We already know that the CDMA (Verizon) and GSM (AT&T and international) iPhones are ever-so-slightly different physically and internally—but just how different are the two iPhones in terms of actual, real-world usage?
On Wednesday, Apple published a new support document with the catchy headline iPhone: Understanding phone features. As it turns out, various rather mundane phone features work differently, depending on whether you’re using a GSM iPhone or a CDMA one.
GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access) are two competing cellular network standards. In the U.S. both Verizon and Sprint largely use CDMA-based networks, with AT&T and T-Mobile using GSM. Internationally, GSM is far more commonplace, with CDMA used prominently in only a handful of countries.
Because of the two different network protocols, some calling features are toggled differently on the two phones. On a GSM iPhone, to turn Call Forwarding, Call Waiting, and Caller ID on or off, you launch the Settings app, tap Phone, and then adjust the appropriate control. Changing those same settings on a CDMA phone, however, requires dialing special codes—*72, *70, and *67, respectively. And for disabling Call Waiting or (outgoing) Caller ID, you need to dial those unique codes every single time you place a call.
Apple’s new document also highlights differences between how the two phones handle conference calls. GSM iPhones can support up to five simultaneous calls, while CDMA iPhones top out at two simultaneous calls. The document also directs CDMA iPhone owners to the iPhone User Guide, which spells out more limitations in CDMA’s implementation of conference calls: you can’t merge calls if the second call is incoming, and you can’t switch between calls if the second call was outgoing—though you can, in that case, merge the calls. And on CDMA iPhones, if you end the second call or the merged call, both calls are terminated. These conference call limitations are endemic to all Verizon CDMA phones, not just the iPhone.
Another difference highlighted in Apple’s knowledge base document is the way the two phones handle dialing pauses—a feature you might need if, for example, you’re dialing into an automated phone system. Soft pauses work identically: you tap and hold * (asterisk) while dialing; when editing a contact’s number, you tap the +*# key and then Pause. But if you want to dial a hard pause—one where the remaining digits aren’t dialed until you tap Dial a second time—your only option is a CDMA iPhone, because GSM iPhones don’t support hard pauses at all. To trigger the hard pause on a CDMA iPhone, you hold down # while dialing, or tap that +*# key and then choose Wait when editing a contact’s number.
If you like putting your callers on Hold—as opposed to merely muting your end of the call—you’ll need a GSM iPhone. (You tap and hold the onscreen Mute button while on a call to trigger Hold.) CDMA networks don’t support that functionality.
Apple also acknowledges in the document that CDMA iPhones may have issues in certain cases when you attempt to dial phone numbers that contain alphabetic characters if they exceed the normal ten-digit limit. The only proposed solution is to manually edit the numbers as necessary.
So, why all these differences? As Verizon once advertised, “It’s the network.” While the two network technologies achieve the same end result—i.e., making your cell phone work—they do so in vastly different ways behind the scenes. CDMA networks package up data—your voice calls and your Internet usage—very differently from GSM phones. These calling differences, much like the fact that CDMA phones don’t support simultaneous data usage while on the phone, are simply related to differences in the core technical makeup of the networks themselves.
Whether these calling differences should influence your decision about whether to go with AT&T or Verizon for your next iPhone is, in the end, a personal decision. Obviously, if you’re already accustomed to the limitations of one network, you needn’t fear using the iPhone on it; the differences Apple describes in the new document are really true for all Verizon and AT&T phones, not just the iPhone. If, on the other hand, you’re considering a network switch, make sure you won’t lose a feature you rely on, like 5-way conference calls.
Presumably, neither Apple nor its customers—and probably not even Verizon—are happy with some of the limitations of CDMA networks. It's hard to say which of those three entities—Apple, Verizon, or consumers—is more eager for Verizon to complete its upgrade to the next-generation LTE standard, which should eliminate most of these frustrations.