Without contributing to angry 3G iPhone customers worldwide--nor criticizing Apple, the carriers or Infineon, the chipset maker currently under siege--let me reduce the "irritation thermometer" a degree or two.First, I must make clear that I'm not defending Apple, AT&T, other worldwide carriers, Infineon or God. Without divine knowledge, I can tell you that everyone else preceding God is working on the dropped call problem currently attributed to Infineon's chipset. The reported problem appears to relate to iPhone connection transfers from cell tower to cell tower. This explanation may change as Apple, the carriers and Infineon further investigate.
Mobile phone users need to understand that signal-related problems with cellular devices usually stem from a number of related factors--not just one. Here are the main factors:
- Components
Mobile devices contain a myriad number of individual components--some related to signal/RF functionality, others to cameras, music players, chipsets, displays and other components. The components, as with your PC or Mac, interact with each other, sometimes causing system crashes, dropped calls, weak signals and other problems. Generally speaking, the non-RF components, such as a camera, are unrelated to RF components, such as the phones antenna or 3G chipset. Components, similar to computers, are chosen from numerous suppliers and frequently change as the mobile device evolves: more features, identified buggy components, cost, etc.
| - Firmware
Firmware are the hard-coded chips built into a mobile device, controlling video displays, RF signal output, touch screens and most other phone functions. Firmware manufacturers, such as Infineon, provide flash firmware updates to fix problems or increase performance. Wikipedia's short article on firmware is a good introduction to the subject. - Software
Little need be said here. Mobile users--especially iPhone users--are very familiar with the software already embedded or occupying internal memory on the iPhone. But keep in mind, especially with the opening of Apple's new Application Store, that adding any software to a mobile phone, just like a computer, has inherent risks. Application developers have rigid protocols for testing software before release, but it's inevitable you will eventually load a software program on your iPhone that causes problems. Software problems are easier to diagnose and fix. First step: remove the software and see if the problem goes away. Like firmware, software developers release upgrades and updates that resolve problems and increase functionality. - Carrier Infrasructure (Towers, cellular radios, etc.)
If you read my previous post here on MTI, you're aware of AT&T's steps to install more cell towers, 3G radios and other RF devices that control its network. However, AT&T, as with all carriers in the U.S. and abroad, rely on roaming partners (covered next) that handle cell phone call pass-offs as you move out-of-range of the current tower. - Roaming Partners
Cell phone carriers share towers and other RF equipment with other carriers to avoid duplication, effectively increasing the geographic areas offering coverage. Without roaming partners, U.S. and other other carriers would have significant coverage gaps, resulting in an increase in call drops. 3G or broadband coverage areas are one of the weaknesses in U.S. coverage and that, in part, accounts for both voice call drops and slow data downloads, most especially on a data-intensive device such as the 3G iPhone. Until recently, T-Mobile, which uses AT&T and other roaming partners, didn't have its own network. It piggy-backed off coverage supplied by its roaming partners. (Check out GSM World, a great site that explains roaming and lists carrier roaming partners.) - Location
"Location, location, location"--the often-used explanation for real estate prices--is even more true with cellular. Forget the carriers' TV commercials ("More Bars," "Best Network," "Fewer Dropped Calls"). Cell phone RF strength varies from moment-to-moment, especially when you're mobile, and no carrier can predict the strength and quality of the signal on your handset at any point in time. Generally, speaking, you'll get a stronger, more stable signal, if you're outside away from buildings, trees and other RF obstacles, but RF signal strength and call drops are unpredictable, despite the coverage maps carriers show on their websites. - Weather
Inclement weather affects RF signals from your handset to-and-from cell phone towers. As you move through space in your car, bus, train or walking, weather conditions, as with tower locations, will affect signal strength, call quality, 3G availability and, yes, dropped calls. Read this short article on weather and other factors affecting your mobile phone. - Voice & Data Traffic
(See my previous MTI article on the 3G iPhone straining AT&T's network.) In general, as greater demand is placed on mobile carrier networks, performance deterioriates. The carriers continue monitoring network quality, making adjustments in cell tower switching, installing additional antennas and adding roaming partners. RF propagation is very complex, as you've probably sensed by now.
Before U.S. users started rapidly switching from wired to wireless phones, the problems encountered were due primarily to old analog networks (TDMA is a one example.) When the carriers went digital, they improved call quality and coverage, but U.S. users increased dramatically. Penetration is now approaching 85% of the entire population with 260,000,000 handsets in use.
