NI 9792 WSN Real-Time Gateway User Guide and Specifications
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NI Wireless Sensor Networks
The NI WSN system is built on an IEEE 802.15.4 wireless mesh network. The 802.15.4 radio in each
NI WSN device provides for low-power communication of measurement data across a large network of
devices. The NI-WSN software builds on top of that to provide network configuration and reliable
communication from the host PC or PAC to the NI WSN-32
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node devices.
Mesh Networking
The NI WSN system consists of two types of devices: gateways and nodes. Gateways act as the network
coordinator, in charge of node authentication, message buffering, and bridging from the 802.15.4
wireless network to the wired Ethernet network. Nodes primarily function as end nodes in the network
to collect data and control DIO channels, but can also be programmed as routers to relay data from other
nodes back to the gateway and Host PC or PAC. Use NI MAX to configure nodes as end nodes or routers.
Figure 1 shows a typical NI Wireless Sensor Network.
The gateways and nodes work together to form a mesh network. The gateway maintains a list of nodes
(by serial number) that have been authorized for network access. When a node powers up, it scans for
available networks, locates either a gateway or router, and attempts to join it. If the gateway has the node
in its list, the node joins the network, downloads the latest configuration from the gateway, and begins
its normal operation of acquiring measurement data and controlling DIO.
Since each node joins a network instead of a particular router or gateway, it can find a new path back
to the gateway in the event that the signal is lost or blocked to its existing network route. In this way,
the mesh network is inherently self-forming and self-healing. However, this may also cause network
throughput to decrease, as there is no way to force a router or end node to join to a particular device in
the network. Each time a node joins through a router, the overall throughput of that node is halved, due
to the fact that the node must hop to get its messages back to the gateway. Figure 14 shows an example
of one possible mesh configuration.
