AIS duplex vs multiplex, EasyAIS gets it right
I’m pleased to report—at least in part because of discussions here—that EasyAIS has rewritten its Web pages to clearly explain how its multiplexing receiver functions within the Class A and B System, particularly in relationship to more expensive full duplex receivers. In fact, they’ve put together the most thorough analysis I know of on the Web (go to home page, click on “AIS Capability). Besides laying out position reporting intervals in time and distance for various possible target vessels, they point up some other factors that suggest “additional uncertainty of class B reception, independent of the used receiver type.” EasyAIS concludes that both multiplex and duplex receivers “show satisfactory results for all class A scenarios,” but when “looking for fast class B targets, both concepts show weak points, as the information update rate is low.” One can argue that multiplexers are weaker in this regard, but the point is that users need to get educated about AIS target intervals as Class B becomes an actuality, and hats off to EasyAIS for now contributing to that education. (And Panbo rocks again!)
..except that I don't think they really meant duplex (which means transmit and receive simultaneously in my world). Should it read something like:
"Differences between dual channel simplex Rx and dual channel multi-plex Rx"...????
I am still of the opinion that the "problems" with Class B have been blown out of proportion. Let's face it, there aren't many units out there yet, so asside from the trials by the UK Coastguard and the massive simulations conducted by the USCG, there is little or no firm data to base any conclusions on. Why don't we just wait and see how it turns out in reality before condemming it.