RACOM RipEX 1.6.0, Руководство пользователя

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2.2.1. Detailed Description
Bridge mode is suitable for Point-to-Multipoint networks, where Master-Slave applications with polling-
type communication protocol are used. RipEX in bridge mode is as easy to use as a simple transparent
device, while providing communication reliability and spectrum efficiency by employing a sophisticated
protocol in the radio channel.
In bridge mode, the radio channel protocol do not solve collisions. There is a CRC check of data integrity,
however, i.e. once a message is delivered, it is 100% error free.
All the messages received from user interfaces (ETH&COM's) are immediately transmitted to the radio
channel.
ETH - The whole network of RipEX radiomodems behaves as a standard ethernet network bridge.
Each ETH interface automatically learns which devices (MAC addresses) are located in the local LAN
and which devices are accessible over the radio channel. Consequently, only the ethernet frames ad-
dressed to remote devices are physically transmitted on the radio channel. This arrangement saves
the precious RF spectrum from extra load which would be otherwise generated by local traffic in the
LAN (the LAN to which the respective ETH interface is connected).
One has to be very careful when RipEX in Bridge mode is connected to LAN, because all LAN traffic
is then broadcast to the Radio channel.
COM1,COM2 - All frames received from COM1(2) are broadcast over the radio channel and transmitted
to all COM's (COM1 as well as COM2) on all radio modems within the network, the other COM on the
source RipEX excluding.
There is a special parameter TX delay (Adv. Config., Device), which should be used when all substations
(RTU's) reply to a broadcast query from the master station. In such case massive collisions would ensue
because all substations (RTU's) would reply at nearly the same time. To prevent such collision, TX
delay should be set individually in each slave RipEX. The length of responding frame, the length of
radio protocol overhead, modulation rate have to be taken into account.
2.2.2. Functionality example
In the following, common acronyms from SCADA systems are used:
• FEP - Front End Processor, designates the communication interface equipment in the centre
• RTU - Remote Telemetry Unit, the terminal SCADA equipment at remote sites
The single digits in illustrations are “site names” and do not necessarily correspond with actual addresses
of both the RipEX's and SCADA equipment. Address configuration examples are given in the
next
chapter .
Step 1
Polling cycle starts:
FEP sends a request packet for RTU3 through COM1 to
the connected RipEX.
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RipEX in detail