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Frequency Hopping Spread Spectrum vs. Dual Band

Old 10-09-2019, 01:46 AM
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Default Frequency Hopping Spread Spectrum vs. Dual Band

I need some technical expertise on this question. With our remote control product, we use a frequency hopping spread spectrum (FHSS) two-way transmission system on 5 channels of the 433 MHz band. The signal is designed to hop 5x per second.

Our competitor uses a dual band, one-way system on 433 MHz and 916 MHz (although they only have FCC approval on 868 MHz - another story).

They are basically claiming to the unknowing public that "two bands are better than one," and that FHSS is archaic technology since it was initially developed many decades ago.

I am hopeful that I can find an RF transmission expert who can provide me with proof, in the form of some type of clear and easily understandable example, which shows the benefits of two-way FHSS vs one-way dual band.

Thanks in advance for your assistance!

Last edited by Remote Control for Boats; 10-09-2019 at 05:47 AM.
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Old 10-09-2019, 05:40 AM
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Single band was utilized by Tesla over 100 years ago. Dual band is just two single frequencies.

The concept of spread spectrum originated in WW2, but was not put into widespread practice until the 1960s, and really came into its own in the 1990s.

There are nice things about using two bands, but spread spectrum has a lot of advantages as well.

When Spektrum developed DSM, originally it was a single frequency system for cars and then later for airplanes in the DX6 Parkflyer System. DSM2 was two frequencies that were alternately used, and was the basis for our first full-range products suitable for any aircraft. It worked great up until we had a hundred pilots flying at a time, in events like Joe Nall. DSMX was developed to address the issues of using only 2 frequencies - it uses 23 frequencies, and is the leading model control protocol in the world.

If you want mathematical proof for the superiority of spread spectrum, I suggest you turn to your local university's math and electronic engineering departments.

Andy
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Old 10-09-2019, 05:57 AM
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Originally Posted by AndyKunz View Post
Single band was utilized by Tesla over 100 years ago. Dual band is just two single frequencies.

The concept of spread spectrum originated in WW2, but was not put into widespread practice until the 1960s, and really came into its own in the 1990s.

There are nice things about using two bands, but spread spectrum has a lot of advantages as well.

When Spektrum developed DSM, originally it was a single frequency system for cars and then later for airplanes in the DX6 Parkflyer System. DSM2 was two frequencies that were alternately used, and was the basis for our first full-range products suitable for any aircraft. It worked great up until we had a hundred pilots flying at a time, in events like Joe Nall. DSMX was developed to address the issues of using only 2 frequencies - it uses 23 frequencies, and is the leading model control protocol in the world.

If you want mathematical proof for the superiority of spread spectrum, I suggest you turn to your local university's math and electronic engineering departments.

Andy
Thanks for your reply and suggestion. I need simple, easy to understand proof that I can present to the boating public.

I thought about mentioning that FHSS is commonly & widely used with Bluetooth and Wi-Fi, which everyone has certainly heard of. To the best of my limited knowledge, Dual Band is not often used for any recent devices or technology, and definitely not with something so important as wireless remote control of a small boat or yacht.

True or untrue?
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Old 10-09-2019, 06:14 AM
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Your phone probably supports FHSS WiFi on two bands - 2.4 and 5.8. For each, it's only connecting to one or the other, and is thus single band FHSS once running, but it has two bands available to it. If one is overloaded (usually 2.4) then you can tell it to move to 5.8, but it's usually a manually-selected thing (though it can be automatic).

The truth is, there are advantages to both. The best solution would be multiple bands, frequency hopping within each. That is, technically, just a matter of expanding the spectrum of allowed frequencies.

Since you're talking boats, you especially need to understand the problems of operating 2.4gHz over water and how greatly it diminishes range. It is far from the best band to use. Right there your competitor has a huge advantage because 433 & 868MHz are going to have much better performance over the water, but you being on 433 isn't an issue.

Andy
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Old 10-09-2019, 06:17 AM
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Note also that 5 frequencies, though much better than 1, is hardly taking advantage of spread spectrum. And hopping at 200ms intervals isn't much of a spreading. The ability to use more channels more quickly is where you start to see the benefits of spreading. Jamming (whether intentional or not) is far more difficult if you spread out shorter bursts over wider area more frequently.

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Old 10-09-2019, 06:20 AM
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Originally Posted by AndyKunz View Post
Your phone probably supports FHSS WiFi on two bands - 2.4 and 5.8. For each, it's only connecting to one or the other, and is thus single band FHSS once running, but it has two bands available to it. If one is overloaded (usually 2.4) then you can tell it to move to 5.8, but it's usually a manually-selected thing (though it can be automatic).

The truth is, there are advantages to both. The best solution would be multiple bands, frequency hopping within each. That is, technically, just a matter of expanding the spectrum of allowed frequencies.

Since you're talking boats, you especially need to understand the problems of operating 2.4gHz over water and how greatly it diminishes range. It is far from the best band to use. Right there your competitor has a huge advantage because 433 & 868MHz are going to have much better performance over the water, but you being on 433 isn't an issue.

Andy
Hi Andy,

We have a two-way system (transceiver + receiver) that uses a FHSS transmission over 5 channels on 433 MHz. The competitor uses a one-way system (transmitter + receiver) on a dual band system that actually uses 433 MHz and 916 MHz. They have FCC approval on 868 MHz, but not on 916 MHz.

The transceiver + receiver signal "hops" over 5 channels at a rate of 5x per second.

Thoughts?

Thanks again,
Brian

Last edited by Remote Control for Boats; 10-09-2019 at 06:23 AM.
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Old 10-09-2019, 06:29 AM
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See previous reply. You replied before you read my second post.

Andy
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Old 10-09-2019, 06:42 AM
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Thanks again Andy,

I am wondering if we hope continuously over the same 5 channels on 433 MHz and stay on those 5 channels only, or if we hope 5 channels, and then another 5, and so on.

Much appreciated!
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Old 10-09-2019, 07:18 AM
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How many channels are in your spectrum? How tightly are your channels transmitted? How selective is your receiver? How long are your transmissions? How do you determine which channels to use and when? How much spare bandwidth do you have?

What's your website? I'd love to see what you're doing now, how you document it, etc.

Andy
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