Less than 2 weeks in market and it is no secret that iPhone 3G faces trouble with 3G calls and high rate data transmission.
When the problem was first reported, Apple's CEO Steve Jobs belittled it as he declared that it affected only 2% of the iPhone 3G user base i.e. just around 60,000 users. Nonetheless, Apple was quick to release update 2.0.1 that failed to solve the problem, followed by update 2.0.2 that did.
As usual with Apple, no details or explanations were given regarding the whole matter, but luckily for us, an AT&T insider agreed to explain it all to RoughlyDrafted Magazine.
Here is what he said (and don't worry, we'll explain it in simpler words afterwards):
"In UMTS (AT&T 3G system) power control is key to the mobile and network success. If the UE (User Equipment = mobile phone) requires too much downlink power then the base station or Node B (base antenna) can run out of transmitter power and this is what was happening".
"As you get more UEs (phones) 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) dropped calls due to a lack of downlink power."
Put simply, a bug in iPhone 3G caused it to ask the network for more power than necessary. When several iPhone 3Gs connected to the same node do that, they drain the network's power, forcing it to drop calls and use lower transmission bandwidth.
"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."
