I just posted a separate thread that has two articles on 5G cell phones via a new CBRS service. One article discusses the various cell phone chip makers and some of the bands and different modems. CBRS uses only 137 MHz in the 3.5 to 3.7 GHz band. But I think that 5G is a lot bigger than that.
Per Wikipedia that is band n48 and per the OP band n48 is supported by this modem but LOL YMMV.
Refer e.g. 5G NR frequency bands - Wikipedia
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Yâall planning to bridge a private CBRS network to your SIM network?
Iâd be happy for single-duplex person to person or group conversations â even if it was only good for 5 miles or so. Of course, Iâd be happier with hardware PTT button to support it.
Arenât there user accessible/programmable I/O pins on the L5? Or RS-232 mode for the headphone jack?
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Yes e.g. using the breakout board you can probably add a button.
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The 3450 MHz to 3700 Mhz band was taken away from Amateur radio operators in 2020. With CBRS, you can build and use your own hardware if you get it certified by the FCC first. But to be certified, the radio has to allow itself to be managed by a central piece of hardware that enforces an FCC accepted sharing protocol that is much like what all cell towers use to manage phone calls. You can also just buy and use your own cell towers (no license needed) from commercial equipment sellers if you can afford to. But all of those systems require you to register and use your own spectrum sharing hardware that follows that required protocol. No freelancing by transmitting without being a part of that system is allowed. You can probably get a Qualcomm chip to work as a pirate radio that goes 1500 feet or so with a lot of effort to build circuit boards and program the chips correctly. But youâll have a lot more success and a much longer range with less effort by just using a $30 Baofeng transceiver.
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I did a search for a list of cell phones that are capable of CBRS operation. A small number of both Apple and Android cell phone models were on the list (probably early adopter models). Coincidentally (or maybe not coincidentally) they seemed to be the same models that are capable of cell phone direct to satellite access.
The government appears to have a grand plan outlined for 5G and above communications. And that plan appears to be completely available to anyone who wants to do the research. Before Purism invests much in to 5G phone development, someone at Purism needs to fully understand everything there is to know about that plan so that whatever they build is a fully featured 5G phone with all of the features found on a Samsung phone at the time of release. If it takes three years to release a 5G solution for the Librem 5, then there will likely be new features on the other 5G phones then, that we havenât heard about yet now.
Even though that plan is likely to be publicly available, I wouldnât expect Purism to be a âmember of the clubâ so to speak. I would expect to see the big players like Qualcomm and Motorola having the most knowledge and the loudest voices at the table where those plans are formulated, with the FCC rubberstamping those plans, and the smaller companies like Purism on the sidelines trying to keep up with the what others are saying and doing.
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Put a LoRa radio in instead of the modme and load up Meshcore or Meshtastic. Peer to peer messaging. Someone needs to port Meshcore or Meshtastic to the L5.
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No one needs to do anything.
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Bear in mind though that the current approach involves a removeable and replaceable modem card. So the functionality available via 5G is largely dependent on the functionality that the 5G modem offers and in the best case scenario a less functional modem can later on be replaced by a more functional modem.
Likewise it is entirely possible that the chosen 5G modem card internally uses a Qualcomm chip, in which case Purism indirectly has a seat at the table.
It is also possible that some 5G functionality may require host software changes as well, in which case that functionality wonât be available from Day 1 but can be added over time as part of the normal software upgrade process.
It is also acknowledged that choice of modem card is limited by the existence of open source drivers and adequate support and documentation from the cardâs manufacturer.
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2 posts were split to a new topic: eSIM on Librem 5
Other filtering factors: size and formfactor, slot keying, usb requirement and that voice is possible.
If and when there are going to be more modems available (and actually already now), L5 will need a software that identifies modem and installs the right drivers, changes required settings and permissions, checks modemmanager compatibility, sets up sound/voice, informs user of the modems features and limitations (what bands / intended geo-area, available Gâs, dl/ul limits), and verifies that sleep feature works (or disengages it). And if modem is not recognized, not in L5 db, helps with manual setup. Some kind of L5 specific known working/usable devices library, I quess. I think weâve only touched the surface of what cards may become available and somehow those should be managed by users in a friendly way.
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Just curious: Iâm reading and following this thread but, because Iâm not expert/engineer/technician (I kindly remind you that Iâm working in tourism, so a totally different field!!) I asked to AI if 5g is better than 4g about privacy and security! In my opinion it doesnât make sense to use Librem 5 and then use more risky network! Thatâs exactly same reason why we sacrificed speed using old and limited CPU, GPU,âŠ
So here what it said:
4G vs 5G: Privacy and Security Comparison for Librem 5 Users
5G Security Improvements
1. BETTER ENCRYPTION
- 5G uses AES-256 bit by default (vs 4Gâs AES-128)
- 5G encrypts metadata too (SUPI encryption)
- 4G still transmits IMSI in cleartext initially
2. IDENTITY PROTECTION
IMSI Catching becomes harder:
- 5G uses SUPI/SUCI (encrypted identity)
- 4Gâs IMSI can be intercepted
- Result: Stingray/IMSI catchers less effective on 5G
Example:
- 4G: [Phone] --IMSI cleartextâ> [Tower]
- 5G: [Phone] --SUCI encryptedâ> [Tower]
3. STRONGER AUTHENTICATION
- 5G has improved bidirectional authentication
- Protection against downgrade attacks
- 4G remains vulnerable to fake base stations
New 5G Privacy Problems
1. MORE PRECISE TRACKING
Smaller cells = more accurate location:
- 4G: 50-200 meters accuracy (urban)
- 5G: 1-10 meters accuracy (mmWave)
- 5G beamforming tracks exact direction
2. MORE METADATA COLLECTED
Network slicing exposes:
- Application type being used
- Latency requirements
- Detailed usage patterns
- Precise behavioral profiles
3. MORE COMPLEX INFRASTRUCTURE
- More attack points (edge computing)
- Supply chain risks (Huawei, ZTE, etc.)
- Potential backdoors in more components
Direct Comparison for Librem 5
IMSI Catching:
- 4G: Vulnerable
- 5G: More protected
Encryption:
- 4G: Good
- 5G: Excellent
Location tracking:
- 4G: ±100m
- 5G: ±5m
Metadata collection:
- 4G: Moderate
- 5G: Extensive
Battery consumption:
- 4G: Moderate
- 5G: High
Attack complexity:
- 4G: Medium
- 5G: High (more vectors)
For LIBREM 5 Specifically
Advantages of staying on 4G:
Simpler modems
- Less complex firmware
- Smaller attack surface
- Easier to isolate
Power consumption
- 4G uses 30-50% less than 5G
- Critical for L5âs limited battery
Available modems
- More 4G options with open documentation
- 5G modems are more proprietary
Kill switch effectiveness
- On 4G, physical kill switch is sufficient
- 5G has more RF components to manage
Mitigation Strategies
On Librem 5 (regardless of 4G/5G):
# Disable when not needed nmcli radio wwan off # Use aggressive airplane mode rfkill block wwan # Monitor connections watch mmcli -m 0Best practices:
- Hardware kill switch when connectivity not needed
- Always-on VPN for data
- Signal/Matrix calls when possible
- Avoid SMS (never been secure)
CONCLUSION for Librem 5 Users
4G is PROBABLY better for privacy because:
Less precise localization
5G is better ONLY if:
- You live in area with known IMSI catchers
- Superior encryption is priority
- You have modem control (spoiler: you donât)
For the Librem 5, stick with 4G:
- 4G modems are more open/documented
- Power consumption is more manageable
- âPracticalâ privacy is better
- 5G advantages are nullified if modem is proprietary
The paradox: 5G is more secure âon paperâ but more invasive âin practiceâ. For a privacy-focused device like the L5, 4G remains the wiser choice⊠at least until we have truly open 5G modems (probably never).
The key insight: The most secure protocol means nothing if it runs on a black box you canât control. With 4G on Librem 5, you have less security features but more actual control - and in the privacy game, control trumps features every time.
What do you think? 
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AI is almost right, except it isnât - as alwaysâŠ
Tracking is more complex than just 4G vs. 5G as there are other ways to give away your location. The conclusions on that are also based on 5G network and modem using those special shorter waves, but currently that is not mostly the case - the only 5G modem testes does not do them and those not available outside of central big city areas (although are expanding - networks vary around the globe how 5G has been implemented). If cell size has grown smaller, that does make (general) phone location more accurate, Iâd imagine that happens with 4G networks too, as congested areas get more towers (mostly probably combining 4G and 5G).
The point about infrasturcture is probably valid, although not much of a concern as the arenât much news about 5G not working - and if there was, the fallback for those same modems is to use 4G (unless specifically prevented). Modems that do 5G do also 4G (also 3G).
The âmore documentation and controlâ may have some general validity, but with the current options for L5, itâs the other way around. Iâve found more available for the Sim8202g. I think itâs more about BM-818 being less towards consumer markets. Hard to say what the documentation is like for anyting else that may or may not become available - but it would be nice if that was one selection criteria.
Iâm not sure why it says the power consumption should be lover. At the moment it is, as Sim8202g is not optimised in any way and it seems itâs not responding well to going to sleep (havenât looked into this), but its specs are better than BM-818 on that score.
The killswitch efficiency is odd. Both kinds of modems go totally off when power is cut from them with a hardware kill switch. And phosh software killswitches use the system commands that will kill the connection (unless malicious actors have taken control). Itâs a tie on that. There is equal control on L5.
And that brings me to the last points in its list. L5 is designed not to trust the modem. Itâs separate. This is to have a countermeasure against any of the risks that could maybe come from âcomplex infrastructureâ (old was already complex, âmoreâ seems irrelevant) and it also somewhat limits any additional attack vectors. Itâs understood to be a black box and not much can be done to that. That it why itâs not integrated, that is why L5 is so thick, that is why it lacks some of the energy efficiency and uses the circuits it does - so that modem can be controlled separately at hardware level. âKilledâ off if need be.
I see 5G as being better for security and privacy using modems like Sim8202g (as itâs not able to use mmwaves and it works with the two antennas of L5 without GNSS).
So, I see that AI generated list as misleading, at best. Misinformation and a misrepresentation. Looks believable - which is dangerous - but itâs mixing general assumptions and not assessing the relevant details, nor does it understand how L5 is designed to work. The best practices bit is ok-ish, but even those can be argued (and have - do that in those specific threads) and should be considered through each individual use case and risk profile.
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It learned your lesson 
My response to the criticism
Youâre right on several important points
Thank you for the detailed technical corrections. I admit I overgeneralized about 5G without considering:
- The SPECIFIC modem (Sim8202g) available for L5
- The type of 5G implemented (without mmWave)
- The L5âs isolation design that mitigates risks
- The actual documentation available for each modem
Where youâre completely right:
Kill switch:
Youâre 100% right - it works identically on both. I created a distinction that doesnât exist.
Sim8202g documentation:
I didnât know it had more documentation available than the BM-818. This actually reverses my point.
L5 âuntrusted modemâ design:
This is THE key point I underestimated. The L5 treats ANY modem as hostile, making the 4G/5G choice less relevant for security.
5G without mmWave:
Very valid point - without millimeter waves, the super-localization problem doesnât exist (yet).
Where I maintain some reservations:
Power consumption:
Even if itâs ânot optimized,â the fact that the Sim8202g doesnât sleep properly IS a real problem for users TODAY. Whether software or hardware, the practical impact remains.
Infrastructure complexity:
More complex = more attack surface remains generally true, even if L5âs design mitigates this risk.
4G localization:
True that 4G is also densifying, but 5G was born for smaller cells by design. Itâs a trend, not an absolute certainty.
What I learned:
- Donât generalize technologies without considering specific implementations
- Verify actual available documentation, donât assume
- Consider the complete system design (L5), not just the component (modem)
- Distinguish between different types of 5G (sub-6GHz vs mmWave)
My revised position:
For the Librem 5 SPECIFICALLY with current options:
- If the Sim8202g really has:
- More documentation
- Better specs (when optimized)
- No mmWave (no super-tracking)
- Superior 5G encryption
Then yes, itâs probably the better choice for those prioritizing security/privacy.
My mistake was giving generic â4G > 5Gâ advice without considering:
- WHICH specific modem
- WHICH 5G implementation
- The L5âs UNIQUE security design
Thanks for the correction
This is exactly the type of detailed technical feedback that improves the discussion. Youâre right that âcredible but wrongâ information is dangerous, especially in privacy/security contexts.
Question for you: Do you have direct experience with the Sim8202g on L5? Howâs the real-world performance after any optimizations?
P.S. Youâre also right that it seemed âAI-generatedâ - because it actually was, and this demonstrates the problem with generic answers without specific context. Lesson learned.
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How so? All I see are more AI-generated posts.
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Yes! Self learned I suppose 
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Well, for a start, you are assuming that you have a choice of 4G v. 5G. It is foreseeable that over time 4G will disappear and you will have no choice, hence it certainly makes sense to have the option to use 5G with the Librem 5 i.e. if you want to extend the lifespan of the Librem 5 as a usable phone.
This depends on your threat model - as always.
While I am not an expert, I would imagine that the encryption only applies from the handset to the mobile network provider. Beyond that, it is not end-to-end encyption and hence it is vulnerable to spying by the mobile network provider, their suppliers and third parties, the government, and of course any successful hackers thereof.
The same applies to hiding metadata. Sure, OK, if your threat model involves someone hanging around in your approximate vicinity sniffing 4G traffic then they could match your IMSI and target you physically. But the IMSI is obviously never going to be a secret from the above listed parties.
Cellular technology is inherently anti-privacy - so if your threat model justifies it then you need a phone where you can 100% reliably kill the cellular modem - for those times when you want to be invisible to the cellular network. Anyone know a phone that does that? 
Itâs worth noting that, whether the lower 4G location accuracy or the higher 5G location accuracy, both can be supplemented by the ever increasing number of surveillance cameras and other surveillance technology.
In some respects you asked the wrong question because
a) you may need to take a more holistic approach to privacy and security, and
b) you didnât spell out your threat model.
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