[Imported] Why choose an Ethernet or Serial radio?


[Imported] Why choose an Ethernet or Serial radio?

>>Message imported from previous forum - Category:Trio Data Radios<<
User: joelw, originally posted: 2018-10-16 21:19:50 Id:24
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.


This is a topic that could provide enough material to fill a day-long seminar. But here are some thoughts. Feel free to add comments of your own..._**


- Serial is typically much more efficient. Very little radio protocol overhead. (Far more efficient than TCP, a little more than UDP)

- Serial systems are in some ways easier to configure. Ethernet radios typically have more configuration options but this gives them more flexibility. In Serial your major concerns are cabling and getting the baud rate etc right. In Ethernet these are all standardized.

- Some people simply NEED to connect to an end device with one interface or the other. Easy choice usually. You can run either thru a terminal server to switch to the other but that's extra $$ and extra work. But there are LOTS of legacy serial devices out there, and lots of companies still making serial, at least for a few more years.

- Ethernet adds extra capabilities eg automatic packet forwarding by the Access Point radio, built in web server for configuration & diagnostics, automatic collision detection, SMTP management, Telnet remote configuration, multiple protocols (data streams) just by assigning each a different IP port number. (eg diagnostics is port 1040, web server is port 80, serial port A is port 30010 etc) In a purely serial radio you need to add extra technology (a simple over the air protocol) to do what we call MultiStream.

- Ethernet makes it easier to interface the radio system to the company's IT system. IT professionals are in many companies now taking over responsibility for SCADA radio systems, as it's all considered to be Information Technology of some sort or another.

- Once the system is on the company network this can be good or bad, or both. There are extra configuration concerns, but most importantly significant extra security concerns. A serial system is typically much more isolated and difficult to hack into. This is why Ethernet radios often have (we do) better security eg username and password to get into the radio.

- TCP provides a "virtual connection" that has high reliability. Adds lots of handshaking & retries etc to make the path more like a wire, without needing to have much smarts in the user protocol.

- Ethernet can be fast or slow. Licensed narrow-band Ethernet radios do exist, typically 9600 baud or 19k2! Lets the signal go farther but must be heavily managed to avoid overloading the channel. Fast Ethernet we still don't really do. 512 kbps is slow compared to 802.11 (WiFi) or similar technologies. But we can go a lot farther because we limit the speed.

- The common belief is that an Ethernet radio is going to typically be faster over-the-air than a comparable serial radio. NOT actually true. The K Series serial radio at 256 kbps will actually be more efficient than the J Series Ethernet radio when it's also at 256 kbps. This is due to the significant extra overhead of IP protocols. UDP is most efficient of these as it's more like a broadcast, but some people can't use it. However, an Ethernet spread spectrum radio is certainly going to be faster than a serial licensed radio. But that's not a fair comparison, the two are very different technologies.