Re: New Updates on Site

"Michael E. Fox - N6MEF" <n6mef@...>

It seems like the target keeps changing.  “If you don’t know where you’re going, any road will take you there.”


Even if a higher speed is possible, it may not be deployable in many locations due to path issues.  Those familiar with deployment of WiFi or digital LMR technologies like P25, DMR, etc. know that the individual circumstances of each path dictate which encoding schemes work and which are just too iffy to be used beyond a certain bit rate.  The denser the constellation, the more perfect the signal needs to be.  Otherwise, what would not be a decoding error at a lower rate becomes an unbearable error level (beyond the ability of FEC to correct) at higher levels.  You can see this on protocol-specific analyzers as the error rate gets higher until FEC breaks down.  To be deployable in multiple environments, a variety of encodings/speeds and channel widths is needed.


So, if you start out at only higher speeds, you may end up with something fast in the lab that is not deployable except in limited situations, like path-perfect, mountain-top to mountain-top situations.  And even with mountain-top to mountain-top, if the link is long, you may need to drop back on the speed to lower the error rate Or, maybe you don’t have the right size channel available so you may need to drop back.  (Mountain-top to mountain-top means you’re taking up that channel over a much wider geography and you need to make room for everyone.)  For the price, the thing needs to be able to be deployed in a variety of different scenarios.  At least make sure that we can select various rates/encoding schemes and channel widths.


Also, I hope whatever you do includes an analyzer that shows the constellation, decoding error rate, modulation quality, etc.  This will be important for determining the link quality at install time or when diagnosing problems.  Otherwise, even if it works, we’re just sitting there with our fingers crossed, not knowing how close we are to it not working.  Examples of the functionality would be something like the analyzer for P25, DMR, etc. in the Anritsu LMR Master or the Aeroflex analyzer line (several models).  They all pretty much show the same information.


I really, REALLY want this product to work.  Hopefully I’m not mentioning anything that the designers/developers don’t already know and are working on.  But I don’t see these real-world issues addressed in the discussion.  So it leads me to wonder…. 





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