Independent tests prove lack of frequency hopping with XPS

[RH1N0]

XJet,

I believe the XBee-PRO OEM module uses direct sequence spread spectrum and that it defaults to 3 retries before a packet is dropped. So would channel hopping need to be implemented on the XPS carrier board? How long does the module take to change to a different channel? And can it test a new channel for interference while still transmitting on the current channel?

As a general observation, I think it's great when a product is user upgradeable via firmware revisions but the buyer should know, at the time of purchase, if they will be required to regularly update or modify their product. Some people like to tinker and others just want to "fit and forget".

[XJet]

	Quote: Originally Posted by RH1N0
	XJet, I believe the XBee-PRO OEM module uses direct sequence spread spectrum and that it defaults to 3 retries before a packet is dropped. So would channel hopping need to be implemented on the XPS carrier board? How long does the module take to change to a different channel? And can it test a new channel for interference while still transmitting on the current channel?

Yes, the XBee/Pro systems are DSSS and do not have any intrinsic frequency-hopping capabilities.

No, they can't perform a channel-scan while receiving data -- incoming data will be lost during the channel-scan operation.

I don't recall the exact channel-change time off the top of my head but JD has said that MaxStream are modifying the firmware for him so that it can change channels more rapidly.

That would mean existing users would have to return their transmitter modules and receivers for two sets of firmware updates -- one involving new code for the XPS firmware and one for the XBee/Pro firmware.

Given the delays involved in just getting "in stock" items shipped, this could be a logistical nighmare. I hope he gets things sorted before spring so we don't see thousands of XPS users all waiting for their systems to be updated and returned.

I also expect the cost (to XPS) could be significant if everyone decides to get their systems updated -- let's hope they have sufficient financial resources to cover that cost.

However, bearing these issues in mind, I suspect XPS will strongly downplay the importance of such an upgrade -- but I wouldn't wish to risk an expensive model to a system with no frequency agility so I'd certainly recommend that people *do* get their systems upgraded when/if that option becomes available.

[sweetpea]

Could those upgrades be made from the optical firmware device that is being finalized now that several people are testing with?

[XJet]

I have no idea, but as far as I know, the XBeePro modules aren't field-upgradable so even if the XPS firmware can be updated I expect the XBeePro will be a "return to base" job.

[Neogenesis]

Great thread........any idea as to when the data is going to be available?



Neo

[3DDevil]

I lost my plane on the weekend.... dam... back to 36Mgz here.... if people want a more complete report let me know....

[klhoard]

	Quote: Originally Posted by XJet
	I have no idea, but as far as I know, the XBeePro modules aren't field-upgradable so even if the XPS firmware can be updated I expect the XBeePro will be a "return to base" job.

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What does "10's of Thousands" (or is he up to Billions) of XPS units times 10 minutes turn-around per unit work out to?
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[3ddd]

TOO F$%KING LONG----HE NEEDS TO DO A STRAIGHT EXCHANGE AND UPGRADE THEM ON HIS OWN TIME

[jonkoppisch]

	Quote: Originally Posted by 3DDevil
	I lost my plane on the weekend.... dam... back to 36Mgz here.... if people want a more complete report let me know....

What happened??

[sweetpea]

This thread is pretty much useless and one sided.

XPS does not post on any site except RCgroups.com

If you want all the information you need post and read there since XPS doesn't spend time at FG (though we all wish they would have chosen FG over RCG)

Here is a link to the thread about the freq hop
http://www.rcgroups.com/forums/showthread.php?t=789453

then you can make-up your own mind with more information from both sides

[Kiwi]

Guys,

I think the tempers and name calling stuff needs to be left out until Xjet gets his tests on here for everyone to see. The guy has said he will post them after the festive break and I have every reason to beleive he will do so.

The only thing I have to say on this is having been in contact with Xjet several times for different reasons is the guy likely will lay it clean on the line as he says it. The guy is in the industry and knows what he is talking about. Its not a hobby for the guy so I am all eyes and ears on what he has found and what he will show.

But until then I will stay in the background guys, just keep it friendly and wait and see. Maybe we are in for a few surprises.

[XJet]

	Quote: Originally Posted by Kiwi
	Guys, I think the tempers and name calling stuff needs to be left out until Xjet gets his tests on here for everyone to see. The guy has said he will post them after the festive break and I have every reason to beleive he will do so.

Thanks Kiwi -- but the one thing many seem to have forgotten in all this is that JD has admitted that XPS won't frequency hop when exposed to sudden levels of strong interference.

So why are a handful questioning this?

Although I'm happy to provide it -- why do these people need evidence -- why do they now not trust JD's word when he says this flaw exists?

When the manufacturer admits to a flaw and independent tests prove it --what's to doubt?

XPS are trying to downplay the significance of this problem but they clearly haven't done a great deal of airborne analysis of the 2.4GHz spectrum and thus believe that these sudden increases in the noise floor are always going to affect the entire band (which, in my experience they don't).

That there are a small (but not insignificant -- especially to those who are affected) number of unfortunate incidents with XPS that bear the hallmarks of the sudden onset of strong interfering signal, I assert that it's a factor which existing and prospective users ought to be aware of.

Others may disagree with this assertion, either for commercial reasons or because they fear it may lead to buyers' remorse.

I think the ideal outcome of this will be for JD to stop making outrageous claims for XPS (as he has continuously done since before its launch) and simply address the current deficiencies -- as he has done in the past with the anntenna issues. XPS can be salvaged -- but JD needs to stop trying to pitch XPS as something it's not and just get on with the job of ensuring that everyone ends up with the robust, reliable 2.4GHz system they thought they were getting.

[bob_nj]

"I lost my plane on the weekend"I'm interested, what happened?

[KrisW]

My Synthesized 72mhz JR stuff works just fine. I was very tempted to bite on the 2.4ghz technology, but I'm really glad I resisted the temptation. I had 2 pcm lockout incidents last year, both were antenna-aircraft orientation caused at long distance(DOH!!!) and quickly averted. It'll be a few years before I try 2.4ghz (If I ever do).

Good thread. . GREAT information. . .nice to see an informed, intelligent, and logically applied perspective on these problems.

[Kiwi]

So Xjet what Mr Drew wrote here and these are his own words is totally BS.??

(Quote Jim Drew on RCU)

I am not sure what answers you are looking for. The bottom line is that we don't have a problem with the system, and I don't expect to ever see a problem. We are the ONLY 2.4GHz system that has the ability to monitor the available frequencies in the 2.4GHz range and change as necessary, in real time. This means that the plane as well as the transmitter can make the change occur. If you flew your plane over a school with a huge 14dbi external 802.xx antenna, that would likely be cause for switching to a new frequency (away from whatever channel that 802.xx was on).

We don't conflict with any other 2.4GHz systems, and they don't conflict with us. Our systems are special, one of a kind radio configurations and no two radio modules have the same ID. It is physically impossible to have a conflict unless two identical ID's were available. We can't even get MaxStream to do that for us for testing the theory, so we know that it will not happen.

Anything is prone to a problem. 2.4GHz will not transmit through large sections of earth (hills, etc.). So, as long as you are flying LOS (line of sight) you will never encounter and issue with the radio link that is related to our system or any other 2.4GHz system available. Even 2.4GHz cameras are not a problem as we can move around their frequency, even with huge drift that occurs in the cheap overseas versions. Our system is extremely well thought out for safety reasons.

People have witnessed and flown the system first hand. We did a range check with the 40% gas plane, and it was so high that we lost it in the camera and could no longer hear the engine running (and it was!) That is some distance. The highest recorded flight to date was 4947 feet, but I believe we have gone higher than that, just not recorded the flights with the altimeter.

If you care to argue, I have no reason to reply. We will be providing a system that will support virtually every major radio system in the industry, providing safer flying.