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[aprssig] Beacon rate/distance

Bob Bruninga bruninga at usna.edu
Mon Oct 12 13:57:58 UTC 2009


Steve makes good counter arguments for the value of SmartBeaconing and that shows the flexibilty and versatility in the APRS network.  That users are able to choose what is best for their needs for any immediate application.  

This user versatility is one of the reasons why we tend to not like some proposed "smart digi" concepts that force users into only one method (must move X distance, or only one report in X minutes).  The network must remain versatile to try to meet the individual needs of the users (with due consideration to others, of course)...  Bob, Wb4APR

>> Conversely, if users set the smart beaconing 
>> to such a low and sparse rate to share the 
>> channel equitably, then in many cases,
>> the inconsistency in position and lack of 
>> regular timing might actually detract somewhat 
>> from the objective of maintaining
>> continuity of communications contact.  
>
> So your latest complaint about SmartBeaconing 
> is that it doesn't maintain the continuity of
> communications because it doesn't transmit at 
> precise intervals?  You're saying you like 
> fixed-rate beaconing because it's fixed rate?  
> I like vanilla ice cream, but I won't make 
> a technical case for it.
>
> The entire point of SmartBeaconing is to 
> provide the most information about vehicle 
> motion (AND HENCE POSITION) with the MINIMUM 
> of channel traffic.  SmartBeaconing's not 
> regular for a reason: the reporting rate is 
> correlated to the motion, and therefore 
> ROAD-RELATIVE position, of the vehicle.  
> It's optimum-quality position information, 
> as opposed to uncorrelated position information.
>
>> Also, the loss of a single packet due to 
>> collision under smart beaconing is the loss
>> of a lot more information than the loss of 
>> a single packet at a regular rate.
>
> As the author of SmartBeaconing, I think 
> I can speak to this.  While it is true, 
> strictly speaking, that more information 
> about the vehicle's _motion_ is lost when 
> a SmartBeaconing packet is lost, than when 
> a fixed-rate position packet is lost, but 
> that doesn't make a positive case for 
> fixed-rate beaconing.  In fact, the 
> QUALITY of position information in each 
> SmartBeaconing packet is much higher than 
> in a fixed-rate packet, because the info 
> in a SmartBeaconing packet is correlated 
> to the vehicle's position on the road 
> (e.g., a corner).   So, you're again 
> complaining about something that 
> SmartBeaconing gives you that fixed-rate 
> beaconing does not give you.
>
>
>> I prefer -regular- rates, so that the 
>> recepients can know what to expect as 
>> to the next position and/or can know 
>> how many positions per hour to expect.  
>
> Bob, this is a mere personal preference, 
> not a sound recommendation based in 
> technical fact.  If you have studied the 
> SmartBeaconing algorithm, you know that 
> it, in fact, DOES guarantee a minimum 
> number of position beacons per hour, 
> but ADDS additional beacons to provide 
> information at crucial positional states, 
> like turning a corner.
>
>> In that context, we came up with 
>> "proportional pathing" which we got 
>> Kenwood and some trackers to implement.
>
> There is nothing wrong with combining 
> SmartBeaconing with your "proportional 
> pathing"; in fact, my personal D710 is 
> set up just that way. 
>
> The idea of sending high-rate positions 
> to short paths has technical merit, and 
> is NOT mutually with exclusive with the 
> QRM-reducing aspects of SmartBeaconing. 
> In fact, in the latest HamHUD II code 
> (available for free on my website) 
> integrates SmartBeaconing and proportional 
> pathing such that the high-rate data 
> (corner pegging) goes out over shorter 
> paths when "proportional pathing" is enabled.
>
> Bob, you of course are free to discuss 
> about your personal preferences for fixed-
> rate beaconing and "proportional pathing".  
> But when you recommend to the APRS 
> community that fixed-rate beaconing is 
> preferable to SmartBeaconing, you should 
> have solid technical reasons for doing so, 
> not "SmartBeaconing is not fixed-rate, 
> so it's bad for the network".
>
> One more thing: if fixed-rate transmission 
> was technically better for network capacity 
> than some form of  randomization, then why 
> are all the cell networks abandoning TDMA 
> in droves for CDMA? 
>
> 73,
>
> Steve Bragg KA9MVA
> HamHUD Nichetronix, LLC



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