Range vs moto talk


#21

Posman,

I am not an engineer but I had plenty of them work for me and nearly 20 years in the Live TV business has put me at both end of transmitters/receivers of Video, Audio and Data. I am well versed in many forms of RF both digital and analog signals (even a little laser encoded data) everywhere from the side of active volcanos to sound stages buried underground.

I think the key thing here is that one digital signal on a similar frequency and even at the same power is not the same as another.

In the case of digital signals, encoding, compression, bandwidth consumed, error correction are all factors.

Handshakes are good things when they work and can also be a barrier to communication when something without a handshake might otherwise get through in part (assuming the encoding, compression and error correction can handle partial packets of information).

Also while not a factor in what you describe additional power can actually be a negative factor if it increases multipath and noise.

Simply put just because the Moto does get through is not an indictment of GoTenna’s methods.


#22

@Posman, @Firqby and everyone else that contributed to this topic, thanks for the engaging and in-depth conversations. Seeing how passionate you are about our product is extremely rewarding to the team here at goTenna!

On to the issue at hand, I think we have a convincing answers to present. We analyzed the FCC report of the Motorola i335 phone, which can be found at this link: https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=Y&application_id=exRI7AR26L4TaEEdbdjA9w%3D%3D&fcc_id=IHDT56HG2

Transmit Power
Although the Motorola i335 nominal output power for the ISM transmitter (902-928 MHz, same as goTenna MESH) is stated at 890 mW, the effective peak power it transmits is actually 1 W as stated in Exhibit 6c “the modulation scheme employed can cause peak fluctuations in output power up to 0.5 dB from maximum pulse average power, which is 890 mW (29.5 dBm)” So the transmit power of the Motorola i335 is the same as goTenna MESH, at 1W.

Modulation Schemes
MSK, FSK, were mentioned as possible alternatives to the GFSK. Back during the architecture phase, we have weighted the pros and cons of these modulations schemes and have concluded GFSK is the best choice. Here is why, MSK (Minimum Shift Keying) effectively reduces the modulation index to 0.5, while improving spectral efficiency, the sensitivity will be degraded by 1.5 to 2.5 dB due to the compromised modulation index (rule of thumb ideal index is 1). FSK, although improves sensitivity, it creates high levels of spurious contents and side lobes, which causes regulation standard violations. The best of both worlds is the GFSK (Gaussian Frequency Shift Keying), it applies a Gaussian filter to the symbols before the frequency modulated signal to suppress the spurs and side lobes, at an expense of 0.5 dB reduced sensitivity.

So by the above data, goTenna MESH and Motorola i335 should have the same range performance, but it does not appear so, and we have a hypothesis - it has to do with the network protocol and the choice between optimizing a point to point system or a scalable mesh network.

Digging into the FCC report of the i335, we found that during transmission, the i335 floods the entire 902 to 928 MHz during a transmission by cycling and repeating through all 50 channels. i.e. Tx channel 1, then 2, then 3, to 50 and repeat. This is a simple but brute force approach to gain frequency diversity and continuous re-transmissions, which effectively improves range at expense of congesting the network. For a point to point, none shareable system, this is the right approach. However, for a scalable mesh network, this approach will cause significant issues - as the number of nodes scale, the overheads and complexity of the routing table scales exponentially, without allowing proper amount of time slots / quite time of nodes in the system, the defining meshing feature of goTenna will fail. So this is a compromise we are willing to make.

Of course, all of the above are concluded from paper studies. We can acquire a few of the Motorola radios and conduct measurements on them in our lab to confirm our hypothesis.

I hope this clears things up a little. Please let us know if you have any questions or found any mistakes in our analysis, and thanks again for being so passionate about our product!

Best,
JC and goTenna team


#23

Hello, Jin_Gotenna! Your preliminary tests are very detailed. Also, thanks you for the modulation theory. I will be very grateful to Gotenna’s team if you do field tests and lab studies of mototalk in comparison with the Gotenna Mesh.


#24

Plus, a wish for the product: given that there are not so many blending units in the world, I would be tempted to take into account the experience of point-to-point experience, since so far it is spread out!


#25

That is a nice explanation. I’m going to show this to some of my Ameteur radio friends. There’s a lot to think about here. Some of our radios use a version of the protocol in those old Motorolas. I may also do some side by side testing since I have a couple of those old Moto phones. Once it warms up a little around here.


#26

There might be something useful buried in those old Motos, but I suspect mostly not.

As JC noted, interesting the way Motorola went about this, but cell networks tend to operate much differently than mesh does. An approach that uses “brute force” works well for centralized networks, but the goTenna plays at the other end of that scale, where finesse and simplicity are advantages when there are only limited resources for/from any single unit, but the additive effects of meshing are what builds the overall effectiveness that users perceive.

While Motorola has fallen on hard times of late, it’s a pretty big outfit compared to goTenna. Gotenna, like most of us, has to play by the rules already set. Players as big as Motrorola, however, are big enough that gaming the rules or even rewriting them through lobbying, campaign contributions, etc is feasible. Kinda curious what was in that FCC report and if what Motorola did was later constrained/outdated by either new regulation or technical change.

Another factor is that even if there is some applicable tech in the Moto, you can’t forget that patents tend to apply to such things. Just because Motorola did something, goTenna can’t just “borrow” an idea without making arrangements to satisfy the patent holder. It might, but when things cost, then cost-benefit analysis has to be applied to determine whether that makes sense to incorporate into future goTenna technology.


#27

Hello Everybody!

As noted by Jin_Gotenna, the floods in all spectrum ISM is perhaps a rough approach, but effective! and experience of Moto in direct talk is 15 years. Their radio DTR still cost decent money and have good reviews.

I’m sure that someone else’s experience is worth considering!


#28

Certainly it’s worth considering the experiences other have. The technology of relatively low-powered radio makes it important to squeeze every possible advantage from the signal when you’re up against some pretty limiting regulatory and physical constraints.

Thing is it sounds a lot like Motorola was taking advantage of the power of a centralized network to game the most it could from the signals. A mesh network may seem superficially similar, but operates rather differently. Where there is some coincidence and possible advantage in looking to the Moto for possible solutions, it’s around the radio portion of the technology. Other than that, JC is making a notable point when he or she cautions about the differences in how the two networks operate in the third to the last paragraph of JC’s long note above.


#29

My testing tools)
Hello, the team! How are the tests going forward.

In the picture: moto 335, 576, 365 and two generations of gothenn. And I still think that gene 2 needs to be improved.


#30

My moto 335 still gives a stable mile!
And gene 2 is capricious after 500 meters.


#31

We don’t have the bandwidth to do any testing around the Moto but if you want to go ahead and share what you learn please do so!


#32

Some testing details would also be good. I’m assuming you are testing in like conditions.


#33

Digging into the FCC report of the i335, we found that during transmission, the i335 floods the entire 902 to 928 MHz during a transmission by cycling and repeating through all 50 channels. i.e. Tx channel 1, then 2, then 3, to 50 and repeat. This is a simple but brute force approach to gain frequency diversity and continuous re-transmissions, which effectively improves range at expense of congesting the network. For a point to point, none shareable system, this is the right approach…

I think, since the team of the Gotenna made a bet on the mesh, it should be taken into account that in addition to the USA in the world there is very little chanse to meet the knot. It may be worthwhile to make the adjustment for gene 2, namely to work in a mesh or a single variant with the full use of the spectrum.


#34

Hello Jin!

I performed a few more measurements of the distance in the dense urban development.
The conditions were as follows:

  1. One Gotenna Mesh unit was located on the 3rd floor of an office building near the window.
  2. The second Gotenna was in the breast pocket of the my shirt.

I received a maximum range of 100 to 250 meters, depending on whether the buildings overlapped the line of LOS.

In similar conditions I had two Motorola i335 phones and a maximum communication range was 800 meters.

Honestly, I was disappointed with this. I had a feeling that Gotenna
did not work at reflected waves at all, but the 900 mHz range is very effective in dense buildings.
Compared to the Gotenna Mesh, the phone was perfectly received handshakes at a range of up to 1 km.

Maybe it’s worth thinking about more efficient use of the spectrum of the Gotenna? If the grid requires a different approach,
then you can provide a forced point-to-point mode in the program settings.

I’m very sad (
Maybe my device has a defect…


#35

Just to note, the goTenna Mesh should not be in your pocket if you want to get maximum range from it. It sounds like this is OK, because you do it with your phone, but the physics involved will limit reception. It needs to be outside of your clothing and as high on the body as possible. That’s why they note a good place is on the top of your backpack.

In your chest pocket means that you will effectively block the signal with your body half the time. You will tend to get reception only when you’re turned so that the GTM gets a line of sight view of the transmitter. It’s also the case that even then, because of mass of the body, the signal is attenuated.

I will say, that as one with decades of experience in radio use, the comparisons between cell phone reception and goTenna performance are apples and oranges. Two very different services with different technical specifications and regulatory limits. If you want a cell phone, get one. The goTenna is something different. For more on these substantial differences, here’s the low down on cell phones:
https://en.wikipedia.org/wiki/Cellular_frequencies
https://www.whistleout.com/CellPhones/Guides/cell-phone-networks-and-frequencies-explained

The goTenna Mesh operates in the 902 to 928 MHz range (in the US) with a transmission scheme that must comply with rather strict limits on bandwidth, power, and transmission mode set by the government. If you were expecting the same thing you get from a cell phone, that’s like expecting a pickup truck to haul the same load as a semi. The problem isn’t the pickup truck, it’s thinking that the little truck that gets you everywhere in town with a useful load can haul as much as a vehicle for heavier payloads that is restricted to major roads. Two different services that serve different needs.


#36

Hello MikeL,

Read the posts above, as well as the analysis of the radio engineer Gotenna. Finally there are reports of the FСС:


https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=Y&application_id=exRI7AR26L4TaEEdbdjA9w%3D%3D&fcc_id=IHDT56HG2

I tested both devices equally, including in front of me.

Yes, I know that Gotenna made a bet on the grid, but I just want to point out the need to optimize the use of the spectrum in point-to-point conditions.

Not all have a relay nearby(


#37

Where do I begin?

It would be helpful if you would point out what you believe is the “special sauce” that could somehow be transferred from the Moto to the Mesh? You seem to be basing this all on observation that the cell phone provides a superior signal, which may in fact be the case and is not surprising at all for a number of reasons. My reading is that there is not anything particularly useful for goTenna here.

Perhaps you’re basing this on the fact that both make use of the same ISM frequencies, which they do. Part of problem is that the requirements for measuring during testing changed between 2007 and 2016 for Part 15 devices. In 2016, for the GTM see page 10 in this document: https://fccid.io/2ABVK80085/Test-Report/Test-report-3233950

For the 2006 Moto test, see age 7a-4: https://fccid.io/IHDT56HG2/Test-Report/MEASUREMENT-PROCEDURES-831635

I’m not a EE, so can’t speak to the specifics here, but I think this is the tip of the iceberg of differences. I do know that there was some controversy over the Motos when they came out. I suspect that may have led to the changes in test procedure based on perceptions that Motorola had gamed the system in it’s favor.

Some of the difference might be attributable to the fact that the Moto relied on feedback from the network to improve its frequency stability. See page 7a-5 at the Moto link cited above. Obviously, if you’re building a non-cellular device suitable for use off-grid, you can’t rely on that. On page 1-2 of this link https://fccid.io/IHDT56HG2/Label/IDENTIFICATION-LABEL-831879 it is suggested that “there is no
connectivity to any networks and the transceiver uses only the FHSS protocol” this statement does not quiet seem to preclude use of the network’s ability to improve frequency stability.

Then there are the number of channels available to hop. The GTM now (at 51 channela) is in the larger of the two groups currently defined, first of at least 25 channels, then of at least 50. The Moto seems to have had 79 in an era that only required at least 15. See https://meshcommunity.gotenna.com/t/range-vs-moto-talk/2032/36 page 6D.1 - 3. Can goTenna increase the number of channels? Perhaps, but there may be other reasons to limit the number of available channels, like system processing capacity, etc.

I’m actually most curious about the antenna used for the ISM service on the Motos. For the GTM, it’s strictly defined as having 1 dBi gain. See page 6 here https://fccid.io/2ABVK80085/Test-Report/Test-report-3233950. The Moto report is broken down into separate chapters, making it a pain to search comprehensively, thus I can’t conclude that the info on what antenna the Moto uses while in the ISM band it shares with the goTenna isn’t in it, just that I didn’t find it.

But this suggests that the Moto used the same antenna for both cell and ISM service. Given that the FCC seems to rely on the fixed antenna concept to impose ERP limits in these low power services, it may very well be the secret sauce that gives the Motos the advantage. If so, this is one area that would be clearly forbidden for goTenna’s engineers to use unless there’s a way to get a waiver to use it. If they did, then the FCC testing would likely need to be repeated with the new antenna.

Nothing in ether report suggests that there’s been anything of much significance left on the table by goTenna’s engineers. I do wish I could find some references to the issues that others saw with testing of the Motos at the time or to what antenna they use when operating in the ISM band.


#38

Hi,

In my comparative analysis, I proceed from the following.

  1. Both devices have the same transmitter power (0.89-1Watt)
  2. Both devices operate in the same range of 902-928 MHz
  3. Both devices use the FHSS technology.
  4. An aerial of Motorola phones in most cases a conventional dipole with a similar gain of 1db.

However, under similar test conditions, the devices show different results for the range of action and not in favor of the GM.

In the commentary of the radio engineer of Gotenna, there is an assumption about possible causes, namely, a different approach to the use of the spectrum.

Unlike GM, motorola uses the entire width of the band 20mhz, successively on each of the 50 channels. Thus, filling the entire spectrum of the ISM, and achieving a good result in range. Gotenna is oriented to a mesh and a similar approach in filling the spectrum can negatively affect the grid. Although it seems to me that the FHSS should minimize the interference for the grid.

I hope radio engineers can optimize the operation of devices.
It is obvious to me that the Moto made 10-15 years ago work simply and reliably in the range of 1 mile, which can not be said about Gotenna Mesh.


#39

Please cite the specific graphs you are referencing here for both the Moto and the GTM.

Also, note that the Moto uses 79 channels, not 50.

While there is some question about antenna limitations when the Motos were tested, the GTM was tested after the antennas were sharply defined. Using whatever Motorola did is unlikely to be an option.

And if there is anything here for goTenna to glean and use, couldn’t the same be said of millions of cell phones that lack the features you attribute to these specific Motorola cell models? For that matter, what about all the Motorolas that could be using this, but which are NOT? This isn’t a question of goTenna overlooking this, but something which is no longer permitted. Considering the financial distress of Motorola in recent years, if they had an advantageous design, why aren’t they using it or at least selling it to others?

I mention selling it, because if there was a good idea here with continuing value in the marketplace, then Motorola would’ve patented it to do exactly that. GoTenna can’t just pick up someone else’s good idea, even where they do exist. No, they’d have to buy the rights to it. So far, there’s nothing I can see worth buying, nothing on offer from cash-strapped Motorola that could bring in such much-needed funds, and no patents cited that could be now used by goTenna.

The clincher in all this is that the Moto ISM was a voice service, right? Big fat bandwidth-sucking voice service, not the modest demands of the GTM’s SMS text service. So something weird is going on since Motorola managed to do that heavy lifting on the same basic RF output as the GTM, at least on paper. Something doesn’t compute right there in that alone. Apples vs oranges? Sounds like it to me.


#40

Also, note that the Moto uses 79 channels, not 50.

Do not mislead people.
The MOTOtalk ISM Band transmitter uses 50 frequencies within each selected hop set.

I specifically gave a link.

https://apps.fcc.gov/eas/GetApplicationAttachment.html?id=831880

and phone models do not matter. MT is a certified technology, which is also used in radio stations of the DTR and DLR series.

I mention selling it, because if there was a good idea here with continuing value in the marketplace, then Motorola would’ve patented it to do exactly that. GoTenna can’t just pick up someone else’s good idea, even where they do exist.

In this discussion, I only compare physics RF and do not discuss marketing issues.