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5.2
Capacity
A Tait DMR network is scalable from a single site with one base station to
a large, wide area network with multiple nodes, 1000 base stations and
300 network gateways. One node is needed for every 100 talk paths in the
network. One or more additional nodes are desirable for redundancy. Each
reciter in a base station provides two voice channels and each gateway a
single voice channel. A network can have up to 20 nodes and a maximum
of 100 sites A table summarizing the DMR network dimensions can be
found at the end of this section.
5.3
DMR Node Operation
In an DMR network, a node has two functions:
• a control node
• a switching node
There is only one control node in a network. In a multi-node network, the
lowest numbered node is the control node. It validates all call requests,
sets up and clears down all calls, and sends call control messages and
routing instructions to the base stations. All nodes in the network can also
function as switching nodes. The switching nodes are used to transfer
audio data between the base stations (as per the control node instructions).
In a single-node network, the node fulfills both functions. Having more
than one node in an DMR network is advantageous, as:
• higher numbers of nodes spreads the load of voice traffic, keeping
queue times down
• if the control node fails, the next lowest numbered switching node will
take over as the control node
5.4
Node Equipment
TN9300 Node Controller
The example below is the 6LQWURQHV6%2;, the platform for the Tait
TN9300 Node Controller.
The node controller performs IP packet switching, call control and
network management functions. It handles inter-channel calls and
connections to dispatchers and third party IP interfaces.
Figure 9: 6LQWURQHV6%2;