Many people asked why iPhone 5 it has a case like the one in the image above, some saying that this kind of images are fake precisely because it has such a case. In short, the two parts of plastic or Gorilla Glass placed in the upper/lower part of the case would actually hide the GSM/CMDA antennas and the Wi-Fi, Bluetooth GPS antennas, plus a possible NFC antenna. The aluminum part in the middle is included to increase the hardness of the device and prevent it from breaking or cracking if it is dropped.
When the iPhone 4 was first launched, it was a GSM-only phone, meaning it only worked on cell networks using the GSM standard. (AT&T, yes. Verizon, no.) The GSM iPhone 4 introduced the idea of an external metal-band antenna. It broke into two sections. One section for cell/data reception, and another section for GPS, Wi-Fi, and Bluetooth. This design worked but was also susceptible to signal degradation if gripped in the wrong spot (aka Antennagate).
When the CDMA version of the iPhone 4 came out in February 2011, the design of the steel bands changed. This design would also carry over to the 4S. The 4S's steel band is comprised of four pieces of steel: two U-shaped pieces at the top and bottom, and two long, flat pieces on the side. The steel sections don't actually touch each other — they are separated by a .65mm piece of plastic. The way I understand the 4S cell antenna to work is this: There are two antennas, one at the top U bracket, and one at the bottom U bracket. The flat steel sides are only there to visually continue the metal band all the way around the phone and for structural reinforcement. The GPS, Wi-Fi, and Bluetooth antennas transmit out of the glass backplate. Long story short, instead of using the entire metal band for antennas like in the 4, the 4S only uses the top and bottom sections as antennas. Since the flat sides do not contribute to transmitting signal and only help with the structure of the device, it makes sense to make them even more integral to the structure. This is what makes a unibody iPhone possible.
This theory comes from an industrial designer from Chicago who explains in detail on the blog or everything I summarized above. If on the iPhone 4S the antennas are connected to the metal strips on the sides, on the iPhone 5 those side strips will not influence the antennas in any way, but the portions in the case will be responsible for all the antennas included in the iPhone. To be honest, the theory seems credible, especially since there are no other credible reasons for including those glass/plastic portions.
Apple is the only one that can confirm the veracity of this theory, but until another one, I think it is quite accurate.
