After the release of iOS 5 beta 4, it seems that some of the developers are able to update from iOS 5 beta 3 to beta 4 over the air and Apple promised a new feature which is over the air updates. iOS OTA update can help significantly reduce download times, since the download required for this kind of updates is fairly smaller and the updates can be downloaded over 3G just as well as they can over Wi-Fi, but you should make sure you have a good enough data plan in before you choose to proceed………….
Apple has made the latest beta of iOS 5 available as an OTA update for the first time and for those who are running iOS 5 Beta 3 can simply go to the General:Software Update menu in the Settings App to download and install the update. The iOS OTA Software update downloads automatically on the iOS device when it is available. However, after the delta update is downloaded, you are prompted to either install it now or later. After the iOS software update is downloaded, you should also see a pending notification badge for the Settings app. The OTA software update works over Wi-Fi and also over 3G. You can continue to use your iOS device when the delta update is being downloaded. It looks like iPhones must have 50% of charge or must be plugged into a power source to download the OTA update. This requirement seems to be more relaxed for iPad as users have been able to download the OTA update with only 12% charge. Though Apple had told us that the OTA updates will be an incremental/delta update rather than downloading the entire iOS firmware. If you consider iOS 5 Beta 4, the iOS 5 beta 4 firmware file for iPod Touch 4G is 773MB, while the delta update is only 128MB, which is a savings of 645MB of data from being downloaded. For iPhone 4, the iOS 5 beta 4 firmware file is 824MB, while the delta update is only 133MB, which is a saving of 691MB of data from being downloaded. It is important to note that the savings will depend on the changes and new features incorporated in the latest iOS software update. The size of the delta updates should also change/increase or decrease if one wants to skip a particular version and want to update straight to the latest iOS 5 beta update.