Hytera DMR System Planner
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2.7.2 Configuring the RSSI Threshold
The RSSI Threshold is a configurable parameter via the CPS. If the signal strength
of the current master site is above the specified RSSI threshold, the terminal will
stay on the site and will not roam. Once the signal strength falls below the threshold,
the auto site roaming will occur to search for a site with higher signal strength. This
parameter actually controls the distance away from a site a user will begin searching
for another site. The RF coverage is not a perfect circle in reality, but to simplify this
explanation, we regard it as a circle.
Please note that the terminal will temporarily leave the current master site to
determine whether a stronger site is available during auto site roaming. Since the
terminal is temporarily away from the master site, it may miss the beginning of a
transmission (i.e. late entry into a call). Therefore, it is not advisable to perform auto
site roaming all the time. The RSSI threshold should be set properly. If it is too low,
the terminal will always stay on the master site with low signal strength even if there
might be a better site available; if it is too high, the terminal will frequently roam and
cause late entry. The figure below illustrates the situations when the RSSI threshold
is set too high or too low. Strong signals exist in the area circled by the dotted line,
and terminals can roam in the light blue area. The RSSI Threshold value ranges
from -120dBm to -80dBm.
Figure 2.7.2-1：Roaming Triggered by RSSI Threshold
The default value is -108dBm, which indicates approximately 80% of the good
coverage. Therefore, roam will occur in the left 20% of the coverage. The default
value is ideal for most configurations, but may not be the best in some particular
configurations. Accordingly, the user must take the actual site configuration into
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