstacles (Excess Path Loss) and a margin to allow for possible fading of the radio signal
(Fade Margin). The following calculation needs to be performed to judge whether a particular link can be
installed:
capability seasonal fade excess space free
L L L L L < + + +
_
Where: Is:
space free
L
_
Free Space Path Loss (dB)
excess
L
Excess Path Loss (dB)
fade
L
Fade Margin Required (dB)