System Description

TD 93025US
9 May 2019 / Ver. I 57
System Description
teleCARE IP
9.5 Wireless Infrastructure RF Planning Considerations
A wireless device must be seen at all possible locations. To avoid an overload of RF
messages from being sent to the wireless server, a message should (preferably) only end up
at one wireless gateway segment, which consists of multiple wireless repeaters and a
gateway. At certain overlapping segments it could be possible that a message ends up at
multiple gateways, but never more than two (maximum three/four in a worse case
scenario).
In each wireless segment, a wireless repeater must be able to see the next and the previous
wireless repeater in the subnet at all times, all the way up to the wireless gateway. The
status of the wireless repeaters in a wireless infrastructure are constantly monitored and a
peripheral lost message will be generated if a section fails to respond. During
configuration, the status of wireless gateway(s) and wireless repeaters are also visible
through the system overview tab in the NISM, available under “Diagnostics -> System
Overview”, refer to Emergency Call System Configuration Manual TD 93019US for detailed
information.
If a valid message is received by multiple repeaters in one or more subnets of a single
gateway segment, the gateway will directly transfer the first instance of the message it
received towards the wireless server for processing. If afterwards an instance with a higher
RSSI value is received, it will be transferred to the wireless server for updating the RSSI
location. For RSSI location determination, RSSI values are only updated for mobile
transceivers like the NITX, this is not required for fixed wireless transceivers like the
universal transmitter NUUTX.
Although the wireless gateway will filter out most of the duplicate messages in its segment,
it is important to carefully plan the locations of the wireless gateways and repeaters
throughout a site. For example, avoid placing multiple wireless gateways too close to each
other around a central location, there this will generate a lot of traffic towards the wireless
server, when a wireless message is received by multiple gateways.
Figure 49. Wireless gateways mounted too close to each other