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6.3 Transmit Data Using LAN
As described in “Increasing network coverage”, data can also be transmitted by using
LAN as a means of increasing the coverage of the network. The main scenarios
associated with this functionality are described in this chapter.
6.3.1 LAN Routing
In the example below the mobile network unit has a connection with two stationary
network units which are connected to the same the LAN infrastructure as the milling
unit.
When the acquisition unit wants to send data to the milling unit for the first time, the
network unit inside the acquisition unit must determine which connected stationary
network unit to use. The following sequence describes the steps taking place on the LAN:
1.
The mobile network unit forwards the data to both stationary network units.
2.
Both stationary network units forward the data onto the LAN.
3.
The data sent on the LAN by one stationary network unit is received by the other, but
is discarded.
4.
The milling unit receives the data from both stationary network units, but discards
the second copy as per the TCP/IP functionality.
5.
As a result of the received data, the milling unit sends data which could, for example,
contain a confirmation.
6.
This data is received by both stationary network units.
7.
Both stationary network units forward this data to the mobile network unit connected
to the acquisition unit.
8.
The mobile network unit only forwards both copies to the acquisition unit, but uses
the second copy to determine which stationary network unit, to use for the
subsequent communication to the milling unit. This decision is based on the signal
strength.
The resulting functionality is similar to that of a network switch. The resulting situation
will be that only stationary network unit B will forward the data that it receives over the
LAN meant for the acquisition unit. Stationary network unit A discards these.