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[BOUNTY] ($205 so far) Enable HSPA+ on 1900 MHz / 1700MHz for VZW Galaxy S3 i535

22nd September 2012, 10:37 PM   |  #11  
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Originally Posted by mybook4

Called the local at&t store. They wouldn't let me try a post paid sim in store unless I signed up for a plan. Very customer friendly, lol.

In other news, incubus posted that the developer edition of the vzw gs3 is available for sale. I'm curious if we can use some of the partitions? Finding someone who has bought this will be tough.



Sent from my SCH-I535 using xda premium

The signatures may not work on the hardware-coded signatures that these phones are looking for though, and even if they do, they probably didn't write its firmware to make the radio activate those bands we want though anyway. However, that phone may be the way for us to get to the solution; the dev edition doesn't have secure boot enabled (most likely, otherwise I wouldn't want one) but the hardware is IDENTICAL to the i535 (regular) version, so maybe if we could raise enough w/ the bounty to get one, we could flash att or t-mo modems, and see if that would enable 1900 wcdma band, right? It would help us on the way to "dev" the right modem file, hehe, since it's the dev edition.
24th September 2012, 04:30 AM   |  #12  
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Someone claims to have flashed an at&t modem on a Verizon GS3 and still been able to boot. Hopefully it isn't a spoof (that would be pretty messed up as it could lead others to hard brick their devices).

http://forum.xda-developers.com/show...php?p=31936888

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24th September 2012, 06:45 AM   |  #13  
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Quote:
Originally Posted by mybook4

Someone claims to have flashed an at&t modem on a Verizon GS3 and still been able to boot. Hopefully it isn't a spoof (that would be pretty messed up as it could lead others to hard brick their devices).

http://forum.xda-developers.com/show...php?p=31936888

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It doesn't seem like a spoof or hoax, judging from the person's membership length and info. The other reason is that from what I've read on the AT&T sections, when they flash a pure (non-modified to utilize the i747 radios) T-Mobile (T999) modem, the i747 doesn't brick either, but it loses signal completely. Unless the information was gathered from those threads (which seems unlikely), it seems somewhat realistic. I don't know why anyone on this forum, after being a member for that long, would make up something that horrific and cause everyone on here to hard brick their phones. Now we just need to get someone with jtag, maybe Adam Outler, to flash an AT&T modem and see what happens.
24th September 2012, 11:02 AM   |  #14  
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Originally Posted by newuser134

It doesn't seem like a spoof or hoax, judging from the person's membership length and info. The other reason is that from what I've read on the AT&T sections, when they flash a pure (non-modified to utilize the i747 radios) T-Mobile (T999) modem, the i747 doesn't brick either, but it loses signal completely. Unless the information was gathered from those threads (which seems unlikely), it seems somewhat realistic. I don't know why anyone on this forum, after being a member for that long, would make up something that horrific and cause everyone on here to hard brick their phones. Now we just need to get someone with jtag, maybe Adam Outler, to flash an AT&T modem and see what happens.

Yeah, but there is one key difference between our GS3 and every other variant... Secure Boot. It's the only reason I'm hesitant/skeptical but I really hope the poster is genuine. If he/she is, I feel he/she should be included in the reward (if it turns out to be a breakthrough that helps us get working 1900Mhz hspa).

If an AT&T modem flash works on our device without bricking it, it must mean that either the modem partition (one of the earliest parts of the boot chain) isn't checked for signature / hardware identifier or that the AT&T modem he used was signed with the same private key used to sign our modems.

I wonder if the AT&T bootloader partitions do any checks of subsequent boot partitions? If they don't, this could be a way around secure boot. If they do, they may check to see if secure boot is enabled before actually enforcing the check. All this is speculation until we receive confirmation from the poster.

... <drumroll>...

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Last edited by mybook4; 24th September 2012 at 11:07 AM.
24th September 2012, 02:15 PM   |  #15  
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Quote:
Originally Posted by mybook4

Yeah, but there is one key difference between our GS3 and every other variant... Secure Boot. It's the only reason I'm hesitant/skeptical but I really hope the poster is genuine. If he/she is, I feel he/she should be included in the reward (if it turns out to be a breakthrough that helps us get working 1900Mhz hspa).

If an AT&T modem flash works on our device without bricking it, it must mean that either the modem partition (one of the earliest parts of the boot chain) isn't checked for signature / hardware identifier or that the AT&T modem he used was signed with the same private key used to sign our modems.

I wonder if the AT&T bootloader partitions do any checks of subsequent boot partitions? If they don't, this could be a way around secure boot. If they do, they may check to see if secure boot is enabled before actually enforcing the check. All this is speculation until we receive confirmation from the poster.

... <drumroll>...

Sent from my SCH-I535 using xda premium

That's what I was wondering about: If any checks are enforced even if a partition does have checks written into it if secure boot is disabled. What is the exact roll of secure boot? Does it only do hardware check on the first partition boot (modem), or is it like a "guard", and forces every subsequent partition look for a signature to? If the latter is true, then disabling secure boot would make ALL signature checks turn off and obsolete, making the phone truly unlocked whether the software code asks for signatures or not. If the initial condition is true (only checks the first boot partition) then like you said, getting a modem file that has no signature check would almost entirely get around secure boot, I wouldn't really bother us any more if we managed to get firmware that has no signature check, kind of like the unsecure aboot.

Why is it so difficult to get a dev with jtag setup to try this for us? To flash a stock AT&T or T-Mobile modem and see what happens?
24th September 2012, 10:03 PM   |  #16  
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I just came to a feeling of "revelation" after reading through some of the AT&T threads about the AT&T Note working on T-Mobile, to the conclusion that if a phone is capable of gsm on ANY band, it MUST also be capable of wcdma on that same band (as long as the phone has wcdma capability on other bands and is not a pre-3G/pre-wcdma era phone, like old flip phones, and we all know our phone is capable of wcdma 2100 AND gsm 1900).

This is why: the difference between gsm and wcdma is frequency/spectrum bandwidth and software manipulation by the CPU, kind of like wave and mp3 files. All the signals go to the same tranceiver, so if the phone has hardware for gsm 1900, it already has the hardware and RF path for wcdma 1900. It also has the ability to take larger chunks of a gsm band and use software to decode a wider frequency portion and turn in into a higher bandwidth (speed) wcdma connection. It's the modem software that does this. This wouldn't work if we were concluding the same thing for interchangeability between gsm and LTE, because LTE uses MiMo (multiple-in Multiple-out connections), and that is a different method of reaching higher data rates, it is not just a different modulation scheme using a wider bandwidth, so gsm and LTE aren't interchangeable even on the same frequency, but gsm and wcdma are. That's how they were able to change 3G into HSPA+ "4G", and receive higher data rates just by changing software, that's why 3G gsm phones can usually also get HSPA+ speeds on AT&T, but they don't call it 4G, just H+. That's why T-Mobile is going to re-farm its EDGE network to run HSPA+ on 1900 MHz, otherwise it would use it for LTE. The antennae are already there, the difference is modifying how the band is used with the help of software. Compare it to putting a large picture on a network of multiple tv screens as one big picture, instead of on just one screen. With the right software and multiple screens (in our case CPU power), it can be done.

That is why the 3G gsm/wcdma capable Verizon iPad 3 (newest version) can also receive AT&T's HSPA+, because the modem software is there, or the same iPhone 4s, if unlocked, can run on Verizon's CDMA 850/1900 and AT&T's wcdma 850/1900 without any hardware differences.

The difference between CDMA, gsm and wcdma is just software to understand the modulation/demodulation and the width of the frequency band, notice how they all use the same frequencies (850/900/1800/1900)? LTE is totally different and requires different bands (like 700, 1700 - this is not the same as 1700 AWS part of the band that is used for t-Mobile's wcdma) and won't work with the others.

All that is needed is the right modem software to literally "patch" the i535 radio to understand wcdma modulation on 1900 MHz, the same way it does on 2100 MHz. Right now it can receive wcdma on 1900 MHz, but it means nothing to the phone, it needs the ability to "read" it, we already know it has the ability to decode wcdma signals.

The only factors that decide this, are provisioning (sim), RF hardware (we know it is there for 1900 MHz) AND, the right modem software. When we put in an AT&T sim, we've provided 2 of these requirement, the one missing is the modem file. If someone can write the correct modem / shuffle the right files onto the right partitions (it may not be just the modem partition as we have seen from the imei problems), I know this phone could do it. I hope this proves it to everyone else the way it just proved it to me. I think that's why the Note was able to run on t-mobile, it had the RF hardware, it just needed the software decoding. Call it a codec if you will, that's all that's missing.

Now, if anyone is able to figure out what is needed, that's a different question, but being able to flash AT&T or t-mobile modems is the very first step. Now we need to figure out if it will brick or not.
Last edited by newuser134; 24th September 2012 at 10:20 PM.
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24th September 2012, 11:21 PM   |  #17  
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wow I really hope this goes somewhere! as I will be planning to use my S3 on Simple Mobile once my contract ends with VZW

40$ vs 70$ is a huge difference for me
24th September 2012, 11:37 PM   |  #18  
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I was able to get 3g on ATT.
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Last edited by Strothmann; 24th September 2012 at 11:41 PM. Reason: added screenshots
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24th September 2012, 11:57 PM   |  #19  
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Originally Posted by Strothmann

I was able to get 3g on ATT.

Anyone know why this says EDGE and shows edge speeds, but the icons say 3G or 4G? Shouldn't phone info say "UMTS" under network type?
25th September 2012, 12:06 AM   |  #20  
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ITs due to me revering back to vzw. when i took the screenshot.

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