Syber News » AT&T Source Details iPhone Dropped Call Issues, But Still Leaves Questions Unanswered

Here’s another explanation for the problems that the iPhone 3G has beensuffering, as detailed by an unnamed AT&T source. Once again, as with some of the other “explanations” and “theories” we have been given to this point, it still doesn’t make complete sense.

According to the source, the issue, supposedly fixed in 2.0.2 (and labeled as “bug fixes”) was all about “power control” on the device. Note that in the following, phones are referred to as “UE” for user equipment, and the base transceiver station towers as “Node B.”

In UMTS, power control is key to the mobile and network success. If the UE requires too much downlink power then the base station or Node B can run out of transmitter power and this is what was happening. As you get more UEs on the cell, the noise floor rises and the cell has to compensate by ramping up its power to the UEs.

If the UE power control algorithm is faulty then they will demand more power from the cell than is necessary and with multiple users this can cause the cell transmitter to run out of power. The net result is that some UEs will drop their call. I have seen the dropped call graphs that correspond to the iPhone launch and when the 2.0.2 firmware was released. The increase in dropped calls were the result of a lack of downlink power.

The power control issue will also have an effect on the data throughput, because the higher the data rate the more power the Node B transmitter requires to transmit. If the UEs have poor power control and are taking more power than is necessary then it will sap the network’s ability to deliver high speed data.

This is one of the reasons why AT&T has been sending text messages to users to persuade them to upgrade to the 2.0.2 software. In a mixed environment where users are running 2.0, 2.0.1, and 2.0.2, the power control problems of 2.0 and 2.0.1 will affect the 2.0.2 users

It is not the network that is fault but the interaction of the bad power control algorithm in 2.0 and 2.0.1 software and the network that is at fault. The sooner everybody is running 2.0.2 software the better things will be. Having seen the graphs the 2.0.2 software has already started to make difference.

If you didn’t bother reading the whole explanation, according to this unnamed source, the problem is that the iPhone with 2.0 and 2.0.1 software sucks too much power from the cell towere. And, there are still plenty of 2.0 and 2.0.1 users out there, sucking up said power. If they all updated to 2.0.2, everything would be happy, so they say.

OK, it actually sounds good. But here’s an unanswered question: if this is the case, why are other 3G phones on the same tower running just fine? As I’ve said previously, I can have six or more other 3G phones of the same type within inches of the iPhone (meaning on the same tower) and they do just fine (and I don’t mean bars; I mean receiving calls, synching emails, etc. etc. while the iPhone can’t even make a call). Why aren’t they affected?

Additionally, my experience yesterday, when I was at a hospital and had 3 phones with me (including my iPhone), all dropped into EDGE, yet on EDGE the iPhone wouldn’t make a call or browse, while the other two phones were happily receiving emails (and I could make calls on them as well).

These unanswered questions make me doubt this is the full answer to the problem. It’s a great explanation, but there are too many holes left unplugged.

Here’s the key: Apple, if you would just open up and tell us with an official statement what’s going on, all this speculation would end. But that’s too easy, right?