WiFi and 2.4 ghz debate (posts moved from another thread)

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Just my 2 cents on WiFi...

Solo uses 2.4 GHZ radio, and uses the WiFi protocol so that it can connect to other things (like tablets). I know it sounds like others don't use this same radio frequency and technology, but things like "Lightbridge" are really the same under the hood.

They work the same wirelessly. In the case of DJI, after the video is transmitted wirelessly to the controller, they make a USB (serial) connection from the controller to the tablet. Using this 2.4 GHZ frequency and technology is necessary for a few reasons, some of which have to do with what frequencies are available and can be used without a license, and others having to do with radio signal propagation properties allowing the data and the distance.

Regardless of what it is called though... It is the same frequency, with the same interference, and limitations, etc..

As an example, the only radio difference between stock Solo and Phantom is the power output of the radios. I am not positive on the exact details, but I believe the stock radios in Solo are 500mw, but are degraded to 400mw in setup (I could be wrong on these exact details) and DJI uses 800mw radios. This results in the distance differences. Simple as that.

For what it's worth, add on antennas greatly improve Solo performance, have less dropped signals, etc.. They range form $8 to $100. The radios in Solo (both controller and copter) are also standard min PCI cards (different than DJI which is proprietary) and so can be swapped for standard 800 mw mini PCI cards without any other changes. These cards are in the $30 range.

People that do this regularly report distance capabilities of 2+ miles. Standard WiFi booster amps, box antennas, etc. can also be added, and people that do that have reported distance of greater than 5 miles (though I defy anyone to be able to see line of site that far).

There is nothing wrong with using "WiFi" and electrically (and due to regulations) there are few alternatives. If you are having problems at very short range, it "could" be interference, but more likely there is just something wrong. It is impossible to know what it is without looking deeper, though there is a set of calibrations that are known as "stick calibration" (but are actually much more) that have fixed this problem for several people.
 
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Earl, To me the issue with using WiFi is that WiFi is everywhere!! It's even in a lot of new cars (and a lot of the owners aren't even aware that their car is transmitting a WiFi signal).

However, other 2.4 GHz signals are not as prevalent and popular as WiFi. As an example, the protocols used by very popular RC transmitters almost NEVER have interference issues with each other, nor with WiFi. I have flown my RC equipment (using various protocols such as JR's, Futaba's, and FrySky's) with NEVER once having a control issue, even when flying in areas with STRONG local WiFi nearby.

In these cases the Solo WiFi falls apart, and aftermarket antennas are trying to solve the problem, but they can't solve it 100%.

So the basis of my comments were (and this should be it's own thread) was that I wish 3DR had used a separate protocol for the RC control similar to what other RC aircraft use (I don't care what they use for downlink of video and data as this is not a critical flight control function).

Heck, even my PixHawk based quad uses a solid RC controller that never has had one problem flying at close or long distances. It uses a separate protocol and link for data.

I know that everyone will say 'just tune this parameter and it will make it better', or 'use this brand aftermarket antenna and it will work better', but this doesn't solve the root issue. The Solo's WiFi controllers use a very popular protocol and frequency spectrum. This protocol and frequency range is only getting more popular and crowded as time goes on. Everything is starting to use WiFi. We're only at the starting tip of the WiFi explosion.

Cars, thermostats, door locks, radio speakers, IPhones, Androids phones, security systems, cameras, dishwashers, refrigerators, home sprinkler controllers, and more every day are starting to use WiFi for communications. This will only continue to explode over time.

The Solo (today) uses this same protocol and frequency range. So it has to fight to live with all of this potential interference.

If 3DR had used a more robust, different protocol for the flight critical controls, then we wouldn't have been in this situation. I can tell you now that I can fly my RC protocol controlled aircraft in places where the Solo would never even connect to the controller, and I would not have an issue at all.

Don't get me wrong, I own and like the Solo, I just wish we didn't have all these WiFi (or potential WiFi) issues to deal with.

Just sayin . . . ;)
 
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Earl, To me the issue with using WiFi is that WiFi is everywhere!! It's even in a lot of new cars (and a lot of the owners aren't even aware that their car is transmitting a WiFi signal).

However, other 2.4 GHz signals are not as prevalent and popular as WiFi. As an example, the protocols used by very popular RC transmitters almost NEVER have interference issues with each other, nor with WiFi. I have flown my RC equipment (using various protocols such as JR's, Futaba's, and FrySky's) with NEVER once having a control issue, even when flying in areas with STRONG local WiFi nearby.

In these cases the Solo WiFi falls apart, and aftermarket antennas are trying to solve the problem, but they can't solve it 100%.

So the basis of my comments were (and this should be it's own thread) was that I wish 3DR had used a separate protocol for the RC control similar to what other RC aircraft use (I don't care what they use for downlink of video and data as this is not a critical flight control function).

Heck, even my PixHawk based quad uses a solid RC controller that never has had one problem flying at close or long distances. It uses a separate protocol and link for data.

I know that everyone will say 'just tune this parameter and it will make it better', or 'use this brand aftermarket antenna and it will work better', but this doesn't solve the root issue. The Solo's WiFi controllers use a very popular protocol and frequency spectrum. This protocol and frequency range is only getting more popular and crowded as time goes on. Everything is starting to use WiFi. We're only at the starting tip of the WiFi explosion.

Cars, thermostats, door locks, radio speakers, IPhones, Androids phones, security systems, cameras, dishwashers, refrigerators, home sprinkler controllers, and more every day are starting to use WiFi for communications. This will only continue to explode over time.

The Solo (today) uses this same protocol and frequency range. So it has to fight to live with all of this potential interference.

If 3DR had used a more robust, different protocol for the flight critical controls, then we wouldn't have been in this situation. I can tell you now that I can fly my RC protocol controlled aircraft in places where the Solo would never even connect to the controller, and I would not have an issue at all.

Don't get me wrong, I own and like the Solo, I just wish we didn't have all these WiFi (or potential WiFi) issues to deal with.

Just sayin . . . ;)
I think you are missing the point. 2,4GHZ is 2.4 GHZ. It doesn't matter if you call it "WiFi" or not. It is the same thing, and subject to the same intereference.

Look at it like this.... The radio and frequency is the hardware. Think of it like a telephone set, with two recievers and a wire between them (simplified I know, but bare with me), You pick up the phone, and now you speak a language (protocol). Two people have to speak the same language (protocol) to talk to each other on the hardware. But, the language they speakit has nothing to do with interference. That is the hardware. In this case that is 2.4 GHZ radio. Whether you use "WiFi" protocol or not is irrelevant.

The difference in interference you see in other RC is due to several things, including different radios and frequencies entirely,and a host of other issues. The difference (at 2,4 GHZ) is mostly due to the location. People are MUCH less likely to fly fixed wing planes and even copters in neighborhoods and schools where these things are being flown.

Bottom line... 2.4 GHZ IS WiFi....from a radio perspective, and that is what matters for interference. Calling it something else, or using a different protocol on it, and using the same frequency makes no difference in interference or distance.
 
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I think you are missing the point. 2,4GHZ is 2.4 GHZ. It doesn't amtter if you call it "WiFi" or not. It is the same thing, and subject to the same intereference.

Look at it like this.... The rasio and frequency is the hardware. Think of it like a telephone set, with two recievers and a wire between them (simplified I know, but bare with me), You pick up the phone, and now you speak a language (protocol). Two people have to speek the same language (protocol) to talk to each other on teh hardware, but it has nothing to do with interference. That is the hardware. In this case that is 2.4 GHZ radio. Whether you use "WiFi" protocol or not is irrelevant.

The difference in interference you see in other RC is due to several things, inclusing different radios and frequencies entirely,and a host of other issues. The difference (at 2,4 GHZ) is mostly due to the location. People are less likely to fly fixed wing planes and even copters in neighborhoods.

Bottom line... 2.4 GHZ IS WiFi....from a radio perspective, and that is what matters for interference. Calling it something else makes no difference.
This is 100% true but I think the protocol contributes greatly to its ability to deal with interference. Some protocols are more efficient and deal with loss of data better.

I honestly don't know the first thing about the protocols 3DR or any other UAV uses. Totally clueless there. But from my 30 years of amateur radio use and dabbling with digital transmissions over RF, I do know protocol make a big difference. There are protocols that will maintain communication around the world with 1 watt and others that wont do it with 100 watts. Same frequency, same hardware.

I have always suspected DJIs lightbridge performance had more to do with protocol than power, antennas or design. But that's only a guess.
 
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This is 100% true but I think the protocol contributes greatly to its ability to deal with interference. Some protocols are more efficient and deal with loss of data better.

I honestly don't know the first thing about the protocols 3DR or any other UAV uses. Totally clueless there. But from my 30 years of amateur radio use and dabbling with digital transmissions over RF, I do know protocol make a big difference. There are protocols that will maintain communication around the world with 1 watt and others that wont do it with 100 watts. Same frequency, same hardware.

I have always suspected DJIs lightbridge performance had more to do with protocol than power, antennas or design. But that's only a guess.
*sigh*... They actually use the same protocol that handles errors etc...... IP... The only difference is the underying language (MAVlink in the case of 3DR) and (again) this has nothing to do with any of this.... DJI bundles all that and calls that "lightbridge" but what you call it doesn't make a difference.

They use the same frequencies, the same error correction, the same video compression. It is only the radio power that is the difference between these two particular units. If you up the wattage on the 3DR radios to be the same as the DJI units (and people do) you get the same performance. Simple as that
 
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*sigh*... They actually use the same protocol that handles errors etc...... IP... The only difference is the underying language (MAVlink in the case of 3DR) and (again) this has nothing to do with any of this.... DJI bundles all that and calls that "lightbridge" but what you call it doesn't make a difference.t
OK, good info. Thank you.

If you up the wattage on the 3DR radios to be the same as the DJI units (and people do) you get the same performance. Simple as that
I personally don't think so. What are the specs? Its not double the power is it? Even it it was double you could not make up the distance difference between the Solo and Phantom by adding even 7 db worth of antenna.

Edit: Sorry I missed this.

"but I believe the stock radios in Solo are 500mw, but are degraded to 400mw in setup (I could be wrong on these exact details) and DJI uses 800mw"

Thats still only 3db. IF its 400 to 800.
 
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Earl,

I'm not referring to the 2.4 GHz band, but to the protocol that Solo uses.

With my 2.4 GHz RC frequency hopping spread spectrum protocol, over 100 users can stand next to each other and have reliable communications with their aircraft. Try this with the Solo when it will only use 2 channels (or 11 if you modify the settings).

It's a totally different protocol from WiFi, even though it shares the same frequency band, all license free.

Check out the radios from companies like: Spektrum, Futaba, FrSky, JR, Airtronix, Hitek, Graupner, etc. They all use a similar, fairly bullet proof, interference free radio system for RC aircraft.

These don't have the issues that Solo has using WiFi for the critical control functions.

I use one of these with my PixHawk quad, and have never had even a glitch in control. Of course this same quad uses a different frequency for video downlink, and yet another frequency for data downlink to interface with Tower or Mission Planner.

I'm only saying that I wish 3DR had used a more robust protocol for the critical flight control functions. They chose WiFi for many reasons, but WiFi isn't as robust as these other proven RC protocols for critical flight control functions.

WiFi is great for the bandwidth it needs to send video, and data over the RF link. It's just not designed to be as bullet proof as the RC protocols that use the same frequency bands are.

Imagine you're out flying your Solo, a simple thing as me driving up with my car and parking next to you (holding your Solo Controller) could knock out your communications with your Solo if my Car had a WiFi hotspot in it that was on the same channel that your controller happened to choose to use with the Solo. This could never affect one of the RC protocol systems, they are designed to not have an issue with interference coming and going.
 
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I think you are missing the point. 2,4GHZ is 2.4 GHZ. It doesn't matter if you call it "WiFi" or not. It is the same thing, and subject to the same intereference.
I'm sorry to say... there is a HUGE difference with the protocols involved. They are not all WiFi on the 2.4 GHz band.

Some signals (protocols) can ignore the WiFi signals as if they were not even there.

I've flown my RC equipment in the same spot where the Solo has lost communications 40 feet from my controller, and my RC equipment hasn't even had one glitch, where the Solo completely lost communications and started RTH.

There also have been competitions and other gatherings where 100's of RC pilots can fly together, without concern from interference by any other RC, or WiFi signals that are in the area.

I'd suggest that you do a little homework into the different types of state of the art RC protocols being used today. I can't say they can't be jammed, nor experience glitches, but they are an order of magnitude more robust than the WiFi protocol. Of course, they are much lower bandwidth, and there are other differences, but they are well suited to flying and controlling critical flight controls on an RC aircraft (which, after all, the Solo is a type of RC aircraft).

As I said, this topic should really be it's own thread. Rich, as a moderator, can you break out this discussion since it's gone of track of the OP?
 
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Here's a video that shows 100 transmitters turned on while a flight is going on, I don't think Solo could come close to working in this environment with it's WiFi protocol:

Start it about the 3:00 point


Please, if I'm wrong, someone perform this same test using 100 Solo's flying.... LOL, I don't think you could get even 20 of them to link!
 
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I'm sorry to say... there is a HUGE difference with the protocols involved. They are not all WiFi on the 2.4 GHz band.

Some signals (protocols) can ignore the WiFi signals as if they were not even there.

I've flown my RC equipment in the same spot where the Solo has lost communications 40 feet from my controller, and my RC equipment hasn't even had one glitch, where the Solo completely lost communications and started RTH.

There also have been competitions and other gatherings where 100's of RC pilots can fly together, without concern from interference by any other RC, or WiFi signals that are in the area.

I'd suggest that you do a little homework into the different types of state of the art RC protocols being used today. I can't say they can't be jammed, nor experience glitches, but they are an order of magnitude more robust than the WiFi protocol. Of course, they are much lower bandwidth, and there are other differences, but they are well suited to flying and controlling critical flight controls on an RC aircraft (which, after all, the Solo is a type of RC aircraft).

As I said, this topic should really be it's own thread. Rich, as a moderator, can you break out this discussion since it's gone of track of the OP?
I work for a fortune 50 in the wireles communications and networking field. While there is always something to learn, I understand it quite well. I have also been flying RC craft for quite a while.

As I said earlier, when you are talking all of RC, you are talking a very wide variety of radio frequencies, wattages, and protocols, as well as using multiple frequencies and frequency hopping.. Notice in your video, they discuss very early on "frequency agility: and "spread spectrum". These are talking about using different frequencies... and dynamically changing frequencies. Each of these technologoes has it's bemefits and idiosyncrasies to be sure. Some are better at lower data rates, some are better with congestion, etc. etc. but we aren't talking about "everything". We are talking about 2.4GHZ.

In this case, the Solo uses 2.4 GHZ, as does DJI and several others. In the case of Solo and Phantom, the frequencies and (carrier) protocols are exactly the same. I will just say it one more time and leave it. The high level protocol (such as MAVlink) has nothing to do with interference. If you are using 2.4 GHZ and use a different protocol, you are getting the same interference regardless. That interference could be from a HAM transmitter, or even a large motor for that matter, as long as it is the same frequency.

Again, in this case, the underlying (ignoring) of messages, and error correction is also the work of another lower level protocol (carrier protocol) and it is the same between them. The general, and video compression is also the same between them. There simply is no difference in how they do any of this.

Think of how they both do this in relation to the IP. There is the hardware (Ethernet, Wifi, 3G, etc. etc) that handles the electrical signals, collision detection, actual retransmission etc.. Then there is the carrier protocol (TCP/IP) that handles packets, errors, resending, etc. Then there is a one or more high level protocols (HTTP, SMTP, SNMP, etc.) that deals in messages that allow applications to actually talk with one another. These high level communications have nothing to do with interference, error correction, etc. They don't even know it exists for the most part. They are encapsulated in the lower level protocol.

They only communication difference (other than the "words" being spoken) between a DJI Phantom and a 3DR Solo is the wattage of the radios... The words don't deal with error correction, the carrier protocol does, and that is the the same. The 3DR solo language (MAVlink) isn't any bigger or different than wht DJI uses. It doesn't effect any of this

And the proof in the pudding, is that when you use the same wattage radios on each of them with the same antennas... They end up with the same dbi at the same distances, and the same performance.
 
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OK I'l leave it at the point that we're at. Also I never mentioned DJI in this thread, I never was trying to compare the Solo to anything that was DJI. If DJI uses the main stream RC protocols, then good for them (in my eyes), but I don't know or care what they use.

I'm talking about the WiFi protocol that Solo is using,IMHO is not as robust as the other RC mainstream protocols being used today. It could be that they RC protocols are frequency agile and use coding methods of their signals to reject interference, etc. They tend to be very wide compared to the narrower WiFi signals, so perhaps this is part of it. The FrSky protocol will use almost the entire 2.4 GHz band, where WiFi signals only use one of eleven different 20/40 MHz channels.

Most RC systems will interfere with WiFi, but rarely if ever will a current RC system ever receive interference from a WiFi signal.

I guess we'll just have to agree to disagree here. But I still wish 3DR didn't choose WiFi for the critical flight controls of the Solo. In my eyes, it's just not as robust as other things that could have been used.
 
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Earl,

I'm not referring to the 2.4 GHz band, but to the protocol that Solo uses.

With my 2.4 GHz RC frequency hopping spread spectrum protocol, over 100 users can stand next to each other and have reliable communications with their aircraft. Try this with the Solo when it will only use 2 channels (or 11 if you modify the settings).

It's a totally different protocol from WiFi, even though it shares the same frequency band, all license free.

Check out the radios from companies like: Spektrum, Futaba, FrSky, JR, Airtronix, Hitek, Graupner, etc. They all use a similar, fairly bullet proof, interference free radio system for RC aircraft.

These don't have the issues that Solo has using WiFi for the critical control functions.

I use one of these with my PixHawk quad, and have never had even a glitch in control. Of course this same quad uses a different frequency for video downlink, and yet another frequency for data downlink to interface with Tower or Mission Planner.

I'm only saying that I wish 3DR had used a more robust protocol for the critical flight control functions. They chose WiFi for many reasons, but WiFi isn't as robust as these other proven RC protocols for critical flight control functions.

WiFi is great for the bandwidth it needs to send video, and data over the RF link. It's just not designed to be as bullet proof as the RC protocols that use the same frequency bands are.

Imagine you're out flying your Solo, a simple thing as me driving up with my car and parking next to you (holding your Solo Controller) could knock out your communications with your Solo if my Car had a WiFi hotspot in it that was on the same channel that your controller happened to choose to use with the Solo. This could never affect one of the RC protocol systems, they are designed to not have an issue with interference coming and going.
I will quit after this. It really isn't worth the time. But I will try to explain before I go. What you are calling "WiFi" is simply spread spectrum radio using several channels (depending on the country you are in) in the frequency band between 2.4000GHZ and 2.4835GHZ. The "channels" are just a construct to cut that up in sections of frequency. In The US, you are limited to 11 channels in that range, in europe it is 13, and in japan it is 14.

When you are talking radio in general, the lower the frequency, the higher the penetration, and farther the range, but the lower the frequency the lower the data rate also. So... while lower frequencies are better for distance, they limit things like Video.

Now you get into regulations. The frequencies available are limited, with some requiring various licenses. The combination off these things is why most RC with Video now runs on 2.4 GHZ

Now... Protocols...
The basic underying protocols handle packets, collisons, re-transmission, spread spectrum, and frequency hopping. The most advanced systems use spead spectrum and frequency hopping within the allowable range. The most advanced (generally available) of those use an Orthogonal Frequency Division Multiplexing (OFDM) algorythm to decide the hopping.. They name that different things, and in the past there were secrets and patents on it, but just about everything does it now...

This is a good discussion form a "WiFi" perspective, but discusses spead spectrum, hopping, and standards.

How WiFi Works

This discusses it in more detail.

http://ece.eng.wayne.edu/~smahmud/ECECourses/ECE5620/Notes/Wi-Fi-Lecture.pdf

Now... This discusses the same thing from an RC perspective. Keep in mind, RC actually led parts of this field, before the days of WiFi hotspots. DSS, DSM, FSSH, FASST, DSMX are all just proprietary names for frequency hopping techniques that have become 802.11(X) standards. They have cool names, but they really go right along with the WiFi standards.

How 2.4GHz Spread Spectrum Radio Control Works

Everything we are talking about uses spread spectrum and frequency hopping... They do it with the most advanced standards released, and they do it the same. That is why you can have 10 computers on a hotspot looking at different web pages. Don't get confused by Internet bandwidth limitations....

How WiFi Works

There is no magic however to any of the spread spectrum and frequency hopping in RC (although it is pretty smart) but with congestion in the 2.4 GHZ band, the tradeoff for continuing communications, is a reduction in bandwidth.. When doing just flight control it doesn't matter much as their is a ton of available overhead. When doing control AND video, you use more bandwidth, less headroom, and so need to call it quits sooner and RTH.

While I have no doubt, 2.4GHZ radios can have a thousand connections, the bandwidth will be limited. That is not a superior protocol, that is a different use. That may be fine for simple flight control, but just wouldn't work for Video. So it is an apples and oranges comparison. This is why the leaders in the industry (DJI and 3DR) have done what they have. They are not dumb...

So while I would agree that there are RC systems that will give you higher penetration and longer distances, I think you will find that they are lower frequency (and data rates). if you want the higher data rates, you go to 2.4 GHZ, and then you are back to spread spectrum frequency hopping, with diverse antennas....Which is exactly what they all do....

More good information here (including the video originally linked) :

Spread Spectrum Radios

Any of these can have problems, and if you are having problems at short range, it most likely means there is something wrong. The nice thing about the WiFi protocol is that you can use off the shelf tools to find out what it is.... I have stock equipment on one Solo and take it out 2000 feet in an area with congested Wifi, with no problems regularly.

Also by using standards, if you need more penetration and/or range you can buy higher power off the shelf WiFi cards, and even add external boosters, as well as various antennas with standard fittings. People get out several miles in congested environments doing this. Frequency hopping and spread spectrum at 2.4GHZ is great, but there is nothing like raw power to cut through anything...

OK... Done... Moving on....
 
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I'm talking about the WiFi protocol that Solo is using,IMHO is not as robust as the other RC mainstream protocols being used today. It could be that they RC protocols are frequency agile and use coding methods of their signals to reject interference, etc. They tend to be very wide compared to the narrower WiFi signals, so perhaps this is part of it. The FrSky protocol will use almost the entire 2.4 GHz band, where WiFi signals only use one of eleven different 20/40 MHz channels.

Most RC systems will interfere with WiFi, but rarely if ever will a current RC system ever receive interference from a WiFi signal.

I guess we'll just have to agree to disagree here. But I still wish 3DR didn't choose WiFi for the critical flight controls of the Solo. In my eyes, it's just not as robust as other things that could have been used.
Sorry but this is not correct.
Your RC system can easily receive interference from wifi. Just switch the wifi link on your Gopro in your plane or drone. Famous reason for many repoted "flyaways" and crashes.
Frysky by no means uses the entire 2.4 spectrum. As all other broadcasters including wifi they have to stick to the same available spectrum and regulations.
Wifi transmission is at least as reliable as your RC link. Actually you find more crowded wifi spots than People standing together with their RC equipment. Just go to a hotel in a big city, let's say NY - there are hundreds of wifi hotspots with several hundred people accessing the network in your range at the same time w/o communication problems.
 
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Sorry but this is not correct.
Your RC system can easily receive interference from wifi. Just switch the wifi link on your Gopro in your plane or drone. Famous reason for many repoted "flyaways" and crashes.
Frysky by no means uses the entire 2.4 spectrum. As all other broadcasters including wifi they have to stick to the same available spectrum and regulations.
Wifi transmission is at least as reliable as your RC link. Actually you find more crowded wifi spots than People standing together with their RC equipment. Just go to a hotel in a big city, let's say NY - there are hundreds of wifi hotspots with several hundred people accessing the network in your range at the same time w/o communication problems.
Exactly... Ooops. I said I was done :)
 
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Just to remind my memory, I got out my spectrum analyzer to check on some things that I said.

WiFi channels in the USA run from Ch 1 on 2412, to Ch 11 on 2462.
2.4 GHz RC FHSS typically use frequencies from 2.4 GHz to 2.485 GHz.

Here is the 2.4 GHz spectrum at my place from 2.4 to 2.5 GHz. The larger hump you see at about 2.462 GHz is my WiFi at Channel 11. The smaller humps could be neighbors WiFi or other 2.4 GHz devices.

RFExplorer_SpectrumAnalyzer_2015_09_23_11_28_03_baseline_noTX.png

Here is what the same frequency range looks like when I turn on a Spektrum (brand) RC transmitter, as you can see, almost the entire WiFi spectrum is used, but there does appear to be some holes. Some of the holes could be due to the integration time of the analyzer and the hopping speed of the RC transmitter. Longer time capturing can cause some of the holes to fill in, but it could be that not every single frequency is used, but most, if not all of the WiFi band does appear to be used:

RFExplorer_SpectrumAnalyzer_2015_09_23_11_32_19_Spektrum_mode.png

Here is the same frequency range, but this time with a FrSky (brand) RC transmitter turned on, as you can see most of the 2.4 GHz frequency band is used (it appears that more than the Spektrum brand is used, but could be the hopping speed of the FrSky vs the Spektrum). Again, some of the holes could be filled in if I waited long enough, but it appears that all of the band is used:

RFExplorer_SpectrumAnalyzer_2015_09_23_11_36_55_FrSky_mode.png

Of course, these RC transmitters are FHSS (frequency hopping spread spectrum), so to be accurate, they don't use the whole frequency band at the same time. The transmitter outputs a relatively narrow signal, that changes frequency frequently. So with this in mind, I suppose that someone could argue that a FrSky transmitter doesn't use the whole band. ;) But to me, it's using the whole band. :>

A WiFi signal is also FHSS, but it's much narrower, and it hops frequency over a much more narrow range. For example I can see my WiFi router hopping between about 2453 to about 2468 or so. So yes, WiFi is also FHSS, but over a much narrower range of frequencies. WiFi is also trying to send a much higher bandwidth signal (higher data rate) than an RC signal.
 

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