Would not be too surprising if the iPhone 5 is similar to the iPhone 4 in many ways. Conventional wisdom now says that the big future change will be the 2012 iPhone 6 with LTE. If you want to make a statement by changing the form factor, that would be the time.
The obvious change will be the addition of a dual-core A5.
The non-obvious change would be to add a second antenna to the GSM model.
This is not the place to discuss RF details, but the big problem with mobile wireless (cell, wifi, bluetooth) is something called fading, which means that, while the *average* strength of the channel is pretty good, it frequently drops DRAMATICALLY, and during that dropped period you obviously lose bits, which means garbled speech and lost packets. Fading has the characteristic that it changed very rapidly both in time (over a period of 10 ms or less) and space (over a few cm, for the wavelengths of interest).
Fading CAN, in theory, be combatted to some extent at the cell tower using concepts like
- beam steering (use multiple antennas on the cell tower to direct energy at the cellphone target, rather than over the full 360 degrees of space)
- MAC diversity (track which phones currently have better quality channels, and give them preferential access)
- Alamouti coding (this is a very clever way of essentially sending the same [but slightly modified] signal to the phone from two different antenna, and the phone picks up, essentially whichever of these signals is stronger. It needs support in the phone to work, whereas the prior two do not --- but it does not need the cell tower to track as finely where the phone is, and its channel quality.)
All three of these are supported by the latest 3G specs, but I do not know which (if any) ATT supports. (And the answer may vary depending on how new the cell tower is.)
However ANOTHER way of combatting fading is to have two antennas in the phone. The hope, then, is that when one of the antennas experiences fading, the other probably does not (remember what I said about fading varying over a spatial scale of a few cm). This actually works astonishingly well.
You need two antennas, two RF chains, and some logic that combines the signals. The simplest form of this logic chooses the stronger signal, but there are smarter things that can be done that combine the two signals.
This is called receive diversity.
(Once you have two antennas, there are a bunch of further things you can do, which ascend to cleverer and cleverer heights, and which ultimately give you fewer dropped packets, better range, and/or higher up and downlink data rates. These tricks are all used in modern wifi, but I expect will not be used much by 3G, though they will be used by 4G.)
Note that VZW mandates that ALL devices on its network have to use receive diversity. (And of course the CDMA iPhone4 does so.) This is probably one reason why they have the reputation they do for being a more "robust" network. In the simplest cases, as I have described, receive diversity does not improve bandwidth, but it does mean far fewer packets are dropped. If ATT had a brain in their head they would mandate the same thing for their network.
My point, however, is that Apple has done all the low-level engineering now to put two cell antennas on a phone and combine the signals. There is no reason they could not apply that same tech to the iPhone5 GSM version --- and the extra reliability would be nice, given the stupid brouhaha (which still gets raised occasionally) about death grips and dropped packets/dropped calls.
