This is a pretty sad story of me ending up using a costliest ipod ! I thought of sharing it with everyone so that the same mistake can be avoided in future.
If you are owning a brand new IPHONE 4, I mean a locked one and if you are trying to unlock it.. Then never go for a software update ! If you wish to upgrade your OS to iOS5, then there are some special steps that you need to do. This is called as “preserving BASEBAND”. In Iphone’s terms, BASEBAND plays a vital role.
What’s a baseband ?
Baseband is something associated with the cellphone’s ant
enna, or say a firmware for the gsm modem. So what does it do ? The iphone’s baseband will take over all the functions associated with the sim card and an antenna. Using this you can a send text msg, make a call, pick the right signals from the towers etc., Baseband has some link to the bluetooth and the WiFi too which I am not pretty much sure !
Now how does your baseband get updated when you update your OS?
Well, whenever apple does an update there will be two separate updates. One is for the baseband firmware and the other is for the OS, both are two different updates but happens the same time. Once you update the baseband, and then there is no way (so far) to downgrade it. Where as, you can downgrade the OS if apple signs the lower versions of it. Which means, when u do an OS upgrade from 4.3.5 to 5 and at the same time if your baseband goes to 4.11.08 from 01.59.00 .. you can get back to 4.3.5 but your baseband remains at 4.11.08 only ! if some one tells you that baseband can be downgraded, plz don’t enter that site it’s a scam for sure.
If they are two different updates, can we ignore the BaseBand and just update the OS alone ? (preserving the baseband)
Yes, you can. And this is what you should have done first case. At first preserving BB was only possible from a MAC machine, ie., we are supposed to create a custom firmware from the stock firmware. By doing this, the BB update present in the stock firmware will be removed in that custom firmware which you have created now. And using the shift+resore option from the iTunes you can do this. For creating the custom firmware, we use a tool named Pwnage in Mac. 
Right now, this can be done with windows PCs also. We need a tool named RedSnow 0.9.9b8, using this we can accomplish the above said steps. This is a trustworthy tool, and you can go ahead with this.
“Baseband gets updated, and so what ? why can’t I unlock my phone now ?”
This question was the first to pop in my mind, all the unlocks for the iphone depends on BASEBANDs only. First of all, you should be pretty clear with whats an unlock and whats a jailbreak. You can jailbreak even iOS5.0.1 beta but u cannot unlock 4.11.08. I guess u must have got a clue with the above said statement.
Whats a jail break ?
Yes, Jailbreaking is something associated with the OS & firmware. By default apple does not allow you to install any other third party applications in your iphone. 
To break that our iphone devs have come up with this “cydia”, that’s just an addition to our OS through which we can install all the apps that were not signed by Apple. In other words “iPhone firmware is modified to allow unsigned code to be run to gain access to files that Apple wouldn’t normally let you access”.
Now what’s unlocking ?
Most of the apple phones are locked with a certain carrier, (AT&T etc.,)..Unlocking is the removal of SIM restrictions on the modem, allowing the use of the iPhone on any carrier. If you think why should I buy a locked phone why not a factory unlocked phone ? Oh, yea the cost factor comes into picture. Factory unlocked costs around 34.5k (INR), and the locked one is around 10k-15k.
There are two types of unlock :
1) Soft unlock (only after a jailbreak you could do a unlock.)
2) hard unlock (use of gevey sim)
Gevey sim is a thin piece or a sheet like which is kept over the normal sim before inserting. Once you place it above, and insert.. all you gotta do is “call 112” (emergency call) for 2 seconds. And then immediately you need to switch the airplane mode on and then off.. That’s it as far as the Gevey sim is concerned. The cost of that sim is around 35$, and there are places in chennai where you can get it for 1K.
I found most of my friends doing the same mistake, “I accidentally updated my OS to iOS5 without preserving my baseband” .. now what can I do ?
Remember, ultrasnow / Redsnow / Snow breeze or the Gevey sim card works based on the basebands. And so far we have no official updates to unlock 4.11.08. At this point there is not much to say. But stay tuned, I am following some iphone devs and hackers for the unlock updates. Until then u should “hacktivate” your phone and use it as an ipod or itouch whatever.. Well if you want to hacktivate your phone, u should get that iOS 5 jailbreak version and do it using RedSnow or SnowBreeze. (if you want more details about this, drop a mail I’ll pass you the links which works)
follow me for more updates at Twitter : @IamWini
