The method to upgrade your iPhone firmware without SIM card is not known yet. But, there is an alternative method that could help. Creating a custom iOS 5 firmware with the help of a jailbreaking tool can help. You can always use the Gevey SIM card to unlock iPhone 4 on the iOS firmware.
How to Unlock iPhone
Once you have upgraded to the iOS 5 firmware, you can use the Ultrasn0w tool. If you do not want to use the SIM card, you always have the Gevey SIM. Ultrasn0w does not support a lot of newer basebands. You can get that option with the Gevey SIM. It does support a few new basebands. If your iPhone 4 has already been unlocked previously with the help of Gevey SIM, you can use that same Gevey SIM card while upgrading to the iOS 5. But, the only thing that you must be careful is to preserve the baseband while doing so. If the baseband gets updated, you will no longer be able to unlock the iOS 5.
The steps are really simple. You will have to follow the on-screen instructions that are made available with the unlocking system that you go with. You can use redsn0w to unlock the iPhone 4 on iOS 5. But, that will only be possible for Mac OS X users. Redsn0wb is not compatible with the Windows OS. So, people using Windows OS have the Gevey SIM alternative left. Windows users can also go ahead with Sn0wbreeze.
Activating without SIM card
A lot of people also want to find out the method to activate your iPhone without the SIM card. There are various methods that can be used for that too. People who do not wish to use the official SIM card want to activate their iPhones without official SIM card. Gevey SIM card method helps. Also your have SIM phonebook method. These methods are not without any risk involved. You can end up damaging your iPhone. Lots of users have complained to have faced battery drainage issues due to these.
But, there are benefits too; which is why people want to take the risk. You can always use the iPod feature on your iPhone by hactivating. But, that is just one small perk. Unlocking solves a lot of problems for iPhone users.
iPhone Unlocking Benefits
You need to jailbreak the iPhone before you can go ahead with the process of unlocking. So, you need to be very careful about the preservation of baseband and all the related stuff. You need to have the appropriate tool for the appropriate firmware and baseband or it would not work. Frequent travelers will find unlocking extremely beneficial. Also, people who are stuck with a bad and expensive data plan or call package with the official network will find this helpful. But, these methods are never 100% safe. You are always at a risk of damaging your iPhone. So, until and unless it is plain and simple jailbreaking and unlocking; you need to be extra careful.

