[Imported] Benefits of EB450 or EH450 as a Repeater
>>Message imported from previous forum - Category:Trio Data Radios<< User: joelw, originally posted: 2018-10-16 21:44:31 Id:37 This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.
**_jweder: In a Trio licensed radio system it is possible for any of the MR450, ER450, EB450 or EH450 radio types to act as a repeater or the system's master radio. What are the benefits of choosing the EB450 or EH450 over the other types?_**
The ER450 and MR450 remote radios may act as repeaters, but they must use store & forwarding via the serial port buffers. This receive-then-transmit mode doubles the latency (delay) in getting a data packet to a distant device. These radios have other limitations which are described elsewhere.
The EB450 is a 19" rack mounted radio specifically designed to act as a full duplex repeater or base station. Full duplex means that the radio can transmit and receive at the same time. (a duplexer is also required) Some protocols require a full duplex link to work properly. Alternately, full duplex may be used in a repeater to minimize the latency of a data packet. The radio will begin retransmitting an incoming packet within a few milliseconds, before the entire message is received, thus the apparent overall latency is almost the same as in a system with no repeater.
The EH450 is also mounted in a 19" rack. It consists of two EB450's and a Hot Standby Controller. (HSC) The HSC monitors both base radios and can automatically switch between them if the active unit fails. As a result a system containing an EH450 repeater or base station will have extremely high reliability.
The EB450 and EH450, when acting as repeaters, have another significant feature not found on the store & forward repeaters. They can be configured to act as Collision Avoidance Masters. In this mode, as soon as an incoming message is detected, they will send a "channel busy" message out to all other radios in the system. This feature is very useful for minimizing collisions due to two or more devices attempting to access the radio network at virtually the same time.
With the MultiStream feature of Trio radios it is possible for two or more protocols to share a single radio channel. In such a case it will be common for more than one device to attempt to access the network at any time. Alternately, even on a system with a single protocol (eg DNP3) it is possible to have multiple devices initiating messages. (eg unsolicited responses) Using an EB450 or EH450 as the repeater in such a system (configured as a collision avoidance Master) will substantially reduce the likelihood of collisions and resulting Retries.