It's criminal that cell phones are bristling with incredibly advanced radio technology and yet they are by law not allowed to communicate directly with each other over a distance of more than a couple hundred meters without assistance from a licensed and centrally controlled base station. Meanwhile a $10 walkie talkie using primitive stone-age radio technology can go many miles with zero infrastructure, but by law is not allowed to be used for data transmission. This is a choice our governments have made, not something inherent to the technology.
A small USB pluggable module that supports LoRa plus an app using Codec2 or similar low rate codec for voice encoding could fill the gap, although having it bundled with the phone would make it a lot less cumbersome to use. For non phone portable solutions, the LilyGo T-Deck Plus/Pro come to mind, but they're not phones so that would imply a 2nd device to carry around.
But needs towers, which in some disaster situations could be not working, or in others simply not trustworthy. If 5G phones radio modules were modified to allow point to point communication, the usable range would still be a small fraction of what is attainable with towers and their high gain antenna arrays.
The issue with this is that the entire architecture trades energy consumption on the eNodeB side for the handset side. One could make a cell phone where one handset was the eNB and one the handset (and, contrary to the parent post’s claim, there would be no issue getting this approved in an ISM band), but the one operating in eNB mode would have atrocious battery life.
It also helps a lot to have one side of the transmission up on a tower with a giant high gain antenna :)
I’ve been tangentially involved in experimenting with Meshtastic and trying to scale it for large events like Burning Man, on the order of 2000–3000 nodes on a single frequency.
Node to node mesh communication is cool and it works surprisingly well at small scale, but the moment we brought high powered repeaters online the difference was night and day. Coverage, reliability, and usability all jumped instantly.
It makes the tradeoff really obvious. Mesh is great for bootstrapping and local traffic, but once you care about real data propagation at scale, centralized infrastructure wins almost every time. Airtime is scarce, coordination matters, and having a small number of well placed high sites beats thousands of mediocre relays.
I still think there’s room for novelty P2P protocols, but mostly as an optimization layer on top of infrastructure, not as the foundation. Every time you push on this problem hard enough, you end up rediscovering the client router model for a reason.
Of course there's no reason to use a mesh when infrastructure is available. That's not why a mesh would be useful. But it doesn't even need to be a mesh to be a useful feature. Walkie talkies aren't a mesh and they remain useful.
It isn't a law thing, but I'm disappointed that LTE Direct didn't go anywhere. That let's cell phone talk to each other over range up a km. The problem is that there LTE Direct requires implementation in the radio firmware, and the companies only did it for government phones. There is also 5G Device-to-Device and I haven't found out if that is supported more widely. There would also need to be frequency allocation, something CBRS (3.5GHz) would work but would be nice to get something with longer range.
You aren't going to get longer ranges with phone, the power and antenna are too limited. Walkie-walkie have bigger antennas (the stubby FRS sort of suck) and more power. Also, walkie-talkie don't have much bandwidth so the data rates would suck.
It's a business model thing, which seems to supplant law these days. Can't meter P2P. Intermediation to prevent usurpation of network effects is the name of the game in the modern day. No one will say that, but it's the quiet part left explicitly unsaid. The negative space of the incentive structure, if you will.
> Meanwhile a $10 walkie talkie using primitive stone-age radio technology can go many miles with zero infrastructure, but by law is not allowed to be used for data transmission.
Is this even true?
I still have two Gotennas from before they pivoted to military use cases, and they were legal to use both in the US and in Europe (on different bands auto-configured via GPS, as far as I remember).
REI also currently stocks at least one set of walkie talkies [1] that can relay short messages from smartphones via Bluetooth.
Wow, you're right, data is technically allowed on FRS frequencies. I didn't realize that. It's not unrestricted though. There are a lot of regulations that constrain how FRS radios can work, much more than for 2.4 Ghz.
You might have conflated the prohibition on encrypted/coded communication with a blanket ban on data vs. voice. Those frequencies are supposed to be used for public communication, which has been interpreted as a requirement that anyone can listen in (as opposed to any member of the public privately communicating with any other member). See 47 CFR Part 95, plain language voice communication.
These days, I'm not sure anyone would seriously rely on a system that sent only unencrypted point-to-point data, so for that use case your original point stands.
There's also a slice of ISM spectrum available around 900-930 MHz in the US, and Europe has an equivalent one around 860 MHz, which is where the (unfortunately discontinued) Gotenna consumer device used to operate.
Happened to my Iridium satellite messenger (for peace of mind when hiking) too... Fortunately, there are several consumer/civilian alternatives to these.
I guess anything that's useful to regular hikers is potentially also useful to the armed, abroad type of hiker, and these are usually better funded, so I can see why startups like these would pivot.
It's unfortunate, GoTenna was (still is) pretty cool. Beartooth is similar and you can just buy them, but they unfortunately still have military-level pricing for what is pretty simple hardware.
Though in their defense, I'm not sure GoTenna was ever "popular." Probably not enough to pay the bills, given their pivot.
Will the walkie talkies work if there are hundreds in a small area all transmitting data with each other? Besides, there's just not that much bandwidth there.
The smartphone is just an advanced walkie-talkie, currently limited only by the mobile operator, the law, the radio chipset, and the OS.
In a true emergency, who can stop you from modifying that architecture? Once you treat the device as an independent radio node (using its DSP power to run custom modems) you can establish a mesh network with a range of several kilometers.
We have a '4x4 car in our pockets; we’ve just been conditioned to treat it like a toy.
Not disagreeing with you, but you’re papering over a lot of complexity.
Note that cellular radios are highly specialized and the filtering circuits are tuned to specific bands. It’s not exactly like having a software defined radio in your pocket.
Next, at the modem level, you’ll need to implement and then sideload custom firmware. Finally, you’ll need to expose the right APDUs to the kernel to manage the whole thing.
TBH it sounds like a fun side project, but my point is you need to repurpose a lot of different parts of the stack to accomplish what you want.
I was pushing on the walkie-talkie case to gain the maximum results from existing phones, that's a true emergency case.
You’re absolutely right that the 5G/LTE baseband is a black-box nightmare to repurpose. But I’m not looking to hack the cellular modem; I’m looking for the dormant '4x4 car' already available.
For instance, many chipsets have an integrated FM receiver that is essentially a high-sensitivity VHF radio. By taking the raw audio output and applying a Software Modem (AFSK/FSK) in the user-space, you bypass the kernel/firmware complexity entirely. You don’t need to sideload a modem driver if you treat the audio jack or the internal FM bus as your physical layer.
The 'complexity' is real if you try to fight the manufacturer's fences, but it vanishes if you understand the full stack. A pair of wired headphones becomes your dipole antenna, and the phone's CPU becomes your DSP engine. It’s not about rebuilding the Ferrari; it’s about realizing there’s a VHF engine hidden in the chassis that doesn't need 'permission' to receive bits.
You just need a software demodulator the catch them, but for sending you'll need an external transmitter (an USB SDR or jack-to-FM).
> For instance, many chipsets have an integrated FM receiver that is essentially a high-sensitivity VHF radio. By taking the raw audio output and applying a Software Modem (AFSK/FSK) in the user-space, you bypass the kernel/firmware complexity entirely. You don’t need to sideload a modem driver if you treat the audio jack or the internal FM bus as your physical layer.
This is fascinating. Happy to do the research myself, but do you have any recommended reading/sources to learn more about this?
I'm glad you find it interesting. I developed the theory at university, studying how ASK and FSK modems work. To build this, you’ll need to understand the Shannon-Hartley theorem, band-pass filtering, Fourier transforms, and convolution.
For the practical 'how-to,' I recommend studying GNU Radio and SDR++; they show how to process IQ data or raw audio streams directly, and for sure there are other libraries. On the 'ancestor' side, look at the AX.25 Packet Radio protocol and AFSK (Audio Frequency Shift Keying). These are the same 'softmodem' principles used in FidoNet nodes decades ago.
GSM Arena can help you find phones with integrated FM receivers. You'll notice that many features are market-dependent, meaning: the receiver is often physically present but simply disabled by software.
The smartphone is talking to a highly sensitive receiver fed by a large sensitive antenna listening carefully in the direction of the smartphone. The base station is transmitting back a carefully directed beam with orders of magnitude more power than a smartphone. The system is highly asymmetrical. Ohh and maybe there is not one but many base stations talking concurrently to the smartphone so that if one looses some data the flow is maintained.
Walkie talkies as licensed today wouldn't because they are required by law to use exclusively stone-age radio technology. But modern unlicensed radio technology is incredibly good at sharing scarce 2.4 Ghz spectrum. Sometimes devices do interfere with each other, but they remain useful and they are far better at sharing than any expert would have predicted years ago. Let the radio engineers try.
RF attenuation is proportional to frequency and at 2.4 GHz, it is very high. Also, the distance over which one could communicate depends on antenna height, so if both parties are at ground level, it is not feasible over a few hundred meters unless both are in wide open space.
Source: ham operator who has played with long distance device to device communication without using a repeater.
> RF attenuation is proportional to frequency and at 2.4 GHz, it is very high.
Through building materials, foliage etc, but not in free space/line-of-sight.
> Also, the distance over which one could communicate depends on antenna height, so if both parties are at ground level, it is not feasible over a few hundred meters unless both are in wide open space.
Isn't it just the opposite? Antenna height is only the limiting factor with line-of-sight, otherwise NLOS considerations like attenuation by building materials, multipath propagation etc. start to matter much more. Modern radio standards are extremely good at that.
Of course line-of-sight usually remains the ceiling, since there usually isn't much in the sky to helpfully reflect signals back down, at least with mobile transmitter compatible transmission levels (i.e. excluding shortwave).
> Through building materials, foliage etc, but not in free space/line-of-sight.
Yeah. Even in free space. For example, attenuation at 1 km for 144 MHz (ham VHF band) is about -76 dB while for 2.4 GHz, it is about -100 dB. That 24 dB drop could mean, the signal is below the noise floor of your receiver unless you increase the RF power output which means more battery drain.
For example, BT audio gets cut just moving to the next room despite the RF power of BT transmitters being ~ 5mW( 7 dBm ) and at 10m, the attenuation is -60 dB(just free space loss which is ideal condition), so 53 dBm (7-60) at the receiver is usually sufficient, yet they struggle.
No, attenuation in vacuum is exactly the same, and the difference between humid air, dry air, and vacuum doesn't really matter at frequencies below a few GHz.
> For example, attenuation at 1 km for 144 MHz (ham VHF band) is about -76 dB while for 2.4 GHz, it is about -100 dB.
This is a common misunderstanding of the free-space path loss formula, which is expressed in terms of the idealized isotropic radiator, the length of which is frequency-dependent. In other words, this calculation is assuming a proportionally (much) smaller antenna for the 2.4 GHz case.
With the same antenna size, the path loss is exactly the same. After all, where else should the radiated energy go?
> With the same antenna size, the path loss is exactly the same.
What do you mean? The size of the dipole or monopole antenna is dependent on the wavelength, so obviously the 2.4 GHz is just a few centimeters and not the same size as a VHF antenna.
> After all, where else should the radiated energy go?
Well, most of RF energy is wasted. There are software that can plot the radiation pattern, but even without knowing the exact pattern, very little RF energy is received at the target.
> The size of the dipole or monopole antenna is dependent on the wavelength, so obviously the 2.4 GHz is just a few centimeters and not the same size as a VHF antenna.
Sure, if you want to stay omnidirectional, but you don't have to. You can use one of several antennas based on feedback, beamforming etc.
This is great on paper until some jackass wants to access their home NAS over the public frequency range so they can watch anime all day at their desk, which only works when they use multiple channels at once.
There are tons of cool things society could enjoy if it wasn't for a small handful of shameless actors.
Or even better, where is the tech that can do this disregarding the law? Let's not act that something being illegal never stopped it from achieving mass adoption.
Well obviously cell phones have very powerful tx/rx so my question would be "what is stopping us from using this for p2p", I assume the answer is we don't have software access to the radio, and I assume that's for regulatory reasons but idk
That's not actually true: cell phone rx/tx power is quite low. We can get away with that because all they need to do is get to the nearest tower, which has a ton of power, sensitive antennas, and is very tall. Amateur radios have far more power available to them, but any "p2p" (i.e. simplex in amateur radio) runs into normal RF issues, like obstacles and interference. If you used the existing radios in cell phones to communicate directly with other cell phones, you wouldn't get very far. Even amateur radios, with all their power, use repeaters to the same effect as cell towers.
Many WiFi chips can be put into monitor mode (process all the data packets it can detect over the air) and inject packets for transmissions themselves. This pathway is typically unoptimized and would offer poor bandwidth but it is enough for text and audio.
You would need root to do this, and implement your own protocol on top of it with forward error correcting codes.
Personally, the additional complexity and overheads required for a P2P phone network is not worth while and I'm not sure it would fix that many problems that haven't already been fixed with walkie talkies.
It’s not “too hard”. It’s physically impossible without regulation. There is but one limited RF spectrum that we all share. One bad actor (intentional or misconfigured) can render the entire RF spectrum in their area unusable. The radius of their impact only depends on how much kWHs they have access to and it doesn’t take much to cripple radio communication in a large metropolitan area.
Until some clever cookie can figure out some way to utilize string theory’s extra dimensions for sending signals and then every body can have their own dimension to mess with, collective regulation on broadcasters is the only feasible way.
Nothing is stopping you from getting an HT for communication during power outages, natural disasters, etc. You just have to get a license to make sure you don’t actively harm everyone who is sharing the same spectrum with you especially during said natural disaster.
Theoretically people could cripple RF comms on accident, in reality that almost never happens despite many people possessing devices able to do so. My mikrotik router will let me broadcast all sorts of illegal signals with a few clicks inside their GUI, and yet I never heard about problems with people crippling city blocks with bad router settings. Or from their weird microwave setups. Or trying to run and operate some dilapidated 60 year old radios.
That’s because almost any legal to sell consumer device gets an FCC certification. It can still cause interference, but within limited parameters that significantly limit the blast radius. Most of the interference people experience will be very limited and almost exclusively due to misconfigured or defective devices. Ham operators run into this occasionally and if memory serves correctly, there was a chapter in the ham license exam about how to identify potential bad RF source and how to handle it (the FCC usually recommend politely letting the person with a bad transmitter know that their TV antenna or generator or whatever is causing RF interference before you involve the authorities as most people who encounter this are simply unaware)
The situation would be very different if it were commercially legal to sell devices that are designed to let you broadcast to anyone without FCC certification on the device or enforcement from a governing body. A billion startups would be selling “communicate with your family across town for free” devices that can easily render emergency services radios useless in a city.
Not true. Bluetooth, lora, and zigbee all coexist in the same unlicensed spectrum just fine. There’s no reason phones couldn’t speak these, or that a similar low-power protocol couldn’t be standardized.
> One bad actor can render the entire RF spectrum in their area unusable.
Ok, and? That’s already true for cellular, gps, and wifi today.
> Nothing is stopping you from getting an HT for communication during power outages, natural disasters, etc.
You’re missing the point. People already carry radios everywhere which are more than capable of longer range p2p communications.
The real question is why no such standard exists, despite its obvious utility.
Telling people to just carry an HT is smug and irrelevant. Average people carry phones.
> Not true. Bluetooth, lora, and zigbee all coexist in the same unlicensed spectrum just fine. There’s no reason phones couldn’t speak these, or that a similar low-power protocol couldn’t be standardized.
They already do. Most phones have Bluetooth. All those examples run on the 2.4GHz spectrum and all have the same RF range limitations and challenges. What’s your point?
> Ok, and? That’s already true for cellular, gps, and wifi today.
Hence the enforcement of cellular bands and gps through regulation. Again I’m confused as to what you are trying to say? Anyone can cause an RF jam. It’s illegal. Depending on how much it impact others, you might get a visit from the FCC, a fine or jail.
> You’re missing the point. People already carry radios everywhere which are more than capable of longer range p2p communications.
No they are not. You can’t get more than very short line of sight communication on the UHF band. You need to drop to at least the VHF band for any reasonable non-assisted communication and even still most people communicating in the VHF bands are using repeaters.
> The real question is why no such standard exists, despite its obvious utility.
You just listed 3 standards. Their utility is extremely limited and very unreliable as the distance, foliage, concrete increases between the parties. Telling anyone to rely on UHF transceiver in an emergency is misleading and dangerous. Telling anyone who is worried about communication in an actual emergency situation to have an HT is not smug. It’s the tool you need for the job. Average people carry phones because they are not frequently in such emergency situations. Those who are (emergency services, hardcore hikers, snow skiers, wild adventure types carry radios or satellite phones for this reason.
Plus with the recent low orbit satellite constellations making it possible to fit compatible transceiver in small phones (as opposed to needing a huge antenna for it) it’s even more of a moot point for emergency situations now.
You’re not gonna change antenna theory because you feel it’s smug.
The point is exactly that everybody is carrying a phone, but almost nobody is carrying a walkie-talkie. And why should I carry one more thing? My smartphone has already replaced my music player, camera...
Both European PMR446 and the US FRS are limited to 0.5 W; GSM uses four times that. There are walkie-talkies with very small antennas too. The limiting factor is line-of-sight, in any case.
If you're fine with less than real-time audio, you can get much, much smaller and low power.
1) LTE frequencies are in the frequency intervals 600—900Mhz, or over the Ghz. Higher frequency means smaller antennas.
2) 5G cells are small and very dense, this means less power consumption.
3) LTE and 5G are based on CDMA, a technology that is way more efficient in term of bandwidth efficiency than the FM modulation used by a walkie talkie
> In rural areas and using low frequencies, I believe they can even be larger than GSM.
In Europe GSM is going to be dismantled. And techniques like beamforming and radio resource management reduce the power consumption for 5G base station and phones.
> No, the last CDMA based cell standards were 3G/UMTS and the Qualcomm equivalent (CDMA2000 or what it was). From then on, it’s all been OFDM.
Even if 5G is using more advanced modulations like OFDMA or NONA, the concept is the same if you compare the with FM used by walkie talkie: those are modulations way more effective in term of energy and information effiency than a traditional FM transmission
