From Glenn Fleishman at Macworld:
SAN FRANCISCO — What happens when you put 1,000s of iPhones in close proximity?
They don’t suddenly become super-intelligent — they become stupid. It was clear as early as the Steve Jobs keynote at Macworld on Tuesday that those of us with iPhones were going to have problems with connections. I didn’t expect call and voicemail problems as well.
The iPhone uses 2.5G cellular data networking called Edge. It’s neither very fast (like 3G, which hits hundreds of kilobits per second) nor very slow (like 1xRTT or GPRS, the world’s major modem speed flavors). But it’s also not very efficient for a busy cell network.
With thousands of people in one room in which the iPhone penetration seemed north of 25 percent, perhaps higher, the network showed the strain right away. Edge uses the equivalent of up to 8 voice “slots,” or connections with a cell tower that individually would represent voice calls. It’s dynamic, so it’s not always sucking up that much frequency. The iPhone can drop down to GPRS, which uses 1 to 4 slots; the more slots, the more speed. One slot is about 10 Kbps — a very old modem speed indeed.
I and colleagues in the Moscone West convention hall were mystified before the keynote that the square in the upper left of the iPhone display didn’t have an “E” in it — I’d rarely seen a time when that letter, standing for Edge, wasn’t in the square. (A Wi-Fi icon replaces the “E” when you’re connected to that kind of network.)
The silent “E” meant that that the phones were using GPRS, and in practical use had become unusable. Text messaging, which has an alternate path of sorts and requires very little network
overhead, continued to work fine.
As the week progressed, I’ve continued to see and hear plenty of complaints from people about their iPhone. I’ve been unable to make or receive calls at times, even with the signal strength
indicator showing a perfectly fine signal. The Edge network doesn’t respond at times. The much-vaunted Visual Voicemail feature on the iPhone, which essentially downloads voice messages to the iPhone, kept breaking on me, showing a status wheel spinning but not loading a message. Voicemail notification
often cropped up 30 to 60 minutes after a message had come through, or I’d receive a missed call message without ever having had the phone ring.
Even blocks from Moscone, I still had problems yesterday achieving reliable Edge connectivity. Once I’d escape its orbital pull by about a half mile, things seemed to return to usual.
It’s not odd at a conference to have tens of thousands of people all with cellphones. But the iPhone is designed to be used for practical purposes: everyone is constantly uploading photos,
surfing the Web, checking e-mail, talking. I’d love to know the network use of the average iPhone user, and I’m sure AT&T wouldn’t reveal that. But I suspect that compared with the load that a BlackBerry thumb-typist puts on a cell data network that the iPhone user averages perhaps 50 times that
because of all the graphic-intensive activities, including retrieving Google Maps.
Update: A colleague who specializes in UMTS/HSPA (the 3G version of GSM that’s faster than Edge) and was visiting the Macworld Expo said that he was unable to get even a 3G connection to AT&T’s network in the vicinity of the Moscone convention center. Even though he could normally get peak rates of more than 2 Mbps, and regular rates of several hundred Kbps, his service dropped to GPRS (modem speeds) as well!”